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Sedimentology of the lower cretaceous gates and moosebar formations, northeast coalfields, British Columbia Carmichael, Scott M. M. 1983

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SEDIMENTOLOGY OF THE LOWER CRETACEOUS GATES AND MOOSEBAR FORMATIONS, NORTHEAST COALFIELDS, BRITISH COLUMBIA By SCOTT M.M. CARMICHAEL B . S c , The U n i v e r s i t y of Edinburgh, 1974 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES Department of G e o l o g i c a l Sciences We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA August 1983 © Scott M.M. Carmichael, 1983 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying o f t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head of my department or by h i s or her r e p r e s e n t a t i v e s . I t i s understood t h a t copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n p e r m i s s i o n . Department of G^OlQfrY The U n i v e r s i t y of B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date 'M -e ->E-6 (3/81) i ABSTRACT The Lower Cretaceous Gates and Moosebar Formations i n the Northeast C o a l f i e l d s of B r i t i s h Columbia comprise a 350-450 m t h i c k i n t e r v a l of marine and non-marine, c o a l bearing c l a s t i c sediments. The Moosebar Formation and lowermost u n i t of the Gates Formation (the Torrens Member) c o n s i s t of between 2 and 4 coarsening-upward marine c y c l e s . In the northern p a r t of the study area, non-marine sediments i n the Gates Formation occur interbedded with 3 major marine tongues (the S h e r i f f member, Fal h e r C and Babcock member) which pinch out towards the south. In the study area south of Duke Mountain, sediments i n the Gates Formation above the Torrens Member are e n t i r e l y non-marine. The coarsening-upward marine c y c l e s i n the Moosebar-lower Gates i n t e r v a l were d e p o s i t e d mainly during r e g r e s s i o n s when the s h o r e l i n e s prograded northwards. The c y c l e s are comprised of up to 3 main f a c i e s i n t e r p r e t e d as o f f s h o r e , t r a n s i t i o n zone and shoreface-beach (and l o c a l l y d i s t r i b u t a r y channel) d e p o s i t s . Thin t r a n s g r e s s i v e d e p o s i t s are present at the base of the S h e r i f f member. Lower Gates s h o r e l i n e s are i n t e r p r e t e d as hig h energy and wave dominated. S h o r e l i n e trends f o r the Torrens, S h e r i f f and Babcock Members are approximately E-W, and approximately NW-SE f o r the F a l h e r C. Non-marine d e p o s i t s i n the Gates Formation are i n t e r p r e t e d as forming i n lagoons, f l u v i a l channels and overbank environments w i t h i n a c o a s t a l p l a i n s e t t i n g . The channels are mainly b r a i d e d r i v e r types with anastomosing or s t r a i g h t (non-braided) and meandering r i v e r channels a l s o p r e s e n t . The r i v e r s flowed towards the northwest, n o r t h , northeast and east with n o r t h e a s t e r l y d i r e c t i o n s most common. Up to three separate very coarse f l u v i a l conglomerates, i n t e r p r e t e d as proximal b r a i d e d r i v e r - a l l u v i a l fan d e p o s i t s are present i n the south near Mount B e l c o u r t . Overbank sediments were d e p o s i t e d i n levee, c r e v a s s e spl a y , l a c u s t r i n e and w e l l to p o o r l y d r a i n e d swamp environments The upper Gates marine u n i t (Babcock member) c o n t a i n s both t r a n s g r e s s i v e and r e g r e s s i v e d e p o s i t s . Three types of t r a n s g r e s s i v e d e p o s i t s are r e c o g n i s e d : 1. Thick (maximum 40 m) estuary mouth |shoal r e t r e a t m a s s i f ) sandstones and conglomerates preserved i n l i n e a r b e l t s approximately 0.4-2 km wide t r e n d i n g NW-SE and N-S. 2. A t h i n (maximum 90 cm) but l a t e r a l l y e x t e n s i v e marine l a g . 3. L a g o o n - i n t e r t i d a l d e p o s i t s . Upper Gates r e g r e s s i v e d e p o s i t s i n c l u d e s h e l f to shallow marine sandstones o v e r l a i n by e s t u a r i n e s u b t i d a l channel and shoal d e p o s i t s which i n turn are o v e r l a i n l o c a l l y by t i d a l f l a t and c o a s t a l p l a i n d e p o s i t s with t h i n c o a l seams. Upper Gates s h o r e l i n e s appear to be s t r o n g l y t i d a l l y i n f l u e n c e d . Thick (maximum 10 m), l a t e r a l l y e x t e n s i v e c o a l seams occur in the lower p a r t of the Gates Formation. Coal seams i n the upper Gates are t h i n ( g e n e r a l l y <1.0 m). With the ex c e p t i o n of few very t h i n seams, the Gates c o a l s appear to be e n t i r e l y autochthonous and to have accumulated as peat i n swamps i n a c o a s t a l p l a i n d e p o s i t i o n a l s e t t i n g . Some of the c o a l s i n the lower Gates were d e p o s i t e d i n swamps which extended i n l a n d f o r at l e a s t 75 km from the s h o r e l i n e . The maximum c o a l development i n the Gates Formation (28 m t o t a l c o a l and 6 seams >1.5 m t h i c k ) occurs i n the F o o t h i l l s south of Kinuseo Creek, near the boundary between t r a n s i t i o n a l marine and non-marine f a c i e s b e l t s . C r o s s - s e c t i o n s based on c l o s e l y spaced borehole and outcrop s e c t i o n s i l l u s t r a t e the occurrence and d i s t r i b u t i o n of c o a l seams i n the.Duke, Honeymoon, Babcock, Frame and McConkey P i t s . T h i n n i n g and pinchout of c o a l seams occurs adjacent to f l u v i a l channel and splay d e p o s i t s and near the landward pinchout of the S h e r i f f member. Draping of c o a l seams over f l u v i a l channel d e p o s i t s causes r a p i d v a r i a t i o n s i n interseam t h i c k n e s s which may l e a d to c o r r e l a t i o n problems in the e a r l y stages of e x p l o r a t i o n and a f f e c t the p o t e n t i a l m i n e a b i l i t y of c o a l seams. The main d e t r i t a l components in the Gates sandstones are quartz and c h e r t with s i l i c e o u s rock fragments, carbonate rock fragments, c l a s t i c sedimentary and metasedimentary rock fragments, igneous rock fragments and f e l d s p a r present i n l e s s e r amounts. Mesozoic to Cambrian sedimentary rocks of the Rocky Mountain Front and Main Ranges are i n t e r p r e t e d as the p r i n c i p a l source of the d e t r i t a l components. i v TABLE OF CONTENTS ABSTRACT i TABLE OF CONTENTS i v LIST OF FIGURES ix LIST OF TABLES . xxvi ACKNOWLEDGEMENTS x x v i i INTRODUCTION 1 PREAMBLE 1 GEOLOGICAL SETTING 3 I. T e c t o n i c S e t t i n g 3 I I . Paleogeography and Regional S t r a t i g r a p h y of the Kootenay-Blairmore Assemblage 6 LITHOSTRATIGRAPHIC NOMENCLATURE 12 AGE OF THE MOOSEBAR AND GATES FORMATIONS 14 PART I LITHOSTRATIGRAPHY AND PALEOENVIRONMENTS OF THE MOOSEBAR AND LOWER GATES FORMATIONS ..15 1.1 REGIONAL CORRELATIONS OF THE GATES AND MOOSEBAR FORMATIONS 15 1.2 MARINE DEPOSITS - INTRODUCTION 18 1 .3 REGRESSIVE DEPOSITS 19 1.3.1 Mudstone F a c i e s - D e s c r i p t i o n 19 1.3.2 Mudstone F a c i e s - I n t e r p r e t a t i o n 22 1.3.3 T r a n s i t i o n F a c i e s - D e s c r i p t i o n 27 1.3.4 T r a n s i t i o n F a c i e s - I n t e r p r e t a t i o n 29 1.3.5 Sheet Sandstone F a c i e s - D e s c r i p t i o n 37 F a c i e s A 42 F a c i e s B 45 V F a c i e s C 50 1.3.6 Sheet Sandstone F a c i e s - I n t e r p r e t a t i o n ...51 1.3.7 Comparison of the Lower Gates C o a s t a l F a c i e s with Modern High and Low Energy Beach-to-Offshore Sequences ......53 1.4 TRANSGRESSIVE DEPOSITS 55 1.4.1 F a c i e s D 55 1.4.2 F a c i e s E 56 1.4.3 F a c i e s F 57 1.4.4 O r i g i n of the T r a n s g r e s s i v e D e p o s i t s 57 1.5 SUMMARY OF MARINE PALEOCURRENT DATA 60 1.6 LAGOONAL DEPOSITS ..60 1.7 NON-MARINE DEPOSITS - INTRODUCTION 67 1.8 FLUVIAL CHANNEL DEPOSITS 68 1.8.1 Type 1 Channel D e p o s i t s - D e s c r i p t i o n 68 1.8.2 Type 1 Channel D e p o s i t s - I n t e r p r e t a t i o n ..77 1.8.3 Type 2 Channel D e p o s i t s - D e s c r i p t i o n 78 1.8.4 Type 2 Channel D e p o s i t s - I n t e r p r e t a t i o n ..90 1.8.5 Type 3 Channel D e p o s i t s - D e s c r i p t i o n 96 1.8.6 Type 3 Channel Deposits - I n t e r p r e t a t i o n ..99 1.8.7 Type 4 Channel D e p o s i t s - D e s c r i p t i o n 99 1.8.8 Type 4 Channel Deposits - I n t e r p r e t a t i o n ..106 1.8.9 Type 5 Channel D e p o s i t s - D e s c r i p t i o n 109 1.8.10 Type 5 Channel D e p o s i t s - I n t e r p r e t a t i o n .109 1.8.11 Summary of F l u v i a l P a l e o c u r r e n t Data .....111 1 .9 OVERBANK DEPOSITS 111 1.9.1 N a t u r a l Levee Deposits 112 1.9.2 Crevasse Splay D e p o s i t s ........113 v i 1.9.3 O r i g i n of the Crevasse Splay D e p o s i t s 121 1 .9.4 Lake D e p o s i t s 123 1.9.5 Well to Poo r l y Drained Swamp De p o s i t s .....127 PART II FACIES ASSOCIATIONS IN THE UPPER GATES FORMATION:  TRANSGRESSIVE AND REGRESSIVE MARINE, ESTUARINE, AND  AND COASTAL PLAIN DEPOSITS 129 2.1 INTRODUCTION 129 2.2 FACIES - DESCRIPTION AND INTERPRETATION 130 2.2.1 General 130 2.2.2 F a c i e s 1A - D e s c r i p t i o n 136 2.2.3 F a c i e s 1A - I n t e r p r e t a t i o n 157 2.2.4 F a c i e s 1B - D e s c r i p t i o n 159 2.2.5 F a c i e s 1B - I n t e r p r e t a t i o n 163 2.2.6 F a c i e s 2A - D e s c r i p t i o n 165 2.2.7 F a c i e s 2A - I n t e r p r e t a t i o n 170 2.2.8 F a c i e s 2B - D e s c r i p t i o n ...171 2.2.9 F a c i e s 2B - I n t e r p r e t a t i o n ' ....172 2.2.10 F a c i e s 3A - D e s c r i p t i o n 173 2.2.11 F a c i e s 3B - D e s c r i p t i o n 180 2.2.12 F a c i e s 3A and 3B - I n t e r p r e t a t i o n 185 2.2.13 F a c i e s 3C - D e s c r i p t i o n 189 2.2.14 F a c i e s 3C - I n t e r p r e t a t i o n 190 2.2.15 F a c i e s 4 - D e s c r i p t i o n 193 2.2.16 F a c i e s 4 - I n t e r p r e t a t i o n 195 2.2.17 F a c i e s 5 - D e s c r i p t i o n 198 2.2.18 F a c i e s 5 - I n t e r p r e t a t i o n 201 2.3 UPPER GATES DEPOSITIONAL MODELS 209 v i i 2 . 4 DISCUSSION . .. 211 PART III OCCURRENCE, DISTRIBUTION AND DEPPSITIONAL SETTING OF COAL SEAMS IN THE GATES FORMATION 214 3.1 SEDIMENTOLOGICAL ASPECTS OF COAL OCCURRENCES AND DISTRIBUTION IN THE DUKE MOUNTAIN AREA 214 3.1.1 I n t r o d u c t i o n 214 3.1.2 Coal Seams i n the Duke Mountain Area 216 3.2 SEDIMENTOLOGICAL ASPECTS OF COAL OCCURRENCES AND DISTRIBUTION IN THE BABCOCK AREA 223 3.2.1 I n t r o d u c t i o n 223 3.2.2 Coal Seams i n the Babcock Area 225 3.2.3 D e p o s i t i o n a l F a c t o r s C o n t r o l l i n g the Thickness, D i s t r i b u t i o n and C o n t i n u i t y of the G and I seams 228 3.2.4 Model f o r the D e p o s i t i o n of the G and I seams 233 3.3 COAL OCCURRENCES IN THE FRAME AND MCCONKEY PITS 235 3.4 PLANT COMMUNITIES IN THE GATES PEAT SWAMPS 241 3.5 REGIONAL TRENDS IN COAL DEVELOPMENT IN THE GATES FORMATION 241 3.5.1 R e l a t i o n s h i p Between Regional Coal Development and Paleogeography of the Gates Formation .244 3.6 DEPOSITIONAL SETTING OF COAL SEAMS IN THE GATES FORMATION 246 PART IV SANDSTONE PETROGRAPHY 253 v i i i 4.1 DATA AND METHODS 253 4.2 FRAMEWORK GRAINS 253 4.3 MATRIX AND CEMENTS 258 4.4 MISCELLANEOUS CONSTITUENTS 259 4.5 TEXTURE .259 4.6 SANDSTONE CLASSIFICATION 260 4.7 SOURCE AREA 260 SUMMARY AND CONCLUSIONS 266 REFERENCES 272 LIST OF FIGURES Fi g u r e j_. L o c a t i o n map of the study area showing the outcrop p a t t e r n of the Gates Formation and l o c a l i t i e s mentioned i n the t e x t . F i g u r e 2. G e n e r a l i s e d t e c t o n i c map showing the l o c a t i o n of the C o r d i l l e r a n Orogen, F o r e l a n d Basin and p r i n c i p a l r e -e n t r a n t s on the e a s t e r n Orogen (modified a f t e r Douglas et a l . , 1976 and Eis b a c h e r et a l . , 1974). F i g u r e 3. C o r r e l a t i o n c h a r t of Late J u r a s s i c and E a r l y Cretaceous s t r a t i g r a p h i c u n i t s i n p a r t s of no r t h e a s t e r n B r i t i s h Columbia, A l b e r t a and northwestern Montana (modified a f t e r McLean, 1982). F i g u r e 4. N o n - p a l i n s p a s t i c map showing the d i s t r i b u t i o n of Late J u r a s s i c and E a r l y Cretaceous seaways and important c o a l measure sequences. Compiled from Coal Task Force (1976), Douglas et a l . , (1976); Gibson (1977); Hamblin and Walker, (1979); J e l e t z k y (1971); McLean, (1982); McLean and Wal l , (1981); S t e l c k et a l . , (1972); S t o t t , (1968), (1972), (1974), (1975), (1982); Yurko, (1975). F i g u r e 5_. 1 - Regional c r o s s - s e c t i o n of the Gates and Moosebar Formations, f o o t h i l l s of no r t h e a s t e r n B r i t i s h Columbia ^ — - - ^ r ^at back of t h e s i s ) . F i g u r e 6 . 2 - Regional c r o s s - s e c t i o n of the Gates and Moosebar Formations, f o o t h i l l s of no r t h e a s t e r n B r i t i s h Columbia ( l o c a t i o n of s e c t i o n s shown on Fi g u r e 5_) , - \ K f e i - . ,/at back of t h e s i s ) . « Fi g u r e 7. 3 - Gamma ray l o g c o r r e l a t i o n of s t r a t a e q u i v a l e n t to the Gates and Moosebar Formation i n the p l a i n s ( w e l l l o c a t i o n s shown on F i g u r e 5) „ "* -~ ( a t back of t h e s i s ) . F i g u r e 8. Southern l i m i t of the S h e r i f f member, Babcock member and F a l h e r C marine u n i t s . F i g u r e 9A. Offshore (mudstone f a c i e s ) mudstones and s i l t s t o n e s i n the lower p a r t of the f i r s t coarsening-upward c y c l e i n the Moosebar Formation. The more r e s i s t a n t bands are s i l t s t o n e s and carbonate c o n c r e t i o n s . F i g u r e 9B. T h i s view shows two coarsening-upward, r e g r e s s i v e c y c l e s i n the upper Moosebar Formation. The more r e s i s t a n t sandstones on the lower l e f t represent t r a n s i t i o n zone ( t r a n s i t i o n f a c i e s ) d e p o s i t s at the top of the f i r s t c y c l e . The second c y c l e begins with o f f s h o r e (mudstone f a c i e s ) mudstones and t h i n s i l t s t o n e s which grade upwards i n t o the t r a n s i t i o n f a c i e s c o n s i s t i n g of interbedded s i l t s t o n e s , f i n e - g r a i n e d sandstones and t h i n mudstones. Note the l a r g e carbonate c o n c r e t i o n s i n the upper p a r t of the second c y c l e . Both photographs from outcrops on the northwest s i d e of Mount Frame. X Fig u r e JMO. Core photographs of o f f s h o r e (mudstone f a c i e s ) mudstones and s i l t s t o n e s . B i o t u r b a t i o n i s common i n t h i s f a c i e s and f r e q u e n t l y d e s t r o y s a l l t r a c e of bedding ( F i g u r e s 10b, I0h). Trace f o s s i l s are dominated by h o r i z o n t a l forms c o n s i s t i n g of dark grey s i n g l e or p a i r e d tubes ('h' i n F i g u r e 10f) surrounded by a halo of l i g h t e r c o l o u r e d b i o t u r b a t e d sediment. These represent g r a z i n g t r a i l s of Helminthoida, S c a l a r i t u b a N e r e i t e s or Phycosiphon . A second type of h o r i z o n t a l burrow ( Paleophycus?) I s shown i n F i g u r e 1Og. V e r t i c a l burrows are a l s o present i n the mudstone f a c i e s (e.g., F i g u r e s 10c, 1Oe) but are much l e s s common. T r i c h i c h n u s ( t) burrows are present i n F i g u r e 1Oe. P y r i t e (py) occurs w i t h i n one of the burrows i n t h i s F i g u r e . I t a l s o occurs as l a r g e r i r r e g u l a r , patches (Figure 1Od). P a r a l l e l bedding can be seen i n s e v e r a l of the cores and r i p p l e s are present i n F i g u r e 1Od. A BD 7802 1588 f t b MDD 7918 115.3 m c BD 7802 1577.5 f t d MDD 7811 190.46 m e BD 7802 1581 f t f BD 7802 1563.5 f t g No r e c o r d h MDD 7 915 115.3 m Fig u r e Core photographs of t r a n s i t i o n zone ( t r a n s i t i o n f a c i e s ) d e p o s i t s . F i g u r e 11a. Low angle cross-bedded and p a r a l l e l bedded s i l t s t o n e . Note the sharp base and top and the small mudstone r i p - u p c l a s t s i n the middle of the bed. (MDD 7811, 180.3 m). Fig u r e 11b. S i l t s t o n e bed which shows low angle cross-bedding, i n the lower p a r t and r i p p l e s at the top. T h i s type of sequence i s common i n the t r a n s i t i o n f a c i e s . In outcrop the low angle cross-bedding i s t y p i c a l l y hummocky c r o s s -s t r a t i f i c a t i o n . (MDD 7801, 124.2 m). Fig u r e 11c. T h i s core shows the a l t e r n a t i o n of s t r o n g l y b i o t u r b a t e d mudstone beds with p a r a l l e l bedded s i l t s t o n e s which c o n t a i n ony a few burrows. Helminthoida type burrows are common i n the mudstones at the top and base of the co r e . Both h o r i z o n t a l burrows (? Paleophycus) and v e r t i c a l burrows are present i n the s i l t s t o n e . (MDD 7918, 103.75 m). Fi g u r e 11d. T h i s core shows s i m i l a r bedding s t r u c t u r e s to Fig u r e 11b but c o n t a i n s upward doming l a m i n a t i o n s c h a r a c t e r i s t i c of hummocky c r o s s - s t r a t i f i c a t i o n (H.C.S.). In c o r e s , H.C.S. can r a r e l y be proven due to small core diameters and the g e n t l e d i p s of the l a m i n a t i o n s . (MDD 7918, 103.75 m). Fi g u r e 11e. S t r o n g l y burrowed s i l t s t o n e i n which Paleophycus i s the dominant t r a c e f o s s i l . Helminthoida type burrows are a l s o p r e s e n t . (MDD 7918, 95 m). x i F i g u r e 11f. Trace f o s s i l s i n the mudstone at the base of t h i s core i n c l u d e Helminthoida type burrows and C h o n d r i t e s ( c ) , (MDD 7918, 85.4 m). F i g u r e 11g. Low angle cross-bedding i n a s i l t s t o n e bed. Mudstone r i p - u p c l a s t s at the base i n d i c a t e s that the s i l t s t o n e was d e p o s i t e d by strong e r o s i v e cuments. F i g u r e 11h. F i n e - g r a i n e d p a r a l l e l bedded sandstone which c o n t a i n s abundant Paleophycus burrows. Note the t r u n c a t e d s u b - v e r t i c a l burrow (t) near the top. (MDD 7918, 50.5 m). F i g u r e _1_2. Primary sedimentary s t r u c t u r e s i n the t r a n s i t i o n fac i e s . F i g u r e 12a. Mudstones and s i l t s t o n e s i n the lower p a r t e x h i b i t l e n t i c u l a r and f l a s e r bedding. The t h i c k e r bed i n the upper p a r t shows hummocky c r o s s - s t r a t i f i c a t i o n and c l i m b i n g wave r i p p l e s at the top. F i g u r e 12b. Sharp c r e s t e d symmetrical wave r i p p l e s on the top s u r f a c e of a bed i n the t r a n s i t i o n f a c i e s . F i g u r e J_3. Outcrop of the lower Gates on the northwest s i d e of Mount Frame. The prominent grey sandstone i n the foreground i s the Torrens Member. Note the abrupt and p l a n a r top s u r f a c e which re p r e s e n t s the a n c i e n t backshore. The Torrens i s o v e r l a i n by 10.5 m of black mudstones interbedded with t h i n s i l t s t o n e s and sandstones ( l a g o o n a l d e p o s i t s ? ) . A t h i n (0.5 m) c o a l seam occurs above t h i s at the top r i g h t of the photograph. T h i s i s o v e r l a i n by sandstones and a conglomerate f i l l e d channel ( c ) . Marine sandstones of the S h e r i f f member(s) outcrop on the slope' i n the d i s t a n c e o v e r l y i n g a t h i n t r a n s g r e s s i v e l a g at the' top of the channel d e p o s i t s . F i g u r e J_4. Road cut at the McConkey P i t . The type s e c t i o n of the S h e r i f f member i s along the road behind the h i l l i n the foreground. The f i r s t t h i c k seam on the l e f t i s the 10 m t h i c k J seam. Seams above t h i s i n c l u d e the G seam (2.0 m t h i c k ) and the E seam. E occurs w i t h i n an i n t e r v a l over 20m t h i c k but c o n t a i n s numerous s p l i t s and small f a u l t s . F i g u r e j_5. View of the 10 m t h i c k J seam along the McConkey road cu t . J r e s t s d i r e c t l y on nearshore marine sandstones of the S h e r i f f member and i s o v e r l a i n by i n f e r r e d l a k e - l a c u s t r i n e d e l t a d e p o s i t s c o n s i s t i n g of a coarsening-upward sequence of interbedded mudstones, s i l t s t o n e s and f i n e - g r a i n e d sandstones. Non-marine U n i o n i d b i v a l v e s are common in mudstones immediately above J . Note the w e l l developed p a r a l l e l l a m i n a t i o n s i n the i n f e r r e d lake d e p o s i t s . In t h i s s e c t i o n J i s s t r o n g l y sheared and s t r u c t u r a l l y thickened by 2-3 m along the road. F i g u r e JJ5. Low angle cross-bedding and p a r a l l e l bedding i n lower shoreface sandstones (sheet sandstone f a c i e s A) of the x i i S h e r i f f member. F i g u r e J_7. S k o l i t h o s burrows c o n s i s t i n g of simple, even width, v e r t i c a l tubes i n lower shoreface sandstones (sheet sandstone f a c i e s A) of the S h e r i f f member. Fi g u r e J_8. P a r a l l e l laminated to burrowed sequence i n lower shoreface sandstones (sheet sandstone f a c i e s A) of the S h e r i f f member. F i g u r e J_9. Trace f o s s i l s i n shoreface - beach sandstones (sheet sandstone f a c i e s ) . F i g u r e 19a,b. V e r t i c a l U-shaped burrows, probably D i p l o c r a t e r i o n . In F i g u r e 19b three l a r g e U-shaped s p r e i t e s t r u c t u r e s are v i s i b l e . F i g u r e 19c. P a r a l l e l laminated to burrowed sequence. The burrows are Paleophycus. F i g u r e 19d. Core photograph of burrowed marine sandstones i n the upper part of the S h e r i f f member i n borehole QMD 7705. Trace f o s s i l s i n c l u d e h o r i z o n t a l forms of Ophiomorpha (o) and S k o l i t h o s ( s ) . F i g u r e 19e. S t r o n g l y burrowed sandstone at the top of the S h e r i f f member i n borehole QBD 7701 (186.2 m). Burrows c o n s i s t s of small h o r i z o n t a l to s l i g h t l y i n c l i n e d c i r c u l a r to o v a l tubes with no evidence of branching. These are s i m i l a r to Macaronichnus segregatus ( C l i f t o n and Thompson, 1978). F i g u r e 20. Primary sedimentary s t r u c t u r e s i n cores from nearshore marine sandstones (sheet sandstone f a c i e s B). Fi g u r e 20a. Cross-bedding, p a r a l l e l bedding and r i p p l e s (MDD 7811, 114.15 m). Fi g u r e 20b. Same as 2fj. Note the scoured s u r f a c e at the top of the core (MDD 7811, 112.86 m). Fi g u r e 20c. A l t e r n a t i o n s of p a r a l l e l bedding and r i p p l e s . A s i n g l e h o r i z o n t a l burrow( Paleophycus) i s present at the base.(b). (MDD 7918, 19.6 m). F i g u r e 20d. Cross-bedded sandstone. (MDD 7918, 10.8 m). Fi g u r e s 21a,b. Cross-bedding and p a r a l l e l bedding i n nearshore marine sandstones (sheet sandstone f a c i e s B) a=MDD 7823, 391.7m; b=MDD 7823, 388 m. Fi g u r e 21c. Core photograph of massive root p e n e t r a t e d sandstone at the top of the Torrens Member (MDD 7823, 385.3 m). Fi g u r e 21d. Massive root p e n e t r a t e d sandstone at the top of the S h e r i f f member o v e r l a i n d i r e c t l y by the J c o a l seam. x i i i F i g u r e 22. Summary of "marine" p a l e o c u r r e n t data i n the upper Moosebar (UM) and S h e r i f f member (SH) i n t e r v a l . F i g u r e 23a. S h o r e l i n e p r o f i l e of modern sandy c o a s t l i n e s (modified a f t e r Reineck and Singh (1973), p. 285.) Fi g u r e 23b. C l a s s i f i c a t i o n of f l u v i a l channel p a t t e r n s ( m o d i f i e d a f t e r M i a l l , 1977) . F i g u r e 24. Borehole c r o s s s e c t i o n i n the Duke Mountain area, showing the complex f a c i e s a s s o c i a t i o n s near the landward pinchout of the S h e r i f f member marine u n i t . Note that c o a l seam B2 t h i n s and i s r e p l a c e d by marine sandstones of the S h e r i f f member towards the no r t h . Borehole l o c a t i o n s shown on F i g u r e 83. F i g u r e 2_5. Outcrop s e c t i o n s of the member and lower Gates Formations on the northeast s i d e of the F i v e Cabin Creek s y n c l i n e . Marine d e p o s i t s occur mainly w i t h i n c o a r s e n i n g -upward c y c l e s . Thick conglomerates i n the upper part of s e c t i o n s FC4 and FC6 are i n t e r p r e t e d as d i s t r i b r u t a r y channel f i l l ( b r a i d e d r i v e r ) d e p o s i t s . The conglomerates pinchout towards the southeast i n s e c t i o n FC7 and are re p l a c e d by sandstones which e x h i b i t p a r a l l e l bedding, trough and t a b u l a r cross-bedding and r a r e herringbone c r o s s s t r a t i f i c a t i o n . Trace f o s s i l s i n these sandstones i n c l u d e Macaronichnus segregatus. F i g u r e 26. View of type 1 channel f i l l d e p o s i t s near s e c t i o n s FC4 and FC6 (Figure 25) on the northeast s i d e of the F i v e Cabin Creek s y n c l i n e . The channel d e p o s i t s c o n s i s t of massive conglomerates and c o a r s e - g r a n u l a r sandstones. The base of. the channel i s exposed i n the d i s t a n c e and o v e r l i e s s e v e r a l metres of carbonaceous mudstones which i n turn r e s t on grey, marine sandstones of the S h e r i f f member (lower r i g h t of the photograph). F i g u r e 2_7. F l u v i a l (type 1) conglomerates and sandstones i n borehole QBD 7308. Coal spar i s abundant i n the sandstones on the lower l e f t of the photograph. S c a l e i s 18 cm lon g . F i g u r e 2j5. Primary sedimentary s t r u c t u r e s i n i n t e r t i d a l to shallow s u b t i d a l marine sandstones at the top of s e c t i o n FC 7 i n the F i v e Cabin Creek area. These d e p o s i t s are r e p l a c e d by type 1 d i s t r i b u t a r y channel sandstones and conglomerates in s e c t i o n FC 6, 150 m to the northwest. F i g u r e 28a. Sandstones e x h i b i t i n g trough cross-bedding p a r a l l e l bedding and herringbone c r o s s - s t r a t i f i c a t i o n . F i g u r e 28b. Trough and t a b u l a r cross-bedding and p a r a l l e l bedding. F i g u r e 28c. P a r a l l e l bedding and t a b u l a r c r o s s - b e d d i n g . F i g u r e 29. Outcrop s e c t i o n s of type 2 channel f i l l d e p o s i t s i n x i v the Windy P i t area on the northwest sid e of Babcock Mountain. The lower u n i t of these channel f i l l d e p o s i t s c o n s i s t s predominantly of f i n e - to medium-grained, trough cross-bedded sandstones. The upper u n i t i s c o a r s e r - g r a i n e d and composed of massive, e r o s i o n a l l y based u n i t s of conglomerate and coarse to g r a n u l a r sandstones interbedded with f i n e - to c o a r s e - g r a i n e d pebbly sandstones which e x h i b i t t a b u l a r and trough cross-bedding and o c c a s i o n a l l y p a r a l l e l bedding. F i g u r e 3_0. Outcrop photographs of type 2 channel f i l l d e p o s i t s on the northwest s i d e of Babcock Mountain. F i g u r e 30a. Trough cross-bedded f i n e - to medium-grained sandstones c h a r a c t e r i s t i c of the lower u n i t of type 2 channel f i l l d e p o s i t s . F i g u r e 30b. Massive conglomerate and i n t e r c a l a t e d cross-bedded sandstone i n the upper u n i t . F i g u r e 30c,d. Massive, conglomerate and coarse to g r a n u l a r sandstone at the base of the upper u n i t . Note the ch a n n e l l e d base of the upper u n i t d e p o s i t s i n F i g u r e 30c. F i g u r e 30e. Large set of t a b u l a r cross-bedding i n conglomerate and coarse to g r a n u l a r , pebbly sandstones from the upper u n i t . F i g u r e 30f. Massive to weakly s t r a t i f i e d conglomerate o v e r l a i n by p a r a l l e l and cross-bedded c o a r s e - g r a i n e d sandstones i n the upper u n i t . F i g u r e 3J_. S e c t i o n A - Borehole c r o s s s e c t i o n of the i n t e r v a l , between the F and J seams at Babcock showing the' c h a r a c t e r i s t i c s of type 2 channel f i l l d e p o s i t s , crevasse splay d e p o s i t s , and the draping of the G/l1 seam over the channel. Note the pinchout of the 13 and 12 seams adjacent to the splay and channel d e p o s i t s . A l s o , the t h i c k e n i n g of the G/I-F i n t e r v a l i n the i n t e r c h a n n e l area ( i n boreholes 7303 and 7712). Borehole l o c a t i o n s shown on F i g u r e 32. Se c t i o n c o n s t r u c t e d with the base of the J seam as h o r i z o n t a l datum. F i g u r e 32. Sandstone and conglomerate isopachs i n the i n t e r v a l between c o a l seams J and G/l i n the Babcock a r e a . F i g u r e 32a. Isopachs of the lower u n i t of type 2 channel-and a s s o c i a t e d s p l a y d e p o s i t s . F i g u r e 32b. Isopach of the upper u n i t of type 2 channel d e p o s i t s . F i g u r e 33. Li n e drawing t r a c e d from a photograph of l a r g e s c a l e bedforms i n the upper u n i t of type 2 channel d e p o s i t s . Photograph i s an o b l i q u e view of a c l i f f exposure on the northwest s i d e of Babcock Mountain. Note the occurrence of XV low angle e r o s i o n a l s u r f a c e s i n the lower p a r t of the outcrop. A l a r g e channel with a concave upwards base i s preserved towards the northwest. The more r e c e s s i v e upper p a r t of the outcrop c o n s i s t s of trough and t a b u l a r c r o s s -bedded sandstones. F i g u r e 34. Core from borehole QBD 7715 at Babcock, showing the very abrupt contact (A) between type 2 (upper u n i t ) channel f i l l d e p o s i t s and o v e r l y i n g overbank d e p o s i t s . The channel f i l l sediments c o n s i s t mainly of conglomerates and c r o s s -bedded and r i p p l e d sandstones. These are o v e r l a i n by p a r a l l e l laminated and massive s i l t s t o n e s and carbonaceous mudstones ( i n f e r r e d lake d e p o s i t s i n the abandoned channel) which grade upwards i n t o more massive carbonaceous mudstones ( i n f e r r e d p o o r l y d r a i n e d swamp d e p o s i t s ) and the 2.4 m t h i c k G c o a l seam. Fi g u r e 3_5. D i s t r i b u t i o n of channel f i l l d e p o s i t s i n the i n t e r v a l s between c o a l seams B4 and B5 (Fi g u r e 35a) and B7 and B8 (Fi g u r e 35b) i n the Duke Mountain a r e a . The channel f i l l d e p o s i t s in the B4-B5 i n t e r v a l are i n t e r p r e t e d from t h e i r l o g c h a r a c t e r and c o a l company core d e s c r i p t i o n s . Channel f i l l d e p o s i t s i n the B7-B8 i n t e r v a l are i l l u s t r a t e d in more d e t a i l on F i g u r e J36. The boreholes shown on these maps i n c l u d e only those which were a v a i l a b l e to the author and which penetrated the i n t e r v a l of i n t e r e s t . F i g u r e ^6. Borehole c r o s s s e c t i o n of the i n t e r v a l between c o a l seams B7 and B9 i n the Duke Mountain area showing the c h a r a c t e r i s t i c s of type 3 channel d e p o s i t s and a s s o c i a t e d overbank sediments. The d i s t r i b u t i o n of the l a r g e r channel between seams B7 and B8 and the borehole l o c a t i o n s are shown on F i g u r e 3_5. S e c t i o n c o n s t r u c t e d with the base of the B9 seam as h o r i z o n t a l datum. Fi g u r e 3J7. Outcrop s e c t i o n of the Moosebar Formation, Gates Formation, H u l c r o s s Formation and lower p a r t of the Boulder Creek Formation from a r i d g e on the north s i d e of Dumb Goat Mountain. Three t h i c k conglomerate i n t e r v a l s are present i n the non-marine p a r t of the Gates Formation (type 4 channel d e p o s i t s ) . The rose diagrams show the d i p d i r e c t i o n of imbr i c a t e d pebbles and i n d i c a t e p a l e o c u r r e n t s d i r e c t e d towards the north and n o r t h e a s t . Nearby boreholes (DG 81-01, MBD 7828 and BDD 7601, shown on F i g u r e 6) i n d i c a t e that there are e i t h e r 3 or 4 t h i c k seams (>1.5 mT i n the covered i n t e r v a l s between the Torrens Member and conglomerate 3, and numerous t h i n seams (<1.5 m) between conglomerate 3 and the H u l c r o s s Formation. F i g u r e 38_. View towards the north of the F o o t h i l l s i n the southern p a r t of the study a r e a . The peak i n the ce n t r e i s Mount B e l c o u r t . Dumb Goat Mountain i s l o c a t e d 3 km to the northwest. On Mount B e l c o u r t and Dumb Goat Mountain, Cretaceous rocks d i p towards the southwest beneath a major t h r u s t f a u l t which b r i n g s forward P a l e o z o i c and Mesozoic rocks of the Rocky Mountain Front Ranges. x v i F i g u r e 39. View of par t of the Dumb Goat Mountain outcrop s e c t i o n shown on F i g u r e 37. Fig u r e 40. T y p i c a l c l a s t supported f a b r i c of conglomerates on Dumb Goat Mountain. Note the w e l l developed i m b r i c a t i o n i n s p h e r i c a l c l a s t s . C l a s t s are w e l l rounded and c o n s i s t mainly of q u a r t z i t e and c h e r t with l e s s e r amounts of quartzose sandstone, limestone, s i l t s t o n e , a r g i l l i t e , mudstone and dolomite. F i g u r e 4J_. Tabular cross-bedding i n sandstones o v e r l y i n g conglomerate 2. Fi g u r e 42^ . Summary of " f l u v i a l " p a l e o c u r r e n t data i n the Gates Formation. T h i s diagram does not i n c l u d e data from the upper Gates, no r t h of Kinuseo Creek which i s shown on F i g u r e s 55 and 65. Fi g u r e 43. Sandstone isopach map showing the l o c a t i o n of sp l a y d e p o s i t s i n the i n t e r v a l between c o a l seams G/l and F i n the Babcock area. F i g u r e 4_4. Borehole c r o s s s e c t i o n showing the c h a r a c t e r i s t i c s of crev a s s e splay and other overbank d e p o s i t s i n the i n t e r v a l between c o a l seams G/l and F i n the Babcock area. Note the occurrence of mainly fining-upward sequences i n the proximal splay d e p o s i t s and coarsening-upward sequences i n the d i s t a l splay d e p o s i t s . Borehole l o c a t i o n s are shown on Fi g u r e 4_3. Legend i s shown on F i g u r e 24. Fi g u r e 45. Core from borehole QBD 7219 i n the Babcock area showing the c h a r a c t e r i s t i c s of d i s t a l c r evasse splay d e p o s i t s . L i t h o l o g i e s c o n s i s t of t h i n interbedded s i l t s t o n e s and f i n e - g r a i n e d sandstones which e x h i b i t p a r a l l e l bedding, r i p p l e s and c l i m b i n g r i p p l e l a m i n a t i o n . Core corresponds to the 16 m t h i c k i n t e r v a l above the 11 seam i n borehole 7219 shown on F i g u r e 44. Fi g u r e 46. Core photographs of overbank d e p o s i t s . F i g u r e 46a. I n t r a f o r m a t i o n a l conglomerate composed of s i l t s t o n e r i p - u p c l a s t s . T h i s core i s from a u n i t which i s 55 cm t h i c k and was probably formed by a s i n g l e f l o o d event. (MDD 7823, 360.1 m). Fi g u r e 46b. The i n t e r n a l c h a r a c t e r i s t i c s of the sediment i n t h i s core are i n t e r p r e t e d as the r e s u l t of a s i n g l e sheet f l o o d event; the onset of the f l o o d i s marked by s i l t s t o n e r i p - u p c l a s t s and the e r o s i v e base of the sandstone bed ( e ) . T h i s was followed by the pr o g r a d a t i o n of a t h i n sand sheet which formed the high angle f o r e s e t s ( f ) . As the c u r r e n t s weakened the top of the sand sheet was reworked to form r i p p l e s ( r ) . The f i n a l episode i s represented by the p a r a l l e l bedded s i l t s t o n e s formed by d e p o s i t i o n from suspension at the end of the f l o o d . S i l t s t o n e s at the top e x h i b i t convolute bedding (c) (MDD 7823, 360.1 m). x v i i F i g u r e 46c. P a r a l l e l bedding and c l i m b i n g r i p p l e s i n overbank s i l t s t o n e s . (MXD 7827, 401.2 m). Fi g u r e 46d. I n f e r r e d w e l l d r a i n e d swamp d e p o s i t c o n s i s t i n g of massive root (r) penetrated s i l t s t o n e . Note the small s i l i c e o u s c o n c r e t i o n s at the base. F i g u r e s 46e,f. I n f e r r e d l a c u s t r i n e d e p o s i t s c o n s i s t i n g of p a r a l l e l laminated s i l t s t o n e s and mudstones. Note the two burrows in 46e. Fi g u r e 46g. R i p p l e d f i n e - g r a i n e d sandstone interbedded with dark grey s i l t s t o n e s . S e v e r a l burrows are v i s i b l e i n t h i s c o r e . T h i s type of de p o s i t i s common i n both levee and crevasse splay environments (QBD 7306, 1690 f t ) . F i g u r e 46h. Massive overbank s i l t s t o n e . The absence of bedding may be the r e s u l t of very r a p i d sedimentation, . b i o t u r b a t i o n , or d e s t r u c t i o n by the escape of water d u r i n g compaction. A l t e r n a t i v e l y bedding may be present but would r e q u i r e other techniques (e.g., exposure to X-rays) to make i t v i s i b l e . F i g u r e 4_7. G e n e r a l i s e d c r o s s s e c t i o n showing the f a c i e s present i n the upper Gates between the McConkey P i t and Duchess Mountain. F i g u r e 48. S e c t i o n A - upper Gates c r o s s s e c t i o n i n the Babcock area ( l o c a t i o n of s e c t i o n i s shown on F i g u r e 66). Fi g u r e 49. S e c t i o n B - upper Gates c r o s s s e c t i o n i n the Babcock area ( l o c a t i o n of s e c t i o n i s shown on F i g u r e 66). Legend i s shown on F i g u r e 48. Fi g u r e 50. Cross s e c t i o n of the i n t e r v a l between the B7 c o a l seam and the Hulc r o s s Formation i n boreholes near the Duke P i t (borehole l o c a t i o n s are shown on F i g u r e 35). H o r i z o n t a l datum i s the top of the B9 upper seam. Note that B9) i s eq u i v a l e n t to the D seam on F i g u r e s 4J_ and 42_. Legend i s shown on F i g u r e 48. F i g u r e 5_K Map showing the approximate a r e a l d i s t r i b u t i o n of upper Gates f a c i e s 1A, 2A and 4. (Note: S c a l e of map i s too small to show a l l the s e c t i o n s which penetrate these f a c i e s ; boreholes and w e l l s shown on the map are only those used on the r e g i o n a l c r o s s s e c t i o n s - F i g u r e s 5, 6 and 7.) Fi g u r e 5_2. Isopach map of f a c i e s 1A i n the Babcock area, F i g u r e 53. Core and outcrop photographs of f a c i e s 1A l i t h o l o g i e s . F i g u r e 53a. Poorly s o r t e d conglomerate with a sandy matrix. F i g u r e 53b,d. Well s o r t e d conglomerate/granular sandstone l a c k i n g any f i n e sandy matrix and with very good x v i i i i n t e r g r a n u l a r p o r o s i t y , (b = QMD 7609, 42.5 m; d = QMD 7620, 137 m). F i g u r e 53c. Very w e l l s o r t e d c o a r s e - g r a i n e d sandstone with very good i n t e r g r a n u l a r p o r o s i t y (QMD 7620, 139 m) . F i g u r e 53e. P o o r l y s o r t e d conglomerate with a sandy matrix (QMD 7618, 66 m). F i g u r e 53f. Sandstones and conglomerates at the top of f a c i e s 1A i n QBD 7712. Burrows c o n s i s t i n g of small c i r c u l a r to o v a l tubes ( p o s s i b l y Macaronichnus segregatus) are present i n sandstones at the top of f a c i e s 1A ( b ) . F a c i e s 1B occurs at the top r i g h t from A-B. Note the very sharp c o n t a c t (B) between f a c i e s 1B and the mudstones and s i l t s t o n e s at the base of f a c i e s 2A at the top r i g h t of the c o r e . F i g u r e 53g. P a r a l l e l bedding formed by a l t e r n a t i o n s of f i n e - and c o a r s e - g r a i n e d sandstone and conglomerate near the base of f a c i e s 1A on the south s i d e of Mount Frame. A small scour i s present i n sandstones i n the upper l e f t . These sediments are i n t e r p r e t e d as the r e s u l t of d e p o s i t i o n from strong upper flow regime c u r r e n t s . The sandstones and conglomerates are very c l e a n with good i n t e r g r a n u l a r p o r o s i t y . F i g u r e 54. Core of sediments i n f a c i e s 1A, 1B and the base of f a c i e s 2A from borehole QBD 7201 i n the Babcock a r e a . F i n e -g r a i n e d pebbly sandstones i n the lower p a r t e x h i b i t p a r a l l e l bedding (upper flow regime) and c r o s s - b e d d i n g . In the upper p a r t the sandstones become c o a r s e r - g r a i n e d and are interbedded with conglomerates. Note the much l a r g e r s i z e of c l a s t s i n f a c i e s 1B (between B and C) compared to. f a c i e s 1A and the very abrupt top of f a c i e s 1B. F i g u r e 5_5. P a l e o c u r r e n t data from f a c i e s 1A. F i g u r e 56. Outcrop p a t t e r n and isopachs of f a c i e s 1A i n the Frame and McConkey P i t a r e a s . Note the r a p i d t h i n n i n g and pinchout of f a c i e s 1A on the west sid e of the Frame area and east s i d e of the McConkey area. F i g u r e 57a. Large s c a l e g e n t l y d i p p i n g bedforms i n f a c i e s 1A on the south s i d e of Mount Frame. The D c o a l seam i s exposed below f a c i e s 1A behind the f i e l d a s s i s t a n t . The l i n e drawing showing the l a r g e s c a l e bedforms i n the Frame area (Figure 6J_) i s from t h i s outcrop. F i g u r e 57b. Outcrop of f a c i e s 1A on the south s i d e of the McConkey P i t (note the f i g u r e on road f o r s c a l e ) . In t h i s area f a c i e s 1A t h i n s from approximately 40 m to 0 m over a d i s t a n c e of 500 m and pinchesout i n the area j u s t to the r i g h t of t h i s view. Note the presence of l a r g e s c a l e g e n t l y d i p p i n g s u r f a c e s which taper towards the south (to the r i g h t i n t h i s photograph). x i x F i g u r e 58a. Contact between f a c i e s 1A and the D c o a l seam in the Windy P i t area on the northwest s i d e of Babcock Mountain. Note the low angle i n c l i n e d s u r f a c e s i n f a c i e s 1A d i p p i n g towards the r i g h t (southwest). F i g u r e 58b. Large l o g impression i n pebbly sandstones near the base of f a c i e s 1A i n the McConkey P i t a r e a . F i g u r e 58c. Interbedded sandstones and conglomerates in the upper p a r t of f a c i e s 1A i n the McConkey P i t area. Bedding c o n s i s t s of t a b u l a r cross-bedding o r i e n t e d i n an e a s t -s o u t h e a s t e r l y d i r e c t i o n and p a r a l l e l to g e n t l y i n c l i n e d bedding. Note the r e a c t i v a t i o n s u r f a c e ( r ) i n t h i s s e t . F i g u r e 5_9. E r o s i o n a l c o n t a c t between f a c i e s 1A and the D c o a l seam on the south s i d e of Mount Frame. Note the low angle s u r f a c e at the base of f a c i e s 1A i n F i g u r e 59a. The two i n c l i n e d s u r f a c e s shown i n F i g u r e 59b represent the downdip t e r m i n a t i o n of l a r g e s c a l e low angle i n c l i n e d s u r f a c e s . The s t i c k (arrowed) i s 2 m l o n g . F i g u r e 60a. Large 2-3 m t h i c k , high angle, i n c l i n e d cross-bed i n f a c i e s 1A on the south s i d e of Mount Frame. Set i s bounded at the base and at the top by low angle i n c l i n e d s u r f a c e s which extend from the top to the base of the outcrop. The l a t e r a l extent of these bedforms in t h i s outcrop i s shown on the l i n e drawing ( F i g u r e 61). F i g u r e 60b. Close up view of the cross-bed i n F i g u r e 60a showing the g e n t l y curved f o r e s e t s d i p p i n g to the l e f t (westward) and t h e i r t r u n c a t i o n at the top by a low angle i n c l i n e d s u r f a c e . (Note: T h i s view i s t i l t e d at an angle p a r a l l e l t o the low angle i n c l i n e d s u r f a c e s ) . F i g u r e 6J_. L i n e drawings t r a c e d from photomosaics of f a c i e s 1A i n c l i f f exposures ort the northwest s i d e of Babcock Mountain and the south s i d e of Mount Frame. F i g u r e 62. Outcrop s e c t i o n of f a c i e s 1A and f a c i e s 1B i n the Windy P i t area on the northwest s i d e of Babcock Mountain. F i g u r e 63a. Core photographs showing the abrupt c o n t a c t between f a c i e s 1B (A) and f a c i e s 2A. Note that conglomerates at the top of f a c i e s 1B occur interbedded with a t h i n (<1 cm) sandstone beds s i m i l a r i n appearance to the sandstones i n f a c i e s 2A. The sandstones at the base of f a c i e s 2A are very f i n e - g r a i n e d and occur interbedded with dark grey mudstone. P a r a l l e l bedding, low angle cross-bedding (c) r i p p l e s , l e n t i c u l a r and f l a s e r bedding are present i n these d e p o s i t s . F i g u r e 63b. P y r i t e (py) i n sediments at the base of f a c i e s 2A. (QBD 7302, 231 .5 ni) F i g u r e 63c. R i p p l e s , l e n t i c u l a r bedding and b i o t u r b a t i o n i n sediments at the base of f a c i e s 2A (QBD 7721, 215.55 m). XX F i g u r e 63d. S i l t s t o n e bed at the base of f a c i e s 2A which e x h i b i t s low angle cross-bedding i n the lower p a r t and r i p p l e s at the top. Note the sharp base and i n t e r n a l scour (s) (QBD 7711, 140.85 m). "Figure 63e. Very f i n e - g r a i n e d sandstone bed at the base of f a c i e s 2A which e x h i b i t s p a r a l l e l bedding at the base and r i p p l e s , with numerous T e r e b e l l i n a burrows ( t ) , at the top. (QBD 7715, 258.8 m). F i g u r e 63f. F i n e - g r a i n e d sandstone i n f a c i e s 2A i n which bedding c o n s i s t s of broad concave upwards and upward domed f e a t u r e s (swaley c r o s s - s t r a t i f i c a t i o n ) . Note the low angle i n t e r s e c t i o n s of s t r a t i f i c a t i o n (arrowed) and c h a r a c t e r i s t i c f l a g g y weathering. F i g u r e 64. Symmetrical dunes on the top s u r f a c e of f a c i e s 1B at an outcrop on the northwest s i d e of Babcock Mountain. F i g u r e 6j>. P a l e o c u r r e n t data from f a c i e s 1B, 2A, 2B and 5B. F i g u r e 66. Isopach map of f a c i e s 2A i n the Babcock area. F i g u r e s 67a,b. Swaley c r o s s - s t r a t i f i c a t i o n i n f a c i e s 2A sandstones on the northwest s i d e of Babcock Mountain. Bedding c o n s i s t s of a s e r i e s of superimposed concave upwards shallow s c o u r s . I n t e r n a l l y , the s t r a t i f i c a t i o n i s p a r a l l e l or at a very low angle to the s c o u r s . A shallow 4 m wide, concave upwards f e a t u r e with a scoured base i s present at the r i g h t of F i g u r e 67a. The s t i c k (arrowed) i s 2 m long. F i g u r e s 67c,d. Low. angle cross-bedding i n f i n e - g r a i n e d sandstones'of f a c i e s 2A (c = QBD 7204, 97 f t , d= QBD 7721, 20.7 m). F i g u r e 67e. Core from the upper p a r t of f a c i e s 2a i n borehole QBD 7712 (approximately 215 m). Sandstones are f i n e - g r a i n e d with a few i s o l a t e d pebbles and t h i n pebbly s t r e a k s . Bedding c o n s i s t s of p a r a l l e l bedding and low angle c r o s s -bedding . F i g u r e 68. Isopach map of f a c i e s 3A and 3B i n the Babcock area. F i g u r e 69a. Core from borehole QBD 7711 (113 m) showing the e r o s i o n a l contact between f a c i e s 3A and f a c i e s 2A. Note the presence of c o a l spar and mudstone pebbles i n f a c i e s 3A sandstones and t h e i r c o a r s e r g r a i n - s i z e compared to sandstones i n f a c i e s 2a. F i g u r e 69b. Core from borehole QBD 7306 (1212 f t ) . In t h i s c o r e , f a c i e s 3A sandstones c o n t a i n abundant mudstone r i p - u p c l a s t s . F i g u r e 69c. Core from the upper p a r t of f a c i e s 3A i n borehole QBD 7711 (117 m). Bedding c o n s i s t s mainly of p a r a l l e l x x i l a m i n a t i o n s , d e f i n e d by t h i n a l t e r n a t i o n s of f i n e - g r a i n e d sandstone, s i l t s t o n e and carbonaceous d e b r i s , and r i p p l e s . Compare t h i s to the c o a r s e r and more massive sandstones i n the lower part of f a c i e s 3A i n F i g u r e 69a. F i g u r e s 70a,b,c,d. Core from the lower p a r t of f a c i e s 3A. F i g u r e s 70a,b,c. Cross bedding in medium- to c o a r s e - g r a i n e d sandstones (a = QBD 7209, 940.5 f t ; b = QBD 7209, 935 f t ; c = QBD 7721, 191.7m). F i g u r e 70d. Massive f i n e - to medium-grained sandstone (QBD 7711, 129.6 m). F i g u r e s 70_e,f_,£. Core from the upper part of f a c i e s 3A. F i g u r e 70e. P a r a l l e l l a m i n a t i o n d e f i n e d by t h i n laminae of carbonaceous d e b r i s i n f i n e - g r a i n e d sandstone (QBD 7711, 115 m) . F i g u r e 70f. F i n e - g r a i n e d r i p p l e d sandstone with c u r r e n t r i p p l e s with s i l t s t o n e / c a r b o n a c e o u s drapes. (QBD 7711, 115 m). F i g u r e 70g. R i p p l e s (?wave formed) and t h i n i n t e r l a y e r e d sandstone-mudstone. (QBD 7720, 101.75). F i g u r e 7J_. Core of f a c i e s 3B from borehole QBD 7201 . Note the g r a d a t i o n a l lower contact of f a c i e s 3B with f a c i e s 2A (A) and the abrupt top of f a c i e s 3B (B). In t h i s core f a c i e s 3B i s o v e r l a i n by carbonaceous mudstones of f a c i e s 5. In the lower p a r t of f a c i e s 3B f i n e - g r a i n e d sandstones and s i l t s t o n e s occur interbedded with t h i n laminae of dark grey mudstone and carbonaceous d e b r i s . P a r a l l e l bedding i s w e l l developed. The sandstones coarsen-upwards and a r g i l l a c e o u s m a t e r i a l becomes l e s s common at the top. Note the numerous burrows i n f a c i e s 3B. These i n c l u d e 'U'-shaped (U) and v e r t i c a l (S) types ( S k o l i t h o s ) . F i g u r e 12. Trace f o s s i l s and b i o t u r b a t i o n i n f a c i e s 3B. F i g u r e s 72a,b. Large 'U'-shaped burrows (probably D i p l o c r a t e r i o n or R h i z o c o r a l l i u m ) (QBD 7754, 145.6 m). F i g u r e 72c. S t r o n g l y burrowed i n t e r v a l (QBD 7201, 248'). F i g u r e 72d. Thin v e r t i c a l mudstone f i l l e d burrows i n p a r a l l e l bedded sandstone (QBD 7754, 138 m). F i g u r e s 72e,f. Note the predominance of v e r t i c a l to s u b - v e r t i c a l burrows, the a l t e r n a t i o n of s t r o n g l y burrowed i n t e r v a l s (b) with i n t e r v a l s i n which burrows are absent, t r u n c a t e d burrows (t) and escape t r a c e s (e) (QBD 7201, 255 f t and QBD 7201, 262 f t ) . F i g u r e s 72g,h. Trace formed by burrowing b i v a l v e (?) (QBD 7754, 146.15 m). xxi i Figure 73a. Very fine-grained sandstone bed characterised i n t e r n a l l y by low angle cross-bedding and a rippled top. Base of facies 3B in borehole QBD 7715, 240.7 m. Figures 73b,d. P a r a l l e l lamination and ripples in facies 3B. (b = QBD 7754, 144.65 ; d = QBD 7724, 185.4 m). Figure 73c. Small flecks of disseminated carbonaceous debris on a bedding plane surface in facies 3B sandstones. Currents are indicated by the preferred orientation of the carbonaceous debris. (QBD 7754, 146.3 m) . Figure 73e. Inferred t i d a l f l a t deposits (facies 3C) in borehole QBD 7711. Note the thicker units of sandstone in the lower part (low t i d a l f l a t deposits) overlain by l e n t i c u l a r , flaser bedded and thin interlayered sandstones and mudstones (mid t i d a l f l a t deposits) which grade upwards into massive s i l t y mudstones (high t i d a l f l a t deposits). The C coal seam occurs a few metres above th i s core.). Figure 74. Sedimentary and biogenic structures in facies 3C. Figure 74a. Coarse and f i n e l y interlayered sandstone and mudstone (s), ripples and l e n t i c u l a r bedding ( r ) , truncated bedding (t) and flame structures ( f ) . (QBD 7708, 89.3 m). Figure 74b. Flaser bedding with t h i n l y interlayered s i l t s t o n e and mudstone at the top. (QBD 7721, 181. 1 m) . Figure 74c. Sandstone ripples with mudstone drapes, t h i n l y interlayered sandstone and mudstone amd l e n t i c u l a r bedding. (QBD 7208, 500 f t ) . Figure 74d. Lenticular bedding and thin to coarsely interlayered sandstone and mudstone. (QBD 7711, 108 f t ) . Figure 74e. Bioturbation in facies 3C sandstones and s i l t s t o n e s . (QBD 7719, 73.95 m). Figure 74f. Flaser bedding, l e n t i c u l a r bedding and t h i n l y interlayered sandstone and mudstone. (QBD 7721, 178.9 m). Figure 74g. Lenticular, wavy(w) and ripple bedding. Soft sediment deformation structures occur in the lower right of the core. (QBD 7754, 44 m) . Figure 7_5. . Sedimentary and biogenic structures in facies 4. Figures 75a,b. Strongly bioturbated s i l t s t o n e (MDD 7908, 140.9 m). Figure 75c. Interlayered s i l t s t o n e and mudstone, l e n t i c u l a r and ripple bedding. (MDD 7822, 164.7 m). Figure 75d. Strongly bioturbated s i l t s t o n e . Chondrites burrows (c) are present in the lower part of the core. CMDD 7908, x x i i i 142.9 m). F i g u r e s 75e,f. R i p p l e s and f l a s e r bedding. F l a s e r s are mainly c o n c e n t r a t i o n s of carbonaceous d e b r i s , (e = MDD 7822, 164 m ; f = MUD 7704, 86.6 m) . F i g u r e 76_. Sedimentary and b i o g e n i c s t r u c t u r e s i n f a c i e s 5. F i g u r e 76a. Cross-bedded sandstone from f a c i e s 5B (QBD 7302, 74 ftT7~ F i g u r e s 76b,c. P a r a l l e l bedding, r i p p l e s and c l i m b i n g r i p p l e s i n f a c i e s 5C d e p o s i t s , (b = QBD 7721, 170.7 m ; c = QBD 7721, 191 m) . F i g u r e 76d. Interbedded mudstones and sandstones i n f a c i e s 5C. Note the abundant carbonaceous d e b r i s and c o a l spar ( s ) . (QBD 7714, 91.25 m). F i g u r e 76e. S i l t s t o n e from f a c i e s 5C a few metres below the Gates/Hulcross contact.Note the p y r i t e (py) which occurs a s s o c i a t e d with r o o t s at the top of the core (QBD 7720, 64 m) . F i g u r e 76f. Interbedded mudstones and sandstones i n f a c i e s 5C. Note the small burrow. (QBD 7751, 29.55 m). F i g u r e 76g. Convolute bedding and syn-sedimentary f a u l t s i n f a c i e s 5C d e p o s i t s (QBD 7754, 118.65 m). F i g u r e 76h. Roots i n massive mudstones of f a c i e s 5A. (QBD 7721, 149.3 m). F i g u r e 77a. Trough and t a b u l a r cross-bedding i n outcrops of f a c i e s 5B sandstones on k o s t u i c k Mountain. F i g u r e 77b. Cote of f a c i e s 5A and 5C d e p o s i t s i n QBD 7718 (163 m). Coal and carbonaceous mudstone at the base ( f a c i e s 5A) i s o v e r l a i n by interbedded mudstones and s i l t s t o n e s ( f a c i e s 5C) which are s t r o n g l y b i o t u r b a t e d . Bedding i n these d e p o s i t s c o n s i s t s mainly of p a r a l l e l bedding and o c c a s i o n a l r i p p l e s . F i g u r e 77c. S o f t sediment deformation s t r u c t u r e i n f a c i e s 5C d e p o s i t s (QBD 7721, 161 m). F i g u r e 78a. Core photograph of the Gates/Hulcross c o n t a c t i n borehole QBD 7209. The c o n t a c t i s p i c k e d at the base of the f i r s t conglomerate (A) which i s i n t e r p r e t e d as a t r a n s g r e s s i v e marine l a g d e p o s i t . 35 cm of s t r o n g l y burrowed s i l t s t o n e s below t h i s (A-B) are i n t e r p r e t e d as l a g o o n a l d e p o s i t s . The b i o t u r b a t e d s i l t s t o n e u n i t r e s t s a b r u p t l y on c o a s t a l p l a i n s i l t s t o n e s and sandstones. S e v e r a l other t h i n l a y e r s of coarse sandstone and conglomerate are present interbedded with H u l c r o s s s i l t s t o n e s and mudstones. These are i n t e r p r e t e d as storm xxiv d e p o s i t e d l a g s formed i n the o f f s h o r e environment a f t e r the t r a n s g r e s s i o n . T y p i c a l o f f s h o r e H u l c r o s s sediments are present i n the two columns on the r i g h t . F i g u r e 78b. Core photograph of the Gates/Hulcross c o n t a c t (A) i n borehole QBD 7711. In t h i s core the con t a c t i s represented by a s i n g l e t h i n t r a n s g r e s s i v e l a g of coarse pebbly sandstone. Compare t h i s with F i g u r e 71 a where s e v e r a l l a g s are p r e s e n t . Dark grey, carbonaceous mudstone with a r g i l l a c e o u s c o a l i s present i n the column on the l e f t . F i g u r e 78c. B i o t u r b a t e d s i l t s t o n e at the base of the H u l c r o s s Formation. (QBD 7708, 38.75 m) Fi g u r e 79. Upper Gates d e p o s i t i o n a l models. F i g u r e 8_0. G e n e r a l i s e d g e o l o g i c a l map of the Duke Mountain area. F i g u r e 8J_. Cross s e c t i o n i n the Duke P i t - Duchess Mountain area showing the l o c a t i o n of the major marine u n i t s , f l u v i a l channel d e p o s i t s and c o a l seams. Refer to F i g u r e 82 f o r legend. L o c a t i o n of c r o s s s e c t i o n i s shown on F i g u r e s 3_5 and 80. Fi g u r e 82. Cross s e c t i o n i n the Honeymoon P i t area showing the l o c a t i o n of the major marine u n i t s , f l u v i a l channel d e p o s i t s and c o a l seams. The x12.5 v e r t i c a l exaggeration of t h i s c r o s s s e c t i o n causes the angle at which B5 i s draped over the channel to appear much g r e a t e r than on a 1:1 s e c t i o n (where i t i s l e s s than 3 ° ) . L o c a t i o n of c r o s s s e c t i o n i s shown on F i g u r e s 3_5 and 80. Figu r e 83. Map showing the southern l i m i t of the S h e r i f f member marine u n i t and i t s e f f e c t . o n the t h i c k n e s s and'' d i s t r i b u t i o n of the B2 c o a l seam. Cross s e c t i o n i s shown on F i g u r e 24. Figu r e 8_4. Gamma ray and d e n s i t y l o g c o r r e l a t i o n from boreholes in the Honeymoon P i t area, showing the b a s i s f o r the B5 c o r r e l a t i o n and i t s "draping" over f l u v i a l channel d e p o s i t s . Borehole l o c a t i o n s are shown on F i g u r e 35. Fi g u r e 8_5. G e o l o g i c a l map and borehole l o c a t i o n s i n the Babcock area. F i g u r e 86. Cross s e c t i o n i n the Babcock area showing the l o c a t i o n of the major marine u n i t s , f l u v i a l channel d e p o s i t s and c o a l seams. Borehole l o c a t i o n s are shown on F i g u r e 85. Figu r e 87. S e c t i o n B - Cross s e c t i o n of the F-J i n t e r v a l i n the Babcock area showing the drap i n g of the G/I1 seam over f l u v i a l channel d e p o s i t s and the pinchout of the 13 and 12 seams adjacent to the channel and splay d e p o s i t s . Borehole l o c a t i o n s are shown on F i g u r e 88. XXV F i g u r e 8_8. Isopach map of the 11 (Figure 88a) and 12 ( F i g u r e 88b ) c o a l seams i n the Babcock area. Shaded areas represent channel and splay d e p o s i t s which are e q u i v a l e n t l a t e r a l l y to these c o a l seams. F i g u r e 89. Model to i l l u s t r a t e the d e p o s i t i o n of the G and I seams i n the Babcock area. F i g u r e 90_. G e n e r a l i s e d g e o l o g i c a l map of the Frame and McConkey P i t s . F i g u r e 9_1_. Cross s e c t i o n i n the Frame P i t showing the l o c a t i o n of the major marine u n i t s , channel d e p o s i t s and c o a l seams. Borehole l o c a t i o n s shown on F i g u r e 90. F i g u r e 9_2. Cross s e c t i o n i n the McConkey P i t showing the l o c a t i o n of the major marine u n i t s , channel d e p o s i t s and c o a l seams. Borehole l o c a t i o n s shown on F i g u r e 90. Legend i s shown on F i g u r e 91. F i g u r e 9_3. Regional maps of t o t a l c o a l isopachs (Figure 93a) and the number of seams over 1.5 m t h i c k i n the Gates Formation (Figure 93b). F i g u r e 9_4. G e n e r a l i s e d paleogeography of the Gates Formation. T h i s f i g u r e was c o n s t r u c t e d using the data on the r e g i o n a l c r o s s s e c t i o n s from t h i s study ( F i g u r e s 5,6 and 1) together with i n f o r m a t i o n on c r o s s s e c t i o n s by Duff and G i l c h r i s t (1981), L e c k i e (unpublished) and i n S t o t t (1968, 1982) f o r the region north of the study area. F i g u r e 9_5. Models to i l l u s t r a t e the d e p o s i t i o n a l s e t t i n g of the c o a l forming environments i n the Gates Formation. F i g u r e 9_6. Map showing the l o c a t i o n of boreholes and outcrop s e c t i o n s from which samples were p o i n t counted to determine composition. F i g u r e 9_7. A t r i a n g u l a r diagram i l l u s t r a t i n g the composition of the framework g r a i n s i n the Gates sandstones. F i g u r e 98. Comparison of framework g r a i n composition of sandstones i n the lower-middle Gates and upper Gates. xxvi LIST OF TABLES Table 1. Summary of the main c h a r a c t e r i s t i c s of the f a c i e s i n  the coarsening-upward marine c y c l e s in the Moosebar  Formation and lower Gates. Table 2. Summary of the main c h a r a c t e r i s t i c s of f l u v i a l channel  d e p o s i t s i n the lower Gates. Table 3. Composition of po i n t counted t h i n s e c t i o n s (lower-middle Gates). Table 4. Composition of p o i n t counted t h i n s e c t i o n s (upper Gates) . xxv i i ACKNOWLEDGEMENTS I wish to thank my s u p e r v i s o r y committee Drs. J.W. Murray, W.C. Barnes, R.M. Bustin and W.H. Mathews f o r t h e i r a d v i c e , encouragement and f o r t h e i r c r i t i c a l reviews of the t h e s i s . I am g r a t e f u l to R.D. G i l c h r i s t f o r b r i n g i n g to my a t t e n t i o n the rese a r c h p o t e n t i a l of the Gates Formation and f o r h i s advice on l o g i s t i c s p r i o r to the f i r s t f i e l d season. I wish to thank D. Johnson, R. Sagi (Denison Mines), E. S c h i l l e r , E. Santiago and E. Panchy (Petro-Canada) and M. M i t c h e l l (Ranger O i l ) f o r t h e i r a s s i s t a n c e d u r i n g the study. S t a f f at the B.C.M.E,M.P.R. Core Storage F a c i l i t y at C h a r l i e Lake were most h e l p f u l and I am p a r t i c u l a r l y g r a t e f u l to G. White, R. Karst and K. C l a r k . I am indebted to E. Montgomery of the Department of G e o l o g i c a l Sciences f o r h i s advice on photographic techniques and dark room i n s t r u c t i o n . F i n a n c i a l support was pro v i d e d by Union O i l of Canada, B r i t i s h Columbia M i n i s t r y of.Energy, Mines and Petroleum Resources and Petro-Canada. Most importantly, I thank my wife Jean f o r her p a t i e n c e , understanding and encouragement. 1 INTRODUCTION  PREAMBLE Major c o a l d e p o s i t s occur i n sediments of Late J u r a s s i c -E a r l y T e r t i a r y age i n the Rocky Mountain region of Western Canada. During the 1970's e x t e n s i v e d r i l l i n g by c o a l companies i n the F o o t h i l l s of n o r t h e a s t e r n B r i t i s h Columbia showed that the main c o a l r e s e r v e s occur i n two i n t e r v a l s , the Gething and Gates Formations of E a r l y Cretaceous age. T o t a l c o a l r e s e r v e s i n these formations are estimated at 7719 megatons (Coal Task Force, 1976) of which 5350 megatons are present i n the Gates Formation. C u r r e n t l y , mines are being developed i n the Gates c o a l measures at two p r o p e r t i e s ( Q u i n t e t t e and Bullmoose) with the f i r s t c o a l p r o d u c t i o n scheduled f o r l a t e 1983. Important c o a l parameters such as t h i c k n e s s , l a t e r a l c o n t i n u i t y , a r e a l d i s t r i b u t i o n and q u a l i t y of c o a l seams are r e l a t e d to t h e i r environment of d e p o s i t i o n . T h i s f a c t has been c l e a r l y demonstrated by s e d i m e n t o l o g i c a l s t u d i e s i n C a r b o n i f e r o u s rocks in the c e n t r a l U n ited S t a t e s and Appalachian areas (Williams and K e i t h , 1963; Wanless et a l . , 1969; Home et a l . , 1978) and Cretaceous and T e r t i a r y rocks i n the Western I n t e r i o r of the United S t a t e s ( F l o r e s , 1981; Marley et a l . , 1979; Ryer, 1981). In the F o o t h i l l s of n o r t h e a s t e r n B r i t i s h Columbia, a l a r g e number of boreholes have been d r i l l e d by c o a l companies i n t o the Gates and u n d e r l y i n g Moosebar Formations. These boreholes provide core and g e o p h y s i c a l l o g data which, supplemented by outcrop i n f o r m a t i o n o f f e r s an e x c e l l e n t o p p o r t u n i t y to study the 2 F i g u r e J_. L o c a t i o n map of the study area showing the outcrop p a t t e r n of the Gates Formation and l o c a l i t i e s mentioned i n the t e x t . 3 d e p o s i t i o n a l environments of the Gates-Moosebar i n t e r v a l . The primary o b j e c t i v e of t h i s t h e s i s i s to d e s c r i b e and i n t e r p r e t the paleoenvironments of the major d e p o s i t i o n a l u n i t s and f a c i e s i n the Gates and Moosebar Formations and to show to what extent d e p o s i t i o n a l f a c t o r s a f f e c t the r e g i o n a l d i s t r i b u t i o n of c o a l i n the Gates Formation and the t h i c k n e s s , c o n t i n u i t y and a r e a l d i s t r i b u t i o n of i n d i v i d u a l c o a l seams. A secondary o b j e c t i v e i s to d e s c r i b e the petrography of sandstones and to i n t e r p r e t t h i s data i n terms of provenance. The area of study i s l o c a t e d i n the F o o t h i l l s between the A l b e r t a and B r i t i s h Columbia border and the Wolverine R i v e r , a d i s t a n c e of approximately 110 km ( F i g u r e 1). In the northwest, data from petroleum w e l l s have been used to extend the study area i n t o adjacent p a r t s of the P l a i n s . During the study, approximately 12,000 m of core were logged from a t o t a l of 75 boreholes. T h i r t e e n major outcrop s e c t i o n s and numerous small outcrop s e c t i o n s were measured. F u r t h e r data, p o i n t s were provided by geophysical" logs from approximately 85 c o a l company boreholes and 14 petroleum w e l l s . GEOLOGICAL SETTING 1. T e c t o n i c S e t t i n g Lower Cretaceous rocks of n o r t h e a s t e r n B r i t i s h Columbia form part of a t h i c k molasse sequence which was d e p o s i t e d i n the Rocky Mountain F o r e l a n d Basin of Western Canada (Figure 2 ). The b a s i n i s bounded to the west by the C o r d i l l e r a n Orogen and to the east by P a l e o z o i c rocks and the Canadian S h i e l d . During the Late Mesozoic and E a r l y Cenozoic, the C o r d i l l e r a n Orogen 4 underwent two main phases of deformation; the Columbian Orogeny from Late J u r a s s i c to e a r l i e s t Late Cretaceous and the Laramide Orogeny from Late Cretaceous to Oligocene time (Douglas et a l . , 1976). These orogenies were the r e s u l t of a complex s e r i e s of subduction episodes and c o l l i s i o n events a s s o c i a t e d with the a c c r e t i o n of s e v e r a l e x o t i c t e r r a n e s to North America (Monger and P r i c e , 1979; D i c k i n s o n , 1976). The e a s t e r n p a r t of the orogen, which r e c e i v e d carbonate and c l a s t i c m i o g e o c l i n a l sediments d u r i n g the P a l e o z o i c and E a r l y Mesozoic, underwent e x t e n s i v e deformation and c r u s t a l s h o r t e n i n g d u r i n g the orogenic phases. The deformation was c h a r a c t e r i s e d by eastward t h r u s t i n g and f o l d i n g and produced a mountainous r e g i o n , the Rocky Mountain Thrust B e l t , which formed the main source area f o r the molasse d e p o s i t s of the F o r e l a n d Bas i n . The F o r e l a n d Basin molasse i s composed of two upward co a r s e n i n g megacycles amounting to a t o t a l t h i c k n e s s of about 5000 m; a l a t e s t J u r a s s i c through E a r l y Cretaceous megacycle, the Kootenay-Blairmore Assemblage, and a Late Cretaceous through Oligocene megacycle, the B e l l y River-Paskapoo Assemblage (Eisbacher et a l . , 1974). The coarse f a c i e s of the molasse prograded from four p r i n c i p a l r e - e n t r a n t s on the eastern s i d e of the orogenic b e l t , the P e e l , the L i a r d , the Peace and the Crowsnest (Figure 2 ). In d e t a i l the coarse f a c i e s of the molasse s h i f t e d d i a c h r o n o u s l y along the t r e n d of the.mountain f r o n t (Eisbacher et a l . , 1974; E i s b a c h e r , 1981). During the Laramide Orogeny, the Late J u r a s s i c to Late Cretaceous molasse d e p o s i t s , along the western margin of the F o r e l a n d Basin, were deformed by f o l d i n g and eastward t h r u s t i n g . 5 300 km. RMTB MFB SFB ' Toe" Rocky Mountain Thrust Belt Mackenzie Fold Belt Selwyn Fold Belt Late Jurassic to Tertiary Rocks of the Rocky Mtn Foreland Basin Re-entrant F i g u r e 2. G e n e r a l i s e d t e c t o n i c map showing the l o c a t i o n of the C o r d i l l e r a n Orogen, F o r e l a n d Basin and p r i n c i p a l r e - e n t r a n t s on the e a s t e r n Orogen (mo d i f i e d a f t e r Douglas et a l . , 1976 and E i s b a c h e r et a l . , 1974). 6 P r e s e n t l y , these rocks are exposed in a s e r i e s of f o l d and t h r u s t s l i c e s along the e a s t e r n margin of the Rocky Mountain Thrust B e l t . 2. Paleogeography and Regional S t r a t i g r a p h y of the Kootenay- Blairmore Assemblage During Late J u r a s s i c and e a r l i e s t Cretaceous time, western A l b e r t a and n o r t h e a s t e r n B r i t i s h Columbia were occupied by seas which connected to the P a c i f i c Ocean to the west ( S t e l c k et a l . , 1972). Northward f l o w i n g r i v e r s from the United S t a t e s p r o g r e s s i v e l y f i l l e d i n the marine b a s i n with sediment. In southeastern B r i t i s h Columbia and southwestern A l b e r t a , t h i c k c o a l seams of the Kootenay Group ( F i g u r e 3) were d e p o s i t e d i n a . d e l t a i c s e t t i n g along the margin of t h i s seaway (Jansa, 1972; Gibson, 1977; Hamblin and Walker, 1979). The upper p a r t of the Kootenay Group c o n s i s t s of the Elk Formation which c o n t a i n s t h i c k conglomerates i n d i c a t i n g the f i r s t pulse of t e c t o n i c d i s t u r b a n c e i n the orogenic b e l t to the southwest (Gibson, 1977) . As the sea r e t r e a t e d to the northwest, non-marine sediments prograded over marine d e p o s i t s . In the F o o t h i l l s and P l a i n s of n o r t h e a s t e r n B r i t i s h Columbia and western A l b e r t a these d e p o s i t s comprise the N i k a n a s s i n Formation and Minnes Group (Figure 3). Coals i n these i n t e r v a l s are t h i n and not economically important. In p o s t - V a l a n g i n i a n time, a major t e c t o n i c event r e s u l t e d i n the u p l i f t of the e n t i r e c e n t r a l p a r t of B r i t i s h Columbia, d e s t r o y i n g the marine connection between the P a c i f i c Ocean and NORTHWESTERN MONTANA FOOTHILLS SOUTHERN ALBERTA Central-Northern Alberta Northeastern British Columbia PLAINS PEACE RIVER PLAINS SOUTHERN ALBERTA CENTRAL ALBERTA LLOYDMINSTER BLACKLEAF FORMATION z < a. Ui IIZ x< 2 i Limestone Unit Limestone] I Unit Cutbank Sandstone Ma Bulla Fn BEAVER MINES FORMATION u -e E u to 2 Grande Cache Member Torrens Mbr Moosebar Member poulder Creek] Fm calcareous Mbr GLADSTONE FORMATION GLADSTONE FORMATION CADOMIN FM CADOMIN FM Hulcross Fm GATES FORMATION MOOSEBAR FORMATION GETHING FORMATION CADOMIN FM Paddy Mbr CadotteMbij Harmon Mbrl BOW ISLAND FORMATION VIKING FM VIKING FM JOLI FOU FM JOLI FOU FM Notikewin Mbr Falher Mbr IWilrich Mbr Bluesky Fm GETHING FORMATION ^[CADOMIN FM| Glauconitic Member Ostracode Zone Sunburst Sandstone Cutbank Sandstone GRAND RAPIDS FM Clearwater Formation Wabiskaw Mbr Ostracode Zone ELLERSLIE FORMATION DEVILLE FM jSparky Mbr GP.Mbr Rex Mbr Lloydminsler Mbr] Cummings Mbr Dina Mbr MORRISON FM KOOTENAY GP NIKANASSIN FM MINNES GROUP NIKANASSIN FM JURASSIC DEVONIAN DEVONIAN F i g u r e 3. C o r r e l a t i o n c h a r t of Late J u r a s s i c and E a r l y Cretaceous s t r a t i g r a p h i c uni i n p a r t s of n o r t h e a s t e r n B r i t i s h Columbia, A l b e r t a and northwestern Montana (modifi a f t e r McLean, 1982). 8 the F o r e l a n d Basin ( S t e l c k et a l . , 1972, p. 4). T h i s event a l s o l e d to e x t e n s i v e u p l i f t and e r o s i o n of p r e - V a l a n g i n i a n sediments i n the F o r e l a n d B a s i n . Along the mountain f r o n t , conglomerates and sandstones of the Cadomin Formation (Figure 3) were d e p o s i t e d i n a l l u v i a l fans and b r a i d e d r i v e r s (McLean, 1977). These fans and r i v e r s fed a trunk stream, the S p i r i t R i v e r Channel (Figure 7A of Mclean, 1977), flowing northwest and bounded on the east by an e r o s i o n a l scarp. E x t e n s i v e areas covered by a. s i n g l e t h i n bed of conglomerate are i n t e r p r e t e d by McLean as pediment d e p o s i t s formed a f t e r a long p e r i o d of e r o s i o n . In Aptian time the A r c t i c Ocean t r a n s g r e s s e d south i n t o the F o r e l a n d Basin ( S t e l c k et a l . , 1972, p. 9). South of the advancing seaway, t h i c k c o a l s of the Gething Formation (Figure 3) were d e p o s i t e d i n the F o o t h i l l s between the Peace and Smoky R i v e r s . These c o a l s are i n t e r p r e t e d by S t o t t (1972), as having formed on the p l a i n of a major d e l t a complex whose main depocentre was l o c a t e d i n the F o o t h i l l s j u s t south of the Peace R i v e r . F a r t h e r south i n the A l b e r t a F o o t h i l l s , e q u i v a l e n t s t r a t a ( F igure 3) c o n s i s t of a l l u v i a l p l a i n , l a c u s t r i n e and e s t u a r i n e d e p o s i t s of the Gladstone Formation (McLean and W a l l , 1981; McLean, 1982). Coal seams i n the Gladstone Formation are a p p a r e n t l y t h i n and not economically important. By l a t e E a r l y A l b i a n time the marine t r a n s g r e s s i o n of the A r c t i c Ocean i n t o the F o r e l a n d Basin had reached c e n t r a l A l b e r t a (Williams and S t e l c k , 1975, p. 6). The southernmost extent of t h i s seaway i s u n c e r t a i n . McLean and Wall (1981, F i g u r e 5c) show the southern l i m i t as j u s t north of Calgary although they admit 9 there i s the p o s s i b i l i t y that i t c o u l d have reached c o n s i d e r a b l y f a r t h e r south. T h i s t r a n s g r e s s i o n was fo l l o w e d by a major r e g r e s s i o n which r e s u l t e d i n the r e t r e a t of the seaway back i n t o n o r t h e a s t e r n B r i t i s h Columbia and n o r t h - c e n t r a l A l b e r t a . During the r e g r e s s i o n , c o a s t a l and non-marine sediments prograded north over o f f s h o r e marine d e p o s i t s . In the F o o t h i l l s of no r t h e a s t e r n B r i t i s h Columbia the l a t t e r are represented by the Moosebar Formation (Figure 3) while the c o a s t a l and non-marine d e p o s i t s are i n c l u d e d i n the o v e r l y i n g Gates Formation. E q u i v a l e n t s t r a t a i n the A l b e r t a F o o t h i l l s and P l a i n s are shown i n F i g u r e 3. In the F o o t h i l l s of n o r t h e a s t e r n B r i t i s h Columbia, the extent of t h i s r e g r e s s i v e c y c l e i s w e l l d e f i n e d by the northern l i m i t of non-marine f a c i e s i n the Gates, which occurs j u s t south of the Peace River (Figure 18 of S t o t t , 1968). The non-marine sediments of t h i s r e g r e s s i v e c y c l e c o n t a i n the most ext e n s i v e c o a l d e p o s i t s i n the Late J u r a s s i c to E a r l y Cretaceous molasse. In the F o o t h i l l s of n o r t h e a s t e r n B r i t i s h Columbia, c o a l seams of economic t h i c k n e s s are present i n the Gates Formation from the A l b e r t a / B r i t i s h Columbia border to j u s t south of the Pine R i v e r . In the A l b e r t a F o o t h i l l s , the Grande Cache Member of the Malcolm Creek Formation, which i s e q u i v a l e n t to the lower tw o - t h i r d s of the Gates Formation, c o n t a i n s t h i c k seams as f a r south as Waiparous Creek, approximately 80 km northwest of Calgary ( F i g u r e 2 of McLean, 1982). Together the Gates Formation and the Grande Cache Member comprise a c o a l bearing sequence which extends f o r approximately 700 km i n the F o o t h i l l s . In the P l a i n s , e q u i v a l e n t s t r a t a i n the Upper 10 M a n n v i l l e Group (Figure 3) c o n t a i n t h i c k c o a l seams over a l a r g e area of c e n t r a l A l b e r t a (Figure 10 of Yurko, 1976). In southwestern A l b e r t a and southeastern B r i t i s h Columbia, t h i s c o a l b e a r i n g sequence grades i n t o non-marine sediments ( p a r t s of the Beaver Mines Formation and Upper M a n n v i l l e Group, F i g u r e 4) which i n c l u d e red and green c o l o u r e d shales or mudstones (Mellon, 1967) without s i g n i f i c a n t c o a l development. F o l l o w i n g the d e p o s i t i o n of the Gates Formation i n n o r t h e a s t e r n B r i t i s h Columbia, the s h o r e l i n e r e t r e a t e d back south to near the A l b e r t a / B r i t i s h Columbia border i n the F o o t h i l l s (Figure 18 of S t o t t , 1968). T h i s marine t r a n s g r e s s i o n was f o l l o w e d by a r e g r e s s i o n d u r i n g which c o a s t a l and non-marine sediments of the Boulder Creek Formation (Figure 3) prograded north over o f f s h o r e d e p o s i t s of the H u l c r o s s Formation (Figure 3). The northern l i m i t of non-marine sediments i n t h i s r e g r e s s i v e phase was again near the Peace River (Figure 18 of S t o t t , 1968). A f t e r the d e p o s i t i o n of the Boulder Creek r e g r e s s i v e d e p o s i t s , i n l a t e s t Middle A l b i a n time, a major marine t r a n s g r e s s i o n extended the Boreal seaway south to connect up with the Tethyan seas advancing n o r t h from the Gulf of Mexico ( J e l e t z k y , 1971, pp. 44,45). T h i s event e f f e c t i v e l y marks the end of the Kootenay-Blairmore megacycle. In summary, the Gates Formation and e q u i v a l e n t s t r a t a form one of three major c o a l - b e a r i n g sequences i n the Late J u r a s s i c to E a r l y Cretaceous Kootenay-Blairmore Assemblage of the Rocky Mountain F o r e l a n d Basin of Western Canada. The c o a l d e p o s i t s i n the Kootenay-Blairmore Assemblage formed i n swamps in a d e l t a i c , 11 LATE JURASSIC -EARLIEST CRETACEOUS APTIAN -EARLIEST ALBIAN LATE EARLY ALBIAN -EARLY ALBIAN EARLY MIDDLE ALBIAN SEAS ~ _~" COAL MEASURES Figure Non-palinspastic map showing the d i s t r i b u t i o n of Late Jurassic and Early Cretaceous seaways and important coal measure sequences. Compiled from Coal Task Force (1976), Douglas et a l . , (1976); Gibson (1977); Hamblin and Walker, (1979); Jeletzky (1971); McLean, (1982); McLean and Wall, (1981); Stelck et a l . , (1972); Stott, (1968), (1972), (1974), (1975), (1982); Yurko, (1975). 1 2 e s t u a r i n e , and c o a s t a l p l a i n s e t t i n g , south of seaways which p e r i o d i c a l l y occupied the northern part of the For e l a n d B a s i n . F i g u r e 4 shows the l o c a t i o n of some of the seaways and the d i s t r i b u t i o n of the major c o a l b e a r i n g sequences. The purpose of these maps i s to show the changes i n d i s t r i b u t i o n of the main c o a l forming sequences and t h e i r general r e l a t i o n s h i p with the Late J u r a s s i c and E a r l y Cretaceous seas. They are not intended to a c c u r a t e l y r e f l e c t the paleogeography. The f i r s t major c o a l bearing sequence i s represented by the Kootenay c o a l measures, which were d e p o s i t e d i n southeastern B r i t i s h Columbia and southwestern A l b e r t a d u r i n g a p e r i o d of r e g r e s s i o n . The second major c o a l - b e a r i n g f u r t h e r north i n swamps southeast of a t r a n s g r e s s i v e seaway. The thirdsequence i s represented by the Gething Formation, which was d e p o s i t e d f u r t h e r north i n swamps southeast of a t r a n s g r e s s i v e seaway. The t h i r d major c o a l -b e a r i n g sequence i s t h a t of the Gates Formation and e q u i v a l e n t s t r a t a . T h i s t h i r d sequence was d e p o s i t e d d u r i n g a major r e g r e s s i v e phase which r e s u l t e d i n the development of c o a l swamps over l a r g e areas of w e s t - c e n t r a l A l b e r t a and n o r t h e a s t e r n B r i t i s h Columbia. LITHOSTRATIGRAPHIC NOMENCLATURE In t h i s s e c t i o n a b r i e f account of the h i s t o r i c a l background of the Moosebar Formation and Gates Formation s t r a t i g r a p h i c nomenclature i s presented. For a more complete account of t h i s s u b j e c t , r e f e r to S t o t t (1968, 1982). The Moosebar and Gates Formations occur w i t h i n the lower part of the F o r t S t . John Group. These formations were 13 o r i g i n a l l y d e f i n e d by McLearn (1923) from type l o c a l i t i e s along the Peace R i v e r . South of the Peace R i v e r , i n the v i c i n i t y of the Pine R i v e r , Wickenden and Shaw (1943) d e f i n e d a s u c c e s s i o n of sandstones, shales and conglomerates o v e r l y i n g the Moosebar Formation as the Commotion Formation. The Commotion Formation was l a t e r s u b d i v i d e d by S t o t t (1968) i n t o three members, the Gates, H u l c r o s s and Boulder Creek Members, with the lower u n i t , the Gates Member, e q u i v a l e n t to the Gates Formation of the Peace River area. Use of the terms Commotion Formation and Gates Member was g e n e r a l l y r e s t r i c t e d to the F o o t h i l l s area south of the Pine R i v e r . Recently, S t o t t (1982) abandoned the term Commotion and r a i s e d the Gates, H u l c r o s s and Boulder Creek to f o r m a t i o n a l s t a t u s throughout the e n t i r e F o o t h i l l s area of n o r t h e a s t e r n B r i t i s h Columbia. S t r a t a e q u i v a l e n t to the Moosebar and Gates Formations i n the subsurface east of the F o o t h i l l s ( F i g u r e 3) i n c l u d e the W i l r i c h , F a l h e r and Notikewin Members, of the S p i r i t R i v e r Formation ( A l b e r t a Study Group, 1954). Recently McLean (1982) f o r m a l l y i n t r o d u c e d the term Torrens Member f o r a prominent marine sandstone u n i t at the base of the Gates Formation and e q u i v a l e n t rocks i n the A l b e r t a F o o t h i l l s (the Malcolm Creek Formation). The Torrens Member g r a d a t i o n a l l y o v e r l i e s marine mudstones and t h i n sandstones in the upper part of the Moosebar Formation and i s o v e r l a i n a b r u p t l y by c o a l b e a r i n g , non-marine sediments i n the Gates and Malcolm Creek Formations. The type s e c t i o n of the Torrens Member (McLean, 1982) i s at Mount Torrens, near the A l b e r t a / B r i t i s h Columbia border. T h i s u n i t occurs e x t e n s i v e l y i n the northern A l b e r t a F o o t h i l l s and has been c o r r e l a t e d by McLean as f a r north as the Wapiti R i v e r . Coal companies working i n the F o o t h i l l s of nort h e a s t e r n B r i t i s h Columbia g e n e r a l l y r e f e r to the f i r s t t h i c k sandstone i n t e r v a l beneath the lowermost economic c o a l seam as the Torrens Member. Regional c o r r e l a t i o n s e c t i o n s of the Moosebar and Gates Formations d e s c r i b e d i n s e c t i o n 1.1 i n d i c a t e that n o r t h of the Wapiti River the term Torrens Member has i n the past been a p p l i e d to a s t r a t i g r a p h i c a l l y higher marine sandstone than that d e s c r i b e d by McLean in the type s e c t i o n . AGE OF THE MOOSEBAR AND GATES FORMATIONS The m a c r o f o s s i l and c o r r e l a t i v e m i c r o f o s s i l zones of the Moosebar and Gates Formations are shown i n S t o t t ( F i g u r e 5 of S t o t t , 1982). The Moosebar Formation i s assigned to the lower pa r t of the A r c t h o p l i t e s spp. Zone (Ammonitida) and the Gates Formation to the upper part of A r c t h o p l i t e s spp. Zone and the lower p a r t of J e l e t z k y ' s (1968) Unnamed zone F. J e l e t z k y (1980) c o n s i d e r s the A r c h t h o p l i t e s spp. Zone as l a t e E a r l y A l b i a n i n age and Unnamed zone F as e a r l y Middle A l b i a n . Thus, the age of the Moosebar Formation i s l a t e E a r l y A l b i a n and the Gates Formation l a t e E a r l y A l b i a n to e a r l y Middle A l b i a n , based on m a c r o f o s s i l d a t i n g . 1 5 PART I. LITHOSTRATIGRAPHY AND PALEOENVIRONMENTS OF THE MOOSEBAR AND LOWER GATES FORMATIONS 1.1 REGIONAL CORRELATIONS OF THE GATES AND MOOSEBAR FORMATIONS The major d e p o s i t i o n a l u n i t s i n the Gates and Moosebar Formations i n the F o o t h i l l s , and e q u i v a l e n t s t r a t a i n the P l a i n s , are i l l u s t r a t e d by three r e g i o n a l c r o s s s e c t i o n s ( F i g u r e s 5, 6 and 7, i n pockets at back of t h e s i s ) . The l o c a t i o n of these s e c t i o n s i s shown on Fi g u r e 5. C r o s s - s e c t i o n s 1 and 2 are based on c o a l company borehole data and measured outcrop s e c t i o n s i n the F o o t h i l l s while s e c t i o n 3 i s a gamma-ray l o g c o r r e l a t i o n of s t r a t a e q u i v a l e n t to the Gates and Moosebar Formations i n 14 petroleum w e l l s i n the P l a i n s . The NW-SE o r i e n t a t i o n of these r e g i o n a l c r o s s - s e c t i o n s i s c o n s t r a i n e d by the d i s t r i b u t i o n of data p o i n t s . In the F o o t h i l l s t h i s . o r i e n t a t i o n i s p a r a l l e l to the t e c t o n i c s t r i k e which has the advantage that the e f f e c t s of shor t e n i n g between data p o i n t s due to f o l d i n g and t h r u s t i n g i s s m a l l . F i g u r e s 5, 6 and 7 are l i t h o l o g i c a l c r o s s s e c t i o n s and are not intended to i n f e r c o r r e l a t i o n on a time s t r a t i g r a p h i c b a s i s . At the present, i n the study area, d e t a i l e d time s t r a t i g r a p h y of the Gates-Moosebar i n t e r v a l i s not a v a i l a b l e . In the Moosebar-lower Gates i n t e r v a l , however, a prominent b e n t o n i t e l a y e r can be c o r r e l a t e d r e g i o n a l l y and thus pro v i d e s a u s e f u l time l i n e . North of borehole MOD 76-6 (Figure 6), t h i s b e n t o n i t e i s present i n the lower p a r t of the Moosebar Formation, while to the south i t occurs s t r a t i g r a p h i c a l l y h i g h e r , i n the upper p a r t of the Moosebar Formation and near the base of the Torrens Member. T h i s 16 r e l a t i o n s h i p i s f u r t h e r evidence that the Gates c o a s t a l system prograded i n a n o r t h e r l y d i r e c t i o n . B e ntonites are o c c a s i o n a l l y present i n the non-marine f a c i e s of the Gates, but cannot be r e g i o n a l l y c o r r e l a t e d . The Torrens Member can be c o r r e l a t e d from the A l b e r t a / B r i t i s h Columbia border i n the F o o t h i l l s , northwest as fa r as the Wolverine R i v e r . Between the Wolverine R i v e r and the area j u s t south of Kinuseo Creek, the Torrens Member i s o v e r l a i n by a t h i n non-marine i n t e r v a l which i n turn i s o v e r l a i n by a t h i c k marine u n i t c o n s i s t i n g mainly of sandstone. In t h i s t h e s i s , t h i s marine u n i t w i l l be r e f e r r e d to i n f o r m a l l y as the " S h e r i f f member." The S h e r i f f member i s w e l l exposed along a road cut (Figure 14) at the McConkey P i t (note: the McConkey P i t was p r e v i o u s l y c a l l e d the S h e r i f f P i t ) where i t c o n s i s t s of a 32 m t h i c k coarsening-upward u n i t of marine sandstone and minor s i l t s t o n e o v e r l y i n g a t h i n t r a n s g r e s s i v e sandstone which i n turn r e s t s on a t h i n non-marine i n t e r v a l (Figure 5). North of the Wolverine R i v e r , t h i s non-marine i n t e r v a l pinches out and i s rep l a c e d by marine d e p o s i t s . In the petroleum w e l l s on F i g u r e 7 and i n some F o o t h i l l s s e c t i o n s the S h e r i f f member c o n s i s t s of two coarsening-upward marine c y c l e s . The d i s t r i b u t i o n and southern l i m i t of the S h e r i f f member i s shown on F i g u r e 8. In the upper p a r t of the Gates Formation, a second major marine u n i t has been i d e n t i f i e d . T h i s u n i t i s w e l l developed i n the Babcock area where i t c o n s i s t s of a t h i c k sequence of marine sandstone, conglomerates and minor mudstones and s i l t s t o n e s . G e o l o g i s t s from Denison Mines r e f e r to t h i s u n i t i n f o r m a l l y as the "Babcock member." T h i s nomenclature w i l l be fo l l o w e d i n the 17 F i g u r e 8. Southern l i m i t of the S h e r i f f member, Babcock member and F a l h e r C marine u n i t s . 18 present study. The d i s t r i b u t i o n and southern l i m i t of marine d e p o s i t s i n the Babcock member i s shown i n F i g u r e 8. A t h i r d marine u n i t , between the S h e r i f f and Babcock members i s i d e n t i f i e d i n borehole QWD 7115, north of the Wolverine R i v e r , on the b a s i s of l o g c h a r a c t e r and the c o a l companies core d e s c r i p t i o n . T h i s marine u n i t has not been rec o g n i s e d i n the F o o t h i l l s south of the Wolverine R i v e r , but i s present i n the petroleum w e l l s to the e a s t . North of the study area, D.A. Lec k i e (pers. comm., 1982) has i d e n t i f i e d up to 9 coarsening-upward, marine c y c l e s i n s t r a t a e q u i v a l e n t to the Moosebar and Gates Formations i n the P l a i n s . The marine u n i t between the S h e r i f f and Babcock members i s e q u i v a l e n t to L e c k i e ' s F a l h e r C c y c l e and t h i s name w i l l be used i n the present t h e s i s . The d i s t r i b u t i o n of the F a l h e r C i s shown on F i g u r e 8. The S h e r i f f member c o r r e l a t e s with L e c k i e ' s F a l h e r F c y c l e and the Babcock member with the lower p a r t of the Notikewin Member. 1.2 MARINE DEPOSITS - INTRODUCTION The marine d e p o s i t s i n the Moosebar and lower Gates Formations can be broadly c l a s s i f i e d i n t o two main c a t e g o r i e s : r e g r e s s i v e 1 d e p o s i t s and t r a n s g r e s s i v e d e p o s i t s . The r e g r e s s i v e d e p o s i t s occur w i t h i n coarsening-upward 1 Throughout the t h e s i s , the terms r e g r e s s i o n and t r a n s g r e s s i o n are used i n the sense of seaward p r o g r a d a t i o n of the s h o r e l i n e ( r e g r e s s i o n ) and landward m i g r a t i o n of the s h o r e l i n e ( t r a n s g r e s s i o n ) without n e c c e s s a r i l y implying changes i n sea l e v e l . 19 c y c l e s which are e a s i l y r e c o g n i s a b l e i n outcrops, cores and ge o p h y s i c a l l o g s . Most of the marine sediments i n the Moosebar-lower Gates i n t e r v a l occur w i t h i n coarsening-upward c y c l e s ranging i n t h i c k n e s s from 10 to. 60 m. Two or three c o a r s e n i n g -upward c y c l e s are present i n the Moosebar Formation and Torrens Member. The S h e r i f f member c o n s i s t s of one or two c o a r s e n i n g -upward c y c l e s and the Fa l h e r C normally c o n s i s t s of a s i n g l e coarsening-upward c y c l e . Thin t r a n s g r e s s i v e d e p o s i t s have been recognised at the base of the S h e r i f f member below c o a r s e n i n g -upward r e g r e s s i v e d e p o s i t s . 1.3 REGRESSIVE DEPOSITS Core and outcrop s t u d i e s of the Moosebar Formation, Torrens Member and S h e r i f f member i n d i c a t e s that the coarsening-upward r e g r e s s i v e d e p o s i t s i n these i n t e r v a l s can be su b d i v i d e d i n t o three main l i t h o f a c i e s which w i l l be r e f e r r e d to as mudstone f a c i e s , t r a n s i t i o n f a c i e s ( c o n s i s t i n g of interbedded mudstones, s i l t s t o n e s and sandstones) and sheet sandstone f a c i e s ( t a b l e 1). A d e s c r i p t i o n and i n t e r p r e t a t i o n of the d e p o s i t i o n a l environment of these three l i t h o f a c i e s i s given i n the f o l l o w i n g s e c t i o n s . 1.3.1 Mudstone F a c i e s - D e s c r i p t i o n T h i s f a c i e s i s present i n the lower p a r t of the Moosebar Formation at the base of the f i r s t coarsening-upward c y c l e (Figure 9) where i t v a r i e s i n t h i c k n e s s from 25-60 m. In the o v e r l y i n g c y c l e s and i n the S h e r i f f member, the mudstone f a c i e s i s t h i n or absent. The dominant l i t h o l o g y i s dark grey mudstone, o c c a s i o n a l l y Table 1. Summary of the main c h a r a c t e r 1 s t t e a of thQ f a c i e s Jn the  coarsenIng-upward mar tne eveIes in the Moosebar format Ion  and lower Gates. Mein L l t h o l o g y Thickness Main Bedding Bloturbatlon Remarks Inf e r r e d Types DeposI -t l o n a l Environ-ment Mudstone Facies Mudstone, t h i n (max. 15 cm) s i 1tstones P a r a l l e l bedding Strong, horizontal burrows and t r a i l s predominate Occurs below the O f f -t r a n s l t l o n f a c i e s shore Mar Ine at the base of the coarsening-upward marine c y c l e s T r a n s i t i o n Facies Interbedded mudstones s i l t s t o n e s and very f i n e - g r a i n e d sandstones P a r a l l e l bedding. Variable, more low angle cross intense In bedding, hummocky mudstones and cross s t r a t i f i -c a t i o n r i p p l e s , l e n t i c u l a r bedding si 1tstones Horizontal and v e r t i c a l traces Occurs gra d a t i o n - Marine-a l l y above the T r a n s l -mudstone f a d e s Hon Zone or, in s e c t i o n s where the mudstone f a c i e s i s absent, at the base of the coarsenIng-upward c y c l e . Sheet Sandstone Facies Very f i n e - to coarse-grained sandstone see below Very f i n e - to medIum-gr a 1ned sandstone Comprises approx. the lower 2/3 of the sheet sandstone f a d e s P a r a l l e l bedding, low angle cross-bedding Occurs at the top of the coarsening-upward c y c l e s . In some s e c t i o n s the e n t i r e coarsening-upward c y c l e i s composed of t h i s f a c i e s . Can be subdivided into 3 main f a c i e s ( F a d e s A.B.C) Varlable-absent to moderate. Burrows 1ncIude vert l e a l , 'U'-shaped and h o r i z o n t a l types. Often confined to d i s -t i n c t strongly burrowed Interva1s. Marine-Shore-face /Beach ( l o c a l 1 y d l s t r l b u tary channel) Lower-Middle Shore-face Fine- to medtum-gralned sandstone Fine- to coarse-grained sandstone Approximately the upper t/3 of the sheet sandstone f a c i e s • P a r a l l e l beddtng trough and tabular cross-bedding r i p p l e s Cross bedding massive beds Weak. Burrows r e s t r i c t e d to thin, strongly burrowed i n t e r -v a l s . Roots common In top 50 cm Absent Upper Shore-f ace Beach Forms e r o s i o n a l l y D l s t r l b u based, f i n i n g - - t a r y . upward u n i t s . Channel r e p l a c i n g f a c i e s 8 at the top of the c y c l e s to o 21 interbedded with t h i n (max. 15 cm) l i g h t to medium grey s i l t s t o n e s . In outcrops bands of small (2-15 cm) r u s t y weathering carbonate c o n c r e t i o n s p a r a l l e l to bedding are common (Fig u r e 9). Strong b i o t u r b a t i o n i s c h a r a c t e r i s t i c of t h i s f a c i e s and f r e q u e n t l y d e s t r o y s a l l t r a c e of bedding ( F i g u r e 10). In i n t e r v a l s which are l e s s s t r o n g l y b i o t u r b a t e d , p a r a l l e l bedding i s the most common sedimentary s t r u c t u r e . In a d d i t i o n to p a r a l l e l bedding, low angle cross-bedding and r i p p l e s are present i n some of the t h i c k e r s i l t s t o n e s . F r e q u e n t l y , these sedimentary s t r u c t u r e s are preserved i n the lower p a r t of the s i l t s t o n e beds while the tops are e x t e n s i v e l y reworked by burrowing organisms. Trace f o s s i l s i n the mudstone f a c i e s are d i s t i n c t i v e and are dominated by h o r i z o n t a l forms. V e r t i c a l burrows are a l s o present but are much l e s s common. In the mudstones and t h i n s i l t s t o n e s , the dominant t r a c e c o n s i s t s of black , c i r c u l a r to ov a l tubes 0.2-2 mm wide and elongate ribbons up to 3 cm i n . le n g t h , w i t h i n a 0.5-1 cm wide 'halo' of b i o t u r b a t e d mudstone (Fi g u r e 10). These t r a c e s are s i m i l a r to the g r a z i n g t r a i l s of Helminthoida, S c a l a r i t u b a , N e r e i t e s and Phycosiphon (Hantzschel, 1962; Chamberlain, 1978). The d i s t i n c t i o n between these 4 types depends mainly on the shape of the t r a i l on bedding plane s u r f a c e s . As the t r a c e f o s s i l s i n t h i s f a c i e s have been s t u d i e d mainly i n co r e s , which provide only l i m i t e d bedding plane s u r f a c e s , the exact s p e c i e s cannot be determined. Other l e s s common h o r i z o n t a l t r a c e s , found mainly i n the s i l t s t o n e s , i n c l u d e 3 mm-1 cm diameter, e l l i p t i c a l burrows without d i s t i n c t i n t e r v a l s t r u c t u r e ( p o s s i b l y Paleophycus). 22 V e r t i c a l burrows occur mainly i n the s i l t s t o n e s and i n c l u d e t h i n 1 mm diameter tubes up to 8 cm long s i m i l a r to T r i c h i c h n u s (Figure 10e) and other u n i d e n t i f i e d s p e c i e s ( F i g u r e 10c). A u t h i g e n i c p y r i t e i s f a i r l y common i n the mudstone f a c i e s and occurs as s m a l l c i r c u l a r patches and tubes u s u a l l y l e s s than 2 mm diameter but o c c a s i o n a l l y i n l a r g e r areas 1-2 cm i n diameter and up to 4 cm long (Figure I0d). O f t e n , the p y r i t e i s present i n or near burrows ( F i g u r e 10e). 1.3.2 Mudstone F a c i e s - I n t e r p r e t a t i o n The dominant t r a c e f o s s i l i n the mudstone f a c i e s , which c o n s i s t s of h o r i z o n t a l t r a c e s of a s p e c i e s s i m i l a r to Helminthoida, i s c h a r a c t e r i s t i c of marine sediments d e p o s i t e d below f a i r weather wave base (Chamberlain, 1978). On the b a s i s of t h i s evidence together with the o v e r a l l s i m i l a r i t y of the mudstone f a c i e s d e p o s i t s with other modern and a n c i e n t o f f s h o r e d e p o s i t s and t h e i r s t r a t i g r a p h i c p o s i t i o n , the mudstones and s i l t s t o n e s of the mudstone f a c i e s are i n t e r p r e t e d as o f f s h o r e d e p o s i t s . By comparison with other s u b l i t t o r a l l i t h o f a c i e s (Johnson, 1978, p. 234), the mudstones are i n t e r p r e t e d as mainly f a i r weather suspension d e p o s i t s , while the p a r a l l e l bedded, low angle cross-bedded and r i p p l e d s i l t s t o n e s probably r e p r e s e n t coa r s e r m a t e r i a l s u p p l i e d to the o f f s h o r e d u r i n g storms. The strong b i o t u r b a t i o n i n the mudstone f a c i e s i n d i c a t e s t hat r a t e s of i n f a u n a l reworking exceeded or kept pace with sedimentation (Howard, 1978) and i s probably the r e s u l t of slow sedimentation r a t e s . Figure 9A. Offshore (mudstone f a c i e s ) mudstones and s i l t s t o n e s i n the lower part of the f i r s t coarsening-upward c y c l e i n the Moosebar Formation. The more r e s i s t a n t bands are s i l t s t o n e s and carbonate c o n c r e t i o n s . Figure 9B. This view shows two coarsening-upward, r e g r e s s i v e c y c l e s i n the upper Moosebar Formation. The more r e s i s t a n t sandstones on the lower l e f t represent t r a n s i t i o n zone ( t r a n s i t i o n f a c i e s ) d e p o s i t s at the top of the f i r s t c y c l e . The second c y c l e begins with off s h o r e (mudstone f a c i e s ) mudstones and t h i n s i l t s t o n e s which grade upwards i n t o the t r a n s i t i o n f a c i e s c o n s i s t i n g of interbedded s i l t s t o n e s , f i n e - g r a i n e d sandstones and t h i n mudstones. Note the l a r g e carbonate c o n c r e t i o n s i n the upper part of the second c y c l e . Both photographs from outcrops on the northwest side of Mount Frame. 2 4 25 F i g u r e J_0. Core photographs of o f f s h o r e (mudstone f a c i e s ) mudstones and s i l t s t o n e s . B i o t u r b a t i o n i s common i n t h i s f a c i e s and f r e q u e n t l y d e s t r o y s a l l t r a c e of bedding ( F i g u r e s 10b, lOh). Trace f o s s i l s are dominated by h o r i z o n t a l forms c o n s i s t i n g of dark grey s i n g l e or p a i r e d tubes ('h' i n F i g u r e 10f) surrounded by a h a l o of l i g h t e r c o l o u r e d b i o t u r b a t e d sediment. These rep r e s e n t g r a z i n g t r a i l s of Helminthoida, S c a l a r i t u b a N e r e i t e s or Phycosiphon . A second type of h o r i z o n t a l burrow ( Paleophycus?) i s shown i n F i g u r e 1Og. V e r t i c a l burrows are a l s o present i n the mudstone f a c i e s (e.g., F i g u r e s 10c, 1Oe) but are much l e s s common. T r i c h i c h n u s (t) burrows are present i n F i g u r e 1Oe. P y r i t e (py) occurs w i t h i n one of the burrows i n t h i s F i g u r e . I t a l s o occurs as l a r g e r i r r e g u l a r patches ( F i g u r e 1Od). P a r a l l e l bedding can be seen i n s e v e r a l of the c o r e s and r i p p l e s are present i n F i g u r e 1Od. A BD 7802 1 588 f t b MDD 7918 115. 3 m c BD 7802 1 577 .5 f t d MDD 781 1 1 90. 46 m e BD 7802 1 581 f t f BD 7802 1563 .5 f t g No r e c o r d h MDD 7915 115. 3 m 2fo 27 The formation of p y r i t e i n modern muds has been summarised by Berner (1970). He concluded that b a c t e r i a l r e d u c t i o n of d i s s o l v e d sulphate and the decomposition of organic sulphur compounds leads to the pr o d u c t i o n of hydrogen s u l p h i d e which then r e a c t s with i r o n to form monosulphides. These i n turn r e a c t with elemental sulphur to form p y r i t e . The occurrence of p y r i t e in mudstone f a c i e s sediments suggests, t h e r e f o r e , that l o c a l reducing c o n d i t i o n s p r e v a i l e d w i t h i n the sediment near the sediment water i n t e r f a c e d u r i n g d e p o s i t i o n . 1.3.3 T r a n s i t i o n F a c i e s - D e s c r i p t i o n T h i s f a c i e s ' occurs above the mudstone f a c i e s or, i n the coarsening-upward c y c l e s where the mudstone f a c i e s i s absent, the t r a n s i t i o n f a c i e s i s present at the base of the c y c l e beneath the sheet sandstone f a c i e s . The cont a c t between the mudstone f a c i e s and the t r a n s i t i o n f a c i e s i s represented by an inc r e a s e i n the number and t h i c k n e s s of s i l t s t o n e beds (Figure 9). On gamma ray l o g s , t h i s c o n t a c t i s represented by a sharp decrease i n the amount of gamma r a d i a t i o n . The t r a n s i t i o n f a c i e s i s 15-25 m t h i c k i n the upper Moosebar c y c l e s and 0-15 m t h i c k in the S h e r i f f member. L i t h o l o g i e s c o n s i s t of mudstones, s i l t s t o n e s and very f i n e -g r a i n e d sandstones, which form t h i c k e n i n g and coarsening-upward c y c l e s . The mudstones are g e n e r a l l y s i l t y and dark grey. In cores the s i l t s t o n e s and sandstones are l i g h t to medium grey but in outcrop weather medium to dark y e l l o w i s h brown. Large greyish-orange carbonate c o n c r e t i o n s are present i n some outcrops ( F i g u r e 9b). These c o n c r e t i o n s occur as i s o l a t e d 28 spheres, 30-75 cm i n diameter, or as more continuous bands s e v e r a l metres long and 30-50 cm t h i c k , p a r a l l e l to bedding. R i p p l e s and other bedding s t r u c t u r e s preserved w i t h i n the c o n c r e t i o n s suggests a p o s t - d e p o s i t i o n a l o r i g i n . The lower p a r t of the t r a n s i t i o n f a c i e s c o n s i s t s of mudstones i n u n i t s up to 3 m t h i c k interbedded with t h i n (1-15 cm t h i c k ) s i l t s t o n e s , which e x h i b i t p a r a l l e l bedding, low angle cross-bedding, r i p p l e s and l e n t i c u l a r bedding (Figure 11). In the upper p a r t of the t r a n s i t i o n f a c i e s , mudstones are l e s s common and the s i l t s t o n e s become t h i c k e r and are g r a d u a l l y r e p l a c e d by very f i n e - g r a i n e d sandstones i n beds up to 1 m t h i c k . In some c y c l e s composite beds of very f i n e - g r a i n e d sandstone, with i n t e r n a l e r o s i o n s u r f a c e s , up to 4 m t h i c k occur near the top of the t r a n s i t i o n f a c i e s . Disseminated carbonaceous m a t e r i a l i s common on bedding p l a n e s . The lower c o n t a c t s of the s i l t s t o n e / s a n d s t o n e beds are abrupt or e r o s i o n a l and small mudstone r i p - u p c l a s t s are o c c a s i o n a l l y present near the base. Load c a s t s , f l u t e c a s t s , groove marks and small o r i e n t e d wood fragments are o c c a s i o n a l l y present on the b a s a l s u r f a c e . Primary sedimentary s t r u c t u r e s i n the s i l t s t o n e / s a n d s t o n e s i n the upper pa r t of the t r a n s i t i o n f a c i e s i n c l u d e p a r a l l e l bedding, low angle cross-bedding, hummocky c r o s s - s t r a t i f i c a t i o n and r i p p l e s . O c c a s i o n a l l y , the lower p a r t s of some beds are massive. Symmetrical wave r i p p l e s ( F i g u r e 12a) are common on the tops of beds. Climbing wave r i p p l e l a m i n a t i o n was observed i n the upper part of some beds. Small s c a l e slump s t r u c t u r e s are present i n a few beds. I n t e r v a l s of t h i n l y - b e d d e d mudstone and s i l t s t o n e which e x h i b i t p a r a l l e l , l e n t i c u l a r and f l a s e r bedding occur 29 .interbedded with the sandstones. Strong b i o t u r b a t i o n i s common i n the mudstones and t h i n n e r s i l t s t o n e s of the t r a n s i t i o n f a c i e s . The dominant t r a c e f o s s i l s are "Helminthoida type" h o r i z o n t a l t r a c e s , s i m i l a r to those present i n the mudstone f a c i e s . Chondrites and Paleophycus are a l s o present (Figure 11). In the t h i c k e r beds of s i l t s t o n e and sandstone, h o r i z o n t a l , v e r t i c a l and 'U'-shaped burrows are present but i n d i v i d u a l beds are r a r e l y s t r o n g l y b i o t u r b a t e d . H o r i z o n t a l g r a z i n g t r a i l s are common on the top s u r f a c e s of these beds and h o r i z o n t a l burrows (Paleophycus) are o c c a s i o n a l l y present w i t h i n beds. The v e r t i c a l burrows are 0.2-2 cm wide and up to 12 cm long. Some of the longer burrows probably represent escape t r a c e s formed d u r i n g p e r i o d s of r a p i d sedimentation. The tops of some v e r t i c a l burrows are t r u n c a t e d . In the s y n c l i n e extension outcrop s e c t i o n ( F i g u r e 5), a 20 . cm t h i c k bed of pebbly, coarse to gr a n u l a r sandstone i s present i n the t r a n s i t i o n f a c i e s , 4.5 m above the base of the- S h e r i f f member. T h i s sandstone occurs interbedded with mudstones, s i l t s t o n e s and very f i n e - g r a i n e d , hummocky c r o s s - s t r a t i f i e d sandstones. The base of the sandstone i s abrupt and planar while the top s u r f a c e c o n s i s t s of a s e r i e s of symmetrical dunes (amplitudes up to 10 cm) spaced approximately 0.5 m a p a r t . The average trend of the dune c r e s t s i s 66°-246°. 1.3.4 T r a n s i t i o n F a c i e s - I n t e r p r e t a t i o n The o v e r a l l c o a r s e n i n g of l i t h o l o g i e s and i n c r e a s e i n the amounts of wave and c u r r e n t formed sedimentary s t r u c t u r e s are evidence that the t r a n s i t i o n f a c i e s was de p o s i t e d i n shallower 30 F i g u r e JJ_. Core photographs of t r a n s i t i o n zone ( t r a n s i t i o n f a c i e s ) d e p o s i t s . F i g u r e 11a. Low angle cross-bedded and p a r a l l e l bedded s i l t s t o n e . Note the sharp base and top and the small mudstone r i p - u p c l a s t s i n the middle of the bed. (MDD 7811, 180.3 m). F i g u r e 11b. S i l t s t o n e bed which shows low angle c r o s s - b e d d i n g i n the lower p a r t and r i p p l e s at the top. T h i s type of sequence i s common i n the t r a n s i t i o n f a c i e s . In outcrop the low angle c r o s s - b e d d i n g i s t y p i c a l l y hummocky c r o s s -s t r a t i f i c a t i o n . (MDD 7801, 124.2 m). F i g u r e 11c. T h i s core shows the a l t e r n a t i o n of s t r o n g l y b i o t u r b a t e d mudstone beds with p a r a l l e l bedded s i l t s t o n e s which c o n t a i n ony a few burrows. Helminthoida type burrows are common i n the mudstones at the top and base of the c o r e . Both h o r i z o n t a l burrows (? Paleophycus) and v e r t i c a l burrows are present i n the s i l t s t o n e . (MDD 7918, 103.75 m). F i g u r e 11d. T h i s core shows s i m i l a r bedding s t r u c t u r e s to F i g u r e 11b but c o n t a i n s upward doming l a m i n a t i o n s c h a r a c t e r i s t i c of hummocky c r o s s - s t r a t i f i c a t i o n (H.C.S.). In c o r e s , H.C.S. can r a r e l y be proven due to small core diameters and the g e n t l e d i p s of the l a m i n a t i o n s . (MDD 7918, 103.75 m). F i g u r e 11e. S t r o n g l y burrowed s i l t s t o n e i n which Paleophycus i s the dominant t r a c e f o s s i l . Helminthoida type burrows are a l s o p r e s e n t . (MDD 7918, 95 m). Fi g u r e 11f. Trace f o s s i l s in the mudstone at the base of t h i s core i n c l u d e Helminthoida type burrows and Ch o n d r i t e s ( c ) , (MDD 7918, 85.4 m). Fi g u r e 11g. Low angle c r o s s - b e d d i n g i n a s i l t s t o n e bed. Mudstone r i p - u p c l a s t s at the base i n d i c a t e s that the s i l t s t o n e was d e p o s i t e d by s t r o n g e r o s i v e cuments. F i g u r e 11h. F i n e - g r a i n e d p a r a l l e l bedded sandstone which c o n t a i n s abundant Paleophycus burrows. Note the t r u n c a t e d s u b - v e r t i c a l burrow (t) near the top. (MDD 7918, 50.5 m). 31 32 F i g u r e J_2. Primary sedimentary s t r u c t u r e s i n the t r a n s i t i o n f a c i e s . F i g u r e 12a. Mudstones and s i l t s t o n e s i n the lower p a r t e x h i b i t l e n t i c u l a r and f l a s e r bedding. The t h i c k e r bed i n the upper p a r t shows hummocky c r o s s - s t r a t i f i c a t i o n and c l i m b i n g wave r i p p l e s at the top. ? F i g u r e 12b. Sharp c r e s t e d symmetrical wave r i p p l e s on the top s u r f a c e of a bed i n the t r a n s i t i o n f a c i e s . . 33 34 water depths than the u n d e r l y i n g mudstone f a c i e s . The a l t e r n a t i o n of s t r o n g l y b i o t u r b a t e d mudstones and s i l t s t o n e s with s i l t s t o n e s and sandstones which are only weakly b i o t u r b a t e d suggests that the t r a n s i t i o n f a c i e s was dep o s i t e d i n an environment c h a r a c t e r i s e d by r a p i d v a r i a t i o n s i n sedimentation r a t e s (Howard, 1978). Based on i t s s t r a t i g r a p h i c p o s i t i o n and by comparison with other modern and anc i e n t s h o r e l i n e d e p o s i t s (Campbell, 1971; Howard and Reineck, 1972; Wunderlich, 1972; B a l s l e y , 1980) the t r a n s i t i o n f a c i e s d e p o s i t s are i n t e r p r e t e d as forming i n the t r a n s i t i o n zone between the o f f s h o r e and lower shoreface ( F i g u r e 23a) . The e r o s i o n a l base of the t h i c k e r s i l t s t o n e and sandstone beds together with the presence of mudstone r i p - u p c l a s t s , t r u n c a t e d burrows, i n t e r n a l e r o s i o n s u r f a c e s and f l u t e and groove marks on the basal s u r f a c e i n d i c a t e s that these beds were de p o s i t e d from high energy, e r o s i v e c u r r e n t s . S u p e r f i c i a l l y , these beds resemble t u r b i d i t e s but low angle and hummocky c r o s s -s t r a t i f i c a t i o n are not f e a t u r e s of the c l a s s i c a l t u r b i d i t e model (Bouma, 1962). Comparison with r e c e n t l y p u b l i s h e d s t u d i e s of storm i n f l u e n c e d s h e l f d e p o s i t s (Johnson, 1978; Hamblin and Walker, 1979; Bourgeois, 1980; K r e i s a , 1981; Mount, 1982), suggests that the s i l t s t o n e and sandstone beds were d e p o s i t e d mainly as a r e s u l t of storm processes. In modern coast and s h e l f areas, the passage of a storm r e s u l t s i n i n c r e a s e d wave h e i g h t s and wave energie s which causes a lowering of the depth at which wave induced c u r r e n t s can 35 i n t e r a c t with the sea f l o o r (wave base). In the nearshore, l a r g e volumes of sediment are eroded and t r a n s p o r t e d o f f s h o r e . The o f f s h o r e t r a n s p o r t mechanism i s c o n t r o v e r s i a l ; Hayes (1967), suggested that the sediment i s t r a n s p o r t e d by a d e n s i t y ( t u r b i d i t y ) c u r r e n t , generated by the seaward r e t u r n of storm surge waters from the nearshore area as the storm d e c l i n e s . S w i f t (1976, p. 268), suggests that "downwelling c o a s t a l j e t s " produced by alongshore and onshore winds, a c t i n g i n c o n j u n c t i o n with in t e n s e r i p c u r r e n t s may provide a mechanism. As a r e s u l t of the lowering of wave base, the water depths in which wave induced c u r r e n t s can erode the s e a f l o o r are i n c r e a s e d . Butman et a l . (1979) have noted sediment suspension near the sea f l o o r , produced by wave induced c u r r e n t s from the passage of a moderate storm, at 60 m water depth. Below the depths at which storm induced c u r r e n t s can erode and re-suspend sediment, c u r r e n t energy may s t i l l be s u f f i c i e n t l y strong to move sediment on the sea f l o o r . In modern sh e l v e s , wave r i p p l e s formed by storm induced o s c i l l a t o r y c u r r e n t s have been observed i n water depths of as much as 200 m (Ewing, 1973; Butman et a l . , 1979). Most i n f o r m a t i o n on sedimentary s t r u c t u r e s and sequences i n shallow marine storm d e p o s i t s has come from s t u d i e s of a n c i e n t r a t h e r than modern marine sediments. Hummocky c r o s s -s t r a t i f i c a t i o n i s a common bedform i n a n c i e n t storm d e p o s i t s and i n the t r a n s i t i o n f a c i e s of the Moosebar and Gates Formations. The term hummocky c r o s s - s t r a t i f i c a t i o n (H.G.S.) was c o i n e d by Harms et a l . (1975) f o r g e n t l y u n d u l a t i n g s e t s of c r o s s -s t r a t i f i c a t i o n that cut each other at low angles and i n which 36 the laminae are randomly o r i e n t e d and may be both concave-up or convex-up. Laminae t y p i c a l l y conform to the curved shapes of hummocks and troughs which have wavelengths of one to f i v e metres and amplitudes of 10-20 cm (Walker, 1979, p. 81). Harms et a l . (1975), suggested that H.C.S. formed by the d e p o s i t i o n from suspension of sand on hummock and trough topography, formed by the a c t i o n of storm waves. An a l t e r n a t i v e i n t e r p r e t a t i o n , proposed by Hamblin and Walker (1979) i s that the hummocky sandstone beds may have been emplaced by t u r b i d i t y c u r r e n t s and subsequently reworked by storm wave a c t i o n . T h i s second i n t e r p r e t a t i o n i s p r e f e r r e d f o r the H.C.S. beds i n the t r a n s i t i o n f a c i e s which have f l u t e c a s t s and groove marks along the b a s a l s u r f a c e . P a r a l l e l bedding i n the sandstones and s i l t s t o n e s may have formed as a r e s u l t of d e p o s i t i o n from suspension i n c u r r e n t v e l o c i t i e s e i t h e r below that necessary to generate r i p p l e s (Reineck and Singh, 1973, p. 106) or under upper flow regime, c o n d i t i o n s ( J o p l i n g , 1967). In most cases i t i s u n c l e a r which process i s represented i n t r a n s i t i o n f a c i e s d e p o s i t s , but i n beds which c o n t a i n mudstone r i p - u p c l a s t s and t r u n c a t e d burrows i t i s c l e a r that the p a r a l l e l bedding was formed from strong upper flow regime c u r r e n t s and not from suspension. Symmetrical wave r i p p l e s on the top s u r f a c e s of p a r a l l e l , low angle cross-bedded and H.C.S. beds are i n t e r p r e t e d by Mount (1982) as forming under lower flow regime c o n d i t i o n s d u r i n g the d e c l i n e of the storm-generated c u r r e n t . F l a s e r and l e n t i c u l a r bedding i n some u n i t s of the t r a n s i t o n f a c i e s suggests that these sediments were d e p o s i t e d i n areas with l i m i t e d sand supply 37 and v a r i a b l e c u r r e n t c o n d i t i o n s . These s t r u c t u r e s may have formed dur i n g f a i r weather p e r i o d s as a r e s u l t of normal wave and t i d a l c u r r e n t v a r i a t i o n s or as a r e s u l t of c u r r e n t v a r i a t i o n s a s s o c i a t e d with moderate storm a c t i v i t y . The symmetrical dunes which are present i n a t h i n bed of coarse to granula r sandstone near the base of the S h e r i f f member in the s y n c l i n e extension outcrop s e c t i o n are s i m i l a r to bedforms d e s c r i b e d from modern shelves o f f New Zealand ( G i l l i e , 1979) and Vancouver I s l a n d (Yorath et a l . , 1979). L e c k i e (1981) and L e c k i e and Walker (1982) have d e s c r i b e d s i m i l a r bedforms i n marine u n i t s i n the Gates Formation north of the study a r e a . In the modern examples the dunes are formed by o s c i l l a t o r y wave motion on the sea bottom i n water depths of 20-100 m. T h i s seems the most probable o r i g i n f o r the symmetrical dunes at the base of the S h e r i f f member. The source of the coarse to granular sand and pebbles i n which the dunes are found i s u n c e r t a i n . These sediments may have been t r a n s p o r t e d o f f s h o r e by strong storm induced c u r r e n t s or have been d e r i v e d l o c a l l y from beds of coarse nearshore on c o a s t a l p l a i n d e p o s i t s exposed on the sea f l o o r d u r i n g the marine t r a n s g r e s s i o n at the base of the S h e r i f f member. 1.3.5 Sheet Sandstone F a c i e s - D e s c r i p t i o n T h i s f a c i e s occurs at the top of the coarsening-upward r e g r e s s i v e c y c l e s . In the S h e r i f f member near i t s landward pinchout, south of Kinuseo Creek, ( F i g u r e 8), the mudstone and t r a n s i t i o n f a c i e s are absent and the e n t i r e marine u n i t c o n s i s t s of the sheet sandstone f a c i e s . In areas where the sheet 38 F i g u r e _1_3« Outcrop of the lower Gates on the northwest s i d e of Mount Frame. The prominent grey sandstone i n the foreground i s the Torrens Member. Note the abrupt and p l a n a r top s u r f a c e which r e p r e s e n t s the a n c i e n t backshore. The T o r r e n s i s o v e r l a i n by 10.5 m of black mudstones i n t e r b e d d e d with t h i n s i l t s t o n e s and sandstones ( l a g o o n a l d e p o s i t s ? ) . A t h i n (0.5 m) c o a l seam occurs above t h i s a t the top r i g h t of the photograph. T h i s i s o v e r l a i n by sandstones and a conglomerate f i l l e d channel ( c ) . Marine sandstones of the S h e r i f f member(s) outcrop on the slope i n the d i s t a n c e o v e r l y i n g a t h i n t r a n s g r e s s i v e l a g at the t o p of the channel d e p o s i t s . F i g u r e J_4. Road cut a t the McConkey P i t . The type s e c t i o n of the S h e r i f f member i s along the road behind the h i l l i n the foreground. The f i r s t t h i c k seam on the l e f t i s the 10 m t h i c k J seam. Seams above t h i s i n c l u d e the G seam (2.0 m t h i c k ) and the E seam. E occurs w i t h i n an i n t e r v a l over 20m t h i c k but c o n t a i n s numerous s p l i t s and s m a l l f a u l t s . F i g u r e j_5. View of the 10 m t h i c k J seam along the McConkey road c u t . J r e s t s d i r e c t l y on nearshore marine sandstones of the S h e r i f f member and i s o v e r l a i n by i n f e r r e d l a k e - l a c u s t r i n e d e l t a d e p o s i t s c o n s i s t i n g of a coarsening-upward sequence of interbedded mudstones, s i l t s t o n e s and f i n e - g r a i n e d sandstones. Non-marine Unionid b i v a l v e s are common i n mudstones immediately above J . Note the w e l l developed p a r a l l e l l a m i n a t i o n s i n the i n f e r r e d lake d e p o s i t s . In t h i s s e c t i o n J i s s t r o n g l y sheared and s t r u c t u r a l l y t h i c k e n e d by 2-3 m along the road. 4 0 F i g u r e J_7. S k o l i t h o s burrows c o n s i s t i n g of simple, even width, v e r t i c a l tubes i n lower shoreface sandstones (sheet sandstone f a c i e s A) of the S h e r i f f member. F i g u r e J J 3 . P a r a l l e l laminated to burrowed sequence i n lower shoreface sandstones (sheet sandstone f a c i e s A) of the S h e r i f f member. 42 sandstone f a c i e s o v e r l i e s the t r a n s i t i o n f a c i e s , the c o n t a c t i s p i c k e d at the base of the f i r s t t h i c k sandstone bed above which few or no mudstone beds occur. The dominant l i t h o l o g y of t h i s f a c i e s i s sandstone. In some s e c t i o n s , the sandstones c o n t a i n t h i n pebbly s t r e a k s . O c c a s i o n a l l y , t h i n mudstones are present near the base of the u n i t . These d e p o s i t s form u n i t s which range i n t h i c k n e s s from 12-32 m and which e x h i b i t s h e e t - l i k e geometry ( F i g u r e s 5, 6 and 7 ) . The Torrens Member which can be c o r r e l a t e d over a d i s t a n c e of 110 km i n a NW-SE d i r e c t i o n i s the most widespread example of the sheet sandstone (Figure 13). The sandstones are t y p i c a l l y l i g h t to medium grey and weather commonly to greyish-orange. G r a i n - s i z e i n the sandstones ranges from very f i n e - to c o a r s e - g r a i n e d and coarsens-upward w i t h i n the f a c i e s . G e n e r a l l y , the sandstones are c l e a n and very w e l l s o r t e d . O c c a s i o n a l l y , they c o n t a i n dark grey laminae of s i l t s t o n e or carbonaceous m a t e r i a l . In many s e c t i o n s i t i s p o s s i b l e to s u b d i v i d e " t h e sheet sandstone f a c i e s i n t o a lower u n i t ( f a c i e s A) and an upper u n i t ( f a c i e s B) based on the type and d i s t r i b u t i o n of p h y s i c a l and b i o g e n i c s t r u c t u r e s . In a few s e c t i o n s the upper u n i t i s r e p l a c e d by a t h i r d f a c i e s ( f a c i e s C ) . F a c i e s A T h i s f a c i e s occupies approximately the lower two-thirds of the sheet sandstone f a c i e s . Primary sedimentary s t r u c t u r e s i n t h i s i n t e r v a l c o n s i s t of low angle cross-bedding and p a r a l l e l bedding (F i g u r e s 16, 18). The bases of s e t s are commonly 43 F i g u r e J_9. Trace f o s s i l s i n shoreface - beach sandstones (sheet sandstone f a c i e s ) . F i g u r e 1 9a,b. V e r t i c a l U-shaped burrows, probably D i p l o c r a t e r i o n . In F i g u r e 19b three l a r g e U-shaped s p r e i t e s t r u c t u r e s are v i s i b l e . F i g u r e 19c. P a r a l l e l laminated to burrowed sequence. The burrows are Paleophycus. F i g u r e 19d. Core photograph of burrowed marine sandstones i n the upper p a r t of the S h e r i f f member i n borehole QMD 7705. Trace f o s s i l s i n c l u d e h o r i z o n t a l forms of Ophiomorpha (o) and S k o l i t h o s ( s ) . F i g u r e 19e. S t r o n g l y burrowed sandstone at the top of the S h e r i f f member i n borehole QBD 7701 (186.2 m). Burrows c o n s i s t s of smal l h o r i z o n t a l to s l i g h t l y i n c l i n e d c i r c u l a r to o v a l tubes with no evidence of branching. These are s i m i l a r to Macaronichnus segregatus ( C l i f t o n and Thompson, 1978) . 44 45 e r o s i o n a l with a few centimetres of scour i n t o the u n d e r l y i n g bed. Hummocky c r o s s - s t r a t i f i c a t i o n was observed at the base of t h i s f a c i e s i n the S h e r i f f member on the McConkey road c u t . Mudstone pebbles and r i p - u p c l a s t s together with c o a l spar are present i n some beds but are not common. B i o t u r b a t i o n i n f a c i e s A ranges from weak to moderate. In a l l s e c t i o n s , p h y s i c a l sedimentary s t r u c t u r e s c l e a r l y predominate over b i o g e n i c s t r u c t u r e s . Strong b i o t u r b a t i o n i s commonly c o n f i n e d to the upper p a r t s of beds, whereas the lower p a r t s show l i t t l e or no b i o t u r b a t i o n . F i g u r e 18 shows an example of a p a r a l l e l to burrowed sequence i n f a c i e s A. O c c a s i o n a l l y the tops of burrows are tr u n c a t e d by the o v e r l y i n g bed. Trace f o s s i l s i n f a c i e s A i n c l u d e h o r i z o n t a l , v e r t i c a l and l a r g e 'U'-shaped burrows (Fi g u r e s 17, 18, 19). A common burrow c o n s i s t s of 0.5-1 cm diameter, c i r c u l a r to o v a l h o r i z o n t a l tubes which form dense boxworks (Paleophycus - F i g u r e 19c). Ophiomorpha i s present i n both h o r i z o n t a l and v e r t i c a l forms (Figure I9d). The 'U'-shaped burrows c o n s i s t of n e a r l y v e r t i c a l to s l i g h t l y i n c l i n e d s p r e i t e f i l l e d burrows up to 15 cm ac r o s s (probably D i p l o c r a t e r i o n - F i g u r e s 19a,b) V e r t i c a l tubes 2-5 mm in diameter s i m i l a r to S k o l i t h o s , are a l s o p r e s e n t . F a c i e s B Thi s f a c i e s occupies approximately the upper o n e - t h i r d of the sheet sandstone f a c i e s . Primary sedimentary s t r u c t u r e s i n t h i s i n t e r v a l c o n s i s t of cross-bedding, p a r a l l e l bedding and o c c a s i o n a l r i p p l e s . In c o n t r a s t to f a c i e s A, where low angle cross-bedding occurs, f a c i e s B c o n t a i n s mainly hi g h angle c r o s s -46 F i g u r e 2Cj« Primary sedimentary s t r u c t u r e s i n c o r e s from nearshore marine sandstones (sheet sandstone f a c i e s B). F i g u r e 20a. Cross-bedding, p a r a l l e l bedding and r i p p l e s (MDD 7811, 114.15m). F i g u r e 20b. Same as 2fJ. Note the scoured s u r f a c e at the top of the core (MDD 7811, 112.86 m). F i g u r e 20c. A l t e r n a t i o n s of p a r a l l e l bedding and r i p p l e s . A s i n g l e h o r i z o n t a l burrow( Paleophycus) i s present at the base ( b ) . (MDD 7918, 19.6 m) . F i g u r e 20d. Cross-bedded sandstone. (MDD 7918, 10.8 m). 47 48 F i g u r e s 2 1 a , b. Cross-bedding and p a r a l l e l bedding i n nearshore marine sandstones (sheet sandstone f a c i e s B) a=MDD 7823, 391.7m; b=MDD 7823, 388 m. Fig u r e 21c. Core photograph of massive root p e n e t r a t e d sandstone at the top of the Torrens Member (MDD 7823, 385.3 m). Fi g u r e 21d. Massive root p e n e t r a t e d sandstone at the top of the S h e r i f f member o v e r l a i n d i r e c t l y by the J c o a l seam. 49 50 bedding. In outcrops both trough and t a b u l a r c r o s s -s t r a t i f i c a t i o n was observed. Sets range in t h i c k n e s s from 5-25 cm. P a r a l l e l bedding i s present throughout t h i s i n t e r v a l . O c c a s i o n a l l y , p a r a l l e l bedding a l t e r n a t e s with r i p p l e s ( F i g u r e 20) . With the exception of the very top of the i n t e r v a l , b i o t u r b a t i o n i n f a c i e s B i s r e s t r i c t e d to a few i s o l a t e d burrows or t h i n , densely burrowed i n t e r v a l s of a s p e c i e s s i m i l a r to Paleophycus. The top 30 cm-1 m of f a c i e s B i s o f t e n s t r o n g l y b i o t u r b a t e d . In most cases t h i s b i o t u r b a t i o n i s caused by r o o t s ( F i g u r e s 21c, 21d). The burrows at the top of f a c i e s B are d i s t i n c t i v e and c o n s i s t of dense networks of h o r i z o n t a l to s l i g h t l y i n c l i n e d tubes 1 mm i n diameter. T h i s t r a c e i s s i m i l a r to Macaronichnus segregatus, d e s c r i b e d by C l i f t o n and Thompson (1978) from i n t e r t i d a l sediments on the Oregon c o a s t . In outcrops the top s u r f a c e of f a c i e s B i s abrupt and p l a n a r . In some s e c t i o n s f a c i e s B i s o v e r l a i n d i r e c t l y by a t h i c k c o a l seam (Figure 15) while i n other s e c t i o n s the o v e r l y i n g beds c o n s i s t of black carbonaceous mudstones, s i l t s t o n e s and t h i n c o a l seams (Figure 13). F a c i e s C T h i s f a c i e s has been re c o g n i s e d i n only a few s e c t i o n s at the top of the sheet sandstone f a c i e s where i t occurs i n p l a c e of f a c i e s B. The l i t h o l o g i e s i n f a c i e s C c o n s i s t mainly of sandstones which are g e n e r a l l y c o a r s e r and l e s s w e l l s o r t e d than i n f a c i e s B. In some s e c t i o n s conglomerates up to 1 m t h i c k are present at the base of the f a c i e s or as t h i n pebbly l a y e r s 51 s c a t t e r e d throughout. These d e p o s i t s form u n i t s 6-10 m t h i c k which have abrupt or e r o s i o n a l bases and which f i n e upwards i n the top 0.5-2 m. Clay pebbles and c o a l spar are common i n most s e c t i o n s . In some outcrop s e c t i o n s , impressions of l a r g e l o g s are present near the base. Primary sedimentary s t r u c t u r e s c o n s i s t mainly of c r o s s -bedding with o c c a s i o n a l p a r a l l e l bedding and r i p p l e s . O c c a s i o n a l l y , the sandstones are massive. The cross-bedding occurs i n s e t s 5-50 cm t h i c k which commonly decrease i n t h i c k n e s s towards the top. The top c o n t a c t of f a c i e s C i s abrupt and o v e r l a i n by non-marine carbonaceous mudstones, s i l t s t o n e s and c o a l . In outcrops i n the F i v e Cabin Creek area, f a c i e s C i s o v e r l a i n by t h i c k conglomerates i n t e r p r e t e d as f l u v i a l i n o r i g i n . 1.3.6 Sheet Sandstone F a c i e s - I n t e r p r e t a t i o n The s t r a t i g r a p h i c p o s i t i o n of the sheet sandstone f a c i e s , above o f f s h o r e and t r a n s i t i o n zone d e p o s i t s and below c o a l b e a r i n g non-marine sediments, c l e a r l y i n d i c a t e s that t h i s f a c i e s was d e p o s i t e d i n a shallow m a r i n e - c o a s t a l environment. T h i s i s supported by the occurrence of marine t r a c e f o s s i l s (e.g. Ophiomorpha, Paleophycus). Based on the coarsening-upward nature of the sandstones, the d i s t r i b u t i o n of p h y s i c a l sedimentary s t r u c t u r e s and b i o t u r b a t i o n p a t t e r n s , f a c i e s A and B are i n t e r p r e t e d as forming i n shoreface and beach environments (Figure 23a). Comparison with other modern and a n c i e n t shoreface-beach sequences suggests that f a c i e s A was d e p o s i t e d i n the lower shoreface while f a c i e s B r e p r e s e n t s upper shoreface 52 and beach (foreshore/backshore) d e p o s i t s . The p a r a l l e l to burrowed beds i n f a c i e s A are s i m i l a r to sequences d e s c r i b e d by Howard (1972) and B a l s l e y (1980) from other lower shoreface d e p o s i t s . Howard (1972) i n t e r p r e t s the p a r a l l e l to burrowed sequences as the r e s u l t of i n t e r m i t t e n t d e p o s i t i o n and e r o s i o n a s s o c i a t e d with a l t e r n a t e storm and f a i r weather c o n d i t i o n s . The occurrence of trough and t a b u l a r c r o s s - s t r a t i f i c a t i o n i n f a c i e s B i n d i c a t e s d e p o s i t i o n was a s s o c i a t e d with strong u n i d i r e c t i o n a l c u r r e n t s . Such c o n d i t i o n s are common i n the upper shoreface and lower foreshore of many modern beaches. P a r a l l e l bedding i n f a c i e s B i s i n t e r p r e t e d as the r e s u l t of sheet flow a s s o c i a t e d with upper flow regime c o n d i t i o n s . On modern beaches, upper flow regime p a r a l l e l bedding i s common i n foreshore areas as a r e s u l t of swash processes ( C l i f t o n et a l . , 1971), and on the shallower p a r t s of bars i n the. nearshore a r e a . The p a r a l l e l -t o - r i p p l e bedding i n f a c i e s B i s s i m i l a r to the p l a n e - t o - r i p p l e bedding d e s c r i b e d by Davidson-Arnott and Greenwood (1976) on the seaward and landward slo p e s of nearshore bars i n Kouchibouguac Bay, New Brunswick. The abrupt pla n a r top of f a c i e s B corresponds c l o s e l y to the an c i e n t backshore. The i n t e r p r e t a t i o n of f a c i e s C i s u n c e r t a i n . The main c h a r a c t e r i s t i c s of t h i s f a c i e s , which i n c l u d e the g e n e r a l l y c o a r s e r g r a i n - s i z e of l i t h o l o g i e s r e l a t i v e to f a c i e s A and B, abrupt or e r o s i o n a l base and presence of l a r g e s c a l e c r o s s -bedding, suggest that f a c i e s C probably r e p r e s e n t s a channel f i l l d e p o s i t . The s t r a t i g r a p h i c p o s i t i o n of f a c i e s C, above lower shoreface d e p o s i t s and l a t e r a l to nearshore (upper 53 shoreface-beach) sediments i s c o n s i s t e n t with a d i s t r i b u t a r y channel or r i p channel {Davidson-Arnott and Greenwood, 1976; Hunter et a l . , 1979) i n t e r p r e t a t i o n . The t h i c k n e s s of the channel f i l l d e p o s i t s i n f a c i e s C (6-10 m) i s much l a r g e r than the t h i c k n e s s of r i p channel d e p o s i t s d e s c r i b e d by Hunter et a l . , (1979), from the Oregon c o a s t . Based on t h i s evidence, a d i s t r i b u t a r y channel i n t e r p r e t a t i o n f o r f a c i e s C i s c o n s i d e r e d more l i k e l y . 1.3.7 Comparison of the lower Gates C o a s t a l F a c i e s with Modern  High Energy and Low Energy Beach-to-Qffshore Sequences Modern beaches can be c l a s s i f i e d i n t o two main types depending on the wave energy along the c o a s t l i n e (Reineck and Singh, 1973, p. 286): High energy beaches along c o a s t s where wave a c t i o n i s strong,, and low energy beaches along c o a s t s where wave a c t i o n i s m i l d . The beaches along the Oregon and C a l i f o r n i a c o a s t s ( C l i f t o n et a l . , 1971; Hunter et a l . , 1979; Howard and Reineck, 1981) are the best documented examples of high energy beaches. Examples of low to intermediate wave energy beaches i n c l u d e Sapelo I s l a n d on the Georgia coast (Howard, et a l . , 1972; Howard and Reineck, 1972; Wunderlich, 1972), Galveston I s l a n d i n the Texas Gulf Coast (Bernard and Leblanc, 1965) and the beaches along Kouchibouguac Bay, New Brunswick (Davidson-Arnott and Greenwood, 1974, 1976). Foreshore f a c i e s of modern h i g h and low energy beaches are broadly s i m i l a r . Shoreface f a c i e s , however, d i f f e r a c c o r d i n g to the wave regime, with high wave energy areas being dominated by p h y s i c a l sedimentary s t r u c t u r e s , w h i l s t intermediate to low wave 54 energy areas r e c o r d an a l t e r n a t i o n between p h y s i c a l and b i o g e n i c s t r u c t u r e s ( E l l i o t , 1978, p. 152). A recent comparison of the d e p o s i t i o n a l f a c i e s i n the beach to o f f s h o r e sequence from a high energy coast ( C a l i f o r n i a ) and a low energy coast (Sapelo I s l a n d , Georgia) by Howard and Reineck (1981) i n d i c a t e s that the two areas do not d i f f e r g r e a t l y i n t h e i r f a c i e s or o v e r a l l v e r t i c a l sequence of sedimentary s t r u c t u r e s . The f a c i e s do, however, show s i g n i f i c a n t d i f f e r e n c e s i n t h i c k n e s s : At, Sapelo I s l a n d , the shoreface sequence i s 2 m t h i c k while the C a l i f o r n i a shoreface i s 9 m t h i c k . The u n d e r l y i n g t r a n s i t i o n f a c i e s i s 3 m t h i c k at Sapelo I s l a n d and 9 m t h i c k i n C a l i f o r n i a . The v a r i a t i o n s in t h i c k n e s s are the d i r e c t r e s u l t of d i f f e r e n t wave ene r g i e s in the two areas. Higher wave energie s on the C a l i f o r n i a coast r e s u l t i n a lowering of the average depth of wave base and consequently an i n c r e a s e i n the t h i c k n e s s of shoreface and t r a n s i t i o n f a c i e s compared to Sapelo I s l a n d . Three main l i n e s of evidence suggest that the lower Gates s h o r e l i n e s were high energy and wave dominated: 1. Shoreface - beach environments i n the lower Gates c o a s t a l f a c i e s are developed over l a r g e areas and there i s no evidence f o r numerous t i d a l i n l e t s or t i d a l channels which would be expected i f the s h o r e l i n e were t i d e dominated (Hayes, 1975). 2. The t h i c k n e s s of t r a n s i t i o n zone and shoreface f a c i e s i s comparable to the t h i c k n e s s of these f a c i e s i n modern high energy c o a s t a l areas and very much g r e a t e r than that found along low to intermediate energy s h o r e l i n e s . T h i s p o i n t alone, however, i s not c o n c l u s i v e evidence that the lower 55 Gates s h o r e l i n e s were high energy and wave dominated s i n c e i t might be argued that the combination of r e g i o n a l subsidence, e u s t a t i c sea l e v e l r i s e and hig h sediment input to the s h o r e l i n e c o u l d produce t h i c k t r a n s i t i o n and shoreface d e p o s i t s . 3. Conglomerates are present i n the lower Gates nearshore f a c i e s i n the study area, i n the F o o t h i l l s north of the study area ( L e c k i e , 1981; Le c k i e and Walker, 1982) and i n e q u i v a l e n t s t r a t a i n the subsurface to the east (Youn, 1982; Cant, 1982, 1983). The presence of conglomerates i n the nearshore f a c i e s c l e a r l y i n d i c a t e s high wave en e r g i e s along the lower Gates s h o r e l i n e s . 1.4 TRANSGRESSIVE DEPOSITS Three d i s t i n c t f a c i e s are present at the base of the S h e r i f f member which, on the b a s i s of t h e i r c h a r a c t e r i s t i c s and s t r a t i g r a p h i c p o s i t i o n , are i n t e r p r e t e d as t r a n s g r e s s i v e d e p o s i t s . 1.4.1 F a c i e s D T h i s f a c i e s crops out i n the McConkey road cut and on the northwest sid e of Mount Frame. In the McConkey road cut s e c t i o n (Figure 5), f a c i e s D c o n s i s t s of 6.1 m of sandstones with minor conglomerates and s i l t s t o n e s . These d e p o s i t s e r o s i o n a l l y o v e r l i e carbonaceous mudstones and a t h i n c o a l at the top of a 13.5 m t h i c k i n t e r v a l of i n f e r r e d l a g o o n - c o a s t a l swamp d e p o s i t s . The sandstones are f i n e - to medium-grained and w e l l s o r t e d . Primary sedimentary s t r u c t u r e s i n c l u d e p a r a l l e l bedding and low angle 56 cross-bedding. Mudstone r i p - u p c l a s t s are o c c a s i o n a l l y present i n the sandstones. 'U'-shaped burrows s i m i l a r to R h i z o c o r a l l i u m occur near the base of the u n i t but are not common. Thin pebbly s t r e a k s occur s c a t t e r e d throughout. These are more numerous near the base of the u n i t where they are up to 30 cm t h i c k . A s i l t s t o n e bed, 50 cm t h i c k occurs interbedded with the sandstones 2 m above the base. In the Frame s e c t i o n (Figure 6), f a c i e s D c o n s i s t s of 7.5 m of sandstones and conglomerates. These d e p o s i t s e r o s i o n a l l y o v e r l i e a 35 cm c o a l seam at the top of a 10.8 m i n t e r v a l of i n f e r r e d l a g o o n - c o a s t a l swamp d e p o s i t s above the Torrens Member. F a c i e s D i n t h i s s e c t i o n c o n s i s t s of two d i s t i n c t u n i t s . The lower u n i t i s 3.9 m t h i c k and c o n s i s t s of medium- to co a r s e -gra i n e d , w e l l s o r t e d sandstones interbedded with t h i n pebbly s t r e a k s . The sandstones are trough cross-bedded and c o n t a i n small mudstone r i p - u p c l a s t s . Burrows s i m i l a r to Macaronichnus  segregatus are common near the base of the' sandstone. T h i s lower u n i t i s e r o s i o n a l l y o v e r l a i n by massive, coarse to g r a n u l a r pebbly sandstones and conglomerates which occur w i t h i n a channel up to 4.6 m t h i c k . The base of the channel i s concave upwards and the top i s abrupt and p l a n a r . 1.4.2 F a c i e s E T h i s f a c i e s occurs between f a c i e s D and the o f f s h o r e marine d e p o s i t s at the base of the S h e r i f f member. In the Frame s e c t i o n , f a c i e s E c o n s i s t s of 35 cm of massive conglomerate. Pebbles i n the conglomerate are 0.5-2 cm i n diameter. T h i s u n i t i s c o a r s e r than the u n d e r l y i n g channel f i l l d e p o s i t s . In the 57 McConkey roa"d cut s e c t i o n , f a c i e s E i s 1 .5 m t h i c k and c o n s i s t s of 5-20 cm t h i c k beds of f i n e - g r a i n e d conglomerate and coarse to granular sandstone, interbedded with s t r o n g l y b i o t u r b a t e d s i l t s t o n e and f i n e - g r a i n e d s i l t y sandstone. The base of t h i s u n i t i s e r o s i o n a l and o v e r l a i n by 20 cm of conglomerate. The upper con t a c t i s abrupt and o v e r l a i n by o f f s h o r e marine mudstones and hummocky c r o s s s t r a t i f i e d sandstones at the base of S h e r i f f member r e g r e s s i v e c y c l e . 1.4.3 F a c i e s F Thi s f a c i e s crops out i n the S y n c l i n e E x t e n s i o n outcrop s e c t i o n near Babcock Mountain (Figure 5 ) . In t h i s s e c t i o n f a c i e s F c o n s i s t s of 10 cm of i n t e n s e l y b i o t u r b a t e d s i l t s t o n e . T h i s bed a b r u p t l y o v e r l i e s 8.5 m of carbonaceous mudstones, s i l t s t o n e s , sandstones and t h i n c o a l seams i n t e r p r e t e d as lagoon and c o a s t a l swamp d e p o s i t s ( d e s c r i b e d i n s e c t i o n 1.6). Sediments which o v e r l i e f a c i e s F near the base of the S h e r i f f member c o n s i s t of marine ( t r a n s i t i o n zone) mudstones interbedded with t h i n very f i n e - g r a i n e d sandstones. 1.4.4 O r i g i n of the T r a n s g r e s s i v e D e p o s i t s Marine t r a n s g r e s s i o n s are i n i t i a t e d by the i n t e r a c t i o n of 3 main f a c t o r s : 1. Rate of sediment supply to the c o a s t . 2. Rate of subsidence. 3. E u s t a t i c sea l e v e l changes. Along d e l t a i c c o a s t l i n e s , marine t r a n s g r e s s i o n s are u s u a l l y i n i t i a t e d by a r e d u c t i o n i n sediment supply to the s h o r e l i n e 58 caused by major r i v e r d i v e r s i o n s upstream on the d e l t a i c or c o a s t a l p l a i n (Coleman, 1976). Once the sediment supply i s cut o f f , waves begin to erode the d e l t a i c sediments. T r a n s g r e s s i v e s h o r e l i n e sands are formed i f r e l a t i v e sea l e v e l i s r i s i n g and there i s a source of sand a v a i l a b l e (note: r e l a t i v e sea l e v e l changes are produced by v a r i a t i o n s i n subsidence r a t e s and e u s t a t i c sea l e v e l changes). During the e a r l y stages of a t r a n s g r e s s i o n , sediment eroded from the o l d e r d e l t a f r o n t d e p o s i t s p r o v i d e s a p o t e n t i a l source of sand. As the c o a s t l i n e migrates landward, the t r a n s g r e s s i v e s h o r e l i n e sands onlap lagoonal or d e l t a p l a i n d e p o s i t s (Oomkens, 1970). With continued r i s e of r e l a t i v e sea l e v e l , the t r a n s g r e s s i v e s h o r e l i n e sands are themselves drowned and may be e n t i r e l y removed by wave a c t i o n ; i n the nearshore zone, waves and longshore c u r r e n t s erode and remove the f i n e r sediments from the area, l e a v i n g behind a coarse l a g on the sea f l o o r of the c o a r s e s t and h e a v i e s t m a t e r i a l l e f t over from the eroded a r e a . Along modern, t r a n s g r e s s i v e s h o r e l i n e s , r a p i d shoreface e r o s i o n occurs d u r i n g storms ( S w i f t , 1976; Hayes^and Kana, 1976). The p r e s e r v a t i o n of t r a n s g r e s s i v e s h o r e l i n e sands depends mainly on the r a t e of r e l a t i v e sea l e v e l r i s e ; i f t h i s r a t e i s r a p i d , there i s a g r e a t e r chance of p r e s e r v a t i o n of the t r a n s g r e s s i v e s h o r e l i n e d e p o s i t s . I f , however, r e l a t i v e sea l e v e l r i s e i s slow, then the t r a n s g r e s s i v e s h o r e l i n e d e p o s i t s may be completely removed by shoreface e r o s i o n and the t r a n s g r e s s i v e r e c o r d then w i l l c o n s i s t only of a t h i n l a g d e p o s i t . F a c i e s D i s i n t e r p r e t e d as a t r a n s g r e s s i v e s h o r e l i n e 59 d e p o s i t . The c h a r a c t e r i s t i c s of f a c i e s D i n the McConkey road c u t , when compared with modern and a n c i e n t t r a n s g r e s s i v e s h o r e l i n e f a c i e s (Hayes and Kana, 1976; E l l i o t , 1978; K r a f t and John, 1979), suggest that these may be beach, washover fan or f l o o d t i d a l d e l t a d e p o s i t s . The presence of burrows s i m i l a r to Macaronichnus segregatus i n sandstones near the base of f a c i e s D in the Frame s e c t i o n suggests that these are i n t e r t i d a l - s h a l l o w s u b t i d a l d e p o s i t s . The massive channel f i l l sandstones and conglomerates i n the upper p a r t of f a c i e s D i n t h i s s e c t i o n are i n t e r p r e t e d as t i d a l i n l e t d e p o s i t s . F a c i e s E i s i n t e r p r e t e d as a t r a n s g r e s s i v e marine l a g d e p o s i t based on i t s s t r a t i g r a p h i c p o s i t i o n and s i m i l a r i t y with other modern and a n c i e n t marine l a g d e p o s i t s (Oomkens, 1967, 1970; Kumar and Sanders, 1976). The 20 cm conglomerate at the base of f a c i e s E i n the McConkey road cut presumably formed by the reworking of the upper part of the t r a n s g r e s s i v e s h o r e l i n e sands. Thinner l a y e r s of coarse sand and conglomerate above t h i s , which a l t e r n a t e with s t r o n g l y b i o t u r b a t e d s i l t s t o n e and sandstone, were probably t r a n s p o r t e d i n t o the area from the nearshore on adjacent p a r t s of the s e a f l o o r d u r i n g storms. The s t r o n g l y b i o t u r b a t e d s i l t s t o n e s and sandstones r e f l e c t the intense burrowing a c t i v i t y on the sea f l o o r d u r i n g f a i r weather p e r i o d s . F a c i e s F i s i n t e r p r e t e d as forming by the a c t i o n of burrowing organisms on the s e a f l o o r d u r i n g the t r a n s g r e s s i o n . The absence of t r a n s g r e s s i v e s h o r e l i n e d e p o s i t s suggests t h a t , i n the S y n c l i n e E x t e n s i o n outcrop area, a source of sand was absent d u r i n g the t r a n s g r e s s i o n . The absence of a marine l a g may 60 be due to the f a c t that e r o s i o n of the u n d e r l y i n g l a g o o n - c o a s t a l p l a i n d e p o s i t s was minimal or that these sediments c o n t a i n e d no coarse m a t e r i a l which c o u l d be reworked i n t o a l a g deposit.. 1.5 SUMMARY OF MARINE PALEOCURRENT DATA Pal e o c u r r e n t data c o l l e c t e d from sandstone beds i n the t r a n s i t i o n f a c i e s i n the upper Moosebar and S h e r i f f member are shown on F i g u r e 22. Measurements were made of f l u t e and groove marks on the base of sandstone beds ( t u r b i d i t e s / s t o r m d e p o s i t s ) , the axes of symmetrical wave r i p p l e s on the tops of sandstone beds and the axes of symmetrical dunes on the top of a conglomerate bed near the base of the S h e r i f f member. The o r i e n t a t i o n of the f l u t e and groove marks i n d i c a t e s the marine p a l e o s l o p e was d i p p i n g towards the north-northwest. The average t r e n d of the r i p p l e c r e s t s i s approximately east-west which i s probably c l o s e to the tr e n d of the lower Gates p a l e o s h o r e l i n e s . T h i s i n t e r p r e t a t i o n i s supported by the tr e n d of the southern l i m i t of the S h e r i f f member ( F i g u r e 8), which i s a l s o east-west. 1.6 LAGOONAL DEPOSITS Sediment i n t e r p r e t e d as lagoonal i n o r i g i n occurs between the Torrens and S h e r i f f Members, south of the Wolverine R i v e r and near the landward pinchout of the S h e r i f f member i n the Duke Mountain area. S i m i l a r d e p o s i t s are a l s o present l o c a l l y immediately above the Torrens Member south of Duke Mountain and in s t r a t a o v e r l y i n g the S h e r i f f member. The l i t h o l o g i e s i n the i n t e r v a l between the Torrens and S h e r i f f Members c o n s i s t of F i g u r e 22. Summary of "marine" paleocurrent' data i n the upper Moosebar (UM) and S h e r i f f member (SH) i n t e r v a l . 62 Offshore Transit ion Zone) Shoreface Fore shore Backshore Dunes M^HWL M LWL F i g u r e 23a. S h o r e l i n e p r o f i l e of modern sandy c o a s t l i n e s ( m o d i f i e d a f t e r Reineck and Singh (1973), p. 285.) Fi g u r e 23b. C l a s s i f i c a t i o n of f l u v i a l channel p a t t e r n s (modified a f t e r M i a l l , 1977) . 63 black shaly mudstones, s i l t s t o n e s , sandstones and t h i n c o a l seams which are present i n i n t e r v a l s 8-13 m t h i c k ( F i g u r e s 5, 6). The mudstones form u n i t s up to 6 m t h i c k , interbedded with t h i n s i l t s t o n e s . O c c a s i o n a l l y the mudstones are carbonaceous. Interbedded s i l t s t o n e s and f i n e - g r a i n e d sandstones form coarsening-upward sequences 2-4 m t h i c k . P a r a l l e l bedding and r i p p l e s are common sedimentary s t r u c t u r e s i n the sandstones and s i l t s t o n e s . Trough cross-bedding i s o c c a s i o n a l l y present i n sandstones near the top of the coarsening-upward sequences. L o c a l l y , the s i l t s t o n e s are s t r o n g l y b i o t u r b a t e d . 'U'-shaped burrows are present i n some sandstones and h o r i z o n t a l t r a c k s and t r a i l s occur on the tops of some beds. Roots are common in sandstones near the top of the coarsening-upward sequences. In the S y n c l i n e Extension outcrop s e c t i o n ( F i g u r e 5), a 1.5 m t h i c k channel occurs at the top of a c o a r s e n i n g upward sequence. The channel f i l l c o n s i s t s of medium- to c o a r s e - g r a i n e d sandstone with trough cross-bedding near the base, and r i p p l e d r i f t c r o s s l a m i n a t i o n near the top. Between one and three t h i n (<50 cm) c o a l seams are present i n these s e c t i o n s . These occur mainly at the top of the i n t e r v a l s , above the coarsening-upward sequences. North of the Wolverine River (Figure 1) the i n f e r r e d l agoonal d e p o s i t s p i n c h out and are r e p l a c e d by marine d e p o s i t s . South of Kinuseo Creek (F i g u r e 1), e q u i v a l e n t s t r a t a are non-marine and i n c l u d e t h i c k c o a l seams. F i g u r e 24 i s a c r o s s s e c t i o n based on c l o s e l y spaced borehole data i n the Duke P i t area which shows the c h a r a c t e r i s t i c s of i n f e r r e d l a g o o n a l d e p o s i t s near the landward North South 15 10 5 0 BS9 Coal Conglomerate Sandstone f ) Siltstone/Mudstone 1"" -J Carbonaceous mudstone * Cross-bedding //// Tabular cross-bedding —<r~ Low angle cross-bedding - = - Parallel bedding -^rcv, Ripples (c*climbing) Lenticular bedding Wavy bedding Wood fragments Mdst./sltst. rip-up clasts cry Soft sediment deformation structures k. Roots -0- Burrows <%> Bioturbation mdst. 1 fine sstJ I | coarse ssti conglomerate F i g u r e 24. Borehole c r o s s s e c t i o n i n the Duke Mountain area, showing the complex f a c i e s a s s o c i a t i o n s near the landward pinchout of the S h e r i f f member marine u n i t . Note that c o a l seam B2 t h i n s and i s r e p l a c e d by marine sandstones of the S h e r i f f member towards the north, Borehole l o c a t i o n s shown on F i g u r e 83. 65 pinchout of the S h e r i f f member. F a c i e s a s s o c i a t i o n s i n the area are complex. The lagoonal d e p o s i t s are up to 27 m t h i c k and c o n s i s t of two d i s t i n c t types of f a c i e s . In the lower p a r t of the i n t e r v a l , above the B1 c o a l seam, lag o o n a l sediments c o n s i s t of dark grey to black carbonaceous mudstone, s i l t s t o n e , f i n e - to c o a r s e - g r a i n e d sandstones and t h i n (<0.75 m) c o a l seams. The sandstones occur i n beds up to 3 m t h i c k and are o c c a s i o n a l l y interbedded with t h i n conglomerates. Primary sedimentary s t r u c t u r e s i n the sandstones i n c l u d e p a r a l l e l bedding, c r o s s -bedding and r i p p l e s . S o f t sediment deformation s t r u c t u r e s are o c c a s i o n a l l y p r e s e n t . Small mudstone r i p - u p c l a s t s occur i n a few beds. B i o t u r b a t i o n i n the sandstones ranges from weak to s t r o n g . Burrows i n c l u d e Macaronichnus segregatus and other u n i d e n t i f i e d h o r i z o n t a l , v e r t i c a l and 'U'-shaped types. Roots are a l s o found. The sandstones occur interbedded with moderately to s t r o n g l y b i o t u r b a t e d mudstones, s i l t s t o n e s and t h i n c o a l seams. Towards the north, the mudstones s i l t s t o n e s and .coals pinchout and are r e p l a c e d by a 13 m t h i c k i n t e r v a l of sandstone c o n t a i n i n g marine t r a c e f o s s i l s - Paleophycus, Asterosoma and Macaronichnus segregatus (?shoreface-beach d e p o s i t s ) of the S h e r i f f member. S t r a t a e q u i v a l e n t to the l a g o o n a l d e p o s i t s i n the south i n c l u d e lower c o a s t a l p l a i n sediments which i n c l u d e f l u v i a l - d i s t r i b u t a r y channel d e p o s i t s , overbank d e p o s i t s and the B2 (lower) c o a l seam, which i n t h i s area i s up to 2.4 m t h i c k . In boreholes 7801 and 7914 (Figure 24), the f i r s t l agoonal f a c i e s grades upwards i n t o the second type which c o n s i s t s of t h i n interbedded s i l t s t o n e s and f i n e to medium gr a i n e d sandstone. These d e p o s i t s are up to 12m t h i c k . The sandstones 66 occur i n beds up to 1 m t h i c k and have abrupt or e r o s i o n a l bases. Small s i l t s t o n e r i p - u p c l a s t s are common and some beds c o n t a i n abundant carbonaceous m a t e r i a l . Primary sedimentary s t r u c t u r e s i n c l u d e p a r a l l e l bedding, low angle cross-bedding, r i p p l e s , wavy and l e n t i c u l a r bedding. Sof t sediment deformation s t r u c t u r e s are o c c a s i o n a l l y p r e s e n t . A few beds are massive. Burrows are common and i n c l u d e v e r t i c a l and 'U'-shaped types. Small fining-upward and coarsening-upward sequences are prese n t . These d e p o s i t s grade upwards i n t o rooted carbonaceous mudstones which are o v e r l a i n by the 3.5 m t h i c k B3 c o a l seam. The i n t e r p r e t a t i o n of these d e p o s i t s as lagoonal must be con s i d e r e d t e n t a t i v e i n view of the s i m i l a r i t i e s between lagoonal d e p o s i t s and the f a c i e s of other d e p o s i t i o n a l s e t t i n g s such as d e l t a p l a i n s (Heward, 1981). Faunal evidence to support a lagoonal i n t e r p r e t a t i o n has not been found. There a r e , however, s e v e r a l other l i n e s of evidence which, taken together, suggest t h i s i s the most l i k e l y i n t e r p r e t a t i o n . These i n c l u d e the f o l l o w i n g : 1. S t r a t i g r a p h i c p o s i t i o n and f a c i e s a s s o c i a t i o n s ; the i n f e r r e d lagoonal d e p o s i t s are re p l a c e d to the north by marine shoreface-beach d e p o s i t s and to the south by c o a s t a l p l a i n d e p o s i t s with t h i c k c o a l seams. 2. The occurrence of marine t r a c e f o s s i l s i n sandstones interbedded with t h i n c o a l seams, thus i n d i c t i n g both a marine and a non-marine i n f l u e n c e . 3. The g e n e r a l l y f i n e g r a i n - s i z e of the d e p o s i t s , i n d i c a t i n g , a q u i e t , low energy d e p o s i t i o n a l environment. 4. The occurrence i n some beds of strong b i o t u r b a t i o n . 67 Sub-environments w i t h i n modern lagoons (Reineck and Singh, 1973, p.350-354; Hayes and Kana, 1976; E l l i o t , 1978) i n c l u d e lagoon bottom muds, channels, washover fans, f l o o d t i d a l d e l t a s , t i d a l f l a t s and lagoon margin d e l t a s . In view of t h i s v a r i e t y of sub-environments w i t h i n a lagoonal s e t t i n g , i t i s d i f f i c u l t to apply s p e c i f i c environmental i n t e r p r e t a t i o n s to the d i f f e r e n t lagoonal f a c i e s i n the Gates Formation. The t h i c k e r i n t e r v a l s of mudstone and s i l t s t o n e were probably d e p o s i t e d mainly by suspension i n the lower-energy c e n t r a l p a r t s of the lagoon. Strong b i o t u r b a t i o n , which i s common in these d e p o s i t s , r e f l e c t s the h i g h r a t e of organic p r o d u c t i v i t y i n the lagoonal s e t t i n g . The small c o a r s e n i n g -upward s i l t s t o n e / s a n d s t o n e c y c l e s i n the outcrop s e c t i o n s may represent the p r o g r a d a t i o n of small lagoon margin d e l t a s formed duri n g the p r o g r e s s i v e i n f i l l i n g of the lagoon. Thin c o a l s which o v e r l i e rooted h o r i z o n s at the top of these c y c l e s i n d i c a t e s u b a e r i a l exposure and the encroachment of swamps or c o a s t a l marshes over the lagoonal d e p o s i t s . The absence of t h i c k c o a l s a s s o c i a t e d with lagoonal d e p o s i t s i n d i c a t e s that the peat forming environments were s h o r t - l i v e d . The l a g o o n a l sandstones which occur i n the i n t e r v a l above the B1 c o a l seam in the Duke Mountain area ( F i g u r e 24), are i n t e r p r e t e d as washover fan or f l o o d - t i d a l d e l t a d e p o s i t s , based on t h e i r c h a r a c t e r i s t i c s and f a c i e s a s s o c i a t i o n s . The lagoonal f a c i e s which occurs between these d e p o s i t s and the B3 c o a l seam may have formed in t i d a l f l a t s along the margin of the lagoon. 1.7 NON-MARINE DEPOSITS - INTRODUCTION 68 The non-marine d e p o s i t s i n the Gates Formation can be broadly c l a s s i f i e d i n t o two main c a t e g o r i e s : 1. F l u v i a l channel d e p o s i t s F l u v i a l d e p o s i t s i n the lower Gates Formation c o n s i s t mainly of sandstones and conglomerates. A wide v a r i e t y of channel f i l l sequences, ranging i n t h i c k n e s s from a few metres to 42 m t h i c k are p r e s e n t . Based on d i f f e r e n c e s i n l i t h o l o g y , g r a i n - s i z e , sedimentary s t r u c t u r e s , t h i c k n e s s and l i t h o l o g i c a l a s s o c i a t i o n s , 5 major types of channel d e p o s i t s have been i d e n t i f i e d ( t a b l e 2). These are d e s c r i b e d i n the f o l l o w i n g s e c t i o n . 2. Overbank d e p o s i t s Sediment which was d e p o s i t e d i n i n t e r c h a n n e l areas, f a l l s under the general category of overbank d e p o s i t s . Overbank l i t h o l o g i e s c o n s i s t of c o a l , mudstones, s i l t s t o n e s , and sandstones. In most cases overbank sandstones can e a s i l y be d i f f e r e n t i a t e d from f l u v i a l channel sandstones, as the former are thinner' and occur interbedded with s i l t s t o n e s and mudstones. T h i c k e r u n i t s of overbank sandstone are present i n the proximal p a r t s of crevasse s p l a y s . These sandstones are s i m i l a r to small f l u v i a l channel sequences and can only be d i s t i n g u i s h e d on the b a s i s of f a c i e s a s s o c i a t i o n s . 1.8 FLUVIAL CHANNEL DEPOSITS 1.8.1 Type 1 Channel Deposits - D e s c r i p t i o n Type 1 channel d e p o s i t s occur below marine sediments of the Table 2. Summary of the main c h a r a c t e r i s t i c s of f l u v i a l  channel d e p o s i t s in the lower Gates. Channel Type Ma i n LIthology Maximum Thickness Ma in Bedding Type Remarks I n t e r p r e t a t i o n Type 1 Channel Deposits Conglomerate, f i n e - to coarse-grained sandstone 32 m Massive beds. . tabular and trough cross bedding p a r a l I e l bedding. Pebb1e 1mbrlca 11 on 1s common In the conglomerates. Occurs s t r a t l g r a -p h l c a l l y above or below the marine sandstones of the Sh e r i f f member. Braided River ( D i s t r i b u t a r y ) Depos1t Type 2 Channel Deposits see below 42 m see below Occurs In the Babcock area bet-ween the J and G/I coal seams. Composite channel f i l l composed of 2 types of deposits (1over un1t and upper u n i t ) . Compos 1te Channel F i l l Depos1ts Lower Unit Fine- to coarse-gra1ned sandstone 22 m Trough cross-bedd i ng. Composed of s i n g l e or stacked fInlng--upward sequences 2-13 m thick Anastomosing or Low SinuosIty (Non-Braided) Rlver Depos 11 Upper Un i t Cong1omerate granular sandstone, f ine-to coarse-grained sandstones 25 m Massive beds. tabu1 ar and t rough cross-bedding p a r a l l e l bedding. Deposits occur In channels with concave-upward bases Braided R 1 ver Depos1t Type 3 Channel Deposit Conglomerates, granular sandstones, f i n e -to coarse-grained sandstone 12 m Mass 1ve beds, tabular and trough cross bedding para 11e1 bedd1ng Occurs between the 67 and B9 coal seams in the Ouke Mtn. Area. Channel width approx. 2.8 km. Braided River Depos1t Type 4 Channel Deposit Very coarse conglomerates, sandstones. 40 m Massive beds, pebbles often Imbricated, tab-u l a r and trough cross-bedding p a r a l l e i bedding. Occurs In southern part of study area near Mt. Belcourt Proximal Braided RIver-AIluvtal Fan Depos1ts Type S Channel Deposits Fine- to coarse-grained sandstone 14 m Trough c r o s s -beddlng. p a r a l l e i bedding, r i p p l e s Mos t common 1n upper Gates In southern part of study area. Meanderlng Rlver Depos1t 70 S h e r i f f member i n boreholes QBD 7308 and QBD 7309 in the Babcock area and i n the northwest Frame outcrop s e c t i o n (Figure 6 ). S i m i l a r d e p o s i t s are a l s o present above the S h e r i f f member i n outcrops and boreholes i n the F i v e Cabin Creek area ( s e c t i o n s FC6, FC4, F i g u r e 27) . In borehole 7308 (Figure 6), type 1 channel d e p o s i t s c o n s i s t of f i n e - to c o a r s e - g r a i n e d pebbly sandstones and conglomerates ( F i g u r e 27). These d e p o s i t s are present i n a 32 m t h i c k i n t e r v a l which e r o s i o n a l l y o v e r l i e s 1.5 m of carbonaceous mudstone and c o a l . The gamma ray l o g over t h i s i n t e r v a l has a "blocky" p a t t e r n , r e f l e c t i n g the absence of any w e l l developed fining-upward or coarsening-upward sequence i n the channel and the presence of abrupt lower and upper c o n t a c t s . The conglomerates are massive and c l a s t supported, with a sandstone matrix and are p o o r l y s o r t e d . Pebbles i n the conglomerates are w e l l rounded and 0.5-2 cm i n diameter. Primary sedimentary s t r u c t u r e s i n the sandstones i n c l u d e cross-bedding and p a r a l l e l bedding. R i p p l e s are present i n sandstones near the top of the u n i t . O c c a s i o n a l l y , the sandstones are massive. Some of the sandstones c o n t a i n mudstone pebbles and r i p - u p c l a s t s . C l a s t s . Coal spar i s f a i r l y common. Three c l o s e l y spaced outcrop s e c t i o n s i n the F i v e Cabin Creek area ( F i g u r e 25) i l l u s t r a t e some of the l a t e r a l f a c i e s v a r i a t i o n s i n t h i s type of channel d e p o s i t . L i t h o l o g i e s c o n s i s t of conglomerates, granular sandstones and medium- to c o a r s e -g r a i n e d sandstones. In s e c t i o n FC4, type 1 channel d e p o s i t s are 14 m t h i c k . The lower 8 m of t h i s i n t e r v a l c o n s i s t s of massive conglomerate which e r o s i o n a l l y o v e r l i e s a t h i n i n t e r v a l of 71 S.E. FC 7 FC 6 FC 4 I 150m. I 200m. I poor ly e x p o s e d n o n - m a r i n e depo s i t s Non-marine . M a c a r o n i c h n u s aegrega tus burrows . U - s h a p e d burrows • Tabu l a r c r o s s - b e d d i n g . Pebb le imbr i ca t i on . O r i e n t e d wood f r agment s -f- Burrows X Roots Cross-bedding Tabular cross-bedding Trough cross-bedding Low angle crosa-beddtng Hummocky cross-stratification Parallel bedding Ripples Wood fragments F i g u r e 2j>. Outcrop s e c t i o n s of the Moosebar and lower Gates Formations on the nort h e a s t s i d e of the F i v e Cabin Creek s y n c l i n e . Marine d e p o s i t s occur mainly w i t h i n c o a r s e n i n g -upward c y c l e s . Thick conglomerates i n the upper part of s e c t i o n s FC4 and FC6 are i n t e r p r e t e d as d i s t r i b r u t a r y channel f i l l ( b r a i d e d r i v e r ) d e p o s i t s . The conglomerates pinchout towards the southeast i n s e c t i o n FC7 and are r e p l a c e d by sandstones which e x h i b i t p a r a l l e l bedding, trough and t a b u l a r c r o s s - b e d d i n g and rare herringbone c r o s s s t r a t i f i c a t i o n . Trace f o s s i l s i n these sandstones i n c l u d e Macaronichnus segregatus. 72 F i g u r e 26. View of type 1 channel f i l l d e p o s i t s near s e c t i o n s FC4 and FC6 ( F i g u r e 25) on the n o r t h e a s t s i d e of the F i v e Cabin Creek s y n c l i n e . The channel d e p o s i t s c o n s i s t of massive conglomerates and c o a r s e - g r a n u l a r sandstones. The base of the channel i s exposed i n the d i s t a n c e and o v e r l i e s s e v e r a l metres of carbonaceous mudstones which i n turn r e s t on grey, marine sandstones of the S h e r i f f member (lower r i g h t of the photograph). 73 F i g u r e 27. F l u v i a l (type 1) conglomerates and sandstones i n borehole QBD 7308. Coal spar i s abundant i n the sandstones on the lower l e f t of the photograph. S c a l e i s 18 cm long. 74 Fi g u r e 28_. Primary sedimentary s t r u c t u r e s i n i n t e r t i d a l to shallow s u b t i d a l marine sandstones at the top of s e c t i o n FC 7 i n the F i v e Cabin Creek area. These d e p o s i t s are r e p l a c e d by type 1 d i s t r i b u t a r y channel sandstones and conglomerates in s e c t i o n FC 6, 150 m to the northwest. Fi g u r e 28a. Sandstones e x h i b i t i n g trough c r o s s - b e d d i n g p a r a l l e l bedding and herringbone c r o s s - s t r a t i f i c a t i o n . F i g u r e 28b. Trough and t a b u l a r c r oss-bedding and p a r a l l e l bedding. F i g u r e 28c. P a r a l l e l bedding and t a b u l a r c r o s s - b e d d i n g . 76 carbonaceous mudstone above the S h e r i f f member marine sandstones(Figure 26). The conglomerate i s c l a s t supported, with a sandstone matrix. Pebbles i n the conglomerate are w e l l rounded, l o c a l l y i m b r i c a t e d and t y p i c a l l y 1-2 cm i n diameter (max. 6 cm). The average d i p d i r e c t i o n of the long a x i s i n im b r i c a t e d pebbles, based on 50 measurements, i s 193° i n d i c a t i n g a p a l e o c u r r e n t d i r e c t i o n toward the north (013°). The beds o v e r l y i n g t h i s conglomerate c o n s i s t of p a r a l l e l and cross-bedded sandstone interbedded with a 1 m t h i c k u n i t of massive conglomerate which pinches out l a t e r a l l y w i t h i n 15 m of s e c t i o n FC4. Two hundred metres to the southeast, in s e c t i o n FC6, the lower 8 m t h i c k conglomerate i n s e c t i o n FC4 has s p l i t i n t o two beds 2 m and 4 m t h i c k and the amount of interbedded sandstone has i n c r e a s e d . Between s e c t i o n s FC6 and FC7, 150 m to the southeast, the conglomerates p i n c h out w i t h i n a covered i n t e r v a l and are r e p l a c e d by 8 m of medium- to c o a r s e - g r a i n e d pebbly sandstones, which r e s t a b r u p t l y on marine sandstones of the S h e r i f f member. Bedding i n these sandstones c o n s i s t s of t a b u l a r cross-bedding, trough cross-bedding and p a r a l l e l bedding ( F i g u r e 28). Set t h i c k n e s s e s range from 5-30 cm. A few t a b u l a r c o s e t s , which have opposing d i p d i r e c t i o n s between 140° and 150° apart are i n t e r p r e t e d as herringbone c r o s s - s t r a t i f i c a t i o n . Measurements of the d i p of 32 t a b u l a r f o r e s e t s shows two s t r o n g modes to the northwest and west-northwest and a few d i p s to the northeast and southwest (Figure 25). The average vec t o r of t h i s data i s towards 302°. Small elongate wood or p l a n t fragments are present on a few bedding s u r f a c e s . Twenty measurements of the 77 long axes of these fragments shows a p r e f e r r e d north-south o r i e n t a t i o n . Cross-bedded sandstones at the top of t h i s u n i t are i n t e n s e l y burrowed. The burrows c o n s i s t of s m a l l , 1-2 mm diameter tubes s i m i l a r to Macaronichnus segregatus. 1.8.2 Type 1 Channel Deposits - I n t e r p r e t a t i o n In a f l u v i a l s e t t i n g , t h i c k u n i t s of massive, c l a s t supported conglomerate which c o n t a i n i m b r i c a t e d c l a s t s , are c h a r a c t e r i s t i c of l o n g i t u d i n a l bars and channel l a g d e p o s i t s ( M i a l l , 1977). The presence of these u n i t s i n type 1 channel d e p o s i t s , together with t h e i r o v e r a l l s i m i l a r i t y to other b r a i d e d r i v e r d e p o s i t s (e.g., M i a l l , 1977; C o l l i n s o n , 1978) suggests that type 1 channel d e p o s i t s formed i n a b r a i d e d r i v e r system'(Figure 23b). The c l o s e a s s o c i a t i o n of these channel d e p o s i t s with marine sediments i n d i c a t e s that the r i v e r s were l o c a t e d c l o s e to the s h o r e l i n e and thus acted as d i s t r i b u t a r y channels. In boreholes 7308, 7309 and on Mount Frame, type 1 channel d e p o s i t s are l o c a t e d above t h i n c o a l seams, mudstones, s i l t s t o n e s and sandstones i n t e r p r e t e d as l a g o o n - c o a s t a l swamp d e p o s i t s ( d e s c r i b e d i n s e c t i o n 1.6) and below marine, coarsening-upward r e g r e s s i v e d e p o s i t s i n the S h e r i f f member. Th i s p o s i t i o n suggests that the channels i n these s e c t i o n s were l o c a t e d i n p a r t s of the lower c o a s t a l p l a i n which were subsequently t r a n s g r e s s e d by the sea. In the F i v e Cabin Creek area, type 1 channel d e p o s i t s occur above nearshore marine d e p o s i t s at the top of the S h e r i f f member and are o v e r l a i n by c o a l b e a r i n g c o a s t a l p l a i n d e p o s i t s . T h i s p o s i t i o n i n d i c a t e s that the channel i n the F i v e Cabin Creek area i s younger than i n 78 boreholes 7308, 7309 and on Mount Frame and was formed d u r i n g the r e g r e s s i v e phase a s s o c i a t e d with d e p o s i t i o n of the S h e r i f f member. Measurements of imbr i c a t e d pebbles i n conglomerates i n the F i v e Cabin Creek outcrops i n d i c a t e s that the r i v e r flowed towards the no r t h . In t h i s a r e a , the channel was at l e a s t 200 m wide, based on the extent of the conglomerate outcrops. In s e c t i o n FC 7 (Fi g u r e 25), burrows s i m i l a r to Macaronichnus  segregatus are present i n cross-bedded sandstones marginal to the channel f i l l conglomerates. Based on the presence of these burrows, which are con s i d e r e d by C l i f t o n and Thompson (1978) as an i n d i c a t i o n of i n t e r t i d a l - s h a l l o w s u b t i d a l environments, together with t h e i r s t r a t i g r a p h i c p o s i t i o n and sedimentary s t r u c t u r e s , the sandstones at the top of s e c t i o n FC 7. are i n t e r p r e t e d as forming i n bars near the mouth of the d i s t r i b u t a r y channel. 1.8.3 Type 2 Channel Deposits - D e s c r i p t i o n Type 2 channel d e p o s i t s c r o p out i n the Windy and L i t t l e Windy P i t areas on the northwest s i d e of Babcock Mountain and are a l s o present i n many boreholes i n t h i s area ( F i g u r e s 29, 31). L i t h o l o g i e s c o n s i s t of sandstone and conglomerate which form composite channel f i l l sequences up to 42 m t h i c k . Two d i s t i n c t u n i t s are recognised i n type 2 channel d e p o s i t s ; a lower u n i t i n which the channel d e p o s i t s c o n s i s t mainly of sandstone and an upper u n i t i n which the channel d e p o s i t s c o n s i s t of t h i c k u n i t s of conglomerate and sandstone. These d e p o s i t s are i l l u s t r a t e d on F i g u r e s 29, 30, 31, 32, 33, 34). 79 Lower Unit of Type 2 Channel D e p o s i t s The lower u n i t of type 2 channel d e p o s i t s i s up to 22 m t h i c k and c o n s i s t s of f i n e - to c o a r s e - g r a i n e d sandstone, o c c a s i o n a l l y interbedded with t h i n ( l e s s than 1 m t h i c k ) conglomerates. These d e p o s i t s form fining-upward sequences 2-13 m t h i c k . In some s e c t i o n s , the lower u n i t c o n s i s t s of a s i n g l e fining-upward sequence while i n ot h e r s , the lower u n i t c o n s i s t s of stacked fining-upward sequences separated by abrupt or e r o s i o n a l c o n t a c t s . O c c a s i o n a l l y , sandstones i n the lower u n i t show no obvious g r a i n - s i z e v a r i a t i o n s or f i n e upwards only i n the top 1-2 m. In cores the sandstones are l i g h t to medium grey and weather l i g h t brown i n outcrop. Bedding c o n s i s t s mainly of trough cross-bedding ( F i g u r e 30a). Sets are 5 cm-1.5 m t h i c k and commonly decrease i n t h i c k n e s s v e r t i c a l l y w i t h i n the f i n i n g upward u n i t s . R i p p l e s are o c c a s i o n a l l y present at the top of the u n i t s . P a r a l l e l bedding and t a b u l a r cross-bedding are a l s o present but are not common. In cores the sandstones l o c a l l y appear massive. Mudstone c l a s t s and c o a l spar are present i n some s e c t i o n s . P a l e o c u r r e n t data i n the lower u n i t of type 2 channel d e p o s i t s were c o l l e c t e d by measuring the o r i e n t a t i o n of f o r e s e t s i n trough cross-beds at two l o c a l i t i e s approximately 2 km a p a r t . While i t would have been p r e f e r a b l e t o have measured the d i r e c t i o n of trough axes, as these show l e s s d i s p e r s i o n than trough f o r e s e t s (Dott, 1973), the predominance of two dimensional exposures made i t d i f f i c u l t to c o l l e c t t h i s type of data. At the two l o c a l i t i e s , 58 and 66 measurements r e s p e c t i v e l y were made of the maximum d i p d i r e c t i o n of trough f o r e s e t s . P l o t s 80 G5b G5a B6 B5 B4 igure :29. Outcrop s e c t i o n s of type 2 channel f i l l d e p o s i t s i n the Windy P i t area on the northwest s i d e of Babcock Mountain. The lower u n i t of these channel f i l l d e p o s i t s c o n s i s t s predominantly of f i n e - to medium-grained, trough cross-bedded sandstones. The upper u n i t i s c o a r s e r - g r a i n e d and composed of massive, e r o s i o n a l l y based u n i t s of conglomerate and coarse to g r a n u l a r sandstones interbedded with f i n e - t o c o a r s e -g r a i n e d pebbly sandstones which e x h i b i t t a b u l a r and trough c r o s s - b e d d i n g and o c c a s i o n a l l y p a r a l l e l bedding. 81 F i g u r e 3CJ. Outcrop photographs of type 2 channel f i l l d e p o s i t s on the northwest s i d e of Babcock Mountain. F i g u r e 30a. Trough cross-bedded f i n e - to medium-grained sandstones c h a r a c t e r i s t i c of the lower u n i t of type 2 channel f i l l d e p o s i t s . F i g u r e 30b. Massive conglomerate and i n t e r c a l a t e d cross-bedded sandstone i n the upper u n i t . F i g u r e 30c,d. Massive, conglomerate and c o a r s e to g r a n u l a r sandstone at the base of the upper u n i t . Note the c h a n n e l l e d base of the upper u n i t d e p o s i t s i n F i g u r e 30c. F i g u r e 30e. Large set of t a b u l a r c r o s s - b e d d i n g i n conglomerate and coarse to g r a n u l a r , pebbly sandstones from the upper u n i t . F i g u r e 30f. Massive to weakly s t r a t i f i e d conglomerate o v e r l a i n by p a r a l l e l and cross-bedded c o a r s e - g r a i n e d sandstones i n the upper u n i t . 82 1 (560 m) 7751 (1800 m) (1220 m) 7303 (2300 m) 7712 LEGEND Coal [**_] Carbonaceous Mudstone | | Mudstone | ;x;| Sitstone | •';.' j Sandstone Conglomerate ' Cross Bedding ^-<2r' Trough Cross Bedding s/ss Tabular Cross Bedding -= • ParaJel Bedding —c<\ Ripples cr> Soft Sediment Deformation Structures Mudstone and Siltstone Rip-up Clasts Wood Fragments Gamma Ray mdst. fine sat.* ; coarse sst.> conglomerate 1 SECT ION A r 3 0 r _20 -10 0 metres F i g u r e 3J_. S e c t i o n A - Borehole c r o s s s e c t i o n of the i n t e r v a l between the F and J seams at Babcock showing the c h a r a c t e r i s t i c s of type 2 channel f i l l d e p o s i t s , crevasse s p l a y d e p o s i t s , and the d r a p i n g of the G/I1 seam over the channel. Note the pinchout of the 1 3 and 1 2 seams adjacent to the s p l a y and channel d e p o s i t s . A l s o , the t h i c k e n i n g of the G/l - F i n t e r v a l i n the i n t e r c h a n n e l area ( i n boreholes 7 3 0 3 and 7 7 1 2 ) . Borehole l o c a t i o n s shown on F i g u r e 32. S e c t i o n c o n s t r u c t e d with the base of the J seam as h o r i z o n t a l datum. CO co 027 / Windy Pit Data n=43 o . soo tooo contours in metres Rose diagrams represent dip of tabular cross-bedding 84 n»66 079° n-58 Windy Ph Data Little Windy Pit Data? Outcrop..^/ 500 1000 contours in metres Rose diagrams represent direction ot dipping surfaces In trough cross-bedded sandstone F i g u r e 3_2. Sandstone and conglomerate isopachs i n the i n t e r v a l between c o a l seams J and G/I i n the Babcock a r e a . F i g u r e 32a. Isopachs of the lower u n i t of type 2 channel and a s s o c i a t e d s p l a y d e p o s i t s . F i g u r e 32b. Isopach of the.upper u n i t o f " t y p e 2 channel d e p o s i t s . 85 of these data (Figure 32a) show a wide d i s p e r s i o n but, as the number of measurements i s l a r g e , i t i s probable that the average v e c t o r i s c l o s e to the average d i p d i r e c t i o n of the trough axes. At both l o c a l i t i e s the average v e c t o r i s towards 079° suggesting l i t t l e v a r i a t i o n i n channel t r e n d between the two l o c a l i t i e s . The map of the d i s t r i b u t i o n of the lower u n i t of type 2 channel d e p o s i t i s shown i n F i g u r e 32a. T h i s map i n d i c a t e s that the lower u n i t d e p o s i t s are present i n a channel which i s t r e n d i n g ENE-WSW. Two l a r g e lobes on the southern margin of the channel are i n t e r p r e t e d as crevasse s p l a y s . The c h a r a c t e r i s t i c s of the c r e v a s s e splay d e p o s i t s are d e s c r i b e d i n s e c t i o n 1.9.2. The width of the lower u n i t channel cannot be determined as i t s northern margin has been eroded. A minimum width of 1 km i s i n d i c a t e d from the area i n which channel d e p o s i t s are p r e s e n t . Upper U n i t of Type 2 Channel D e p o s i t s D e p o s i t s i n the upper u n i t occur w i t h i n a NE-SW t r e n d i n g channel which extends f a r t h e r southeast than the lower, u n i t channel ( F i g u r e 32b). The northern margin of the upper u n i t channel has a l s o been eroded. A minimum channel width of 1.5 km i s i n d i c a t e d from the area i n which upper u n i t d e p o s i t s are pr e s e n t . The c o n t a c t between the lower and upper u n i t s i s e r o s i o n a l (Figure 30c, 30d). In s e c t i o n s where the lower u n i t i s absent (e.g., borehole 7751, F i g u r e 31), the base of the upper u n i t r e s t s d i r e c t l y on f i n e - g r a i n e d overbank d e p o s i t s . L i t h o l o g i e s i n the upper u n i t c o n s i s t of conglomerates, g r a n u l a r sandstones and f i n e - t o c o a r s e - g r a i n e d , pebbly sandstones. The conglomerates are predominantly c l a s t supported. 86 T h i n , matrix supported conglomerates are present l o c a l l y . Pebbles i n the conglomerate are w e l l rounded and t y p i c a l l y 0.5-1.5 cm i n diameter (max. 4 cm). Mudstone c l a s t s and c o a l spar are present i n some s e c t i o n s . The conglomerates and g r a n u l a r sandstones occur mainly near the base of the u n i t , where they form massive beds up to 8 m t h i c k ( F i g u r e s 29, 30c,30d,3l) interbedded with p a r a l l e l and cross-bedded pebbly sandstone. O c c a s i o n a l l y , the conglomerates and g r a n u l a r sandstones e x h i b i t a weak p a r a l l e l s t r a t i f i c a t i o n or form s e t s of low and high angle t a b u l a r f o r e s e t s up to 50 cm t h i c k ( F i g u r e s 29,30e). L i t h o l o g i e s i n the upper p a r t of the upper u n i t c o n s i s t of f i n e -to c o a r s e - g r a i n e d pebbly sandstones, o c c a s i o n a l l y interbedded with t h i n conglomerates. G r a i n - s i z e i n these sandstones f i n e s upwards or remains f a i r l y c o n s t a n t . Primary sedimentary s t r u c t u r e s c o n s i s t of t a b u l a r and trough cross-bedding, with the former more common. Set t h i c k n e s s e s range from 5-25 cm. In most s e c t i o n s cross-bedded sandstones near the top of the upper u n i t are o v e r l a i n g r a d a t i o n a l l y by s e v e r a l metres of t h i n , interbedded f i n e - g r a i n e d sandstones and s i l t s t o n e s which i n t u r n are o v e r l a i n by carbonaceous mudstone and c o a l . Primary sedimentary s t r u c t u r e s i n the sandstones and s i l t s t o n e s c o n s i s t of p a r a l l e l bedding and r i p p l e s . S o f t sediment deformation s t r u c t u r e s are a l s o common. In a few s e c t i o n s , cross-bedded medium- to c o a r s e - g r a i n e d sandstones at the top of the upper u n i t are o v e r l a i n a b r u p t l y by carbonaceous mudstones ( F i g u r e 34). Upper u n i t channel f i l l d e p o s i t s are w e l l exposed along a c l i f f on the northwest s i d e of Babcock Mountain ( F i g u r e 33). In Northwest Section B5 1 Southeast cross-bedded sandstones channel channel channel channel .' massive conglomerates .and parallel to cross-•.bedded sandstones A-B at section B5 is 13 metres thick. F i g u r e 33. Lin e drawing t r a c e d from a photograph of l a r g e s c a l e bedforms i n the upper u n i t of type 2 channel d e p o s i t s . Photograph i s an o b l i q u e view of a c l i f f exposure on the northwest s i d e of Babcock Mountain. Note the occurrence of low angle e r o s i o n a l s u r f a c e s i n the lower p a r t of the outcrop. A l a r g e channel with a concave upwards base i s preserved towards the northwest. The more r e c e s s i v e upper part of the outcrop c o n s i s t s of trough and t a b u l a r cross-bedded sandstones. 00 88 F i g u r e 34. Core from borehole QBD 7715 at Babcock, showing the very abrupt c o n t a c t (A) between type 2 (upper u n i t ) channel f i l l d e p o s i t s and o v e r l y i n g overbank d e p o s i t s . The channel f i l l sediments c o n s i s t mainly of conglomerates and c r o s s -bedded and r i p p l e d sandstones. These are o v e r l a i n by p a r a l l e l laminated and massive s i l t s t o n e s and carbonaceous mudstones ( i n f e r r e d lake d e p o s i t s i n the abandoned channel) which grade upwards i n t o more massive carbonaceous mudstones ( i n f e r r e d p o o r l y d r a i n e d swamp d e p o s i t s ) and the 2.4 m t h i c k G c o a l seam. 90 the lower p a r t of t h i s outcrop, massive u n i t s of conglomerate and g r a n u l a r sandstone, which range i n t h i c k n e s s from 1-5 m, occur interbedded with p a r a l l e l and cross-bedded pebbly sandstones ( s e c t i o n s B4 and B5, F i g u r e 29) or as stacked u n i t s separated by a g e n t l y d i p p i n g e r o s i o n a l s u r f a c e ( s e c t i o n s B5, F i g u r e 29). These d e p o s i t s occur w i t h i n a s e r i e s of nested channels which have concave upwards bases and are approximately 20-80 m wide. The massive conglomerate and g r a n u l a r sandstone u n i t s are o v e r l a i n by up to 6.5 m of t a b u l a r and trough c r o s s -bedded sandstones. The co n t a c t between the massive conglomerates and cross-bedded sandstones i s abrupt and p l a n a r . P a l e o c u r r e n t data i n the upper u n i t of type 2 channel d e p o s i t s was c o l l e c t e d by measuring the d i r e c t i o n of d i p of t a b u l a r f o r e s e t s . The data from the L i t t l e Windy P i t area (Figure 32b) has a unimodal d i s t r i b u t i o n with an average v e c t o r towards 027°. The data from the Windy P i t area (Figure 32b) shows a more d i s p e r s e d p a t t e r n , with an average v e c t o r towards 04° and a st r o n g mode towards the northwest. 1.8.4 Type 2 Channel Deposits - I n t e r p r e t a t i o n These d e p o s i t s are i n t e r p r e t e d as composite channel f i l l sequences i n a sand and g r a v e l dominated r i v e r system. The occurrence of two d i s t i n c t types of channel f i l l d e p o s i t s (lower u n i t and upper u n i t ) i n type 2 channels i n d i c a t e s t h a t , d u r i n g i t s e x i s t e n c e , the r i v e r system underwent a major change i n channel p a t t e r n . Upper Unit of Type 2 Channel D e p o s i t s - I n t e r p r e t a t i o n 91 D e p o s i t s of the upper u n i t are s i m i l a r to f a c i e s of modern and a n c i e n t b r a i d e d r i v e r s (Rust, 1972, 1976, 1979; M i a l l , 1977; C o l l i n s o n , 1978). The u n i t s of massive conglomerate and g r a n u l a r sandstone at the base of the upper u n i t are i n t e r p r e t e d as channel l a g and l o n g i t u d i n a l bar d e p o s i t s . In outcrops on the northwest s i d e of Babcock Mountain, massive conglomerates and gr a n u l a r sandstones occur w i t h i n channels which have concave-upwards bases and h o r i z o n t a l t o p s . T h i s channel shape i s c h a r a c t e r i s t i c of low s i n u o s i t y r i v e r s (Moody-Stuart, 1966) and c o n t r a s t s with the t a b u l a r shape of channels of meandering r i v e r s . In modern braided r i v e r s , l o n g i t u d i n a l bars are diamond or lozenge shaped i n p l a n , and are elongated p a r a l l e l to the flow d i r e c t i o n ( M i a l l , 1977). They are b e l i e v e d by some workers to be i n i t i a t e d as lags i n the middle of the channel (Leopold and Wolman, 1957; Rust, 1972). The la r g e planar crossbeds i n conglomerate and granular sandstone may have formed as l i n g u o i d bars or d e l t a i c outgrowths from o l d e r bar remnants ( M i a l l , 1977). I n t e r c a l a t e d cross-bedded sandstone were probably d e p o s i t e d d u r i n g p e r i o d s of low water (Doeglas, 1962). Cross-bedded sandstones at the top of the upper u n i t represent dune or bar bedforms formed i n the r i v e r d u r i n g lower flow regime c o n d i t i o n s ( M i a l l , 1977). Tabular cross-bedding i s common.in t h i s i n t e r v a l . In modern braided r i v e r s , t a b u l a r c r o ss-bedding r e s u l t s from the m i g r a t i o n of sand waves and avalanche s l i p faces on the margins of l i n g u o i d or t r a n s v e r s e bars ( C o l l i n s o n , 1970; N.D. Smith, 1970, 1972, 1974). Th i n , p a r a l l e l bedded and r i p p l e d sandstones and s i l t s t o n e s which o v e r l i e the cross-bedded sandstones i n some s e c t i o n s are 92 i n t e r p r e t e d as the f i n a l channel f i l l d e p o s i t s formed i n the channel as i t was abandoned or p o s s i b l y levee d e p o s i t s . In a few s e c t i o n s the t h i n sandstones and s i l t s t o n e s are absent and cross-bedded sandstones at the top of the upper u n i t are o v e r l a i n d i r e c t l y by carbonaceous mudstones. In these s e c t i o n s channel cut o f f was apparently very abrupt and the a c t i v e channel was transformed r a p i d l y i n t o a shallow pool i n which mud was d e p o s i t e d . Lower U n i t of Type 2 Channel D e p o s i t s - I n t e r p r e t a t i o n The c h a r a c t e r i s t i c s of the lower u n i t are not d i a g n o s t i c of any s i n g l e f l u v i a l s t y l e and as a r e s u l t i n t e r p r e t a t i o n of t h i s u n i t i s d i f f i c u l t . Before d i s c u s s i n g the p o s s i b l e i n t e r p r e t a t i o n s i t i s u s e f u l to summarize some of the main c h a r a c t e r i s t i c s of the lower u n i t : 1. D e p o s i t i o n a l sequences c o n s i s t of s i n g l e or stacked f i n i n g -upward u n i t s of f i n e - to c o a r s e - g r a i n e d sandstones and l o c a l l y t h i n conglomerates. The base of these sequences i s abrupt or e r o s i o n a l . 2. Primary sedimentary s t r u c t u r e s c o n s i s t predominantly of l a r g e s c a l e trough cross-bedding. Set t h i c k n e s s e s commonly decrease towards the top of fining-upward sequences. 3. Tabular cross-bedding i s very r a r e and absent i n most s e c t i o n s . 4. L a t e r a l a c c r e t i o n s u r f a c e s ( e p s i l o n cross-bedding) have not been recognised i n outcrops of the lower u n i t . 5. P a l e o c u r r e n t data shows no s i g n i f i c a n t v a r i a t i o n at two l o c a l i t i e s 2 km apart, along the trend of the channel. 93 6. Thick crevasse splay d e p o s i t s are present i n the same i n t e r v a l as the lower u n i t channel d e p o s i t s i n boreholes to the south. The absence of t a b u l a r cross-bedding i n most s e c t i o n s suggests that mid-channel f o r e s e t bars were absent and t h e r e f o r e the r i v e r system was not b r a i d e d . On M i a l l ' s (1977) c l a s s i f i c a t i o n of f l u v i a l channels ( F i g u r e 23b), t h i s leaves three other "end member" channel types, meandering, s t r a i g h t and anastomosing channels as p o s s i b l e i n t e r p r e t a t i o n s of the lower u n i t . The c l a s s i c f a c i e s model of meandering r i v e r s ( A l l e n , 1964, 1970) c o n s i s t s of a fining-upward sequence formed as a r e s u l t of the l a t e r a l m i g r a t i o n of overbank and p o i n t bar d e p o s i t s over c o a r s e r - g r a i n e d channel f l o o r d e p o s i t s . Stacking of p o i n t bar sequences c o u l d produce superimposed fining-upward sequences, s i m i l a r to those i n the lower u n i t d e p o s i t s . The best example of stacked p o i n t bar d e p o s i t s are those d e s c r i b e d by P u i g d e f a b r i g a s and Van V l i e t (1978) from the Oligocene of the Southern Pyrenees. E x c e p t i o n a l exposures i n t h i s area permit the i d e n t i f i c a t i o n of l a t e r a l a c c r e t i o n s u r f a c e s i n the upper p a r t of the p o i n t bar and s c r o l l bar topography on the top surface of the bar, c l e a r l y i n d i c a t i n g a meandering r i v e r o r i g i n . D e s p i t e the presence of good outcrops of lower u n i t sandstones at Babcock, l a t e r a l a c c r e t i o n s u r f a c e s have not been r e c o g n i s e d . The absence of l a t e r a l a c c r e t i o n s u r f a c e s , however, does not preclude a meandering r i v e r o r i g i n . Jackson (1978) has shown that these bedforms are not u b i q u i t o u s i n modern meandering r i v e r s . Perhaps the stro n g e s t argument a g a i n s t a 94 meandering r i v e r i n t e r p r e t a t i o n i s the p a l e o c u r r e n t evidence which shows no s i g n i f i c a n t v a r i a t i o n i n channel t r e n d at two l o c a l i t i e s 2 km a p a r t . S t r a i g h t (non-braided) r i v e r s (Figure 23b) are not common and p r e s e n t l y occur mainly as d e l t a d i s t r i b u t a r i e s where the slope i s very low ( M i a l l , 1981). Moody-Stuart (1966), K e l l i n g (1968), Thompson (1970) and Sykes (1974) have a l l d e s c r i b e d fining-upward sequences which they a t t r i b u t e to low s i n u o s i t y (non-braided) r i v e r systems. The channel f i l l sequences d e s c r i b e d by K e l l i n g (1968) are s i m i l a r to those of the lower u n i t of type 2 channels and c o n s i s t of s i n g l e or stacked f i n i n g -upwards sequences with a t h i n conglomerate l a g at the base o v e r l a i n by trough cross-bedded sandstone i n which set t h i c k n e s s e s decrease upwards. The'cross-bedded sandstones are o v e r l a i n by f l a t bedded or r i p p l e d sandstones at the top of the sequences and these in turn are capped by t h i n overbank d e p o s i t s and by a c o a l seam. K e l l i n g i n t e r p r e t s each fining-upward c y c l e , as the r e s u l t of the c r e a t i o n , i n f i l l i n g and eventual abandonment of separate f l u v i a l channels, probably c r e a t e d by streams of low s i n u o s i t y ; the cross-bedded sands are formed by r a p i d dumping of sediment from a high energy flow along the l e n g t h of the channel. The t h i r d p o s s i b l e i n t e r p r e t a t i o n f o r the lower u n i t d e p o s i t s i s that they formed i n an anastomosing r i v e r system(Figure 23b). Anastomosing r i v e r s are c h a r a c t e r i s e d by two or more s t a b l e channels showing low to high s i n u o s i t y . D e p o s i t i o n i s c h a r a c t e r i s e d by r a p i d v e r t i c a l aggradation r e s u l t i n g i n the formation of t h i c k but r e l a t i v e l y narrow 95 channel f i l l d e p o s i t s . Low channel g r a d i e n t s and s i n u o s i t i e s r e s u l t i n frequent overbank f l o o d i n g and d e p o s i t i o n of f i n e -g r a i n e d sediment i n wetlands (peat bogs, backswamps and floodponds). Levees and crevasse s p l a y s are common i n anastomosed r i v e r systems. Modern anastomosing r i v e r d e p o s i t s have been d e s c r i b e d by Smith and Smith (1980) and Rust (1981). Smith and Putnam (1980) have i n t e r p r e t e d Lower Cretaceous Upper M a n n v i l l e d e p o s i t s i n A l b e r t a and Saskatchewan as formed i n an anastomosing r i v e r system. They suggest the mechanism f o r anastomosis c o n s i s t s of e i t h e r a r i s i n g l o c a l base l e v e l c o n t r o l downriver or subsidence of the depocentre r e l a t i v e to a downriver reach. There i s no s i n g l e morphologic or sedimentologic c r i t e r i o n which i s unique to anastomosing r i v e r s . Smith and Putnam (1980) suggest that a d i s t i l l a t i o n of many d i f f e r e n t c r i t e r i a can a i d i n the i d e n t i f i c a t i o n of a n c i e n t anastomosed r i v e r d e p o s i t s . Important c r i t e r i a i n c l u d e the presence of l a t e r a l l y s t a b l e (few e p s i l o n c r o s s - b e d s ) , m u l t i p l e i n t e r c o n n e c t e d channels and exte n s i v e i n t e r c h a n n e l wetlands. The c h a r a c t e r i s t i c s of the lower u n i t channel d e p o s i t s and t h e i r a s s o c i a t i o n with e x t e n s i v e i n t e r c h a n n e l wetland d e p o s i t s (swamp, splay and lake d e p o s i t s ) suggests that the lower u n i t channel d e p o s i t s may have formed i n an anastomosing r i v e r system. S t r a t a e q u i v a l e n t to the lower u n i t i n w e l l s 12-20 km east of Babcock i n c l u d e the c o a s t a l d e p o s i t s of the F a l h e r C marine u n i t . The marine t r a n s g r e s s i o n at the base of the F a l h e r C u n i t would have r e s u l t e d i n a r i s i n g l o c a l base l e v e l downstream and thus p r o v i d e s a p o t e n t i a l c a u s a l mechanism f o r 96 channel anastomosis i n the Babcock a r e a . In summary, t h e r e f o r e , the most l i k e l y i n t e r p r e t a t i o n s f o r the lower u n i t d e p o s i t s are that they formed e i t h e r i n a s t r a i g h t (non-braided) or anastomosing r i v e r system. 1.8.5 Type 3 Channel D e p o s i t s - D e s c r i p t i o n Type 3 channel d e p o s i t s are present i n boreholes from the Duke Mountain area, i n the i n t e r v a l between c o a l seams B7 and B9. The d i s t r i b u t i o n and trend of these d e p o s i t s has been mapped using borehole data and i s shown on F i g u r e 35b. A c r o s s s e c t i o n ( F i g u r e 36) of the B7-B9 i n t e r v a l i n the southern p a r t of the Duke P i t , i l l u s t r a t e s the geometry and c h a r a c t e r i s t i c s of type 3 channel d e p o s i t s . Type 3 channel d e p o s i t s i n t h i s i n t e r v a l occur w i t h i n a northeast-southwest o r i e n t e d b e l t which, i n the southern p a r t of the Duke P i t has a width of approximately 2.8 km. Channel d e p o s i t s of a s i m i l a r type are a l s o present i n the i n t e r v a l between c o a l seams B8 and B9. but are much l e s s extensive.-The t h i c k n e s s of type 3 channel d e p o s i t s on the Duke P i t c r o s s s e c t i o n (Figure 36) i s f a i r l y constant a c r o s s the width of the channel and ranges from 10-12 m. The channel f i l l comprises e r o s i o n a l l y based u n i t s , 3-6 m t h i c k c o n s i s t i n g of massive conglomerates or g r a n u l a r sandstones at the base o v e r l a i n by cross-bedded and o c c a s i o n a l l y massive, medium- to c o a r s e - g r a i n e d pebbly sandsones. G r a i n - s i z e i n the sandstones remains constant or f i n e s upward w i t h i n the u n i t s . Both t a b u l a r and trough c r o s s -bedding are present, but t a b u l a r s e t s are more common. Set t h i c k n e s s e s range from 5-80 cm. Coal spar and mudstone r i p - u p 97 F i g u r e 3_5. D i s t r i b u t i o n of channel f i l l d e p o s i t s i n the i n t e r v a l s between c o a l seams B4 and B5 ( F i g u r e 35a) and B7 and B8 (F i g u r e 35b) i n the Duke Mountain a r e a . The channel f i l l d e p o s i t s i n the B4-B5 i n t e r v a l are i n t e r p r e t e d from t h e i r l o g c h a r a c t e r and c o a l company core d e s c r i p t i o n s . Channel f i l l d e p o s i t s i n the B7-B8 i n t e r v a l are i l l u s t r a t e d in more d e t a i l on F i g u r e 3_6. The boreholes shown on these maps i n c l u d e only those which were a v a i l a b l e to the author and which penetrated the i n t e r v a l of i n t e r e s t . Northwest MDD 7902 MDD 7823 MDD 7810 MDD 7905 MDD 7822 MDD 7906 Southeast MUD 8105 Coal Seam * Croaa-beddfrig sss; Tabular croaa-bedding Parallel bedding ~-<* Rlpplea (c-cSmbkig) Wood fragments Jl Roota Mdat-/altst. rip-up claata _ Carbonaceoua mudatone cr? Soft aediment deformation atructureal Figure 36. Borehole cross section of the interval between coal seams B7 and B9 in the Duke Mountain area showing the c h a r a c t e r i s t i c s of type 3 channel deposits and associated overbank sediments. The d i s t r i b u t i o n of the larger channel between seams B7 and B8 and the borehole locations are shown on Figure 3]5. Section constructed with the base of the B9 seam as horizontal datum. KO CO 99 c l a s t s are common near the bases of the u n i t s . The cross-bedded sandstones at the top of type 3 channel d e p o s i t s are o v e r l a i n by a 3 to 7 m t h i c k i n t e r v a l of interbedded f i n e - g r a i n e d sandstones and s i l t s t o n e s . The sandstones range i n t h i c k n e s s from a few centimetres to 2.2 m and are t h i c k e s t near the base of the i n t e r v a l . The base of sandstone beds i n t h i s i n t e r v a l are abrupt or e r o s i o n a l and small s i l t s t o n e r i p - u p c l a s t s are o c c a s i o n a l l y p r e s e n t . Primary sedimentary s t r u c t u r e s i n c l u d e p a r a l l e l bedding, r i p p l e s and c l i m b i n g r i p p l e s . Some beds are massive due to strong b i o t u r b a t i o n . S o f t sediment deformation s t r u c t u r e s are common near the top. Roots and p l a n t fragments are present i n some beds. These d e p o s i t s grade upwards i n t o massive, b i o t u r b a t e d s i l t s t o n e s and carbonaceous mudstones which are o v e r l a i n by the B8 c o a l seam. 1.8.6 Type 3 Channel D e p o s i t s - I n t e r p r e t a t i o n These d e p o s i t s are very s i m i l a r to the upper u n i t of type 2 channel d e p o s i t s and t h e r e f o r e they are a l s o i n t e r p r e t e d as br a i d e d r i v e r d e p o s i t s . Type 3 d e p o s i t s d i f f e r from type 2 (upper u n i t ) d e p o s i t s i n that they do not form p a r t of a composite channel f i l l sequence showing d i f f e r e n t f l u v i a l s t y l e s . 1.8.7 Type 4 Channel Deposits - D e s c r i p t i o n Type 4 channel d e p o s i t s are present i n cores and outcrops in the southern p a r t of the study area near Mount B e l c o u r t ( F i g u r e s 6, 37, 38, 39). L i t h o l o g i e s c o n s i s t mainly of coarse 100 conglomerates, with minor amounts of f i n e - to c o a r s e - g r a i n e d « sandstones, o c c u r r i n g i n u n i t s 12-40 m t h i c k . Near Mount B e l c o u r t , up to 3 separate conglomerate u n i t s are present i n the non-marine part of the Gates Formation. The t h i c k e s t and l a t e r a l l y most extensive conglomerate, which w i l l be r e f e r r e d to as conglomerate 1, occurs i n the lower p a r t of the Gates Formation. Pebbles i n t h i s conglomerate are of t e n c o a r s e r than in conglomerates higher i n the s e c t i o n . The data on c r o s s s e c t i o n 2 (Fi g u r e 6) suggests that conglomerate 1 may be present in a continuous northwest-southeast t r e n d i n g b e l t , 20 km long near Mount B e l c o u r t . Conglomerates at the same s t r a t i g r a p h i c l e v e l are a l s o present i n borehole BD 7808, 18 km east of Mount B e l c o u r t and BD8003, 15 km northeast of Mount B e l c o u r t . Conglomerates higher i n the s e c t i o n (conglomerate 2 and conglomerate 3, F i g u r e 6) are a r e a l l y l e s s e x t e n s i v e than conglomerate 1. The g r e a t e s t cumulative t h i c k n e s s of conglomerate i n the Gates Formation i n t h i s area i s 50 m. Th i s occurs on Dumb Goat Mountain, 3 km northwest of Mount B e l c o u r t ( F i g u r e s 38, 39). The conglomerates are p o o r l y s o r t e d and mainly c l a s t supported with a sandstone matrix. Matrix supported conglomerates are present l o c a l l y but are much l e s s common. C l a s t s are w e l l rounded and range i n s i z e from small pebbles to cobbles. Most c l a s t s have intermediate diameters of 2-3 cm or more. The l a r g e s t c l a s t observed measured 16x7x7 cm. Rounded c l a s t s o f t e n show good i m b r i c a t i o n ( F i g u r e 40). In outcrops on Dumb Goat Mountain ( F i g u r e s 37,39) conglomerates, o c c a s i o n a l l y interbedded with t h i n l e n s e s of 101 igure 37. Format i Creek F Mounta i the non d e p o s i t imbrica towards MBD 782 are e i t i n t e r v a numerou Hu l c r o s Outcrop s e c t i o n of the Moosebar on, H u l c r o s s Formation and lower ormation from a r i d g e on the nort n. Three t h i c k conglomerate i n t e r -marine p a r t of the Gates Formati s ) . The rose diagrams show the d i ted pebbles and i n d i c a t e p a l e o c u r the n o r t h and n o r t h e a s t . Nearby 8 and BDD 7601, shown on F i g u r e 6 her 3 or 4 t h i c k seams (>1.5 m) i Is between the Torrens Member and s t h i n seams (<1.5 m) between con s Formation. Formation p a r t of t h s i d e of v a l s are on (type p d i r e c t i r e n t s d i r boreholes ) i n d i c a t n the cov conglome glomerate Gates he Boulder Dumb Goat present i n "4 channel on of e c t e d (DG 81-01 , e that there ered r a t e 3, and 3 and the 102 F i g u r e 38. View towards the north of the F o o t h i l l s i n the southern p a r t of the study area. The peak i n the ce n t r e i s Mount B e l c o u r t . Dumb Goat Mountain i s l o c a t e d 3 km to the northwest. On Mount B e l c o u r t and Dumb Goat Mountain, Cretaceous rocks d i p towards the southwest beneath a major t h r u s t f a u l t which b r i n g s forward P a l e o z o i c and Mesozoic rocks of the Rocky Mountain Front Ranges. 1 04 sandstone, form e r o s i o n a l l y based, massive u n i t s up to 24 m t h i c k . Impressions of l a r g e logs are common near the bases. Large s c a l e bedforms c o n s i s t i n g of g e n t l y d i p p i n g s u r f a c e s which extend h o r i z o n t a l l y f o r d i s t a n c e s of approximately 20-30 m are present i n outcrops of conglomerates 2 and 3. These bedforms form e r o s i o n a l s u r f a c e s w i t h i n u n i t s of massive conglomerate or occur at the base of massive conglomerate u n i t s which o v e r l y h o r i z o n t a l l y bedded sandstone and t h i n conglomerates. They are a l s o present between u n i t s of massive conglomerate without any evidence of e r o s i o n . Two main types of v e r t i c a l sequences are present i n type 4 channel d e p o s i t s . These w i l l be r e f e r r e d to as type 4A and type 4B sequences. In type 4A sequences (e.g., Conglomerate 1 on Dumb Goat Mountain and i n boreholes MXD 7827 and BDD 7601, F i g u r e 6) sandstones are minor and almost the e n t i r e i n t e r v a l c o n s i s t s of conglomerate. The tops of these sequences are very abrupt; overbank d e p o s i t s c o n s i s t i n g of t h i n interbedded s i l t s t o n e s and f i n e - g r a i n e d sandstones which grade upwards i n t o carbonaceous mudstone and c o a l r e s t d i r e c t l y on top of the conglomerates. Type 4B sequences d i f f e r from type 4A i n that sandstones make up a much l a r g e r p r o p o r t i o n of the i n t e r v a l and the top con t a c t of the channel f i l l sequences i s l e s s abrupt. Conglomerate 2 on Dumb Goat Mountain ( F i g u r e s 6, 37) i s an example of t h i s type of sequence. The lower p a r t of conglomerate 2 c o n s i s t s of a u n i t of massive conglomerate, 10.5 m t h i c k . T h i s i s o v e r l a i n by a 20 m t h i c k i n t e r v a l of cross-bedded sandstones (Figure 41) and t h i n conglomerates. Towards the top, the sandstones become f i n e r - g r a i n e d and e x h i b i t p a r a l l e l bedding and 105 F i g u r e 4 0 . T y p i c a l c l a s t supported f a b r i c of conglomerates on Dumb Goat Mountain. Note the w e l l developed i m b r i c a t i o n i n elliptical c l a s t s . C l a s t s are w e l l rounded and c o n s i s t mainly of q u a r t z i t e and c h e r t with l e s s e r amounts of q u a r t z o s e sandstone, limestone, s i l t s t o n e , a r g i l l i t e , mudstone and dolomite. F i g u r e 4J_. Tabular cross-bedding in sandstones o v e r l y i n g conglomerate 2 . 1 06 r i p p l e d r i f t c r o s s l a m i n a t i o n . P a l e o c u r r e n t data from type 4 channel d e p o s i t s on Dumb Goat Mountain are shown on F i g u r e 37. Measurements of pebble i m b r i c a t i o n show p a l e o c u r r e n t s d i r e c t e d towards the northeast for conglomerates 1 and 2 and towards the north f o r conglomerate 3. 1.8.8 Type 4 Channel Deposits - I n t e r p r e t a t i o n The conglomerates and sandstones of type 4 channel d e p o s i t s are i n t e r p r e t e d as proximal b r a i d e d r i v e r d e p o s i t s by comparison with the f a c i e s and environments of modern and a n c i e n t , coarse a l l u v i a l sediments (Rust, 1972, 1978, 1979; C o l l i n s o n , 1978; M i a l l , 1977). Type 4 channel d e p o s i t s have been recognised only i n the area near Mount B e l c o u r t . The l a r g e s i z e of c l a s t s i n the conglomerates i n d i c a t e s that d u r i n g d e p o s i t i o n of the Gates Formation, the area near Mount B e l c o u r t must have been l o c a t e d c l o s e to the mountain f r o n t . In t h i s s e t t i n g i t i s p o s s i b l e that type 4 b r a i d e d channels were l o c a t e d e n t i r e l y w i t h i n an a l l u v i a l fan. On l a r g e , modern day a l l u v i a l fans, i n a humid c l i m a t e , i t i s d i f f i c u l t to separate the processes from those of proximal braided r i v e r s ( C o l l i n s o n , 1978) and thus the r e s u l t i n g f a c i e s are l i k e l y to be very s i m i l a r . D i s t i n c t i o n between the d e p o s i t s of a n c i e n t humid a l l u v i a l fans and proximal b r a i d e d r i v e r s depends to a l a r g e extent on the geometry of the d e p o s i t s ; a l l u v i a l fans t y p i c a l l y form a "cone" shaped wedge of sediment or, i n the case of c o a l e s c i n g a l l u v i a l fans (bajadas), a narrow l i n e a r wedge p a r a l l e l to the mountain f r o n t , while the geometry 1 07 of b r a i d e d r i v e r , d e p o s i t s would l i k e l y be more l i n e a r and o r i e n t e d at a h i g h angle to the mountain f r o n t . Boreholes are too widely spaced to a c c u r a t e l y d e f i n e the shape of i n d i v i d u a l conglomerate u n i t s and thus i t i s not known whether type 4 proximal b r a i d e d r i v e r d e p o s i t s were l o c a t e d o u t s i d e or w i t h i n an a l l u v i a l f an. Conglomerate 1, however, which c o n t a i n s the c o a r s e s t c l a s t s and i s l a t e r a l l y more ex t e n s i v e p a r a l l e l to the mountain f r o n t than conglomerates 2 and 3, i s the best candidate f o r an a l l u v i a l fan i n t e r p r e t a t i o n . Massive c l a s t supported conglomerate, i n which the c l a s t s are f r e q u e n t l y i m b r i c a t e d , i s the most common f a c i e s i n type 4 d e p o s i t s . In modern proximal b r a i d e d r i v e r s t h i s f a c i e s occurs as channel lags and i n l o n g i t u d i n a l bars (Rust, 1972; Boothroyd and Ashley, 1975). Thick u n i t s of c l a s t supported conglomerate in type 4 channel d e p o s i t s are i n t e r p r e t e d as the r e s u l t of s t a c k i n g of channel and bar sequences. The occurrence of i n t e r n a l e r o s i o n s u r f a c e s w i t h i n some t h i c k conglomerates supports t h i s i n t e r p r e t a t i o n . Thinner u n i t s of p a r a l l e l bedded and cross-bedded sandstones interbedded with the t h i c k conglomerates are probably the r e s u l t of a c c r e t i o n d u r i n g a low water stage (Doeglas, 1962). Matrix supported conglomerates which are present l o c a l l y i n some s e c t i o n s are i n t e r p r e t e d as d e b r i s flow d e p o s i t s . Debris flows u s u a l l y extend only a few k i l o m e t r e s from a mountainous source area and are most t y p i c a l of a l l u v i a l fans ( B u l l , 1972; Rust, 1978, 1979). Tabular c r o s s -bedding i n sandstones at the top of type 4B sequences may have formed as a r e s u l t of the m i g r a t i o n of sand waves or avalanche s l i p faces on the margins of l i n g u o i d or t r a n s v e r s e bars. 108 The modern a l l u v i a l d e p o s i t s of the Kosi R i v e r (Gole and C h i t a l e , 1966; C o l l i n s o n , 1978) are a good modern analogue, i n terms of r i v e r type and t e c t o n i c s e t t i n g , f o r type 4 channel d e p o s i t s . The s c a l e of the Kosi R i v e r d e p o s i t s , however, i s much l a r g e r . 109 1.8.9 Type "5 Channel Deposits - D e s c r i p t i o n Type 5 channel d e p o s i t s have been recognised i n only a few cores and i n outcrops on Dumb Goat Mountain above conglomerate 3 ( F i g u r e s 6, 37) . These d e p o s i t s occur mainly i n the upper Gates i n the southern p a r t of the study area. They are a l s o present lower i n the s e c t i o n between the E and F seams at Babcock and above the #3 seam in borehole 7726 (Figure 6) i n the Saxon a r e a . L i t h o l o g i e s c o n s i s t mainly of f i n e - to c o a r s e - g r a i n e d sandstones. G e n e r a l l y , the sandstones form a s i n g l e f i n i n g -upward sequence 3-8 m t h i c k . In a few s e c t i o n s , s t a c k i n g of fining-upward sequences produces t h i c k e r u n i t s up to 14m t h i c k . The base of these u n i t s i s abrupt or e r o s i o n a l . Sandstones near the base are t y p i c a l l y massive and o f t e n c o n t a i n mudstone r i p - u p c l a s t s and c o a l spar. Thin pebbly s t r e a k s are present i n a few s e c t i o n s near the base. Primary sedimentary s t r u c t u r e s c o n s i s t mainly of trough cross-bedding which occurs i n s e t s 5 cm - 1m t h i c k . Sets t h i c k e r than 30 cm are uncommon. In some s e c t i o n s , set t h i c k n e s s decreases towards the top. Tabular cross-bedding i s a l s o present, but i s l e s s common. P a r a l l e l bedding and r i p p l e s occur at the top of the fining-upward sequences. Type 5 channel d e p o s i t s are o v e r l a i n g r a d a t i o n a l l y by t h i n interbedded f i n e - g r a i n e d sandstones and s i l t s t o n e s . These d e p o s i t s are g e n e r a l l y o v e r l a i n by carbonaceous mudstone and c o a l . 1.8.10 Type 5 Channel Deposits - I n t e r p r e t a t i o n 1 10 F i g u r e 42^ Summary of " f l u v i a l " p a l e o c u r r e n t data i n the Gates Formation. T h i s diagram does not i n c l u d e data from the upper Gates, north of Kinuseo Creek which i s shown on F i g u r e s 5_5 and 65. 111 Type 5 channel d e p o s i t s are i n t e r p r e t e d as forming in a meandering r i v e r system based on t h e i r s i m i l a r i t i e s with the c l a s s i c fining-upward f a c i e s model of meandering r i v e r s ( A l l e n 1964, 1970). By analogy with t h i s model the massive and c r o s s -bedded sandstones i n type 5 fining-upward sequences are i n t e r p r e t e d as channel f i l l and p o i n t bar d e p o s i t s , while the o v e r l y i n g p a r a l l e l bedding and r i p p l e d sandstones are i n t e r p r e t e d as forming i n the shallower p a r t s of the p o i n t bar and l e v e e s . 1.8.11 Summary of F l u v i a l P a l e o c u r r e n t Data P a l e o c u r r e n t data c o l l e c t e d from f l u v i a l channel sandstones and conglomerates i n the non-marine i n t e r v a l above the Torrens Member i s shown on Figure.42. T h i s f i g u r e does not i n c l u d e a d d i t i o n a l data from channel d e p o s i t s i n the upper Gates north of Kinuseo Creek which i s shown i n F i g u r e s 55 and 65. Measurements were.made of trough and.tabular cross-bedding, trough axes, pebble i m b r i c a t i o n and o r i e n t e d wood fragments and l o g s i n the channel d e p o s i t s . The data shows average p a l e o c u r r e n t v e c t o r s towards the northwest, north, northeast and e a s t . Most of the p a l e o c u r r e n t s are in a n o r t h e a s t e r l y d i r e c t i o n . T h i s measured data i s i n agreement with channel trends mapped i n areas with c l o s e l y spaced boreholes ( F i g u r e s 32, 35). 1.9 OVERBANK DEPOSITS Overbank d e p o s i t s are the most common f a c i e s encountered i n the non-marine i n t e r v a l s i n the Gates Formation. Many of the 1 12 f a c i e s present i n Gates overbank d e p o s i t s have c h a r a c t e r i s t i c s s i m i l a r to those d e s c r i b e d by Coleman (1966) and K r i n i t z s k y and Smith (1969) i n recent sediments of the A t c h a f a l a y a River Basin, Lousiana. The A t c h a f a l a y a River Basin c o n s i s t s of some 7680 km2 of swamplands and lakes which were formed when the low l y i n g c e n t r a l p a r t of the lower M i s s i s s i p p i a l l u v i a l v a l l e y became completely surrounded by a l l u v i a l r i d g e s of the present and former M i s s i s s i p p i R i v e r system. S p e c i f i c environments recognised and d e s c r i b e d by Coleman (1966) i n c l u d e p o o r l y d r a i n e d (stagnant) swamps, w e l l - d r a i n e d swamps, l a k e s , l a c u s t r i n e d e l t a s and channels. In the Gates Formation four main overbank f a c i e s have been i d e n t i f i e d based l a r g e l y on Coleman's d e s c r i p t i o n of the Recent sediments i n the A t c h a f a l a y a River Basin and summaries of overbank d e p o s i t s i n Reineck and Singh (1973) and C o l l i n s o n (1978) . 1. N a t u r a l levee d e p o s i t s 2. Crevasse splay ( i n c l u d i n g l a c u s t r i n e d e l t a ) d e p o s i t s 3. Lake d e p o s i t s 4. Well t o p o o r l y d r a i n e d swamp d e p o s i t s 1.9.1 N a t u r a l Levee Deposits Levees are wedge shaped r i d g e s of sediment b o r d e r i n g stream channels, formed by d e p o s i t i o n of sediment when floodwaters from the stream overtops i t s banks (Reineck and Singh, 1973, p. 244). N a t u r a l levee d e p o s i t s i n the Gates Formation c o n s i s t of fining-upward sequences of interbedded f i n e - to medium-grained sandstones and s i l t s t o n e s . The sandstones are c h a r a c t e r i s e d by 113 abrupt or e r o s i o n a l bases and range i n t h i c k n e s s from a few centimetres to 2.2 m. Small s i l t s t o n e r i p - u p c l a s t s and carbonaceous laminae are present i n some beds. Primary sedimentary s t r u c t u r e s c o n s i s t of r i p p l e s , c l i m b i n g r i p p l e s and p a r a l l e l bedding. Cross-bedding ( s e t s l e s s than 10 cm t h i c k ) and massive beds are o c c a s i o n a l l y present but are much l e s s common. Soft sediment deformation s t r u c t u r e s are f r e q u e n t l y present i n the upper p a r t s of the fining-upward sequences. Roots and burrows are present i n some beds. Levee d e p o s i t s o v e r l i e channel f i l l d e p o s i t s and grade upwards i n t o f i n e - g r a i n e d , b i o t u r b a t e d and roo t e d s i l t s t o n e s , and mudstones which are f r e q u e n t l y o v e r l a i n by c o a l . They are a l s o found i n cores marginal to channel f i l l d e p o s i t s and i n t h i s p o s i t i o n are d i f f i c u l t to d i s t i n g u i s h from c r e v a s s e splay d e p o s i t s which are s i m i l a r . 1.9.2 Crevasse S p l a y 1 Deposits •• In the Babcock area crevasse splay d e p o s i t s are an 1 Crevasse splay and l a c u s t r i n e d e l t a d e p o s i t s are s i m i l a r . In ancient d e p o s i t s they are d i s t i n g u i s h e d mainly on the b a s i s of f a c i e s a s s o c i a t i o n , with l a c u s t r i n e d e l t a d e p o s i t s o c c u r r i n g s t r a t i g r a p h i c a l l y above lake d e p o s i t s . In the Gates Formation p o s i t i v e i d e n t i f i c a t o n of sediments as l a c u s t r i n e i n o r i g i n i s of t e n d i f f i c u l t and so consequently the term cr e v a s s e s p l a y w i l l be a p p l i e d to a l l d e p o s i t s of t h i s type, i r r e s p e c t i v e of the f a c i e s which they o v e r l i e . 1 1 4 important component of the overbank f a c i e s i n the i n t e r v a l s between c o a l seams J and G/l and the G/I and F seams. These d e p o s i t s have been s t u d i e d using core and l o g data from c l o s e l y spaced boreholes. Sandstone isopach maps ( F i g u r e s 32a, 43) have been c o n s t r u c t e d f o r both i n t e r v a l s to show the d i s t r i b u t i o n of the splay and a s s o c i a t e d f l u v i a l channel d e p o s i t s . On the sandstone isopach map of the lower part of the J -G/l1 i n t e r v a l ( F i g u r e 32a), two l a r g e lobes are present southeast of a major, ENE-WSW t r e n d i n g f l u v i a l channel (lower p a r t of type 2 channel d e p o s i t s d e s c r i b e d i n s e c t i o n 1.8.3). Sediments i n these lobes are i n t e r p r e t e d as crevasse splay d e p o s i t s based on t h e i r shape, f a c i e s a s s o c i a t i o n s and i n t e r n a l c h a r a c t e r i s t i c s . The crevasse s p l a y s extend f o r a d i s t a n c e of approximately 1.3 km away from the channel and are approximately 1.3-1.6 km wide. The d i s t r i b u t i o n of crevasse splay d e p o s i t s i n the i n t e r v a l between c o a l seams G/l1 and. F are.shown on the sandstone isopach map (Figure '43). In t h i s i n t e r v a l , splay d e p o s i t s are present i n 12 boreholes w i t h i n an area of approximately 4.4 km2. The d e p o s i t s t h i c k e n toward the south suggesting that the s p l a y d e p o s i t s o r i g i n a t e d from a f l u v i a l channel i n that d i r e c t i o n . The d i s t r i b u t i o n and trend of t h i s f l u v i a l channel i s u n c e r t a i n due to the l a c k of boreholes south of the splay d e p o s i t s . In these i n t e r v a l s , two d i s t i n c t types of sequences are present i n the proximal and d i s t a l p a r t s of the crevasse s p l a y s . The c h a r a c t e r i s t i c s of proximal and d i s t a l s p l a y d e p o s i t s are shown on F i g u r e s 31, 44 and 45. 115 F i g u r e 4_3. Sandstone isopach map showing the l o c a t i o n of s p l a y d e p o s i t s i n the i n t e r v a l between c o a l seams G / I l and F i n the Babcock a r e a . 116 PS - Proximal Splay Deposits DS-D l s ta l Splay Deposits F i g u r e 44. Borehole c r o s s s e c t i o n showing the c h a r a c t e r i s t i c s of cr e v a s s e s p l a y and other overbank d e p o s i t s i n the i n t e r v a l between c o a l seams H a n d F i n the Babcock a r e a . Note the occurrence of mainly fining-upward sequences i n the proximal s p l a y d e p o s i t s and coarsening-upward sequences i n the d i s t a l s p l a y d e p o s i t s . Borehole l o c a t i o n s are shown on F i g u r e 43. Legend i s shown on F i g u r e 2 4. 1 17 Proximal Splay Deposits These d e p o s i t s c o n s i s t of very f i n e - to medium-grained sandstone with l e s s e r amounts of s i l t s t o n e . The sandstones are g e n e r a l l y s i l t y and o c c a s i o n a l l y c o n t a i n carbonaceous laminae.. Proximal s p l a y d e p o s i t s are c h a r a c t e r i s e d by f i n i n g - upward sequences which range i n t h i c k n e s s from 0.5-5 m. S t a c k i n g of fining-upward sequences r e s u l t s i n proximal splay d e p o s i t s which are up to 22 m t h i c k . Based on t h e i r t h i c k n e s s and i n t e r n a l c h a r a c t e r i s t i c s , proximal splay d e p o s i t s can be s u b d i v i d e d i n t o 2 main types: Type A: Examples of type A sequences are present i n boreholes 7712 between the F and G/l1 c o a l seams (Figure 44) and i n borehole 7751 above the J seam (F i g u r e 31). The main l i t h o l o g y i n type A sequences i s sandstone which occurs i n u n i t s 1.5 - 5 m t h i c k . The base of these u n i t s i s abrupt or e r o s i o n a l . S i l t s t o n e pebbles, r i p - u p c l a s t s and c o a l spar are common immediately above the base. Primary sedimentary s t r u c t u r e s i n the lower p a r t of the sandstones c o n s i s t mainly of trough c r o s s - b e d d i n g . Set t h i c k n e s s v a r i e s between 5-20 cm. P a r a l l e l bedding and r i p p l e s are o c c a s i o n a l l y p r e s e n t . In a few c o r e s , sandstones above the base are massive. Bedding i n the upper part of the sandstones c o n s i s t s mainly of c u r r e n t r i p p l e and c l i m b i n g r i p p l e l a m i n a t i o n and p a r a l l e l bedding. In most s e c t i o n s the sandstones grade upward i n t o a sequence of t h i n interbedded s i l t s t o n e s and sandstones i n which s o f t sediment deformation s t r u c t u r e s and p a r a l l e l bedding are common. In a few cores the tops of the sandstones are 1 18 abrupt and they are o v e r l a i n d i r e c t l y by s i l t s t o n e . Type B: Examples of type B sequences are present i n boreholes 7201 and 7712 between the F and G/l1 c o a l seams (Figure 44). Sandstones and s i l t s t o n e s i n type B sequences occur mainly w i t h i n fining-upward u n i t s which range i n t h i c k n e s s from 0.5-3 m. The base of these u n i t s i s abrupt or e r o s i o n a l . O c c a s i o n a l l y , the sandstones occur i n beds up to 1.5 m t h i c k , with abrupt bases and tops, and without any obvious g r a i n - s i z e v a r i a t i o n s . Upper flow regime p a r a l l e l bedding and r i p p l e s are common i n type B sequences. C r o s s -bedding i s present i n a few beds. In borehole 7201, sequences are present which suggest d e c r e a s i n g flow power d u r i n g d e p o s i t i o n . These c o n s i s t of the f o l l o w i n g : e r o s i v e base; massive bed with s i l t s t o n e r i p - u p c l a s t s , upper flow regime p a r a l l e l bedding, r i p p l e s , s i l t s t o n e . In s e v e r a l beds, t a b u l a r f o r e s e t s up to 20 cm t h i c k occur d i r e c t l y above the base. T h e s e . f o r e s e t s are o v e r l a i n by r i p p l e s and then p a r a l l e l bedding (Figure 46b). Convolute bedding i s o c c a s i o n a l l y present i n the s i l t s t o n e s . In borehole 7201 the top of the type B sequence i s marked by a 1 m t h i c k bed of sandstone which has been s t r o n g l y b i o t u r b a t e d by burrowing organisms. D i s t a l Splay Deposits These d e p o s i t s are c h a r a c t e r i s e d by coarsening-upward sequences of interbedded sandstone, s i l t s t o n e and minor mudstone which range i n t h i c k n e s s from 1-6 m ( F i g u r e s 44, 45). S t a c k i n g 119 F i g u r e £5. Core from borehole QBD 7219 i n the Babcock area showing the c h a r a c t e r i s t i c s of d i s t a l c r evasse s p l a y d e p o s i t s . L i t h o l o g i e s c o n s i s t . o f t h i n interbedded s i l t s t o n e s and f i n e - g r a i n e d sandstones which e x h i b i t p a r a l l e l bedding, r i p p l e s and c l i m b i n g r i p p l e l a m i n a t i o n . Core corresponds to the 16 m t h i c k i n t e r v a l above the 11 seam i n borehole 7219 shown on F i g u r e 44. 121 of coarsening-upward sequences r e s u l t s i n d i s t a l splay d e p o s i t s which are up to 13 m t h i c k . The coarsening-upward sequences are best d e f i n e d by the gamma ray l o g and are o f t e n not immediately apparent from an i n i t i a l examination of the co r e . D i s t a l s p l ay d e p o s i t s g r a d a t i o n a l l y o v e r l y i n f e r r e d lake or swamp d e p o s i t s and are o c c a s i o n a l l y present above proximal s p l a y d e p o s i t s . They are o v e r l a i n a b r u p t l y by swamp and l o c a l l y by proximal splay d e p o s i t s . The sandstones i n d i s t a l splay d e p o s i t s are very f i n e - to f i n e - g r a i n e d and s i l t y with o c c a s i o n a l carbonaceous laminae. They occur i n beds up to 1.5 m t h i c k and commonly t h i c k e n v e r t i c a l l y w i t h i n the coarsening-upward sequences. Interbedded s i l t s t o n e s are darker i n c o l o u r and grade l o c a l l y i n t o s i l t y mudstone. Often the s i l t s t o n e s and mudstones are s t r o n g l y b i o t u r b a t e d by burrowing organisms and o c c a s i o n a l l y by r o o t s . Primary sedimentary s t r u c t u r e s c o n s i s t mainly of p a r a l l e l bedding, c u r r e n t r i p p l e s ( F i g u r e s 45,46) and c l i m b i n g r i p p l e l a m i n a t i o n . Cross bedding i s very r a r e . S o f t sediment deformation s t r u c t u r e s (mainly convolute bedding) are f a i r l y common i n these d e p o s i t s . 1.9.3 O r i g i n of the Crevasse Splay Deposits Crevasse s p l a y s are formed d u r i n g f l o o d s when l a r g e q u a n t i t i e s of f l o o d water and sediment break through the c o n f i n i n g levees of r i v e r channels i n t o the adjacent overbank area. The d e p o s i t s of crevasse s p l a y s occur as fans or tongues of sand elongated away from the r i v e r and o r i g i n a t i n g at a crevasse channel cut i n the levee ( A l l e n , 1965; Coleman, 1969). 122 F l o o d i n g by modern r i v e r s i s achieved by crevasse and overbank mechanisms ( E l l i o t , 1974, 1978). During c r e v a s s i n g , sediment laden f l o o d waters flow i n t o the adjacent overbank area v i a small d i s c r e t e crevasse channels. Based on t h e i r s i m i l a r i t y to s mall channel f i l l d e p o s i t s and f a c i e s a s s o c i a t i o n s , type A sequences are i n t e r p r e t e d as crevasse channel d e p o s i t s . The stacked fining-upward sequences are a t t r i b u t e d t o repeated f l o o d e p i sodes. During overbank f l o o d i n g , sediment laden waters s p i l l over the r i v e r banks as sheet flows. The c o a r s e s t sediment i s d e p o s i t e d adjacent to the channel as a l t e r n a t i o n s of t h i n , e r o s i v e based graded u n i t s with p a r a l l e l and c u r r e n t r i p p l e l a m i n a t i o n s . McKee, et a l . (1967) has d e s c r i b e d modern sheet f l o o d d e p o s i t s , from a s i n g l e f l o o d that are up to 3.6 m t h i c k . The dominant sedimentary s t r u c t u r e i n these d e p o s i t s i s upper flow regime p a r a l l e l bedding. Other s t r u c t u r e s present i n c l u d e c l i m b i n g r i p p l e l a m i n a t i o n , cross-bedding and convolute, bedding. Low to high angle f o r e s e t s occur at the margin of sand sheets. Based on t h e i r s i m i l a r i t y with these d e p o s i t s , type B sequences are i n t e r p r e t e d as sheet f l o o d d e p o s i t s . Fining-upward sandstone u n i t s comprising the sequence: e r o s i v e base, massive bed with s i l t s t o n e r i p - u p c l a s t s , upper flow regime p a r a l l e l bedding, r i p p l e s , s i l t s t o n e presumably represent a s i n g l e f l o o d episode. Sets of high angle t a b u l a r cross-bedding are i n t e r p r e t e d as forming by the p r o g r a d a t i o n of avalanche s l i p f aces at the margins of sand sheets. In a d d i t i o n to forming by overbank f l o o d i n g from the r i v e r channels, sheet f l o o d d e p o s i t s i n these splay d e p o s i t s may have o r i g i n a t e d by overbank f l o o d i n g from the 1 23 crevasse channels themselves. The g r a i n - s i z e of crevasse splay d e p o s i t s f i n e s away from the r i v e r channel (Welder, 1959; Coleman, 1976, p. 38). Thus, du r i n g the p r o g r a d a t i o n of crevasse splay d e p o s i t s i n t o an overbank area a coarsening-upward sequence i s formed. There are numerous examples of coarsening-upward sequences i n modern and a n c i e n t splay d e p o s i t s (e.g., E l l i o t , 1974; Coleman, 1976; Home et a l . , 1977; E t h r i d g e et a l . , 1981). In the s p l a y d e p o s i t s between the J and F seams at Babcock (F i g u r e s 31, 44), coarsening-upward sequences occur mainly i n the d i s t a l p a r t s of the s p l a y s while fining-upward sequences, a s s o c i a t e d with crevasse channel and sheet flow d e p o s i t s , predominate i n the proximal p a r t of the s p l a y s . 1.9.4 Lake D e p o s i t s I n f e r r e d l a c u s t r i n e d e p o s i t s c o n s i s t of medium to dark grey, o c c a s i o n a l l y l i g h t olive-brown mudstones interbedded with t h i n s i l t s t o n e s and very f i n e - g r a i n e d sandstones. Thin p a r a l l e l l a m i n a t i o n i s c h a r a c t e r i s t i c of th'irs f a c i e s and i s formed by f i n e a l t e r n a t i o n s of mudstone and s i l t s t o n e or very f i n e - g r a i n e d sandstone, or by a l t e r n a t i n g c o l o u r bands (0.1-1 cm t h i c k ) i n mudstone ( F i g u r e s 34, 46e, 4 6 f ) . Other primary sedimentary s t r u c t u r e s present i n c l u d e l e n t i c u l a r bedding and r i p p l e s . S o f t sediment deformation s t r u c t u r e s are o c c a s i o n a l l y p r e s e n t . B i o t u r b a t i o n v a r i e s from absent to s t r o n g . Burrows i n these d e p o s i t s g e n e r a l l y c o n s i s t of 0.5-2 cm wide, v e r t i c a l or i n c l i n e d tubes. In the McConkey road cut s e c t i o n , b i v a l v e s were found i n a 124 0.5 m t h i c k bed of massive mudstone, 1 m above the J c o a l seam. T h i s mudstone i s o v e r l a i n by a 6 m t h i c k coarsening-upward sequence of p a r a l l e l laminated mudstones, s i l t s t o n e s and t h i n very f i n e - g r a i n e d sandstones. The b i v a l v e s were subsequently i d e n t i f i e d as non-marine u n i o n i d s of the subgenus Pleurobema  r a f i n e s q u e 1820 by Dr. J.A. J e l e t z k y (G.S.C., Ottawa). Lake d e p o s i t s and some swamp d e p o s i t s are s i m i l a r and o f t e n d i f f i c u l t to d i s t i n g u i s h . The presence of p a r a l l e l l a m i n a t i o n , the absence of root s and the g e n e r a l l y lower l e v e l s of b i o t u r b a t i o n are the main c h a r a c t e r i s t i c s which were used to d i s t i n g u i s h lake d e p o s i t s from swamp d e p o s i t s . Lake d e p o s i t s i n the Gates Formation occur i n two d i s t i n c t f a c i e s a s s o c i a t i o n s . Most commonly they are present above swamp d e p o s i t s and are o v e r l a i n by coarsening-upward sequences of crevasse s p l a y / l a c u s t r i n e d e l t a d e p o s i t s . The l a c u s t r i n e d e p o s i t s merge t r a n s i t i o n a l l y upwards with the s p l a y / l a c u s t r i n e d e l t a d e p o s i t s and there i s no sharp break between the two fac i e s . In the second type of a s s o c i a t i o n , l a c u s t r i n e sediments o v e r l i e a b r u p t l y f l u v i a l channel f i l l d e p o s i t s and grade upwards i n t o swamp or splay d e p o s i t s . An example of t h i s type of f a c i e s a s s o c i a t i o n i s i l l u s t r a t e d by the core photographs of borehole QBD 7715 (Fi g u r e 34) from the Babcock area. In t h i s example a 5 m i n t e r v a l of dark grey p a r a l l e l laminated and massive, carbonaceous mudstones and s i l t s t o n e s are present above c r o s s -bedded, c o a r s e - g r a i n e d and pebbly f l u v i a l channel f i l l sandstones. The mudstones and s i l t s t o n e s are o v e r l a i n by a 2.5 m t h i c k c o a l seam. The c h a r a c t e r i s t i c s of the mudstones and 125 F i g u r e £6. Core photographs of overbank d e p o s i t s . F i g u r e 46a. I n t r a f o r m a t i o n a l conglomerate composed of s i l t s t o n e r i p - u p c l a s t s . T h i s core i s from a u n i t which i s 55 cm t h i c k and was probably formed by a s i n g l e f l o o d event. (MDD 7823, 360.1 m). Fi g u r e 46b. The i n t e r n a l c h a r a c t e r i s t i c s of the sediment i n t h i s core are i n t e r p r e t e d as the r e s u l t of a s i n g l e sheet f l o o d event; the onset of the f l o o d i s marked by s i l t s t o n e r i p - u p c l a s t s and the e r o s i v e base of the sandstone bed ( e ) . T h i s was f o l l o w e d by the p r o g r a d a t i o n of a t h i n sand sheet which formed the h i g h angle f o r e s e t s ( f ) . As the c u r r e n t s weakened the top of the sand sheet was reworked to form r i p p l e s ( r ) . The f i n a l episode i s repr e s e n t e d by the p a r a l l e l bedded s i l t s t o n e s formed by d e p o s i t i o n from suspension a t the end of the f l o o d . S i l t s t o n e s at the top e x h i b i t convolute bedding (c) (MDD 7823, 360. 1 m) . Fi g u r e 46c. P a r a l l e l bedding and c l i m b i n g r i p p l e s i n overbank s i l t s t o n e s . (MXD 7827, 401.2 m). Fi g u r e 46d. I n f e r r e d w e l l d r a i n e d swamp d e p o s i t c o n s i s t i n g of massive root (r) p e n e t r a t e d s i l t s t o n e . Note the s m a l l s i l i c e o u s c o n c r e t i o n s at the base. F i g u r e s 46e,f. I n f e r r e d l a c u s t r i n e d e p o s i t s c o n s i s t i n g of p a r a l l e l laminated s i l t s t o n e s and mudstones. Note the two burrows i n 46e. Fi g u r e 46g. R i p p l e d f i n e - g r a i n e d sandstone interbedded with dark grey s i l t s t o n e s . S e v e r a l burrows are v i s i b l e i n t h i s c o r e . T h i s type of de p o s i t i s common i n both levee and cr e v a s s e s p l a y environments (QBD 7306, 1690 f t ) . F i g u r e 46h. Massive overbank s i l t s t o n e . The absence of bedding may be the r e s u l t of very r a p i d sedimentation, b i o t u r b a t i o n , or d e s t r u c t i o n by the escape of water d u r i n g compaction. A l t e r n a t i v e l y bedding may be present but would r e q u i r e other techniques (e.g., exposure to X-rays) to make i t v i s i b l e . 127 s i l t s t o n e s , together with t h e i r s t r a t i g r a p h i c p o s i t i o n , suggest that these sediments were d e p o s i t e d from suspension i n a lake which formed i n the channel a f t e r i t was suddenly cut o f f and abandoned. These two types of f a c i e s a s s o c i a t i o n s suggest that l a k e s on the Gates c o a s t a l p l a i n were present i n two d i s t i n c t d e p o s i t i o n a l s e t t i n g s ; as shallow floodponds and lakes formed by drowning of swamps i n i n t e r c h a n n e l areas, and i n abandoned f l u v i a l channels. Lakes which formed i n i n t e r c h a n n e l areas are l i k e l y to have been more e x t e n s i v e than those formed i n abandoned f l u v i a l channels. 1.9.5 Well to Poo r l y Drained Swamp Deposits Swamps c o n s t i t u t e low, f l a t areas p e r i o d i c a l l y covered or sa t u r a t e d with water and which support a cover of woody v e g e t a t i o n with or without an undergrowth of shrubs (Coleman and Gagliano, 1965). In the A t c h a f a l a y a River B a s i n , Coleman (1966) has r e c o g n i s e d two types of swamps based' on the q u a l i t y of the drainage. P o o r l y d r a i n e d swamps occur i n areas i s o l a t e d from r i v e r drainage systems. In these swamps, standing water i s present year round and sediment accumulates under reducing c o n d i t i o n s . Well d r a i n e d swamps are i n f l u e n c e d by r i v e r drainage systems and sediment accumulates under a l t e r n a t e o x i d i z i n g and reducing c o n d i t i o n s . In the Gates Formation, sediment i n t e r p r e t e d as p o o r l y d r a i n e d swamp d e p o s i t s , c o n s i s t s of dark grey to blac k , very carbonaceous mudstones and c o a l . The carbonaceous mudstones o f t e n c o n t a i n abundant c o a l spar 1 28 and w e l l preserved p l a n t fragments. I n t e r n a l l y these d e p o s i t s are u s u a l l y massive but o c c a s i o n a l l y e x h i b i t p a r a l l e l bedding. The carbonaceous mudstones are present i n i n t e r v a l s up to 6 m t h i c k and are e a s i l y r e c o g n i s a b l e on g e o p h y s i c a l logs by t h e i r very h i g h gamma ray reading, a s s o c i a t e d with t h e i r high c l a y and organic content. They are u s u a l l y present above and below c o a l seams or as rock s p l i t s w i t h i n seams. They a l s o occur interbedded with l e v e e , crevasse s p l a y , lake and w e l l d r a i n e d swamp d e p o s i t s . Sediments i n t e r p r e t e d as w e l l d r a i n e d swamp d e p o s i t s have higher s i l t contents and are l e s s carbonaceous than p o o r l y d r a i n e d swamp d e p o s i t s . Well d r a i n e d swamp d e p o s i t s c o n s i s t of l i g h t t o medium grey s i l t y mudstones and s i l t s t o n e s . In ge n e r a l these d e p o s i t s are massive due to strong b i o t u r b a t i o n caused by both ro o t s and burrows. Primary sedimentary s t r u c t u r e s are rare but where present u s u a l l y c o n s i s t of p a r a l l e l l a m i n a t i o n s . Well d r a i n e d swamp d e p o s i t s occur interbedded with p o o r l y d r a i n e d swamp d e p o s i t s , l e v e e , crevasse s p l a y and lake d e p o s i t s . 129 PART II FACIES ASSOCIATIONS IN THE UPPER GATES FORMATION:  TRANSGRESSIVE AND REGRESSIVE MARINE, ESTUARINE AND COASTAL PLAIN  DEPOSITS 2.1 INTRODUCTION Marine d e p o s i t s are i d e n t i f i e d based on f o s s i l and t r a c e f o s s i l evidence i n the upper Gates above the D c o a l seam, north of Q u i n t e t t e Mountain, and the e q u i v a l e n t seam, B9, i n the Honeymoon and Duke P i t areas ( F i g u r e s 5, 6). North of Q u i n t e t t e Mountain, marine d e p o s i t s occur w i t h i n a 35-50 m t h i c k i n t e r v a l c o n s i s t i n g mainly of sandstones and conglomerates which g e o l o g i s t s from Denison Mines r e f e r to as the Babcock member. The southern l i m i t of t h i s member i s shown on F i g u r e 8. South of Q u i n t e t t e Mountain, in the Honeymoon and Duke P i t areas (Figure 1), the marine i n t e r v a l i s t h i n n e r and l i t h o l o g i e s c o n s i s t of interbedded mudstones, s i l t s t o n e s and sandstones. A 30-50 m t h i c k , non-marine i n t e r v a l c o n t a i n i n g t h i n c o a l seams occurs between the upper Gates marine u n i t and the Hul c r o s s Formation. Because the upper Gates sediments o v e r l i e the i n t e r v a l c o n t a i n i n g the t h i c k c o a l seams i n the Gates Formation, they are present i n numerous boreholes i n the Frame, McConkey, Babcock, Honeymoon and Duke P i t ar e a s . The g r e a t e s t c o n c e n t r a t i o n of data i s in the Babcock area, where a t o t a l of 63 boreholes i n t e r s e c t complete or p a r t i a l upper Gates s e c t i o n s . Most of these boreholes are l o c a t e d w i t h i n a 24 km2 area on Babcock Mountain, where the average spacing i s approximately 500 m. In a d d i t i o n to borehole data, there are good outcrops of conglomerates and sandstones i n the Babcock member between Q u i n t e t t e Mountain and 130 the Wolverine R i v e r . The combination of outcrop and core data from c l o s e l y spaced boreholes provides an e x c e l l e n t o p p o r t u n i t y i n which to study i n d e t a i l the s h o r e l i n e d e p o s i t s of the upper Gates. Approximately 4800 m of core from 64 boreholes was examined from the upper Gates Formation. Furt h e r data p o i n t s are pr o v i d e d by ge o p h y s i c a l l o g s from numerous other boreholes and 12 petroleum w e l l s . S e v e r a l outcrop s e c t i o n s were measured i n the sandstones and conglomerates of the Babcock member. 2.2 FACIES - DESCRIPTION AND INTERPRETATION 2.2.1 General The upper Gates i s d i v i d e d i n t o 11 f a c i e s based on d i f f e r e n c e s i n l i t h o l o g y , g r a i n - s i z e v a r i a t i o n s , sedimentary s t r u c t u r e s and t r a c e f o s s i l s . The s t r a t i g r a p h i c p o s i t i o n , f a c i e s a s s o c i a t i o n s and main l i t h o l o g i e s of these f a c i e s are i l l u s t r a t e d on a g e n e r a l i s e d c r o s s s e c t i o n from the McConkey P i t i n the north to Duchess Mountain i n the south (Figure 47). T h e i r c h a r a c t e r i s t i c s are shown i n more d e t a i l on two c r o s s s e c t i o n s based on 10 core and 2 outcrop s e c t i o n s , i n the Babcock area ( F i g u r e s 48, 49) and a c r o s s s e c t i o n , based on data from 7 cored s e c t i o n s , i n the Duke P i t area (Figure 50). In the f o l l o w i n g s e c t i o n s , the upper Gates f a c i e s w i l l be d e s c r i b e d and i n t e r p r e t e d . In order to make the d e s c r i p t i v e p a r t more readable, the i n t e r p r e t e d d e p o s i t i o n a l environment of each of the 11 f a c i e s i s l i s t e d on Fi g u r e 47. 131 N.W. D Seam Facies 4 ... Lagoon-lntertldal 3C ... Tidal Flat 3B ... Subtldal Shoal 3A ... Subtldal Channel 2B ... Shallow Marine -Channel Fill Deposits 2A ... Subtldal Shelf-Shallow Marine 1B ... Transgressive Marine Lag 1A ... Estuarine Deposits 5 ... Coastal Plain Deposits , ... Marine Transgression 30 20 metres 10 0 B9 Seam kilometres 10 S.E. Figure 4_7. Generalised cross s e c t i o n showing the f a c i e s present i n the upper Gates between the McConkey P i t and Duchess Mountain. (1.4km) ROMAN MTN SOUTH ijerrt day arotfon surfaea matrtts r 2 0 • i Coa l l-EQENO o o ^ - ^ ^ d ^ g . . . .. Low . n g * . croM -beddaig L i ^ J Sandston. <v Trou^i cro«a b e d d i g L ^ J SHaton . _ . _ pfcnar boddhg k. Roota I I Mudatone "*><* •» + Burrowe _ ..-oif Flaaar baddrig Mdat/atat rtrM> daata l l Conglomerate tir* Lanttcular bedding —• Wavy baddhg Carbonaceoua mudatone c o Soft aedbnam deformation atrocturea Facias 2B Shallow Marin.-Channel Fill F a c i e i 2A Subtldal 3helf-Shallow Marina Faciaa 1B Transgressive Marine Lag Facies 1A Estuarine Deposits Facies 5 Coasta l Plain Deposits Facies 3C Tidal Flat (occur, locafly at the top of ) a c l . s 3 A / 3 B ) Facies 3B Subtldal Shoal Facies 3A -Subtidal Channel SECTION A F i g u r e 48. S e c t i o n A - upper Gates c r o s s s e c t i o n in the Babcock area { l o c a t i o n of s e c t i o n i s shown on F i g u r e 66). to 7306 (0.9km) 7306 (1.4km) 7302 (l.ikra) K03TUIK MTN (1.0km) 7401 (4.0km) 7513 SOUTH Cr*.ast> congLl SECTION B F i g u r e 4J3. S e c t i o n B - upper Gates c r o s s s e c t i o n in the Babcock area ( l o c a t i o n of s e c t i o n i s shown on F i g u r e 66). Legend i s shown on F i g u r e 48. co CO Northwest 7908 2.5km 7914 2.1km 7902 1.1km 7823 1.9km 7905 0.6km 7822 3.0km 8105 Gamma Ray Southeast Facies 5...Coastal Plain Deposits Facies 4...Lagoon-lntertidal ...Marine Transgression F i g u r e 50. Cross s e c t i o n of the i n t e r v a l between the B7 c o a l seam and the H u l c r o s s Formation in boreholes near the Duke P i t (borehole l o c a t i o n s are shown on F i g u r e 35). H o r i z o n t a l datum i s the top of the B9 upper seam. Note that B9) i s e q u i v a l e n t to the D seam on F i g u r e s 4J_ and 42!. Legend i s shown on F i g u r e 4 8 . CO 135 F i g u r e 5_1_. Map showing the approximate a r e a l d i s t r i b u t i o n of upper Gates f a c i e s 1A, 2A and 4. (Note: Scale of map i s too small to show a l l the s e c t i o n s which pen e t r a t e these f a c i e s ; boreholes and w e l l s shown on the map are only those used on the r e g i o n a l c r o s s s e c t i o n s - F i g u r e s 5, 6 and 1_. ) 136 2.2.2 F a c i e s 1A - D e s c r i p t i o n F a c i e s 1A occurs above the D c o a l seam at the base of the upper Gates ( F i g u r e s 47, 48, 49). Regional mapping shows that t h i s f a c i e s i s present i n a 2-4 km wide b e l t t r e n d i n g NW-SE between the McConkey P i t and Q u i n t e t t e Mountain ( F i g u r e 51). D e t a i l e d mapping near the Babcock P i t , using c l o s e l y spaced boreholes, i n d i c a t e s that i n t h i s area f a c i e s 1A occurs i n two separate l i n e a r , NW-SE t r e n d i n g b e l t s that are 0.4 to 1.5 km wide (Figure 52). L i t h o l o g i e s c o n s i s t of f i n e to gra n u l a r sandstones and conglomerates ( F i g u r e s 53, 54). The sandstones are w e l l to extremely w e l l s o r t e d c h e r t a r e n i t e s with very l i t t l e a r g i l l a c e o u s matrix. In some s e c t i o n s , c l e a n very w e l l s o r t e d , coarse t o granular sandstones e x h i b i t good i n t e r g r a n u l a r p o r o s i t y ( F i g u r e s 53b,c,d). The conglomerates are mainly c l a s t supported with v a r i a b l e amounts of sandstone matrix, and grade l o c a l l y i n t o pebbly sandstones ( F i g u r e s 5 3 e , f ) . C l a s t s are w e l l rounded; most have diameters l e s s than 1 cm. The l a r g e s t c l a s t observed measured 10x5x4 cm. Pebbles are o c c a s i o n a l l y i m b r i c a t e d . At outcrops on Roman Mountain and i n the McConkey P i t , the d i p d i r e c t i o n of im b r i c a t e d pebbles i n d i c a t e s paleoflow d i r e c t i o n s towards 357° and 317° r e s p e c t i v e l y ( F i g u r e 55). In many s e c t i o n s , conglomerates are more common i n the upper p a r t of the f a c i e s and the d e p o s i t s coarsen-upwards (e.g., F i g u r e 54). In other s e c t i o n s , conglomerates are interbedded with sandstones throughout and there i s no obvious c o a r s e n i n g or fining-upward t r e n d . In a few s e c t i o n s the f a c i e s c o n s i s t s e n t i r e l y of sandstones with l i t t l e v a r i a t i o n i n g r a i n - s i z e . 1 38 F i g u r e 5_3. Core and outcrop photographs of f a c i e s 1A l i t h o l o g i e s . F i g u r e 53a. P o o r l y s o r t e d conglomerate with a sandy matrix. F i g u r e 53b,d. Well s o r t e d conglomerate/granular sandstone l a c k i n g any f i n e sandy matrix and with very good i n t e r g r a n u l a r p o r o s i t y , (b = QMD 7609, 42.5 m; d = QMD 7620, 137 m). F i g u r e 53c. Very w e l l s o r t e d c o a r s e - g r a i n e d sandstone with very good i n t e r g r a n u l a r p o r o s i t y (QMD 7620, 139 m) . F i g u r e 53e. Poorly s o r t e d conglomerate with a sandy matrix (QMD 7618, 66 m). F i g u r e 53f. Sandstones and conglomerates at the top of f a c i e s 1A i n QBD 7712. Burrows c o n s i s t i n g of small c i r c u l a r to o v a l tubes ( p o s s i b l y Macaronichnus segregatus) are present i n sandstones at the top of f a c i e i - 1 A ( b ) . F a c i e s 1B occurs at the top r i g h t from A-B. Note the very sharp c o n t a c t (B) between f a c i e s 1B and the mudstones and s i l t s t o n e s at the base of f a c i e s 2A at the top r i g h t of the c o r e . F i g u r e 53g. P a r a l l e l bedding formed by a l t e r n a t i o n s of f i n e - and c o a r s e - g r a i n e d sandstone and conglomerate near the base of f a c i e s 1A on the south s i d e of Mount Frame. A s m a l l scour i s present i n sandstones i n the upper l e f t . These sediments are i n t e r p r e t e d as the r e s u l t of d e p o s i t i o n from s t r o n g upper flow regime c u r r e n t s . The sandstones and conglomerates are very c l e a n with good i n t e r g r a n u l a r p o r o s i t y . 139 1 40 F i g u r e 54. Core of sediments i n f a c i e s 1A, 1B and the base of f a c i e s 2A from borehole QBD 7201 i n the Babcock a r e a . F i n e -g r a i n e d pebbly sandstones i n the lower p a r t e x h i b i t p a r a l l e l bedding (upper flow regime) and c r o s s - b e d d i n g . In the upper p a r t the sandstones become c o a r s e r - g r a i n e d and are interbedded with conglomerates. Note the much l a r g e r s i z e of c l a s t s i n f a c i e s 1B (between B and C) compared to f a c i e s 1A and the very abrupt top of f a c i e s 1B. TOP FACIES 1A Wood/Log Impressions and Groove Marks McConkey Pit Frame Babcock FACIES 1A Tabular Cross Bedding F i g u r e 5_5. P a l e o c u r r e n t data from f a c i e s 1A. 143 In some areas a t h i n bed of carbonaceous mudstone occurs between f a c i e s 1A and the D c o a l seam. The base of f a c i e s 1A i s abrupt or e r o s i o n a l . In outcrops where the c o n t a c t i s exposed, the b a s a l s u r f a c e i s planar and l o c a l l y c h a n n e l l e d . Groove marks and impressions of small wood fragments or l a r g e logs are common near the base (Figure 58b) and along the b a s a l s u r f a c e . Measurements of these f e a t u r e s shows a p r e f e r r e d NW-SE o r i e n t a t i o n at three separate l o c a l i t i e s ( F i gure 55). V e r t i c a l l o g impressions up to 2 m high are present i n coarse to g r a n u l a r sandstones at the base of f a c i e s 1A at the McConkey P i t . T h e i r v e r t i c a l o r i e n t a t i o n and p o s i t i o n d i r e c t l y above the D c o a l seam suggests that they represent t r e e trunks i n growth p o s i t i o n . In cores the conglomerates are massive, while the sandst.ones e x h i b i t p a r a l l e l bedding, cross-bedding and o c c a s i o n a l l y r i p p l e s . Large s c a l e bedforms are present i n w e l l exposed outcrops of f a c i e s 1A on Babcock Mountain, and the Frame and McConkey P i t s . These bedforms.are i l l u s t r a t e d on l i n e drawings t r a c e d from photo composites ( F i g u r e 61) and on F i g u r e s • 57-60. In the Windy P i t area on the northwest si d e of Babcock Mountain, f a c i e s 1A i s 10-12 m t h i c k and c o n t i n u o u s l y exposed f o r a d i s t a n c e of approximately 400 m. Large s c a l e bedforms c o n s i s t i n g of 5° to 9° d i p p i n g s u r f a c e s extend from the top to near the base of the outcrop ( F i g u r e s 58,61). Most s u r f a c e s are p l a n a r and a few are g e n t l y convex-up. I n d i v i d u a l s u r f a c e s are spaced approximately 0.5-2 m apart and can be t r a c e d h o r i z o n t a l l y f o r d i s t a n c e s of 30-60 m. Over most of the outcrop the s u r f a c e s d i p towards the southwest, at r i g h t angles to the 1 44 NW-SE tre n d of f a c i e s 1A i n t h i s area ( F i g u r e 52). Towards the nor t h e a s t , the d i p d i r e c t i o n i s r e v e r s e d . In a few p l a c e s , the su r f a c e s are tru n c a t e d below more s t e e p l y d i p p i n g s u r f a c e s . A measured outcrop s e c t i o n at t h i s l o c a l i t y i s shown on F i g u r e 62. Sandstones near the base are massive, trough cross-bedded or p a r a l l e l bedded and occur interbedded with l e n s e s of conglomerates. Northwest of t h i s s e c t i o n a 1.5 m t h i c k set of cross-bedding, d i p p i n g towards 197° can be t r a c e d l a t e r a l l y f o r a d i s t a n c e of 20 m at the base of the f a c i e s . The upper p a r t of the outcrop c o n s i s t s of sandstones interbedded with t h i n conglomerates; t a b u l a r cross-bedding and p a r a l l e l bedding i s common. Sets are up to 50 cm t h i c k and most d i p towards the southeast (Figure 55). Herringbone c r o s s - s t r a t i f i c a t i o n i n which two t a b u l a r s e t s have d i p d i r e c t i o n s 170° apart was observed at one l o c a l i t y . In a core near t h i s outcrop burrows s i m i l a r to Macaronichnus segregatus were found i n sandstones at the top of f a c i e s 1A immediately below the con t a c t with f a c i e s 1B (Figure 5 3 f ) . At the Frame and McConkey P i t s , f a c i e s 1A i s present i n 12 boreholes and i s c o n t i n u o u s l y exposed f o r s e v e r a l k i l o m e t r e s i n two separate s y n c l i n e s approximately 2.5 km a p a r t . F i g u r e 56 shows the outcrop p a t t e r n and isopachs of f a c i e s 1A i n t h i s a r e a . The maximum t h i c k n e s s of f a c i e s 1A i n the Frame and McConkey P i t i s 20 m and 40 m r e s p e c t i v e l y . On the southeast of the McConkey P i t the f a c i e s t h i n s r a p i d l y from 40 m to 0 m over a d i s t a n c e of approximately 500 m ( F i g u r e s 56, 57b). Rapid t h i n n i n g and pinchout of the f a c i e s a l s o occurs on the west s i d e of Frame s y n c l i n e . Based on the data shown on F i g u r e 56, i t 145 appears that f a c i e s 1A i n t h i s area i s present i n a l i n e a r b e l t , approximately 2 km wide, with a g e n e r a l north-south t r e n d . Two types of l a r g e s c a l e bedforms are present i n a 15-20 m t h i c k and 1 km long c l i f f exposure of f a c i e s 1A on the south s i d e of Frame P i t ( F i g u r e s 57, 59, 60, 61). The f i r s t type c o n s i s t s of low angle (0-17°) s u r f a c e s which d i p towards the southwest. I n d i v i d u a l s u r f a c e s are spaced 1-6 m apart and extend h o r i z o n t a l l y f o r 45-135 m. Most of the s u r f a c e s can be t r a c e d from the top to the base of the outcrop. A few are t r u n c a t e d below more s t e e p l y d i p p i n g s u r f a c e s . Many are s i g m o i d a l while others are f l a t , concave or convex upwards. The second type of l a r g e s c a l e bedform in t h i s outcrop c o n s i s t s of cross-beds i n sets 1.5-3 m t h i c k , which can be t r a c e d h o r i z o n t a l l y f o r d i s t a n c e s up to 30 m and which are i n c l i n e d at angles p a r a l l e l to the low angle bedforms ( F i g u r e s 60,61). Sets occur mainly i n the lower part of the outcrop. F o r e s e t s are t a b u l a r or g e n t l y curved and d i p at angles of. 24-40° i n a west-southwesterly d i r e c t i o n . Tops of s e t s are t r u n c a t e d by the low angle bedforms. Other sedimentary s t r u c t u r e s near the base of the outcrop i n c l u d e trough c r o s s -bedding and p a r a l l e l bedding. Low angle, s o u t h e r l y d i p p i n g s u r f a c e s are present i n outcrops of f a c i e s 1A on the southwest s i d e of the McConkey P i t ( F i g u r e 57b). In the lower p a r t of the outcrop, sandstones and conglomerates are massive or e x h i b i t l a r g e s c a l e cross-bedding ( s e t s up t o 3 m t h i c k ) . I n d i v i d u a l beds are t h i n n e r i n the upper pa r t of the outcrop and towards the south where the f a c i e s pinches out. In these areas, p a r a l l e l bedding and t a b u l a r c r o s s -146 121 12.5: N MCCONKEY AREA " lOm--^. •..1.pm...^ FRAME AREA io I I Om \ 10m..—' Facies 1A pinches out-Jr. J15nv i 257 -241' \ * n-15 n = 5 S 234* n.2 1 Frame line drawing ' (Fig. 61) . , , 55.00 —\ J 206 n-15 Limit of Gates Formation Outcrop • Facies 1A Outcrop — Average Vector of Low Angle Surfaces g Q 0 1 0 o o < Average Vector of High Angle Cross Beds l = ! H ^ 1 ' • Borehole m e , r e s * Outcrop Section F i g u r e 5_6. Outcrop p a t t e r n and isopachs of f a c i e s 1A i n the Frame and McConkey P i t a r e a s . Note the r a p i d t h i n n i n g and pinchout of f a c i e s 1A on the west s i d e of the Frame area and e a s t s i d e of the McConkey ar e a . 147 F i g u r e 57a. Large s c a l e g e n t l y d i p p i n g bedforms i n f a c i e s 1A on the south s i d e of Mount Frame. The D c o a l seam i s exposed below f a c i e s 1A behind the f i e l d a s s i s t a n t . The l i n e drawing showing the l a r g e s c a l e bedforms i n the Frame area ( F i g u r e 6J_) i s from t h i s outcrop. F i g u r e 57b. Outcrop of f a c i e s 1A on the south s i d e of the McConkey P i t (note the f i g u r e on road f o r s c a l e ) . In t h i s area f a c i e s 1A t h i n s from approximately 40 m to 0 m over a d i s t a n c e of 500 m and pinchesout i n the area j u s t to the r i g h t of t h i s view. Note the presence of l a r g e s c a l e g e n t l y d i p p i n g s u r f a c e s which taper towards the south (to the r i g h t i n t h i s photograph). 1 49 F i g u r e 58a. Contact between f a c i e s 1A and the D c o a l seam i n the Windy P i t area on the northwest s i d e of Babcock Mountain. Note the low angle i n c l i n e d s u r f a c e s i n f a c i e s 1A d i p p i n g towards the r i g h t (southwest). F i g u r e 58b. Large l o g impression i n pebbly sandstones near the base of f a c i e s 1A i n the McConkey P i t a r e a . F i g u r e 58c. Interbedded sandstones and conglomerates i n the upper p a r t of f a c i e s 1A i n the McConkey P i t a r e a . Bedding c o n s i s t s of t a b u l a r c r o s s - b e d d i n g o r i e n t e d i n an e a s t -s o u t h e a s t e r l y d i r e c t i o n and p a r a l l e l to g e n t l y i n c l i n e d bedding. Note the r e a c t i v a t i o n s u r f a c e (r) i n t h i s s e t . 150 151 F i g u r e 5_9. E r o s i o n a l c o n t a c t between f a c i e s 1A and the D c o a l seam on the south s i d e of Mount Frame. Note the low angle s u r f a c e at the base of f a c i e s 1A i n F i g u r e 59a. The two i n c l i n e d s u r f a c e s shown i n F i g u r e 59b rep r e s e n t the downdip t e r m i n a t i o n of l a r g e scal'e low angle i n c l i n e d s u r f a c e s . The s t i c k (arrowed) i s 2 m lo n g . 152 1 53 F i g u r e 60a. Large 2-3 m t h i c k , high angle, i n c l i n e d c r o s s - b e d i n f a c i e s 1A on the south s i d e of Mount Frame. Set i s bounded at the base and at the top by low angle i n c l i n e d s u r f a c e s which extend from the top to the base of the o u t c r o p . The l a t e r a l extent of these bedforms i n t h i s outcrop i s shown on the l i n e drawing ( F i g u r e 61). F i g u r e 60b. C l o s e up view of the c r o s s - b e d i n F i g u r e 60a showing the g e n t l y curved f o r e s e t s d i p p i n g to the l e f t (westward) and t h e i r t r u n c a t i o n at the top by a low angle i n c l i n e d s u r f a c e . (Note: T h i s view i s t i l t e d at an angle p a r a l l e l to the low angle i n c l i n e d s u r f a c e s ) . West East D coat seam Approximate Scale 0 50 b s ^ ^ ^ M ^ J met re s FRAME 10 20 30 40 50 Approximate Scale BABCOCK F i g u r e 61. Li n e drawings t r a c e d from photomosaics of f a c i e s 1A in c l i f f exposures on the northwest s i d e of Babcock Mountain and the south s i d e of Mount Frame. cn 1 56 Facies 2A Facies 1A lD" Coal Seam O ° o " - o - » symmetrical dunes locally on top rare herringbone cross-stratification massive beds, low angle inclined bedding and tabular cross-bedding erosional contact parallel bedding (UFR) trough cross-bedding mdst fine sst coarse sst conglomerate F i g u r e 6_2. Outcrop s e c t i o n of f a c i e s 1A and f a c i e s 1B i n the Windy P i t area on the northwest s i d e of Babcock Mountain. 157 bedding (sets 8-40 cm t h i c k ) are common (Figure 58c). R e a c t i v a t i o n s u r f a c e s (Figure 58c) were observed in a few s e t s . F o r e s e t s d i p on average towards 099° (Figure 55). 2.2.3 F a c i e s 1A - I n t e r p r e t a t i o n The occurrence of f a c i e s 1A above a c o a l seam, i t s abrupt-e r o s i o n a l and l o c a l l y c h a n n e l l e d b a s a l c o n t a c t with o r i e n t e d groove, wood and l o g impressions at the base, i s strong evidence that these d e p o s i t s are channel f i l l s . A t i d a l i n f l u e n c e i s i n d i c a t e d by the s o u t h e r l y (landward) d i p p i n g t a b u l a r f o r e s e t s and r a r e herringbone c r o s s s t r a t i f i c a t i o n . The t e x t u r a l and c o m p o s i t i o n a l m a t u r i t y of the sandstones i n d i c a t e s e x t e n s i v e reworking p o s s i b l y a s s o c i a t e d with marine p r o c e s s e s . Macaronichnus segregatus burrows are c o n s i d e r e d by C l i f t o n and Thompson (1978) as i n d i c a t i v e of i n t e r t i d a l or shallow s u b t i d a l environments and t h e i r presence at the top of f a c i e s 1A i n one core i s f u r t h e r evidence of a marine i n f l u e n c e . Based on these c h a r a c t e r i s t i c s , together with i t s s t r a t i g r a p h i c p o s i t i o n below a t r a n s g r e s s i v e marine l a g d e p o s i t ( f a c i e s 1B), i t i s concluded that f a c i e s 1A was d e p o s i t e d i n an e s t u a r i n e environment. St u d i e s of the f a c i e s p a t t e r n s i n the Holocene sediments of the coast of Delaware ( K r a f t , 1971; Sheridan et a l . , 1974) which are being t r a n s g r e s s e d by the A t l a n t i c Ocean i n d i c a t e s that a complex and v a r i e d assemblage of d e p o s i t i o n a l f e a t u r e s i s i n f i l l i n g the r e t r e a t i n g estuary mouths. S p e c i f i c environments i d e n t i f i e d by K r a f t , (1971) i n c l u d e s p i t s , dunes, baymouth b a r r i e r s , an intermeshing network of t i d a l d e l t a s , and lagoons. 158 In view of the complex v a r i e t y of f a c i e s d e p o s i t e d i n a r e t r e a t i n g estuary mouth environment, i t i s d i f f i c u l t to determine s p e c i f i c environments f o r f a c i e s 1A. The most l i k e l y o r i g i n f o r such t h i c k d e p o s i t s of sandstone and conglomerate i s , however, i n t i d a l d e l t a s , in-channel bars or e s t u a r y mouth s h o a l s . The low-angle d i p p i n g s u r f a c e s i n the Babcock and Frame outcrops are o r i e n t e d at approximately r i g h t angles to the t r e n d of f a c i e s 1A which suggests that these are l a t e r a l a c c r e t i o n s u r f a c e s . While these may have formed on c o a r s e - g r a i n e d , p o i n t bars (McGowan and Garner, 1970; Levey, 1978; Gustavson, 1978; Nijman and Puigdefabregas, 1978) i t i s c o n s i d e r e d more l i k e l y that they o r i g i n a t e d from the l a t e r a l m i g r a t i o n of t i d a l d e l t a s or in-channel bars or shoals such as d e s c r i b e d by Nio et a l . , (1980) and van den Berg (1982) f o r the shoals of the Eastern Scheldt estuary mouth i n southwest Netherlands. The high angle f o r e s e t s i n the Frame outcrop may have formed from the d e p o s i t i o n of sediment i n small d e l t a s hear the c o n f l u e n c e of smaller f l o o d dominated t i d a l channels t r a n s v e r s e to the i n -channel shoals and the main e s t u a r i n e channel. There i s good evidence from the isopachs of f a c i e s 2A and the data shown on the c r o s s s e c t i o n s (Figures 48,49,66) that a f t e r the sea t r a n s g r e s s e d and covered f a c i e s 1A d e p o s i t s , they formed l i n e a r , t o p o g r a p h i c a l l y h i g h e r , areas on the sea f l o o r o r i e n t e d at a high angle to the c o a s t l i n e . S i m i l a r f e a t u r e s are preserved on the A t l a n t i c s h e l f of North America (Hoyt and Henry, 1971; S w i f t , 1973; 1974; 1976; S w i f t et a l . , 1972). These f e a t u r e s , termed shoal r e t r e a t m a s s i f s by S w i f t et a l . , (1972), 159 represent the r e t r e a t paths of c o a s t a l depocentres a s s o c i a t e d with l i t t o r a l d r i f t convergences which form at estuary mouths and capes. Thus a f t e r the marine t r a n s g r e s s i o n , f a c i e s 1A d e p o s i t s may have formed es t u a r y s h o a l - r e t r e a t m a s s i f s analogous to those on the modern A t l a n t i c s h e l f . 2.2.4 F a c i e s 1B - D e s c r i p t i o n North of Roman Mountain (Figure 1), the contact between f a c i e s 1A and f a c i e s 2A i s marked by a t h i n (15-90 cm) bed of very coarse conglomerate or pebbly g r a n u l a r sandstone ( F a c i e s 1B). Examples of t h i s f a c i e s i n cores are shown on F i g u r e s 53, 54 and 63. C l a s t s i n t h i s u n i t are on average much co a r s e r than in f a c i e s 1A, t h i s i s the'main c r i t e r i o n used to i d e n t i f y f a c i e s 1B. In areas where f a c i e s 1A i s absent, f a c i e s 1B i s t h i n n e r and o f t e n c o n s i s t s of only a few centimetres of conglomerate or c o a r s e - g r a n u l a r sandstone. In a few s e c t i o n s f a c i e s 1B i s absent and the D c o a l seam i s o v e r l a i n d i r e c t l y by f a c i e s 2A. F a c i e s 1B conglomerates are p o o r l y s o r t e d and c l a s t supported with v a r i a b l e amounts of sandy matrix. C l a s t s are w e l l rounded. The l a r g e s t c l a s t observed measured 13x8x3 cm. Coal spar i s o c c a s i o n a l l y p r e s e n t . In some cores the conglomerates occur i n t e r b w i t h t h i n l a y e r s of mudstone or very f i n e - g r a i n e d sandstone, l e s s than 1 cm t h i c k , s i m i l a r i n appearance to sediments at the base of f a c i e s 2A (Figure 63a). In c o r e s , the sandstones and conglomerates in f a c i e s 1B are massive. In outcrops at Babcock Mountain and the Frame P i t s , symmetrical dunes are o c c a s i o n a l l y present on the top s u r f a c e . ( F i g u r e 64). Dune c r e s t s and troughs are rounded, with 160 amplitudes ranging between 12-30 cm and wavelengths of 0.8-2.4 m. C r e s t s are s t r a i g h t or s l i g h t l y sinuous. The average t r e n d of the dune c r e s t s at the Babcock and at two l o c a l i t i e s at the Frame P i t i s 107°, 106° and 062° (Figure 65). O c c a s i o n a l l y the c r e s t s are s l i g h t l y asymmetric, with the steep s i d e towards the nor t h . In the Babcock outcrop, coarse pebbles are exposed i n the troughs of the dunes. At a second l o c a l i t y at Babcock, the long axes of pebbles and cobbles i n f a c i e s 1B, exposed on a f l a t bedding plane s u r f a c e show a p r e f e r r e d o r i e n t a t i o n towards 110 0 — 290° ( F i g u r e 65). Fi g u r e 64. Symmetrical dunes on the top s u r f a c e of f a c i e s 1B at an outcrop on the northwest s i d e of Babcock Mountain. 161 F i g u r e 63a. Core photographs showing the abrupt c o n t a c t between f a c i e s 1B (A) and f a c i e s 2A. Note that conglomerates at the top of f a c i e s 1B occur interbedded with a t h i n (<1 cm) sandstone beds s i m i l a r i n appearance to the sandstones i n f a c i e s 2A. The sandstones at the base of f a c i e s 2A are very f i n e - g r a i n e d and occur interbedded with dark grey mudstone. P a r a l l e l bedding, low angle c r o s s - b e d d i n g (c) r i p p l e s , l e n t i c u l a r and f l a s e r bedding are present i n these d e p o s i t s . F i g u r e 63b. P y r i t e (py) i n sediments at the base of f a c i e s 2A. (QBD 7302, 231.5 m) F i g u r e 63c. R i p p l e s , l e n t i c u l a r bedding and b i o t u r b a t i o n i n sediments at the base of f a c i e s 2A (QBD 7721, 215.55 m). F i g u r e 63d. S i l t s t o n e bed at the base of f a c i e s 2A which e x h i b i t s low angle cross-bedding i n the lower p a r t and r i p p l e s at the top. Note the sharp base and i n t e r n a l scour (s) (QBD 771 1 , 1 40.85 m). F i g u r e 63e. Very f i n e - g r a i n e d sandstone bed at the base of f a c i e s 2A which e x h i b i t s p a r a l l e l bedding at the base and r i p p l e s , with numerous T e r e b e l l i n a burrows ( t ) , at the top. (QBD 7715, 258.8 m). F i g u r e 63f. F i n e - g r a i n e d sandstone i n f a c i e s 2A i n which bedding c o n s i s t s of broad concave upwards and upward domed f e a t u r e s (swaley c r o s s - s t r a t i f i c a t i o n ) . Note the low angle i n t e r s e c t i o n s of s t r a t i f i c a t i o n (arrowed) and c h a r a c t e r i s t i c f l a g g y weathering. U 2 163 2.2.5 F a c i e s 1B - I n t e r p r e t a t i o n Based on i t s c h a r a c t e r i s t i c s and s t r a t i g r a p h i c p o s i t i o n , f a c i e s 1B i s i n t e r p r e t e d as a t r a n s g r e s s i v e marine l a g d e p o s i t . During a marine t r a n s g e s s i o n , s h o r e l i n e and c o a s t a l p l a i n d e p o s i t s may be eroded to c o n s i d e r a b l e depths by wave and t i d a l c u r r e n t s . Most e r o s i o n occurs when the upper shoreface or b r e a k e r - s u r f zone passes over the former land s u r f a c e . Storms are an important agent of shoreface e r o s i o n ( S w i f t , 1976, p. 255-309). During a storm, l a r g e volumes of sediment are eroded from the upper shoreface and emplaced e i t h e r landward as a s e r i e s of washover fans or seaward i n the lower sh o r e f a c e -o f f s h o r e area ( S w i f t , 1976, p. 255-309; E l l i o t , 1978). If the sediment being eroded c o n t a i n s coarse and heavy m a t e r i a l , these d e p o s i t s may be l e f t behind on the sea f l o o r to form a t h i n l a g d e p o s i t . Examples of t r a n s g r e s s i v e marine l a g d e p o s i t s have been d e s c r i b e d by Oomkens (1.967, 1970) from the Holocene s u c c e s s i o n of the Rhone D e l t a . F a c i e s 1B i s c o a r s e s t and t h i c k e s t i n s e c t i o n s where i t occurs on top of f a c i e s 1A, which suggests that the l a t t e r i s the main source f o r the c o a r s e - g r a i n e d sandstones and conglomerates i n f a c i e s 1B. The t h i n i n t e r b e d s of s i l t s t o n e and very f i n e - g r a i n e d sandstone which occur i n a few cores interbedded with coarse sandstones and conglomerate in f a c i e s 1B are i n t e r p r e t e d as o f f s h o r e d e p o s i t s , based on t h e i r s i m i l a r i t y to sediments at the base of f a c i e s 2A. These beds, together with the l o c a l presence of symmetrical dunes on the top s u r f a c e of f a c i e s 1B, i n d i c a t e s that once formed the coarse sands and pebbles i n the l a g were moved about on the sea f l o o r by bottom 164 FACIES 1B Axes of Symmetrical Dunes SW Frame NE Frame Babcock FACIES 1B Pebble Long Axes 290° n = 116 Babcock FACIES 2A Axes of Symmetrical Wave Ripples n = 13 88° McConkey Pit FACIES 5B Tabular Cross Bedding 292 Roman Mtn 194 Kostuick Mtn FACIES 2B Wood/Log Impressions and Groove Marks n=34 Kostuick Mtn F i g u r e 6_5. P a l e o c u r r e n t data from f a c i e s 1B, 2A, 2B and 5B. 165 c u r r e n t s . Bedforms s i m i l a r t o those i n f a c i e s 1B have been d e s c r i b e d from modern c o n t i n e n t a l shelves o f f New Zealand ( G i l l i e , 1979) and Vancouver I s l a n d (Yorath et a l . , 1979) and i n anci e n t sediments by L e c k i e (1981). In the modern examples the dunes are formed by o s c i l l a t o r y wave motion on the sea bottom produced by storm propagated s w e l l i n water depths of 20-100 m. 2.2.6 F a c i e s 2A - D e s c r i p t i o n F a c i e s 2A i s a l a t e r a l l y e x t e n s i v e sequence up to 28 m t h i c k which occurs above f a c i e s 1B nort h of Roman Mountain (Figure 51). In a few s e c t i o n s , t h i s f a c i e s o v e r l i e s d i r e c t l y the D c o a l seam. Isopachs of f a c i e s 2A ( F i g u r e 68) i n the Babcock area together with the c r o s s - s e c t i o n s ( F i g u r e s 48, 49) show that f a c i e s 2A i s t h i n n e r i n areas where f a c i e s 1A i s t h i c k and t h i c k e r i n s e c t i o n s where f a c i e s 1A i s t h i n or absent. L i t h o l o g i e s c o n s i s t mainly of very f i n e - t o f i n e - g r a i n e d sandstones ( F i g u r e s 63, 67). In most s e c t i o n s g r a i n - s i z e coarsens upward s l i g h t l y w i t h i n the sandstones. The sandstones are w e l l t o extremely w e l l s o r t e d s u b l i t h a r e n i t e s or c h e r t a r e n i t e s . Thin mudstones and s i l t s t o n e s are present a t the base. Towards the nor t h , the mudstones become t h i c k e r and are a l s o found higher up in f a c i e s 2A. Towards the south, i s o l a t e d pebbles or t h i n pebbly s t r e a k s are common i n the upper p a r t of f a c i e s 2A ( F i g u r e 67e). In the southern p a r t of the Babcock area, the upper p a r t of f a c i e s 2A i s r e p l a c e d by t h i c k conglomerates and c o a r s e - g r a n u l a r sandstones of f a c i e s 2B. Thin s i l t s t o n e s and very f i n e - g r a i n e d sandstones which occur interbedded with dark grey mudstones at the base of f a c i e s 166 2A exhibit l e n t i c u l a r , f l a s e r wavy, p a r a l l e l bedding and low angle cross-bedding (Figure 63). The base of the siltstone/sandstone beds are abrupt or erosional and some beds contain small mudstone pebbles or rip-up c l a s t s . In outcrops at the Frame and McConkey P i t s , hummocky c r o s s - s t r a t i f i c a t i o n occurs in very fine-grained sandstones near the base of the fa c i e s . Symmetrical wave ripples are common on the tops of these beds. The average trend of ripple crests i s 088°-268° (Figure 65) . Sandstones of facies 2A crop out on the northwest side of Babcock Mountain. Bedding in these outcrops consist of p a r a l l e l bedding or low angle cross-bedding with frequent concave upwards scours (Figure 63f, 67a, 67b). The scours are 15-50 cm thick and are up to 4 m in width. Bedding within the scours i s p a r a l l e l or at a very low angle to the basal erosion surface. Sets of tabular cross-bedding were observed in a few places. Occasionally the sandstones are massive or contain v e r t i c a l to sub-vertical tubes possibly formed by l i q u i f a c t i o n processes. The sandstones in these outcrops weather c h a r a c t e r i s t i c a l l y as 0.5-2 cm thick flaggy sheets. Bivalves showing evidence of transportation were found in sandstones at the Babcock outcrops. These were subsequently i d e n t i f i e d by Dr. P. Smith (U.B.C.) as marine p e c t i n i d bivalves, probably Entolium and Camptonectes. In a few cores, valves showing random orientations were found concentrated in beds up to 15 cm thick. Horizontal t r a i l s and burrows are f a i r l y common in the mudstones and s i l t s t o n e s at the base of facies 2A..These include F i g u r e 66. Isopach map of f a c i e s 2A i n the Babcock a r e a . 168 F i g u r e s 67a,b. Swaley c r o s s - s t r a t i f i c a t i o n i n f a c i e s 2A sandstones on the northwest s i d e of Babcock Mountain. Bedding c o n s i s t s of a s e r i e s of superimposed concave upwards shallow scours. I n t e r n a l l y , the s t r a t i f i c a t i o n i s p a r a l l e l or at a very low angle to the s c o u r s . A shallow 4 m wide, concave upwards f e a t u r e with a scoured base i s present at the r i g h t of F i g u r e 67a. The s t i c k (arrowed) i s 2 m long. F i g u r e s 67c,d. Low angle cross-bedding i n f i n e - g r a i n e d sandstones of f a c i e s 2A (c = QBD 7204, 97 f t , d= QBD 7721, 20.7 m) . F i g u r e 67e. Core from the upper p a r t of f a c i e s 2a i n borehole QBD 7712 (approximately 215 m). Sandstones are f i n e - g r a i n e d with a few i s o l a t e d pebbles and t h i n pebbly s t r e a k s . Bedding c o n s i s t s of p a r a l l e l bedding and low angle c r o s s -bedding . 1 70 types s i m i l a r to S c a l a r i t u b a / H e l m i n t h o i d a , Chondrites and T e r e b e l l i n a ( F i g u r e 63e). V e r t i c a l burrows are a l s o present but are not common. O c c a s i o n a l l y , i n d i v i d u a l beds or the tops of beds are s t r o n g l y b i o t u r b a t e d . In some cores burrows are p a r t l y r e p l a c e d by p y r i t e . P y r i t e i s a l s o found as 1-2 mm t h i c k laminae in mudstones ( F i g u r e 63b). Trace f o s s i l s are absent or very r a r e in the o v e r l y i n g sandstones. A 1-2 m t h i c k zone of high r a d i o a c t i v i t y (on the gamma ray log) occurs near the top of f a c i e s 2A i n the Babcock area (Figures 48, 49). T h i s r a d i o a c t i v e zone occurs i n sandstones and appears to be caused by high c o n c e n t r a t i o n s (up to 1.9%) of heavy m i n e r a l s (mainly z i r c o n ) which occur as diss e m i n a t e d g r a i n s . 2.2.7 F a c i e s 2A - I n t e r p r e t a t i o n Trace f o s s i l s and p e c t i n i d b i v a l v e s i n f a c i e s 2A show that these sediments were d e p o s i t e d i n a marine environment. According to Chamberlain (1978), H e l m i n t h o i d a / S c a l a r i t u b a and. T e r e b e l l i n a are r e s t r i c t e d to marine sediments d e p o s i t e d below wave base. Some of the sandstone beds at the base of f a c i e s 2A e x h i b i t hummocky c r o s s s t r a t i f i c a t i o n c h a r a c t e r i s t i c of storm d e p o s i t s (Walker, 1979). L i t h o l o g i e s become c o a r s e r - g r a i n e d i n the upper p a r t of f a c i e s 2A, suggesting shallower water depths. Bedding i n sandstones which crop out on the northwest s i d e of Babcock Mountain i s c h a r a c t e r i s e d by p a r a l l e l bedding and low angle cross-bedding with frequent concave-upward scours. L e c k i e and Walker (1982) have d e s c r i b e d s i m i l a r bedding which they c a l l 171 swaley c r o s s - s t r a t i f i c a t i . o n i n lower Gates marine sediments north of the study a r e a . They note that the troughs (swales) are g e n e r a l l y wider and shallower than trough cross-bedding and are r a r e l y a s s o c i a t e d with angle of repose c r o s s s t r a t a . L e c k i e and Walker (1982) i n t e r p r e t swaley c r o s s - s t r a t i f i c a t i o n as forming in a storm-dominated marine environment, probably above wave base. There i s no evidence f o r emergence (e.g., roots) at the top of f a c i e s 2A. On the c o n t r a r y , i n some cores i n the northern part of the Babcock area, f a c i e s 2A i s o v e r l a i n g r a d a t i o n a l l y by sediments at the base of f a c i e s 3B which c o n t a i n abundant marine t r a c e f o s s i l s i n c l u d i n g H e l m i n t h o i d a / S c a l a r i t u b a , which i n d i c a t e s these beds were d e p o s i t e d below wave base. From t h i s evidence i t i s concluded that f a c i e s 2A was de p o s i t e d i n a storm-dominated s h e l f - s h a l l o w marine environment. 2.2.8 F a c i e s 2B - D e s c r i p t i o n In the Babcock area, the upper part of f a c i e s 2A i s g r a d u a l l y r e p l a c e d towards the south by conglomerates and coarse to g r a n u l a r sandstones of f a c i e s 2B (F i g u r e s 48, 49, 66). T h i s f a c i e s i s present i n 7 boreholes and outcrops on Kos t u i c k Mountain (west of Babcock Mountain) and Roman Mountain. Thickness ranges between 0-18 m. In some s e c t i o n s , sandstones of f a c i e s 2A occur above and below f a c i e s 2B. The b a s a l c o n t a c t i s g e n e r a l l y abrupt and o c c a s i o n a l l y g r a d a t i o n a l . The conglomerates i n t h i s f a c i e s show c o n s i d e r a b l e v a r i a t i o n i n g r a i n - s i z e and s o r t i n g . C l a s t s are w e l l rounded and range i n s i z e from 0.5-6 cm. Conglomerates are f r e q u e n t l y more 172 common i n the lower p a r t . These are g e n e r a l l y massive and p o o r l y s o r t e d with a sandstone matrix. Coal spar i s common near the base. On Kostuick Mountain, impressions of logs and wood fragments at the base of f a c i e s 2B show a p r e f e r r e d o r i e n t a t i o n towards O9 0-189° ( F i g u r e 65). In the upper p a r t , l i t h o l o g i e s c o n s i s t mainly of c l e a n , very w e l l s o r t e d coarse to gr a n u l a r sandstones with good p o r o s i t y , interbedded with t h i n conglomerates. Primary sedimentary s t r u c t u r e s i n the sandstones i n c l u d e p a r a l l e l bedding and cros s - b e d d i n g . In borehole 7402 (F i g u r e 48) sandstones at the top of f a c i e s 2B are o v e r l a i n a b r u p t l y by a 1 m t h i c k i n t e r v a l of very a r g i l l a c e o u s c o a l and carbonaceous mudstone. Roots are absent below the c o a l . 2.2.9 F a c i e s 2B - I n t e r p r e t a t i o n The s t r a t i g r a p h i c p o s i t i o n and c h a r a c t e r i s t i c s of t h i s f a c i e s are c o n s i s t e n t with a shallow marine or d i s t r i b u t a r y channel i n t e r p r e t a t i o n . I t i s probable that both environments are p r e s e n t . In most s e c t i o n s f a c i e s 2B has an abrupt base and on Ko s t u i c k Mountain, o r i e n t e d wood and l o g impressions are present along the b a s a l s u r f a c e . These f e a t u r e s suggest that the lower p a r t of the f a c i e s was d e p o s i t e d i n a channel. The o r i e n t e d wood and l o g impressions i n d i c a t e the channel trend was approximately north-south, normal to the t r e n d of axes of symmetrical wave r i p p l e s of f a c i e s 2A (F i g u r e 65). The upper part of the f a c i e s , however, c o n s i s t s of c l e a n , w e l l - s o r t e d , coarse to granular sandstones with good i n t e r g r a n u l a r p o r o s i t y which have c l e a r l y been reworked. These d e p o s i t s are i n t e r p r e t e d 1 73 as forming on shallow marine bars at the mouth of the channel and e x t e n s i v e l y winnowed and reworked by waves and marine c u r r e n t s . The a r g i l l a c e o u s c o a l o v e r l y i n g f a c i e s 2B i n borehole 7402 may be analagous to the t r a n s p o r t e d t e r r e s t i a l o r g a n i c matter, d e s c r i b e d by Coleman (1976), on the mouth bars of M i s s i s s i p p i R i v e r D e l t a d i s t r i b u t a r i e s . There the organic m a t e r i a l comes from logs and organic d e b r i s t r a n s p o r t e d down the r i v e r d u r i n g times of f l o o d . On reaching the nearshore zone, wave a c t i o n g r i n d s down the coarser wood p a r t i c l e s i n t o c o n c e n t r a t i o n s of l a r g e q u a n t i t i e s of organic d e b r i s i n the upper p o r t i o n s of d i s t r i b u t a r y mouth bars. 2.2.10 F a c i e s 3A - D e s c r i p t i o n T h i s f a c i e s occurs above f a c i e s 2A i n numerous boreholes i n the Babcock area where i t ranges in t h i c k n e s s between 14 and 31 m. L a t e r a l l y , t h i s f a c i e s i s r e p l a c e d by f a c i e s 3B ( F i g u r e s 4.8, 49). The isopach map (Figure 68) shows that f a c i e s 3A occurs i n l i n e a r N-S or NE-SW t r e n d i n g areas 0.75-1.5 km wide f l a n k e d by f a c i e s 3B d e p o s i t s . The c r o s s s e c t i o n (Figure 49) suggests that f a c i e s 3A may be i n part e q u i v a l e n t to f a c i e s 2B i n the southern p a r t of the Babcock area. The base of f a c i e s 3A i s e r o s i o n a l . In borehole 7306 (Figure 49), approximately 14 m of sediment appears to have been eroded from the top of f a c i e s 2A, by comparison with nearby boreholes. In other s e c t i o n s , e r o s i o n i s much l e s s (approximately 1-2 m). L i t h o l o g i e s c o n s i s t mainly of f i n e - to c o a r s e - g r a i n e d sandstones, with minor s i l t s t o n e and o c c a s i o n a l i n t e r b e d s of N 500 1000 MM • .77!! VJ. • . 775: . I I #7107 z row •••./••.»» o / J.-.|-.-.-\LV.-.-.-.-.-.-.-;./.•. -30 / -7118 7710^' contours in metres I Distribution of Fac ies 3B ISOPACH MAP FACIES 3A/3B 54 55 Figure 68. Isopach map of facies 3A and 3B in the Babcock area, 175 F i g u r e 69a. Core from borehole QBD 7711 (113 m) showing the e r o s i o n a l c o n t a c t between f a c i e s 3A and f a c i e s 2k. Note the presence of c o a l spar and mudstone pebbles i n f a c i e s 3A sandstones and t h e i r c o a r s e r g r a i n - s i z e compared to sandstones i n f a c i e s 2a. F i g u r e 69b. Core from borehole QBD 7306 (1212 f t ) . In t h i s core, f a c i e s 3A sandstones c o n t a i n abundant mudstone r i p - u p c l a s t s . F i g u r e 69c. Core from the upper part of f a c i e s 3A i n borehole QBD 7711 (117 m). Bedding c o n s i s t s mainly of p a r a l l e l l a m i n a t i o n s , d e f i n e d by t h i n a l t e r n a t i o n s of f i n e - g r a i n e d sandstone, s i l t s t o n e and carbonaceous d e b r i s , and r i p p l e s . Compare t h i s to the c o a r s e r and more massive sandstones i n the lower p a r t of f a c i e s 3A i n F i g u r e 69a. 176 177 F i g u r e s 70a,b,c,d. Core from the lower p a r t of f a c i e s 3A. F i g u r e s 70_a,b,c. Cross bedding i n medium- to c o a r s e - g r a i n e d sandstones (a = QBD 7209, 940.5 f t ; b = QBD 7209, 935 f t ; c = QBD 7721 , 191.7 m). F i g u r e 70d. Massive f i n e - to medium-grained sandstone (QBD 7711, 129.6 m). F i g u r e s 70e,f_,g_. Core from the upper p a r t of f a c i e s 3A. F i g u r e 70e. P a r a l l e l l a m i n a t i o n d e f i n e d by t h i n laminae of carbonaceous d e b r i s i n f i n e - g r a i n e d sandstone (QBD 7711, 115 m) . F i g u r e 70f. F i n e - g r a i n e d r i p p l e d sandstone with c u r r e n t r i p p l e s with s i l t s t o n e / c a r b o n a c e o u s drapes. (QBD 7711, 115 m) . F i g u r e 70g. R i p p l e s (?wave formed) and t h i n i n t e r l a y e r e d sandstone-mudstone. (QBD 7720, 101.75). 1 79 dark grey mudstone (Figures 69, 70). The sandstones are moderately to very w e l l s o r t e d c h e r t or c a l c - a r e n i t e s . Mudstone pebbles and l a r g e r i p - u p c l a s t s are common and c o a l spar i s o c c a s i o n a l l y present near the base ( F i g u r e s 69a,b). In some core s , conglomerates up to 80 cm t h i c k are present at the base. The sandstones i n f a c i e s 3A t y p i c a l l y form s i n g l e or stacked fining-upward sequences, 2.5-13 m t h i c k , with abrupt or e r o s i o n a l bases. In some cores g r a i n - s i z e remains r e l a t i v e l y uniform throughout or f i n e s upward only i n the top few metres. Primary sedimentary s t r u c t u r e s i n the lower p a r t of these sequences i n c l u d e s cross-bedding ( s e t s up to 50 cm t h i c k ) and p a r a l l e l bedding. The sandstones i n the lower part are commonly massive ( F i g u r e s 69a,b). P a r a l l e l l a m i n a t i o n and r i p p l e s c h a r a c t e r i s e the upper p a r t s of the fining-upward sequences ( F i g u r e s 69c, 70e,f,g). Wave- and current-formed r i p p l e s , c l i m b i n g r i p p l e l a m i n a t i o n and f l a s e r bedding are p r e s e n t . F i n e -g r a i n e d carbonaceous m a t e r i a l i s very common in the upper p a r t of f a c i e s 3A and occurs as t h i n laminae i n p a r a l l e l bedded sandstones or as f l a s e r s i n r i p p l e d sandstone. In some cores the sandstones are interbedded with dark grey mudstones up to 1.5 m t h i c k (e.g., borehole 7306, F i g u r e 49). The mudstones c o n t a i n t h i n s t r e a k s of r i p p l e d , l e n t i c u l a r of f l a s e r bedded sandstone. Convolute bedding i s common i n these i n t e r v a l s . O c c a s i o n a l l y the mudstones c o n t a i n s h e l l fragments. Burrows are o c c a s i o n a l l y present near the top of f a c i e s 3A, but elsewhere b i o g e n i c s t r u c t u r e s are notably absent. 180 2.2.11 F a c i e s 3B - D e s c r i p t i o n T h i s f a c i e s occurs i n cores i n the Babcock area where i t i s e q u i v a l e n t l a t e r a l l y to f a c i e s 3A (F i g u r e s 48, 49, 68). L i t h o l o g i e s c o n s i s t of f i n e - to medium-grained sandstones, s i l t s t o n e s and mudstones. These d e p o s i t s t y p i c a l l y form coarsening-upward sequences, 9-18 m t h i c k , which g r a d a t i o n a l l y o v e r l i e f a c i e s 2A (Figure 71). The cont a c t between f a c i e s 2A and 3B i s marked by an inc r e a s e i n the s i l t and c l a y content which shows up c l e a r l y on gamma ray logs ( F i g u r e s 48, 49). The sandstones are moderately to very w e l l s o r t e d f e l d s p a t h i c c h e r t a r e n i t e s or c h e r t a r e n i t e s . They occur i n u n i t s which range i n t h i c k n e s s from a few cent i m e t r e s to 5 m, interbedded with t h i n ( g e n e r a l l y l e s s than 50 cm) s i l t s t o n e s and mudstones. Sandstone u n i t s are t h i c k e r i n the upper p a r t of the f a c i e s . Mudstones and s i l t s t o n e s occur throughout but are more common i n the lower p a r t . F a c i e s 3B i s c h a r a c t e r i s e d by p a r a l l e l beds and numerous burrows ( F i g u r e s 71, 72). The p a r a l l e l bedding i s d e f i n e d by t h i n laminae of s i l t s t o n e or disseminated carbonaceous m a t e r i a l interbedded with the sandstones. Burrows are dominated by 'U'-shaped, v e r t i c a l and s u b - v e r t i c a l types and i n c l u d e A r e n i c o l i t e s , D i p l o c r a t e r i o n , Asterosoma and S k o l i t h o s . H o r i z o n t a l burrows s i m i l a r to H e l m i n t h o i d a / S c a l a r i t u b a are o c c a s i o n a l l y present near the base of f a c i e s 3B. The burrows occur most commonly i n the a r g i l l a c e o u s i n t e r v a l s . S t r o n g l y burrowed beds commonly a l t e r n a t e with i n t e r v a l s i n which burrows are absent or r a r e . Truncated burrows and escape t r a c e s are common ( F i g u r e s 7 2 e , f ) . These b i o t u r b a t i o n p a t t e r n s suggest that d e p o s i t i o n i n f a c i e s 3A 181 F i g u r e 7J_. Core of f a c i e s 3B from borehole QBD 7201. Note the g r a d a t i o n a l lower c o n t a c t of f a c i e s 3B with f a c i e s 2A (A) and the abrupt top of f a c i e s 3B (B). In t h i s c o r e . f a c i e s 3B i s o v e r l a i n by carbonaceous mudstones of f a c i e s 5. In the lower p a r t of f a c i e s 3B f i n e - g r a i n e d sandstones and s i l t s t o n e s occur interbedded with t h i n laminae of dark grey mudstone and carbonaceous d e b r i s . P a r a l l e l bedding i s w e l l developed. The sandstones coarsen-upwards and a r g i l l a c e o u s m a t e r i a l becomes l e s s common at the top. Note the numerous burrows i n f a c i e s 3B. These i n c l u d e 'U'-shaped (U) and v e r t i c a l (S) types ( S k o l i t h o s ) . 182 183 F i g u r e 72. Trace f o s s i l s and b i o t u r b a t i o n i n f a c i e s 3B. F i g u r e s 72a,b. Large 'U'-shaped burrows (probably D i p l o c r a t e r i o n or R h i z o c o r a l l i u m ) (QBD 7754, 145.6 m). F i g u r e 72c. S t r o n g l y burrowed i n t e r v a l (QBD 7201, 248'). F i g u r e 72d. Th i n v e r t i c a l mudstone f i l l e d burrows i n p a r a l l e l bedded sandstone (QBD 7754, 138 m). F i g u r e s 72e,f. Note the predominance of v e r t i c a l to s u b - v e r t i c a l burrows, the a l t e r n a t i o n of s t r o n g l y burrowed i n t e r v a l s (b) with i n t e r v a l s i n which burrows are absent, t r u n c a t e d burrows (t) and escape t r a c e s (e) (QBD 7201, 255 f t and QBD 7201, 262 f t ) . F i g u r e s 72g,h. Trace formed by burrowing b i v a l v e (?) (QBD 7754, 146.15 m). 784-185 was i n t e r m i t t e n t and a l t e r n a t e d with p e r i o d s of e r o s i o n (Howard, 1978) . Other sedimentary s t r u c t u r e s i n f a c i e s 3B i n c l u d e r i p p l e s and r a r e c r oss-bedding. Low angle cross-bedded sandstones (0.1-1 m t h i c k ) with abrupt bases and r i p p l e d tops are present near the base of some cores ( F i g u r e 73a). These beds o c c a s i o n a l l y c o n t a i n small mudstone r i p - u p c l a s t s i n d i c a t i n g they were d e p o s i t e d by high energy events. The top of f a c i e s 3B i s abrupt and o v e r l a i n by f a c i e s 3C or more commonly by s i l t s t o n e s , carbonaceous mudstones and t h i n c o a l seams at the base of f a c i e s 5. 2.2.12 F a c i e s 3A and 3B - I n t e r p r e t a t i o n The i n t e r n a l c h a r a c t e r i s t i c s , a r e a l d i s t r i b u t i o n and f a c i e s a s s o c i a t i o n s of f a c i e s 3A and 3B suggest that they represent s u b t i d a l channel and shoal d e p o s i t s s i m i l a r to those found at the mouths of modern e s t u a r i e s - (Oomkens and Terwindt, 1960; Robinson, 1960; Reineck and Singh, 1973, p. 315-321; Greer, 1975) and t i d e dominated d e l t a s (Meckel, 1975; Wright et a l . , 1975). The most comprehensive d e s c r i p t i o n of modern s u b t i d a l channels and shoals i s provided by Reineck and Singh (1973, p. 315-321) f o r the channels and s h o a l s (sand tongues) of the Nordergrunde and Outer Jade regions i n the North Sea. Channels and shoals are o r i e n t e d p e r p e n d i c u l a r to the s h o r e l i n e . Channels are up to 3 km wide. The shoals range from 2.6-18 km long and average 2 km wide i n the Nordergrunde r e g i o n . Water depths (up to 20 m) and v e l o c i t i e s are g r e a t e s t i n the channels. On the 186 F i g u r e 73a. Very f i n e - g r a i n e d sandstone bed c h a r a c t e r i s e d i n t e r n a l l y by low angle c r o s s - b e d d i n g and a r i p p l e d top. Base of f a c i e s 3B i n borehole QBD 7715, 240.7 m. F i g u r e s 73b,d. P a r a l l e l l a m i n a t i o n and r i p p l e s i n f a c i e s 3B. (b = QBD 7754, 144.65 ; d = QBD 7724, 185.4 m). F i g u r e 73c. Small f l e c k s of d isseminated carbonaceous d e b r i s on a bedding plane s u r f a c e i n f a c i e s 3B sandstones. C u r r e n t s are i n d i c a t e d by the p r e f e r r e d o r i e n t a t i o n of the carbonaceous d e b r i s . (QBD 7754, 146.3 m). F i g u r e 73e. I n f e r r e d t i d a l f l a t d e p o s i t s ( f a c i e s 3C) i n borehole QBD 7711. Note the t h i c k e r u n i t s of sandstone i n the lower pa r t (low t i d a l f l a t d e p o s i t s ) o v e r l a i n by l e n t i c u l a r , f l a s e r bedded and t h i n i n t e r l a y e r e d sandstones and mudstones (mid t i d a l f l a t d e p o s i t s ) which grade upwards i n t o massive s i l t y mudstones (high t i d a l f l a t d e p o s i t s ) . The C c o a l seam occurs a few metres above t h i s c o r e . ) . 187 5 c m 188 sh o a l s , water depths are l e s s and maximum v e l o c i t i e s are lower. In the Nordergrunde r e g i o n , the s h o a l s are seaward ex t e n s i o n s of i n t e r t i d a l f l a t s and are r e f e r r e d to as sand tongues. The l a r g e s t bedforms (sand waves with amplitudes up to 5.5 m and megaripples) are present i n the channels. Bedding types on the shoals i n c l u d e r i p p l e s , megaripples and laminated sands. Channels and shoals migrate l a t e r a l l y at average r a t e s of 27-115 m/year. The t h i n conglomerates at the base of f a c i e s 3A re p r e s e n t s channel l a g d e p o s i t s . Cross-bedding i n the lower p a r t of the f a c i e s i s the r e s u l t of the m i g r a t i o n of dunes or sand waves i n the deeper p a r t s of the channels. In modern t i d a l channels muds and s i l t s are d e p o s i t e d from suspension d u r i n g s l a c k t i d e s . The presence of numerous mudstone r i p - u p c l a s t s i n f a c i e s 3A suggests that these suspension d e p o s i t s were l a r g e l y eroded d u r i n g p e r i o d s of str o n g c u r r e n t a c t i v i t y . T h ick beds of mudstone which are present i n a few c o r e s , may have formed i n deep-protected holes i n the channel as d e s c r i b e d by Greer (1975) fo r t i d a l channels of the Georgia c o a s t . L i t h o l o g i e s are f i n e r - g r a i n e d i n f a c i e s 3B than f a c i e s 3A, r e f l e c t i n g the lower c u r r e n t v e l o c i t i e s over the shoals compared to the channels. The numerous burrows i n t h i s f a c i e s a l s o r e f l e c t s the g e n e r a l l y lower energy l e v e l s . B i o t u r b a t i o n p a t t e r n s i n f a c i e s 3B i n d i c a t e d e p o s i t i o n on the shoals was i n t e r m i t t e n t and a l t e r n a t e d with p e r i o d s of e r o s i o n . P a r a l l e l bedding which predominates i n f a c i e s 3B may have been d e p o s i t e d from suspension c l o u d s generated by s h o a l i n g waves or strong t i d a l c u r r e n t s as envisaged by Reineck and Singh (1973, p. 317) 189 f o r s i m i l a r d e p o s i t s i n the Nordergrunde and Outer Jade Shoals or d u r i n g storms. The fining-upward sequences i n f a c i e s 3A are probably due to the l a t e r a l s h i f t i n g of the channels and s h o a l s . T h i s mechanism i s w e l l documented i n modern t i d a l channels (Oomkens and Terwindt, 1960; Reineck and Singh, 1973, p. 315; Meckel, 1975). Some of the superimposed fining-upward sequences may be the r e s u l t of p a r t i a l e r o s i o n of deeper channel f i l l d e p o s i t s by shallower channels as the system progrades seaward, as suggested by Meckel (1975) fo r the t i d a l channel d e p o s i t s i n the Colorado D e l t a . In the shoals of the Nordergrunde and Outer Jade, sediments become c o a r s e r grained above wave base and mud l a y e r s are absent (Reineck and Singh, 1973, p. 321). Seaward the shoals are r e p l a c e d by t r a n s i t i o n zone muds, s i l t s and storm sand l a y e r s . By analogy with these modern shoal d e p o s i t s , i t i s suggested that the c o a r s e n i n g upward sequences i n f a c i e s 3B are the r e s u l t of the seaward m i g r a t i o n of c o a r s e r - g r a i n e d shoal sediments over f i n e r - g r a i n e d t r a n s i t i o n zone d e p o s i t s . The low angle c r o s s -bedded sandstones which occur interbedded with mudstones at the base of f a c i e s 3B presumably represent storm d e p o s i t s formed below f a i r weather wave base. 2.2.13 F a c i e s 3C - D e s c r i p t i o n T h i s f a c i e s has been recognised i n only a few c o r e s , o v e r l y i n g f a c i e s 3A and o c c a s i o n a l l y f a c i e s 3B. The c o n t a c t with f a c i e s 3A i s g r a d a t i o n a l and d i f f i c u l t to d e f i n e p r e c i s e l y . F a c i e s 3C i s commonly absent and f a c i e s 3A and 3B are o v e r l a i n 190 d i r e c t l y by f a c i e s 5. The maximum t h i c k n e s s of f a c i e s 3C i s approximately 10 m. L i t h o l o g i e s c o n s i s t of f i n e - to medium-grained sandstones, s i l t s t o n e s and s i l t y mudstones. F i n e - g r a i n e d carbonaceous m a t e r i a l i s common on bedding s u r f a c e s . Burrows are o c c a s i o n a l l y present but beds are r a r e l y s t r o n g l y b i o t u r b a t e d . Sandstones comprise approximately 50% of the f a c i e s and are more common in the lower p a r t where they occur i n beds up to 2 m t h i c k ( F i g u r e 73e). In some s e c t i o n s the sandstones c o n t a i n small mudstone r i p - u p c l a s t s . E r o s i o n a l l y - b a s e d fining-upward sequences c o n s i s t i n g of massive or cross-bedded sandstones o v e r l a i n by p a r a l l e l bedded and r i p p l e d sandstones and s i l t s t o n e s are common in the lower p a r t of f a c i e s 3C. The middle part of f a c i e s 3C c o n s i s t s of s i l t y mudstones interbedded with t h i n s i l t s t o n e s and f i n e - g r a i n e d sandstones (max. 15 cm t h i c k ) , which e x h i b i t l e n t i c u l a r and f l a s e r bedding, r i p p l e s , p a r a l l e l bedding and o c c a s i o n a l wavy bedding ( F i g u r e s 73e, 74). Thin a l t e r n a t i n g l a y e r s of sandstone and mudstone are common. Climbing r i p p l e s , t r u n c a t e d r i p p l e s and convolute bedding are present i n a few s e c t i o n s . Small flame and l o a d s t r u c t u r e s are present at the base of some of the sandstones. The sediments i n the middle of f a c i e s 3C grade upwards i n t o massive s i l t y mudstones and s i l t s t o n e s i n the upper p a r t of the f a c i e s which i n turn are o v e r l a i n by carbonaceous mudstones with roots and t h i n c o a l seams at the base of f a c i e s 5. 2.2.14 F a c i e s 3C - I n t e r p r e t a t i o n The upper p a r t of f a c i e s 3C c o n t a i n s abundant sedimentary F i g u r e 74. Sedimentary and b i o g e n i c s t r u c t u r e s i n f a c i e s 3C. F i g u r e 74a. Coarse and f i n e l y i n t e r l a y e r e d sandstone and mudstone ( s ) , r i p p l e s and l e n t i c u l a r bedding ( r ) , t r u n c a t e d bedding ( t ) and flame s t r u c t u r e s ( f ) . (QBD 7708, 89.3 m). F i g u r e 74b. F l a s e r bedding with t h i n l y i n t e r l a y e r e d s i l t s t o n e and mudstone at the top. (QBD 7721, 181.1 m). Fi g u r e 74c. Sandstone r i p p l e s with mudstone drapes, t h i n l y i n t e r l a y e r e d sandstone and mudstone amd l e n t i c u l a r bedding. (QBD 7208, 500 f t ) . F i g u r e 74d. L e n t i c u l a r bedding and t h i n to c o a r s e l y i n t e r l a y e r e d sandstone and mudstone. (QBD 7711, 108 f t ) . F i g u r e 74e. B i o t u r b a t i o n i n f a c i e s 3C sandstones and s i l t s t o n e s . (QBD 7719, 73.95 m). F i g u r e 74f. F l a s e r bedding, l e n t i c u l a r bedding and t h i n l y i n t e r l a y e r e d sandstone and mudstone. (QBD 7721, 178.9 m). F i g u r e 74g. L e n t i c u l a r , wavy(w) and r i p p l e bedding. S o f t sediment deformation s t r u c t u r e s occur i n the lower r i g h t of the c o r e . (QBD 7754, 44 m). 112. 5cm 193 s t r u c t u r e s (e.g., l e n t i c u l a r , f l a s e r , wavy and t h i n , i n t e r l a y e r e d bedding) which show that the environment was c h a r a c t e r i s e d by the a l t e r n a t i o n of bedload and suspension d e p o s i t i o n . T h i s , together with i t s s t r a t i g r a p h i c p o s i t i o n above s u b t i d a l d e p o s i t s and below non-marine carbonaceous mudstones and t h i n c o a l s , suggests that f a c i e s 3C was d e p o s i t e d i n a t i d a l f l a t environment. Studi e s of modern t i d a l f l a t s (Van S t r a a t e n , 1954; K l e i n , 1963; Evans, 1965) have d e f i n e d three d i s t i n c t zones. These zones are (from low t i d e to high t i d e ) , the low t i d a l f l a t , the mid t i d a l f l a t and the high t i d a l f l a t . In the low t i d a l f l a t , bedload t r a n s p o r t predominates and the sediments are mainly sands. Landward, in the mid t i d a l f l a t , mixed suspension-bedload sedimentation produces l e n t i c u l a r , f l a s e r , wavy and t h i n i n t e r l a y e r e d bedding. The high t i d a l f l a t i s c h a r a c t e r i s e d by d e p o s i t i o n of mud from suspension. When these three zones prograde seaward, a f i n i n g upward sequence i s produced. By analogy with the modern t i d a l f l a t sediments, low t i d a l f l a t d e p o s i t s are probably represented by the t h i c k e r beds of sandstone i n the lower part of f a c i e s 3C, m i d - t i d a l f l a t d e p o s i t s by the t h i n interbedded, sandstones, s i l t s t o n e s and mudstones i n the upper p a r t of the f a c i e s and the h i g h t i d a l f l a t d e p o s i t s by the massive s i l t s t o n e s and mudstones at the top of the f a c i e s . 2.2.15 F a c i e s 4 - D e s c r i p t i o n F a c i e s 4 i s present i n cores near the Duke and Honeymoon P i t s i n the i n t e r v a l between the B9 and B10 c o a l seams (F i g u r e 194 50) (note: B9 and B10 are e q u i v a l e n t to the D and C seams r e s p e c t i v e l y i n the Babcock a r e a ) . F a c i e s 4 i s absent n o r t h of the Honeymoon P i t and e q u i v a l e n t beds occur w i t h i n f a c i e s 1A/1B, 2A/B and 3A/B/C. South of the Duke P i t , f a c i e s 4 pinches out and the B9 c o a l seam i s o v e r l a i n d i r e c t l y by f a c i e s 5. F a c i e s 4 ranges in t h i c k n e s s from 0-15 m. L i t h o l o g i e s c o n s i s t of f i n e - g r a i n e d sandstones and s i l t s t o n e s o c c a s i o n a l l y interbedded with t h i n dark grey mudstones. The b a s a l u n i t of f a c i e s 4 i s d i s t i n c t i v e and c o n s i s t s of a s t r o n g l y b i o t u r b a t e d i n t e r v a l , 0.5-6 m t h i c k , which o v e r l i e s a b r u p t l y the B9 c o a l seam or a t h i n bed of carbonaceous mudstone above B9. In some s e c t i o n s the b a s a l u n i t c o n s i s t s of dark grey mudstone interbedded with t h i n s i l t s t o n e and very f i n e - g r a i n e d sandstone beds while i n other s e c t i o n s , mudstones are ra r e and the l i t h o l o g i e s c o n s i s t mainly of interbedded s i l t s t o n e s and very f i n e - g r a i n e d sandstones. B i o t u r b a t i o n i s caused e n t i r e l y by burrowing organisms ( F i g u r e s 75a,b,d). D i s t i n c t s p e c i e s are d i f f i c u l t to i d e n t i f y as the sediments are g e n e r a l l y completely reworked and the shapes of burrows are not w e l l d e f i n e d . H o r i z o n t a l burrows with diameters of 0.5-0.7 cm are most common and v e r t i c a l or s u b - v e r t i c a l and 'U'-shaped burrows are a l s o p r e s e n t . In one core, burrows c o n s i s t i n g of 1 mm diameter, h o r i z o n t a l to i n c l i n e d s i l t s t o n e f i l l e d tubes ( Chondrites?) are p resent i n mudstones at the base of t h i s u n i t ( F i g u r e 75d). P a r a l l e l bedding, l e n t i c u l a r bedding and o c c a s i o n a l r i p p l e s are present i n l e s s s t r o n g l y b i o t u r b a t e d i n t e r v a l s . In many of the c o r e s , the b a s a l u n i t i s o v e r l a i n by coarsening-upward sequences of s i l t s t o n e and sandstone which 195 range i n t h i c k n e s s from 2.5-5.3 m (Figure 50). Bedding i n these sequences c o n s i s t s mainly of p a r a l l e l bedding and r i p p l e s . Trough cross-bedding occurs very r a r e l y i n the upper p a r t . Burrows are common and i n c l u d e l a r g e 'U'-shaped burrows and dense boxworks of h o r i z o n t a l to i n c l i n e d burrows ( Paleophycus ? ) . In a few cores the tops of these sequences are s t r o n g l y b i o t u r b a t e d by burrows or r o o t s . In other s e c t i o n s the beds o v e r l y i n g the b a s a l u n i t c o n s i s t of interbedded sandstones and s i l t s t o n e s . S h e l l fragments showing evidence of t r a n s p o r t a t i o n are present i n a few beds. Primary sedimentary s t r u c t u r e s i n these d e p o s i t s c o n s i s t mainly of f l a s e r bedding and r i p p l e s ( F i g u r e s 7 5 c , e , f ) . Often the f l a s e r s are formed by t h i n laminae of f i n e - g r a i n e d carbonaceous m a t e r i a l . Other sedimentary s t r u c t u r e s present i n c l u d e p a r a l l e l bedding, l e n t i c u l a r bedding and o c c a s i o n a l wavy bedding. Cross-bedding i s r a r e . Burrows are o f t e n present i n the s i l t s t o n e s and o c c a s i o n a l beds are s t r o n g l y b i o t u r b a t e d . In many s e c t i o n s the sandstones and s i l t s t o n e s occur w i t h i n sharply b a s a l f i n i n g -upward sequences which range i n t h i c k n e s s from 0.9-4.6 m. Sandstones at the base of these sequences are t y p i c a l l y massive with s i l t s t o n e pebbles and r i p - u p c l a s t s . R i p p l e s and f l a s e r bedding are common i n the upper p a r t . F a c i e s 4 i s o v e r l a i n g r a d a t i o n a l l y by s i l t s t o n e s , carbonaceous mudstones and t h i n c o a l seams at the base of f a c i e s 5. 2.2.16 F a c i e s 4 - I n t e r p r e t a t i o n The o v e r a l l s t r a t i g r a p h i c context of t h i s f a c i e s ( r e p l a c e d to the north by marine d e p o s i t s of the Babcock member and to the 196 F i g u r e 7J5.. Sedimentary and b i o g e n i c s t r u c t u r e s i n f a c i e s 4. F i g u r e s 75a,b. S t r o n g l y b i o t u r b a t e d s i l t s t o n e (MDD 7908, 140.9 m) . Fi g u r e 75c. I n t e r l a y e r e d s i l t s t o n e and mudstone, l e n t i c u l a r and r i p p l e bedding. (MDD 7822, 164.7 m). Fi g u r e 75d. S t r o n g l y b i o t u r b a t e d s i l t s t o n e . C h o n d r i t e s burrows ( c l are present i n the lower p a r t of the c o r e . (MDD 7908, 142.9 m). F i g u r e s 75e,f. R i p p l e s and f l a s e r bedding. F l a s e r s are mainly c o n c e n t r a t i o n s of carbonaceous d e b r i s , (e = MDD 7822, 164 m ; f = MUD 7704, 86.6 m). 197 198 south by c o a s t a l p l a i n sediments of f a c i e s 5), together with the occurrence of strong b i o t u r b a t i o n , marine t r a c e f o s s i l s , s h e l l fragments and sedimentary s t r u c t u r e s i n d i c a t i v e of a l t e r n a t i n g bedload and suspension d e p o s i t i o n suggests that f a c i e s 5 formed in l a g o o n - i n t e r t i d a l environments. The s t r o n g l y b i o t u r b a t e d f i n e - g r a i n e d d e p o s i t s at the base of the f a c i e s are i n t e r p r e t e d as forming i n areas of the lagoon where low sedimentation r a t e s allowed the infauna to thoroughly rework the sediments. Intense b i o t u r b a t i o n i s very common i n modern and an c i e n t l a g o o n a l sequences (e.g., Warme, 1971; K r a f t , 1971; Reineck and Singh, 1980, p. 427; B a l s l e y , 1980). Coarsening-upward s a n d s t o n e - s i l t s t o n e beds above the b a s a l b i o t u r b a t e d u n i t may represent washover fan or small lagoon margin d e l t a (McGowan, 1970) d e p o s i t s . The sharp based f i n i n g -upward s a n d s t o n e - s i l t s t o n e u n i t s are i n t e r p r e t e d as t i d a l channel p o i n t bar d e p o s i t s , while the t h i n interbedded sandstones and s i l t s t o n e s e x h i b i t i n g f l a s e r , l e n t i c u l a r , wavy bedding and r i p p l e s may have been d e p o s i t e d on t i d a l f l a t s . 2.2.17 F a c i e s 5 - D e s c r i p t i o n F a c i e s 5 c o n s i s t s of a 30-50 m t h i c k i n t e r v a l of interbedded sandstones, s i l t s t o n e s , mudstones and c o a l s which occur above f a c i e s 4 i n the Duke and Honeymoon P i t s and above f a c i e s 3A, 3B, 3C or 2B i n the area to the north ( F i g u r e s 48, 49, 50).Three main s u b - f a c i e s are recognised ( f a c i e s 5A, 5B and 5C) based on d i f f e r e n c e s i n l i t h o l o g y , p h y s i c a l and b i o g e n i c s t r u c t u r e s . 199 F a c i e s 5A L i t h o l o g i e s i n t h i s f a c i e s c o n s i s t of black carbonaceous mudstones and c o a l s . Three c o a l seams are normally present i n f a c i e s 5. In the Babcock area they are r e f e r r e d to as the A, B, C seams. The C seam occurs near the base, the B seam i s present in the middle of the f a c i e s and the A seam occurs near the top, below the Gates/Hulcross c o n t a c t . E q u i v a l e n t seams in the Duke and Honeymoon P i t s are r e f e r r e d to as the B10, B11 and B12 seams. These seams range in t h i c k n e s s from 0-1 m. In most s e c t i o n s they are l e s s than 0.5 m t h i c k . The carbonaceous mudstones are found most commonly above and below the c o a l seams where they occur i n beds up to 4 m t h i c k . They are a l s o present i n t h i n n e r beds interbedded with f a c i e s 5C. I n t e r n a l l y these d e p o s i t s are g e n e r a l l y s t r o n g l y b i o t u r b a t e d and massive. P a r a l l e l bedding i s o c c a s i o n a l l y p resent. Roots and c o a l spar are common and w e l l preserved p l a n t fragments are f r e q u e n t l y present on bedding planes. P y r i t e commonly r e p l a c e s r o o t s adjacent to the A/B12 seam and the C seam. The f o l l o w i n g p l a n t s p e c i e s have been i d e n t i f i e d by Dr. G. E. Rouse (U.B.C.): Asplenium c f . r i g i d i u m C o n i o p t e r i s c f . onychiodes FERNS C o n i o p t e r i s c f . a r t i c a  Sagenopteris c f . w i l l i a m s i i E l a t i d e s c u r v i o f o l i a CONIFERS E l a t i d e s c f . s p l e n d i d a P t i l o p h y l l u m c f . a r c t i c u m CYCAD Ginkgo d i g i t a t a GINGKO 200 c f . C y p e r i t e s sp ANGIOSPERM F a c i e s 5B T h i s f a c i e s c o n s i s t s of f i n e - to c o a r s e - g r a i n e d sandstones with o c c a s i o n a l t h i n beds of s i l t s t o n e . The sandstones are w e l l s o r t e d c h e r t a r e n i t e s and o f t e n c o n t a i n mudstone pebbles, r i p - u p c l a s t s and c o a l spar. These d e p o s i t s occur w i t h i n a b r u p t l y or e r o s i o n a l l y based u n i t s , 2-15 m t h i c k , which f i n e upwards and are o v e r l a i n g r a d a t i o n a l l y by f a c i e s 5C. In some of the t h i c k e r u n i t s , g r a i n -s i z e remains f a i r l y constant i n the lower p a r t and f i n e s upwards only i n the top few metres. I n t e r n a l l y the sandstones are g e n e r a l l y massive or c r o s s -bedded i n the lower part with r i p p l e s , p a r a l l e l bedding and o c c a s i o n a l f l a s e r bedding present near the top ( F i g u r e s 76a, 77a). In some s e c t i o n s , t h i s sequence of sedimentary s t r u c t u r e s occurs i n s m a l l e r , stacked u n i t s of sandstone .1-4 m t h i c k , f r e q u e n t l y separated by t h i n (10-50 cm) beds of s i l t s t o n e . Medium- to c o a r s e - g r a i n e d sandstones i n f a c i e s 5B crop out on Ko s t u i c k Mountain and on Roman Mountain, 5.5 km to the south. Bedding i n these sandstones c o n s i s t s mainly of t a b u l a r and trough cross-bedding (Figure 77a). Sets are 15-50 cm t h i c k . On Kostuick Mountain the average d i p of the t a b u l a r f o r e s e t s i s i n a s o u t h e r l y d i r e c t i o n (192°) ( F i g u r e 6 5 ) . . R e a c t i v a t i o n s u r f a c e s are present i n some s e t s . On Roman Mountain, the average d i p of the t a b u l a r f o r e s e t s i s towards 292° (F i g u r e 65). F a c i e s 5C 201 L i t h o l o g i e s c o n s i s t of interbedded s i l t s t o n e s , mudstones and f i n e - g r a i n e d sandstones. In cores these d e p o s i t s are abundant and normally comprise over 50% of f a c i e s 5. The sandstones t y p i c a l l y occur as a b r u p t l y or e r o s i o n a l l y based beds, 1-70 cm t h i c k . F i n e - g r a i n e d carbonaceous d e b r i s i s l o c a l l y abundant on bedding s u r f a c e s ( F i g u r e 76d). P l a n t fragments are o c c a s i o n a l l y present. Primary sedimentary s t r u c t u r e s are dominated by p a r a l l e l bedding, r i p p l e s and c l i m b i n g r i p p l e l a m i n a t i o n ( F i g u r e s 76, 77b). O c c a s i o n a l l y the sandstones e x h i b i t f l a s e r bedding with the f l a s e r s formed by c o n c e n t r a t i o n s of f i n e - g r a i n e d carbonaceous d e b r i s . Cross bedding i s very r a r e . Convolute bedding and other s o f t sediment deformation s t r u c t u r e s are common (Fig u r e s 76g,77c). B i o t u r b a t i o n caused by burrowing organisms and ro o t s i s common and f r e q u e n t l y d e s t r o y s a l l t r a c e of bedding ( F i g u r e 77b). Burrows c o n s i s t mainly of v e r t i c a l , s u b - v e r t i c a l and o c c a s i o n a l 'U--shaped types which range i n width from 0.1-2 cm. Below he Gates/Hulcross c o n t a c t , burrows and roots i n t h i s f a c i e s are o f t e n r e p l a c e d by p y r i t e . Coarsening-upward sequences up to 5 m t h i c k are common. These are c h a r a c t e r i s e d by an upward i n c r e a s e i n the amount and t h i c k n e s s of sandstone beds and c u r r e n t formed sedimentary s t r u c t u r e s . The tops of these sequences are o f t e n b i o t u r b a t e d by roots and o v e r l a i n by carbonaceous mudstones of f a c i e s 5A. Fining-upwards sequences up to 2 m t h i c k are a l s o p r e s e n t . 2.2.18 F a c i e s 5 - I n t e r p r e t a t i o n 202 F i g u r e 7j>. Sedimentary and b i o g e n i c s t r u c t u r e s i n f a c i e s 5. F i g u r e 76a. Cross-bedded sandstone from f a c i e s 5B (QBD 7302, 74 f t T -F i g u r e s 76b,c. P a r a l l e l bedding, r i p p l e s and c l i m b i n g r i p p l e s i n f a c i e s 5C d e p o s i t s , (b = QBD 7721, 170.7 m ; c = QBD 7721, 191 m). F i g u r e 76d. Interbedded mudstones and sandstones i n f a c i e s 5C. Note the abundant carbonaceous d e b r i s and c o a l spar ( s ) . (QBD 7714, 91.25 m). F i g u r e 76e• S i l t s t o n e from f a c i e s 5C a few metres below the G a t e s / H u l c r o s s contact.Note the p y r i t e (py) which occurs a s s o c i a t e d with r o o t s at the top of the core (QBD 7720, 64 m) . F i g u r e 76f. Interbedded mudstones and sandstones i n f a c i e s 5C. Note the sma l l burrow. (QBD 7751, 29.55 m). F i g u r e 76g. Convolute bedding and syn-sedimentary f a u l t s i n f a c i e s 5C d e p o s i t s (QBD 7754, 118.65 m). F i g u r e 76h. Roots i n massive mudstones of f a c i e s 5A. (QBD 7721, 149.3 m). 203 204 F i g u r e 77a. Trough and t a b u l a r c r o s s - b e d d i n g i n outcrops of facTes 5B sandstones on Kostuick Mountain. F i g u r e 77b. Core of f a c i e s 5A and 5C d e p o s i t s i n QBD 7718 (163 m). Coal and carbonaceous mudstone at the base ( f a c i e s 5A) i s o v e r l a i n by interbedded mudstones and s i l t s t o n e s ( f a c i e s 5C) which are s t r o n g l y b i o t u r b a t e d . Bedding i n these d e p o s i t s c o n s i s t s mainly of p a r a l l e l bedding and o c c a s i o n a l r i p p l e s . F i g u r e 77c. S o f t sediment deformation s t r u c t u r e i n f a c i e s 5C d e p o s i t s (QBD 7721, 161 m). 2 OS" 206 The presence of t h i n c o a l seams, r o o t s and p l a n t fragments together with i t s s t r a t i g r a p h i c p o s i t i o n i n d i c a t e s that f a c i e s 5 i s non-marine, probably lower c o a s t a l p l a i n i n o r i g i n . The carbonaceous mudstones and t h i n c o a l s ( f a c i e s 5A) represent c o a s t a l swamp d e p o s i t s . The absence of t h i c k c o a l seams suggests that the peat-forming environments were short l i v e d . The s t r a t i g r a p h i c p o s i t i o n of the C seam (and i t s e q u i v a l e n t , B10) i n d i c a t e s t h i s c o a l accumulated i n swamps immediately landward of the t i d a l f l a t and lagoonal d e p o s i t s of f a c i e s 3C and f a c i e s 4. The B seam (and i t s e q u i v a l e n t B11) may have accumulated i n swamps s l i g h t l y f a r t h e r i n l a n d . The o v e r a l l d e p o s i t i o n a l s e t t i n g may have been s i m i l a r to the modern day peats d e s c r i b e d by Styan (1982) adjacent to the Boundary Bay t i d a l f l a t s on the F r a s e r River D e l t a and the e s t u a r i n e peats of South C a r o l i n a (Staub and Cohen, 1979). The A seam (and i t s e q u i v a l e n t B12), which occurs immediately below the Gates-Hulcross c o n t a c t are i n t e r p r e t e d as forming i n swamps on the c o a s t a l p l a i n marginal to the t r a n s g r e s s i n g H u l c r o s s sea. F a c i e s 5B are i n t e r p r e t e d as channel f i l l d e p o s i t s . The presence, i n some s e c t i o n s , of cross-bedded sandstones with s i l t s t o n e i n t e r b e d s and f l a s e r bedding i s evidence of a l t e r n a t i n g bedload-suspension d e p o s i t i o n and i s c h a r a c t e r i s t i c of t i d a l channels (Oomkens, 1974; Barwis, 1979). F u r t h e r evidence of t i d a l c u r r e n t s i s the occurrence of s o u t h e r l y (landward) d i p p i n g cross-beds, with r e a c t i v a t i o n s u r f a c e s i n outcrops of f a c i e s 5B on Kostuick Mountain. The range i n t h i c k n e s s of the f a c i e s i n d i c a t e s the channels ranged i n s i z e from small t i d a l c reeks to major f l u v i a l or e s t u a r i n e 207 F i g u r e 78a. Core photograph of the Gates/Hulcross c o n t a c t i n borehole QBD 7209. The c o n t a c t i s p i c k e d at the base of the f i r s t conglomerate (A) which i s i n t e r p r e t e d as a t r a n s g r e s s i v e marine l a g d e p o s i t . 35 cm of s t r o n g l y burrowed s i l t s t o n e s below t h i s (A-B) are i n t e r p r e t e d as l a g o o n a l d e p o s i t s . The b i o t u r b a t e d s i l t s t o n e u n i t r e s t s • a b r u p t l y on c o a s t a l p l a i n s i l t s t o n e s and sandstones. S e v e r a l other t h i n l a y e r s of coarse sandstone and conglomerate are present interbedded with H u l c r o s s s i l t s t o n e s and mudstones. These are i n t e r p r e t e d as storm d e p o s i t e d l a g s formed i n the o f f s h o r e environment a f t e r the t r a n s g r e s s i o n . T y p i c a l o f f s h o r e H u l c r o s s sediments are present i n the two columns on the r i g h t . F i g u r e 78b. Core photograph of the Gates/Hulcross c o n t a c t (A) i n borehole QBD 7711. In t h i s core the c o n t a c t i s r e p r e s e n t e d by a s i n g l e t h i n t r a n s g r e s s i v e l a g of coarse pebbly sandstone. Compare t h i s with F i g u r e 71 a where s e v e r a l l a g s are p r e s e n t . Dark grey, carbonaceous mudstone with a r g i l l a c e o u s c o a l i s present i n the column on the l e f t . F i g u r e 78c. B i o t u r b a t e d s i l t s t o n e at the base of the H u l c r o s s Formation. (QBD 7708, 38.75 m) 2 Off BOTTOM 209 d i s t r i b u t a r i e s . Sediments i n f a c i e s 5C are i n t e r p r e t e d as forming i n f l o o d p l a i n s adjacent to the channels of f a c i e s 5B. These sediments probably accumulated i n a v a r i e t y of d e p o s i t i o n a l s e t t i n g s i n c l u d i n g l e v e e s , crevasse s p l a y s and shallow b r a c k i s h water ponds or l a k e s . The coarsening-upward sequences i n t h i s f a c i e s are i n t e r p r e t e d as forming from the p r o g r a d a t i o n of lev e e s or crevasse splay d e p o s i t s over f i n e r - g r a i n e d overbank sediments. 2.3 UPPER GATES DEPOSITIONAL MODELS P r i o r to the d e p o s i t i o n of the upper Gates, the study area formed part of a c o a s t a l p l a i n , with the s h o r e l i n e l o c a t e d to the north. During the e a r l y p a r t of upper Gates time, the sea began to t r a n s g r e s s south over the c o a s t a l p l a i n . D e p o s i t i o n a l models f o r t h i s t r a n s g r e s s i o n and the r e g r e s s i v e phase which f o l l o w e d are shown on F i g u r e 79. The upper Gates t r a n s g r e s s i o n o c c u r r e d over a c o a s t a l p l a i n which was covered by ext e n s i v e peat swamps (of the D c o a l seam) cut by l a r g e r i v e r channels o r i e n t e d NW-SE and N-S (F i g u r e 79-1). The s h o r e l i n e between the channel mouths probably c o n s i s t e d of t r a n s g r e s s i v e beaches or b a r r i e r i s l a n d s and lagoons, although t h i s i s s p e c u l a t i v e s i n c e any sedimentary r e c o r d of these environments has been l a r g e l y eroded as the sea continued to t r a n s g r e s s south. F a c i e s 1A d e p o s i t s represent t h i c k sediment accumulations which formed at the mouth of e s t u a r i e s . S p e c i f i c environments i d e n t i f i e d i n c l u d e l a t e r a l l y m i g r a t i n g estuary mouth shoals 210 (Figure 79-1) and t i d a l d e l t a s . As the s h o r e l i n e r e t r e a t e d , these e s t u a r y mouth d e p o s i t s were drowned forming l i n e a r s h o a l s on the sea f l o o r ( F igure 79-2), analagous to the estuary shoal r e t r e a t m a s s i f s d e s c r i b e d by Swift (1973) on the A t l a n t i c s h e l f of the e a s t e r n U n i t e d S t a t e s . During the t r a n s g r e s s i o n , s t r o n g e r o s i o n and sediment reworking o c c u r r e d when the surf zone (upper shoreface) passed over the former land s u r f a c e . The eroded sediment was t r a n s p o r t e d onshore (as washover f a n s ) , o f f s h o r e by storm propagated c u r r e n t s (to form the storm d e p o s i t s at the base of f a c i e s 2A) or alongshore i n t o the est u a r y mouths by longshore c u r r e n t s . Sediment which was too heavy to be t r a n s p o r t e d l a r g e d i s t a n c e s was winnowed out to form a t h i n , l a t e r a l l y e x t e n s i v e marine l a g d e p o s i t ( f a c i e s 1B). In some p a r t s of the o f f s h o r e , sediment i n the l a g was moulded i n t o symmetrical dunes (F i g u r e 79-2) by storm induced o s c i l l a t o r y c u r r e n t s near the sea f l o o r . The s h o r e l i n e r e t r e a t e d south as f a r as Roman Mountain. At i t s southern l i m i t ( F i g u r e 79-3) coa r s e sandstones and conglomerates ( f a c i e s 2B) were d e p o s i t e d at the s h o r e l i n e i n e s t u a r i n e channels and i n shallow marine bars or beaches adjacent to the channels. F a r t h e r o f f s h o r e , l a t e r a l l y e x t e n s i v e sandstones of f a c i e s 2A were d e p o s i t e d in s h e l f - shallow marine environments. E x t e n s i v e lagoons and t i d a l f l a t s developed along the margin of the c o a s t a l p l a i n ( F i g u r e 79-3). The lagoon-i n t e r t i d a l sediments are represented by f a c i e s 4 d e p o s i t s i n the Duke Mountain area. F o l l o w i n g a p e r i o d of s t i l l s t a n d , the s h o r e l i n e began to prograde n o r t h . In the Babcock area, the r e g r e s s i v e s h o r e l i n e 21 1 d e p o s i t s formed w i t h i n a sandy e s t u a r i n e system c o n s i s t i n g of s u b t i d a l channels ( f a c i e s 3A d e p o s i t s ) and s h o a l s ( f a c i e s 3B d e p o s i t s ) o r i e n t e d at high angles to the s h o r e l i n e (Figure 79-4). Seaward of the channels and s h o a l s , l a t e r a l l y e x t e n s i v e sandstones of f a c i e s 2A were d e p o s i t e d . T i d a l f l a t s ( f a c i e s 3C d e p o s i t s ) formed along the margins of the e s t u a r y , while f u r t h e r i n l a n d t h i n peats were d e p o s i t e d i n c o a s t a l p l a i n swamps ( f a c i e s 5A d e p o s i t s ) . The swamps were cut by a network of t i d a l channels ( f a c i e s 5B) which p e r i o d i c a l l y f l o o d e d i n t o overbank areas forming e x t e n s i v e s p l a y d e p o s i t s ( f a c i e s 5C). In summary, the upper Gates marine t r a n s g r e s s i o n i s recorded by 3 d i s t i n c t types of d e p o s i t s : 1. Thick (maximum 40 m) but r e l a t i v e l y narrow e s t u a r y mouth (shoal r e t r e a t massif) sandstones and conglomerates ( f a c i e s 1A). 2. A t h i n (maximum 90 cm) but l a t e r a l l y e x t e n s i v e t r a n s g r e s s i v e marine l a g ( f a c i e s 1B). 3. L a g o o n - i n t e r t i d a l d e p o s i t s ( f a c i e s 4) which are preserved only at the southern l i m i t of the marine t r a n s g r e s s i o n . The upper Gates r e g r e s s i v e d e p o s i t s c o n s i s t of a t h i c k , l a t e r a l l y e x t e n s i v e s h e l f - s h a l l o w marine sandbody ( f a c i e s 2A) o v e r l a i n by s u b t i d a l , e s t u a r i n e channel and shoal sediments. These i n turn are o v e r l a i n by t i d a l f l a t ( f a c i e s 3C) and c o a s t a l p l a i n d e p o s i t s ( f a c i e s 5) with t h i n c o a l seams. 2.4 DISCUSSION The i n f e r r e d c o a s t a l morphology of the r e g r e s s i v e upper Gates s h o r e l i n e i n the Babcock area c o n s i s t s of a broad wide-213 mouthed estuary c o n t a i n i n g long, l i n e a r sand shoals and channels. On modern c o a s t l i n e s t h i s type of morphology i s most common i n m a c r o t i d a l ( t i d a l range > 4 m) areas (Hayes, 1975). L e c k i e (1982) has i n t e r p r e t e d r e g r e s s i v e upper Gates s h o r e l i n e d e p o s i t s i n th Bullmoose Mountain area as forming in a low-energy s h o r e l i n e dominated by t i d a l f l a t and, p o s s i b l y , e s t u a r i n e p r o c e s s e s . L e c k i e ( p e r s . comm.) b e l i e v e s t h a t the t i d a l range may have been mesotidal (2-4 m). Thus, there i s good agreement between L e c k i e ' s work and the present study that t i d e s were important along the upper Gates s h o r e l i n e s . The d i f f e r e n c e s in the t i d a l range estimates between the two s t u d i e s are not incompatible; t i d a l range may have v a r i e d along the s h o r e l i n e due to c o a s t a l c o n f i g u r a t i o n . The North Sea coast of the Netherlands, West Germany and Denmark i s a c l a s s i c example of the r e l a t i o n s h i p of c o a s t a l c o n f i g u r a t i o n to t i d a l range and c o a s t a l morphology (Hayes, 1975). In t h i s area t i d a l range v a r i e s from m i c r o t i d a l (0-2 m) i n the Netherlands and northern Denmark to m a c r o t i d a l near the mouths of the Elbe and Weser r i v e r s i n West Germany. The m i c r o t i d a l areas are c h a r a c t e r i s e d by elongate b a r r i e r i s l a n d s , the m e s o t i d a l areas by stunted b a r r i e r i s l a n d s and abundant t i d a l i n l e t s and the m a c r o t i d a l areas by e s t u a r i e s with sand shoals o r i e n t e d p e r p e n d i c u l a r to the s h o r e l i n e . 214 PART I I I . OCCURRENCE, DISTRIBUTION AND DEPOSITIONAL SETTING OF  COAL SEAMS IN THE GATES FORMATION 3.1 SEDIMENTOLOGICAL ASPECTS OF COAL OCCURRENCES AND  DISTRIBUTION IN THE DUKE MOUNTAIN AREA 3.1.1 I n t r o d u c t i o n The Duke Mountain area (Figure 1) forms p a r t of the Monkman Property i n which Petro-Canada i s the p r i n c i p a l owner and op e r a t o r . The general geology of t h i s area has been d e s c r i b e d by S c h i l l e r et a l . (1983). S t r u c t u r a l l y , the area i s c h a r a c t e r i s e d by NW-SE t r e n d i n g a n t i c l i n e / s y n c l i n e p a i r s ( F i g u r e 80). The f o l d s tend to be asymmetrical and are o f t e n doubly p l u n g i n g . Some of the a n t i c l i n e s approach a b o x - f o l d c o n f i g u r a t i o n . Dips i n the area range from 5°-70°. In a d d i t i o n to f o l d s , t h r u s t f a u l t s of v a r y i n g displacements and trends are a l s o present i n t h i s a r e a . Three proposed open p i t s are l o c a t e d i n the northern part of the area (Honeymoon East, Honeymoon West and the Duke P i t ) . A zone of complex f o l d s and f a u l t s , which i n c l u d e s a major east-west t r e n d i n g t h r u s t f a u l t with a displacement of approximately 1 km, separates the Gates c o a l measures i n the Duke and Honeymoon P i t s . The l o c a t i o n of the major marine u n i t s , f l u v i a l channel d e p o s i t s and c o a l seams i n the Gates-Moosebar s e c t i o n are shown on two c r o s s - s e c t i o n s ( F i g u r e s 81,82). F i g u r e 82 i s an east-west c r o s s s e c t i o n i n the Honeymoon P i t s and F i g u r e 81 i s a c r o s s s e c t i o n which extends from the northern p a r t of the Duke P i t southeast towards Duchess Mountain. The d i s t r i b u t i o n and tr e n d 215 F i g u r e 80_. G e n e r a l i s e d g e o l o g i c a l map of the Duke Mountain a r e a . 216 of the S h e r i f f member marine u n i t and t h i c k f l u v i a l channel d e p o s i t s has been mapped using borehole data and i s shown on F i g u r e s 83 and 35. The boreholes l o c a t e d on these F i g u r e s i n c l u d e only those boreholes from which data was a v a i l a b l e t o the author and which penetrated the i n t e r v a l of i n t e r e s t . Isopach maps of the S h e r i f f member and t h i c k f l u v i a l channel d e p o s i t s were not c o n s t r u c t e d due to the s t r u c t u r a l complexity of the area. 3.1.2 Coal Seams i n the Duke Mountain Area The Gates Formation i n t h i s area c o n t a i n s 12 c o a l seams of which up to 6 are over 1.5 m t h i c k . B1 i s the f i r s t seam above the Torrens Member. In the Honeymoon area, t h i s seam occurs w i t h i n a t h i n non-marine i n t e r v a l between the marine sandstones of the Torrens and S h e r i f f Members. Between the Duke P i t and Duchess Mountain, the S h e r i f f member pinchesout (Figures'81, 83) and south of t h i s , B1 i s o v e r l a i n by non-marine sediments. B1 v a r i e s i n t h i c k n e s s from 0.8-3 m. A t h i n development of B1 i n the area between the Duke P i t and Duchess Mountain c o i n c i d e s with the presence of f l u v i a l channel d e p o s i t s i n the o v e r l y i n g s e c t i o n ( F i g u r e s 81, 24). D i r e c t evidence of e r o s i o n of B1 by the channel i s r e s t r i c t e d to only a few boreholes (e.g., 7806) where channel d e p o s i t s r e s t d i r e c t l y on B1. The data shown on F i g u r e 24 suggest that the t h i n development of B1 i n t h i s area i s due mainly to d e p o s i t i o n a l t h i n n i n g and pinchout of the upper pa r t of B1 adjacent to the channel. B2 c o n s i s t s of two seams, B2 upper (0-0.75 m t h i c k ) and B2 lower (0-2.4 m t h i c k ) . The t h i c k e s t development of B2 lower i s DUKE PIT DUCHESS MOUNTAIN SOUTHEAST 50 rri- X12.5 VERTICAL EXAGGERATION 1 km F i g u r e 8J_. Cross s e c t i o n i n the Duke P i t - Duchess Mountain area showing the l o c a t i o n of the major marine u n i t s , f l u v i a l channel d e p o s i t s and c o a l seams. Refer to F i g u r e 82 f o r legend. L o c a t i o n of c r o s s s e c t i o n i s shown on F i g u r e s 35 and 80 . 218 HONEYMOON PIT WEST EAST F i g u r e 82_. Cross s e c t i o n i n the Honeymoon P i t area showing the l o c a t i o n of the major marine u n i t s , f l u v i a l channel d e p o s i t s and c o a l seams. The x12.5 v e r t i c a l e x aggeration of t h i s c r o s s s e c t i o n causes the angle at which B5 i s draped over the channel to appear much g r e a t e r than on a 1:1 s e c t i o n (where i t i s l e s s than 3 ° ) . L o c a t i o n of c r o s s s e c t i o n i s shown on F i g u r e s 3j> a n d 80. 219 N I 1 2 0 ° 4 5 ' Kinuseo Falls Road 7914 B2 p inches -out r -54°44 ' 0 Approximate southern limit of the "Sheri f f Member" marine sandstones B2 lower th i ckens^ ° ^7704 and onlaps B1 3 67821 _i_ ki lometres F i g u r e 8_3. Map showing the southern l i m i t of the S h e r i f f member marine u n i t and i t s e f f e c t on the t h i c k n e s s and d i s t r i b u t i o n of the B2 c o a l seam. Cross s e c t i o n i s shown on F i g u r e 24. 220 in the south, near Duchess Mountain,'where i t i s present a few metres above B1 (Figure 24). Towards the north, the i n t e r v a l between B1 and B2 lower i n c r e a s e s , both B2 seams t h i n and e v e n t u a l l y p i n c h out and are r e p l a c e d by marine sandstones of the S h e r i f f member i n boreholes near the south end of the Honeymoon West P i t . In boreholes i n the Duke P i t , B2 occurs interbedded with sediments i n t e r p r e t e d as l a g o o n a l i n o r i g i n and marine sandstones of the S h e r i f f member. B3 occurs above the marine sandstones of the S h e r i f f member in the north and non-marine sediments which i n c l u d e the B2 and B1 seams i n the south. B3 i s present over the e n t i r e area and v a r i e s i n t h i c k n e s s from 1.6-5.5 m. B4 i s the most important seam i n t h i s a r e a. I t i s present over the e n t i r e area and ranges i n t h i c k n e s s from 2.2-6.7 m. The i n t e r v a l between B3 and B4 i s 3-26 m t h i c k . Sediments i n t h i s i n t e r v a l c o n s i s t mainly of f i n e - g r a i n e d overbank d e p o s i t s . Coal.seam B5 i s present over the e n t i r e area and v a r i e s i n t h i c k n e s s from 1.8 to 3.2 m. In the Honeymoon area, the i n t e r v a l between B4 and B5 i s c h a r a c t e r i s e d by r a p i d v a r i a t i o n s i n t h i c k n e s s over a r e l a t i v e l y short d i s t a n c e . As shown on F i g u r e s 82 and 84 these t h i c k n e s s v a r i a t i o n s are caused by the presence in t h i s i n t e r v a l of t h i c k f l u v i a l channel d e p o s i t s . In the Honeymoon P i t s , channel d e p o s i t s c o n s i s t i n g of sandstones and conglomerates up to 37 m t h i c k have been i d e n t i f i e d i n twelve boreholes. These d e p o s i t s occur w i t h i n a channel which i s approximately 800-900 m wide and trends NNW-SSE (Figure 35). In boreholes which c o n t a i n channel d e p o s i t s , B5 occurs approximately 50 m above B4, while i n boreholes east and west of 221 the channel, B5 i s separated from B4 by only 1 to 4 m of mudstone and s i l t s t o n e s . T h i s l a r g e decrease i n t h i c k n e s s of the B4-B5 i n t e r v a l occurs over a d i s t a n c e of only 500-700 m on the western margin of the channel. In the t r a n s i t i o n a l area west of the channel, the B4-B5 i n t e r v a l c o n s i s t s of a westward t h i n n i n g wedge of crevasse splay and overbank d e p o s i t s . The g e o p h y s i c a l logs on F i g u r e 84 i l l u s t r a t e the b a s i s f o r the B5 c o r r e l a t i o n i n the Honeymoon area. Borehole 8204, l o c a t e d at the p o i n t where B5 s t a r t s to "climb" over the channel p r o v i d e s the key to the c o r r e l a t i o n . In p a r t i c u l a r note the s i m i l a r c h a r a c t e r of the d e n s i t y l o g i n borehole 7914 where B5 i s c l o s e to B4, borehole 8204 in the t r a n s i t i o n a l area and borehole 7801 where B5 occurs 40 m above B4. The d i p of B5 across the t r a n s i t i o n a l area, t a k i n g B4 as a h o r i z o n t a l datum, i s approximately 3°. T h i s d i p appears much gr e a t e r on F i g u r e s 82 and 84 due to v e r t i c a l exaggeration. F a r t h e r south, i n the Duke P i t and Duchess Mountain area, B5 i s separated from B4 by 20-50 m of f i n e - g r a i n e d overbank d e p o s i t s . The t r a n s i t i o n between the Duke P i t and the western part of Honeymoon, where B5 occurs a short d i s t a n c e above B4, i s cut out by a major t h r u s t f a u l t (displacement approximately 1 km). Channel d e p o s i t s i n the B4-B5 i n t e r v a l area a l s o present i n boreholes west of Duchess Mountain (Figure 35). Due to the small number of boreholes i n t h i s area, the channel trend i s u n c e r t a i n but appears to be roughly NW-SE. Coal seams in the i n t e r v a l between B5 and B9 (B6 upper and lower, B7 and B8) are l e s s than 1.5 m t h i c k and l o c a l l y d i s c o n t i n u o u s . In the B7-B8 i n t e r v a l f l u v i a l channel sandstones 79 1 5 (1180 m) 7914 (280 m) 8204 (500 m) 7801 7501 7908 Coal Seam B6 ~ ~ B5 B4 40 30 20 10 0 Honeymoon Pit Log Correlation F i g u r e 84. Gamma ray and d e n s i t y l o g c o r r e l a t i o n from boreholes i n the Honeymoon P i t area, showing the b a s i s f o r the B5 c o r r e l a t i o n and i t s "draping" over f l u v i a l channel d e p o s i t s , Borehole l o c a t i o n s are shown on Fig u r e 35. fx) fx) to 223 and conglomerates up to 12 m t h i c k ( F i g u r e 81, 36) are present i n the Duke and Duchess areas and ea s t e r n s i d e of Honeymoon. Between the Duke P i t and Duchess Mountain, the channel i s 2.8 km wide and trends NW-SE (Figure 35). In the Honeymoon P i t s , the eas t e r n margin of the channel cannot be d e f i n e d due to l a c k of data. The channel trend i s u n c e r t a i n but appears to be approximately north-south. The other sediments i n the B5-B9 i n t e r v a l c o n s i s t of f i n e - g r a i n e d overbank d e p o s i t s . B9 i s present over the e n t i r e area and ranges i n t h i c k n e s s from 3 to 5 m. B9 i s t h i c k e s t i n the south on Duchess Mountain. Towards the n o r t h i t s p l i t s i n t o two t h i n n e r seams, B9 lower and B9 upper, separated by up to 20 m of overbank d e p o s i t s ( F i g u r e 81). A d e t a i l e d l o g c o r r e l a t i o n showing the s p l i t t i n g of B9 i s shown on F i g u r e 50. Three seams (B10, B11, and B12) ranging i n t h i c k n e s s from 0-1 m are present i n the upper part of the Gates Formation between the B9 seam and the H u l c r o s s Formation. B10 occurs above lagoon and t i d a l f l a t d e p o s i t s , B11 i s a s s o c i a t e d with channel and overbank d e p o s i t s and B12 i s present a few metres below the cont a c t of the Gates and H u l c r o s s Formations. 3.2 SEDIMENTOLOGICAL ASPECTS OF COAL OCCURRENCES AND  DISTRIBUTION IN THE BABCOCK AREA 3.2.1 I n t r o d u c t i o n The Babcock area forms part of the Q u i n t e t t e Property i n which Denison Mines are the p r i n c i p a l owners and operat o r s ( F i g u r e 1). T h i s area i s s t r u c t u r a l l y l e s s complex than the Duke 2 2 4 F i g u r e 8_5. G e o l o g i c a l map and borehole l o c a t i o n s i n the Babcock ar e a . 225 Mountain area. On Babcock Mountain the Gates c o a l measures occur w i t h i n a l a r g e box a n t i c l i n e , bounded to the n o r t h e a s t and southwest by f o l d s which trend NW-SE (Figure 85). Dips range from 5°-l2° over most of the box a n t i c l i n e and are up to 75° i n the f o l d s on the f l a n k s of t h i s s t r u c t u r e . Major t h r u s t f a u l t s are present i n the more t i g h t l y f o l d e d areas n o r t h e a s t and southwest of the box a n t i c l i n e . E r o s i o n of the box a n t i c l i n e on the northwest s i d e of Babcock Mountain has produced two wide escarpments (the Windy and L i t t l e Windy P i t areas ) where the Gates c o a l measures crop out or are present at shallow depths. Southeast of these areas, the Gates c o a l measures are present beneath a cover of younger sediments (the H u l c r o s s and Boulder Creek Formations). A l a r g e number of c l o s e l y spaced boreholes have been d r i l l e d i n t h i s area; most are l o c a t e d on top of the box a n t i c l i n e . 3.2.2 Coal Seams i n the Babcock Area F i g u r e 86 shows the d i s t r i b u t i o n ' o f marine u n i t s , f l u v i a l channel d e p o s i t s and c o a l seams i n the Babcock a r e a . Most of the boreholes at Babcock penetrate only as f a r as the top of the S h e r i f f member. Data from outcrop s e c t i o n s and boreholes which penetrated the u n d e r l y i n g marine sandstones of the Torrens Member i n d i c a t e that one or two t h i n c o a l seams (<0.75 m t h i c k ) are present i n the non-marine i n t e r v a l between the S h e r i f f and Torrens Members. Twenty k i l o m e t r e s to the south, i n the Duke Mountain area, t h i s same i n t e r v a l between the S h e r i f f and Torrens Members c o n t a i n s the B1 c o a l seam, which i s up to 3 m t h i c k . BABCOCK 0} 09 o o n n Babcock Member"! "Sheriff Member" Torrens Member 1 2 kilometres ] Siltstone and Mudstone Coarsening-Upward Marine Unit Marine Transgression F i g u r e 8j6. Cross s e c t i o n i n the Babcock area showing the l o c a t i o n of the major marine u n i t s , f l u v i a l channel d e p o s i t s and c o a l seams. Borehole l o c a t i o n s are shown on F i g u r e 8 5 . ro to CTl 227 The important seams in the Babcock area are present in the non-marine in t e r v a l between the Sheriff and Babcock members. This i n t e r v a l contains up to six major coal seams (D, E, F, G/I, J and K), interbedded with f l u v i a l channel and overbank deposits. The K seam i s the f i r s t seam above the Sheriff member and consists of three separate seams (K1, K2, and K3) interbedded with carbonaceous mudstone, s i l t s t o n e and sandstone. The upper K1 and K2 are present over the entire area and range in thickness from 0.2-2.1 m. A lower seam, K3, i s discontinuous and ranges up to 1.6 m in thickness. The J seam occurs a few metres above K and i s the most important seam in the Babcock area. This seam i s present over the entire area and varies in thickness from 3.1-7.6 m. The I seam i s present a few metres above the J seam in the southern part of the Babcock area where i t consists of three separate seams 11, 12 and 13, separated by varying thickness of carbonaceous mudstone, s i l t s t o n e and sandstone. The lower seam 13 i s 0 - 0.5 m thick, 12 , 0 - 2.0 m thick and the upper seam 13, 1.4 - 2.5 m thick. The G seam occurs 40-60 m above the J seam in the northern part of Babcock. G varies in thickness from 0.8-2.8 m and i s separated from the J seam by a thick sequence of f l u v i a l sandstones and conglomerates. During the later stages of exploration in the Babcock area, when a more closely spaced grid of boreholes was obtained, i t was r e a l i s e d that G and the upper I seam (11) are the same. The c o r r e l a t i o n error made in the early stages of exploration was caused by the interval between G and J being very much thicker than the interval 228 between 11 and J . The t h i c k n e s s v a r i a t i o n s are due to the presence of t h i c k f l u v i a l channel d e p o s i t s i n the northern p a r t of the Babcock a r e a . The d e p o s i t i o n a l f a c t o r s a s s o c i a t e d with the c o r r e l a t i o n and d i s t r i b u t i o n of the G and I seams are d i s c u s s e d i n more d e t a i l i n the f o l l o w i n g s e c t i o n . Three seams, F, E, and D, are present i n the i n t e r v a l between the G/l seams and the Babcock member. The F seam ranges i n t h i c k n e s s from 1.6-2.9 m, E i s < 2.8 m t h i c k and D i s 1.4-3.1 m t h i c k . These seams occur interbedded with f l u v i a l channel and overbank d e p o s i t s . F and D are present over the e n t i r e a r ea. E i s present over most of the area but t h i n s and pinches out towards the northwest ( i n boreholes 7308 and 7309) where i t i s r e p l a c e d by f l u v i a l channel d e p o s i t s . The D seam i s o v e r l a i n by a t h i c k i n t e r n a l of marine and e s t u a r i n e sandstones and conglomerates of the Babcock member. Three t h i n seams, A, B and C are present i n the non-marine i n t e r v a l between the Babcock member and the H u l c r o s s Formation. These seams r a r e l y exceed 0.75 m i n t h i c k n e s s . 3.2.3 D e p o s i t i o n a l F a c t o r s C o n t r o l l i n g the Thickness D i s t r i b u t i o n and C o n t i n u i t y of the G and I Seams M u l t i s t o r e y f l u v i a l channel d e p o s i t s up to 42 m t h i c k are present i n the i n t e r v a l between the G and I seams i n boreholes and outcrops on the northwest s i d e of Babcock Mountain. Two d i s t i n c t types of channel f i l l sequences are recognised; a lower u n i t i n which the channel d e p o s i t s c o n s i s t predominantly of sandstone and an upper u n i t i n which the channel d e p o s i t s c o n s i s t of t h i c k u n i t s of both conglomerate and sandstone (see 7510 7751 771 1 7707 7219 7712 7203 2Q-i m e t r e s 10i X19 V e r t i c a l E x a g g e r a t i o n 500 1000 m e t r e s | | Sandstone I**".*.! Conglomerate | •• | Sandstone S t reaks m C o a l | | S i l ts tone /Mudstone Section B F i g u r e 87. S e c t i o n B - Cross s e c t i o n of the F - J i n t e r v a l i n the Babcock area showing the drap i n g of the G/l1 seam over f l u v i a l channel d e p o s i t s and the pinchout of the 13 and 12 seams adjacent to the channel and splay d e p o s i t s . Borehole l o c a t i o n s are shown on F i g u r e 88. to to 230 s e c t i o n 1.8.1 f o r more d e t a i l s of these channel d e p o s i t s ) . The d i s t r i b u t i o n of these two u n i t s i s shown on the isopach map (Figure 32). The two lobes on the isopach map of the lower u n i t are i n t e r p r e t e d as crevasse s p l a y d e p o s i t s ( d e s c r i b e d i n s e c t i o n 1.9.2). Beds e q u i v a l e n t to the channel and crevasse splay d e p o s i t s in boreholes to the south i n c l u d e the lower two I seams (13 and 12) and interbedded overbank d e p o s i t s . As i l l u s t r a t e d on the c r o s s s e c t i o n s ( F i g u r e s 31 and 87), 13 and 12 t h i n and pinch out towards the nor t h adjacent to the channel and crevasse s p l a y s . The lower seam (13) i s r e p l a c e d l a t e r a l l y by crevasse splay d e p o s i t s marginal t o the lower 'sandstone' channel, while the middle seam (12) s p l i t s i n t o two t h i n n e r seams and pinches out w i t h i n a sequence of carbonaceous mudstones above the crevasse s p l a y s . The l o c a t i o n of the pinchout of 12 i s shown on F i g u r e 88. The t h i c k n e s s and d i s t r i b u t i o n of the 12 and G/l1 seams are shown on F i g u r e 88. South of l i n e A-A,'which i s l o c a t e d 1.0-1.8 km from the margin of the upper 'conglomerate' channel, the middle and upper seams 12 and II are separated by a rock s p l i t l e s s than 50 cm t h i c k and form e s s e n t i a l l y a s i n g l e seam. North of t h i s l i n e , the s p l i t between 12 and 11 t h i c k e n s to s e v e r a l metres and the i n t e r v a l between these seams and the J seam t h i c k e n s . North of the l i n e B-B, which i s l o c a t e d approximately 0.25-0.5 km from the margin of the channel, the 11 seam cl i m b s v e r t i c a l l y by 30 m r e l a t i v e to the J seam and i n boreholes to the northwest, 11 ( r e f e r r e d to as G i n t h i s area) i s present above the channel d e p o s i t s . The t r u e d i p angle of the G/l1 seam 231 at the channel margin, t a k i n g the J seam as a h o r i z o n t a l datum, i s approximately 3°. T h i s angle appears much steeper on the c r o s s s e c t i o n s ( F i g u r e s 31, 87) due to t h e i r v e r t i c a l e x a g g e r a t i o n . Seams 12 and G/I1 t h i n towards the east where a second f l u v i a l channel i s present ( F i g u r e s 86, 88). Due to the l a c k of borehole data i n t h i s area, the t r e n d of t h i s second channel i s u n c e r t a i n , but appears to be roughly north-south. In boreholes l o c a t e d i n the area between the two channels, 30-45 m of sediment are present between the G/I1 and F seams, compared to only 7-15 m i n the areas u n d e r l a i n by f l u v i a l channel d e p o s i t s . These f i g u r e s suggest t h a t , d u r i n g d e p o s i t i o n of the G/I1-F i n t e r v a l , the former i n t e r c h a n n e l area subsided at r a t e s three to four times f a s t e r than the areas u n d e r l a i n by channel d e p o s i t s . D i f f e r e n t i a l compaction i s the most l i k e l y e x p l a n a t i o n f o r the d i f f e r e n t subsidence r a t e s ; e a r l y compaction of the channel sandstones and conglomerates would be n e g l i g i b l e compared to the amount of compaction i n the peats (of the 12 and 13 seams) and overbank d e p o s i t s i n the i n t e r c h a n n e l area. The lower 75% Of the G/I1-F i n t e r v a l i n the former i n t e r c h a n n e l area c o n s i s t s l a r g e l y of crevasse s p l a y d e p o s i t s ( d e s c r i b e d i n s e c t i o n 1.9.2). Data from the isopach map ( F i g u r e 43) and c r o s s - s e c t i o n ( F i g u r e 44) i n d i c a t e s that these splay d e p o s i t s were d e r i v e d from a f l u v i a l channel l o c a t e d to the south. During the d e p o s i t i o n of sediments i n the G/I1-F i n t e r v a l the former i n t e r c h a n n e l area probably formed a depressed area between the two b u r i e d a l l u v i a l ' r i d g e s ' and t h i s topography appears to have i n f l u e n c e d the l o c a t i o n of the crevasse s p l a y . 232 SEAM G/11 ISOPACHS a SEAM 12 ISOPACHS F i g u r e 88. Isopach map of theG/[ 1 (F i g u r e 88a) and 12 ( F i g u r e 88b ) c o a l seams i n the Babcock a r e a . Shaded areas represent channel and s p l a y d e p o s i t s which are e q u i v a l e n t l a t e r a l l y to these c o a l seams. 233 3.2.4 Model f o r the D e p o s i t i o n of the G and I'Seams A model f o r the d e p o s i t i o n of the G and I seams i s shown on Fi g u r e 89. During time 1, t h i c k peat swamps of the J seam covered the e n t i r e Babcock area. Assuming a peat to c o a l compaction f a c t o r of X10 f o r bituminous c o a l (Ryer and Langer, 1980), the J peats would have been approximately 30-75 m t h i c k . Between time 1 and time 2, peat d e p o s i t i o n was terminated, presumably by the drowning of the swamp or the i n f l u x of overbank d e p o s i t s i n t o the area. During time 2 r i v e r s were d i v e r t e d i n t o the Babcock area, p o s s i b l y as a r e s u l t of channel a v u l s i o n processes i n nearby areas. The c h a r a c t e r i s t i c s of channel d e p o s i t s on the northwest s i d e of Babcock Mountain suggest that the r i v e r s i n i t i a l l y formed s t r a i g h t , non-braided or anastomosing channels (see s e c t i o n 1.8.4 f o r d e t a i l s ) . Peat d e p o s i t s (of the 13 seam) accumulated i n swamps i n the i n t e r c h a n n e l a r e a s . During p e r i o d s of f l o o d i n g , r i v e r waters broke through the c o n f i n i n g levees of the channel, and sediment was d e p o s i t e d i n the swamp forming two l a r g e c r e v a s s e - s p l a y s . During time 3, i n c r e a s e d d i s c h a r g e and the i n f l u x of coarse sand and g r a v e l caused the r i v e r to widen and change to a braided p a t t e r n . Peats of the 12 seam accumulated i n swamps i n the i n t e r c h a n n e l area. During time 4, the 12 swamp became a r e a l l y more r e s t r i c t e d as a r e s u l t of overbank f l o o d i n g from the channels or drowning of the margins of the swamp. During time 5 the f l u v i a l channels were abandoned, presumably as a r e s u l t of upstream a v u l s i o n p r o c e s s e s . The 11 swamps then migrated outwards and t h i c k peats of the G/I1 seam were d e p o s i t e d over the e n t i r e Babcock a r e a . F i g u r e 89. Model to i l l u s t r a t e the d e p o s i t i o n of the G and I seams in the Babcock a r e a . r o t o 235 During time 6 compaction i n the former i n t e r c h a n n e l area c r e a t e d a de p r e s s i o n which was f l a n k e d by the two b u r i e d a l l u v i a l r i d g e s . T h i s depression acted as a depocentre f o r t h i c k crevasse splay d e p o s i t s which f i l l e d i n the former i n t e r c h a n n e l area from a f l u v i a l source to the southwest. Continued d e p o s i t i o n and d i f f e r e n t i a l compaction between the i n t e r c h a n n e l area and the areas u n d e r l a i n by channel d e p o s i t s r e s u l t e d i n the "draping" of the G/I1 seam over the f l u v i a l channel d e p o s i t s . 3.3 COAL OCCURENCES IN THE FRAME AND MCCONKEY PITS The Frame and McConkey p i t s (note: the McConkey P i t was formerly c a l l e d the S h e r i f f P i t ) are l o c a t e d i n the northern part of the study area between the Murray and Wolverine R i v e r s . These p i t s form p a r t of the Q u i n t e t t e Property i n which Denison Mines are the p r i n c i p a l owners and o p e r a t o r s . At present both p i t s are being developed and f i r s t c o a l p r o d u c t i o n i s scheduled for December 1983 (Ranee, 1983). A g e n e r a l i s e d s t r u c t u r e map of the Frame-McConkey area i s shown i n F i g u r e 90. In the Frame P i t , the Gates c o a l measures occur w i t h i n a NW-SE t r e n d i n g s y n c l i n e ; minor f a u l t s are present on the f l a n k s of the s y n c l i n e . The s t r u c t u r e at the McConkey P i t i s more complex but c o n s i s t s b a s i c a l l y of two NW-SE t r e n d i n g a n t i c l i n e - s y n c l i n e p a i r s . A complex zone of N-S and NW-SE tr e n d i n g t h r u s t f a u l t s i s present on the northeast s i d e of the p i t . S e d i m e n t o l o g i c a l aspects of c o a l occurrences i n the these p i t s have been s t u d i e d i n l e s s d e t a i l than i n the Babcock and Duke Mountain areas due to the complex s t r u c t u r e at the McConkey 236 McCONKEY PIT ad Cut) Section \ \ Frame Outcrop Section h 55 00 FRAME PIT\. Outcrop of Gates Formation • Coal Company Borehole Fault — Syncline -|— Anticline 0 j km J Figure 90. Generalised geological map of the Frame and McConkey P i t s . 237 P i t and the presence of only a r e l a t i v e l y small number of boreholes which penetrate a t h i c k u n f a u l t e d Gates s e c t i o n . Two c r o s s s e c t i o n s ( F i g u r e s 91,92) based on 7 borehole and 2 outcrop s e c t i o n s , show the d i s t r i b u t i o n of c o a l seams, marine u n i t s and channel d e p o s i t s at the Frame and McConkey P i t s . Four coarsening-upward marine c y c l e s are present i n the Moosebar Formation and Torrens Member. The Torrens Member i s o v e r l a i n by an 11-20 m t h i c k non-marine (lagoonal?) i n t e r v a l c o n t a i n i n g up to three t h i n (<0.5 m) c o a l seams. These sediments are o v e r l a i n by t h i n t r a n s g r e s s i v e d e p o s i t s which i n t u r n are o v e r l a i n by a 30-35 m t h i c k coarsening-upward marine c y c l e i n the S h e r i f f member. Thick c o a l seams occur interbedded with f l u v i a l channel and overbank d e p o s i t s i n the non-marine i n t e r v a l between the S h e r i f f and Babcock members. In the Frame P i t , 5 major seams (D,E,F,G and J) are present with an aggregate t h i c k n e s s of about 16.6 m (Ranee, 1983). E, F,.G and J range from 3-5 m t h i c k while D i s l e s s than 2 m t h i c k . The McConkey P i t has 4 c o a l seams (D,E,G and J) with an aggregate t h i c k n e s s of approximately 18 m. Most of the reserves are contained w i t h i n 2 seams (J and E ) . The J seam o v e r l i e s nearshore marine sandstones at the top of the S h e r i f f member and i s up to 10m t h i c k . There i s evidence from outcrops along a road cut a t the McConkey P i t that i n p l a c e s J i s s t r u c t u r a l l y thickened. E c o n s i s t s of s e v e r a l seams interbedded with numerous rock p a r t i n g s i n a zone which i s up to 25 m t h i c k . Thick f l u v i a l channel d e p o s i t s occur i n the i n t e r v a l between the J and G seams at Frame (Figure 91). The Babcock member, c o n s i s t i n g mainly of e s t u a r i n e and 238 FRAME PIT Northwest Frame Outcrop Section 7621 _ 7622 7620 7618 _ _ _ \ Marine Unit Torrens Member Conglomerate > Sandstone / ^ Marine Transgression I ' " — I Sandstone Streaks Moosebar Formation I I Siltstone and Mudstone F i g u r e 9J_. Cross s e c t i o n i n the Frame P i t showing the l o c a t i o n of the major marine u n i t s , channel d e p o s i t s and c o a l seams. Borehole l o c a t i o n s shown on F i g u r e 9 0 . 239 McCONKEY PIT McConkey 7705 7701 7613 Road Cut I I I I Fault repeat of upper Gates Coal Seam (omitted) F i g u r e 92. Cross s e c t i o n i n the McConkey P i t showing the l o c a t i o n of the major marine u n i t s , channel d e p o s i t s and c o a l seams. Borehole l o c a t i o n s shown on F i g u r e 90. Legend i s shown on F i g u r e 91. 240 marine sandstones and conglomerates up to 50 m t h i c k , o v e r l i e s d i r e c t l y the D c o a l seam i n both p i t s . S e v e r a l t h i n (<1 m) c o a l seams are present i n the non-marine i n t e r v a l above the Babcock member. 241 3.4 PLANT COMMUNITIES IN THE GATES PEAT SWAMPS To i n v e s t i g a t e the types of p l a n t communities which formed the peat from which the Gates c o a l s o r i g i n a t e would r e q u i r e d e t a i l e d p a l y n o l o g i c a l , p a l e o b o t a n i c a l and c o a l p e t r o g r a p h i c s t u d i e s . Such s t u d i e s are o u t s i d e the scope of t h i s t h e s i s . During the core and f i e l d work, however, p l a n t f o s s i l s were c o l l e c t e d which provide some p r e l i m i n a r y i n f o r m a t i o n on the types of v e g e t a t i o n i n the peat swamps. Most of the p l a n t f o s s i l s c o l l e c t e d were found in core samples of black carbonaceous mudstone above or below c o a l seams. The p l a n t f o s s i l s were i d e n t i f i e d by Dr. G.E. Rouse (UBC). Based on the types of p l a n t f o s s i l s , t r e e f l o r a i n the Gates swamps i n c l u d e d c o n i f e r s , cycads and gingkos; f e r n s were a common understory f l o r a and a q u a t i c p l a n t s (e.g., C y p e r i t e s sp.) were present l o c a l l y . 3.5 REGIONAL TRENDS IN COAL DEVELOPMENT IN THE GATES FORMATION Two maps have been c o n s t r u c t e d to i l l u s t r a t e r e g i o n a l v a r i a t i o n s i n c o a l development w i t h i n the study area - an isopach map of t o t a l c o a l t h i c k n e s s i n the Gates Formation (Figure 93a) and a map showing the a r e a l d i s t r i b u t i o n of the number of seams over 1.5 m t h i c k ( F i g u r e 93b). These maps were c o n s t r u c t e d using data from the boreholes and petroleum w e l l s on r e g i o n a l c r o s s s e c t i o n s 1, 2 and 3 ( F i g u r e s 5, 6, 7). Seam th i c k n e s s was c a l c u l a t e d using g e o p h y s i c a l l o g s ; where p o s s i b l e , the d e n s i t y l o g was used. In some boreholes and w e l l s t h i s l o g was not a v a i l a b l e and seam t h i c k n e s s was then c a l c u l a t e d u s i n g a 242 combination of gamma ray and neutron logs or gamma ray and sonic l o g s . The f i g u r e s f o r t o t a l c o a l do not i n c l u d e interseam rock s p l i t s or c o a l seams which are l e s s than 0.5 m t h i c k . The purpose of these maps i s to i l l u s t r a t e r e g i o n a l trends i n c o a l development. They do not show the d e t a i l e d v a r i a t i o n s i n the number of seams and t o t a l c o a l t h i c k n e s s i n densely d r i l l e d a r e a s . The borehole data s e l e c t e d from densely d r i l l e d areas and used i n F i g u r e 93 are, however, r e p r e s e n t a t i v e of the surrounding area. The t o t a l c o a l t h i c k n e s s i n the study area v a r i e s between 10 and 28 m. The t h i c k e s t c o a l occurs i n the Duke Mountain area and the area immediately to the south. North of the Duke Mountain area, t h i c k n e s s p r o g r e s s i v e l y decreases, with the exception of a . t h i c k e r b e l t of c o a l near the McConkey P i t . An area of t h i n c o a l i s present i n the F i v e Cabin Creek area, west of Babcock. South of the b e l t of t h i c k c o a l near Duke Mountain, c o a l t h i c k n e s s decreases,.but s t i l l remains f a i r l y high (between 15 and 22m). Within the study area, the number of c o a l seams over 1.5 m t h i c k i n any one s e c t i o n ranges between 2 and 6. The general p a t t e r n shown on F i g u r e 93b i s s i m i l a r to that on the t o t a l c o a l map, with the g r e a t e s t number of t h i c k c o a l s (between 5 and 6) near the Duke Mountain area. South of t h i s area, the number of t h i c k c o a l s ranges between 3 and 5. In boreholes and w e l l s to the north, the number of t h i c k c o a l s decreases to 2 or 3 i n most s e c t i o n s . Between 2 and 3 t h i c k c o a l s are a l s o present i n the F i v e Cabin Creek area. The general t r e n d of a northward r e d u c t i o n i n the number of t h i c k c o a l s and t o t a l c o a l t h i c k n e s s F i g u r e 93. Regional maps of t o t a l c o a l isopachs ( F i g u r e 93a) and the number of seams over t h i c k i n the Gates Formation ( F i g u r e 93b). 244 i s r e v e r s e d on the Bullmoose Property, j u s t north of the study area where there are 4 seams over 1.5 m t h i c k and approximately 12 m of t o t a l c o a l . North of Bullmoose Mountain however, r e g i o n a l c r o s s s e c t i o n s by Duff and G i l c h r i s t (1981) show t h a t the number of t h i c k seams and t o t a l c o a l t h i c k n e s s i n the Gates Formation decreases r a p i d l y . 3.5.1 R e l a t i o n s h i p Between Regional Coal Development and  Paleogeography of the Gates Formation The paleogeography of sediments i n the Gates Formation above the Torrens Member can be s i m p l i f i e d i n t o 3 major d e p o s i t i o n a l areas: marine, t r a n s i t i o n a l and non-marine. The d i s t r i b u t i o n of these areas i s shown on F i g u r e 94. T h i s diagram was c o n s t r u c t e d using the data on r e g i o n a l c r o s s s e c t i o n s 1, 2 and 3 ( F i g u r e s 5, 6, 7) from t h i s study, together with i n f o r m a t i o n on c r o s s - s e c t i o n s by Duff and G i l c h r i s t (1981), L e c k i e (unpublished) and i n S t o t t (1968, 1982) f o r the r e g i o n n o r t h of the study a r e a . The boundaries between the marine, t r a n s i t i o n a l and non-marine areas trend approximately WNW-ESE. North of l a t i t u d e 55°40'N the Gates sediments are predominantly marine; non-marine i n t e r v a l s are very t h i n and there i s no s i g n i f i c a n t c o a l development. In the t r a n s i t i o n a l area which extends from l a t i t u d e 55°40'N to j u s t south of Kinuseo Creek, non-marine i n t e r v a l s a l t e r n a t e with marine u n i t s which pinchout towards the south. Thick c o a l seams are present i n the t r a n s i t i o n a l area i n the F o o t h i l l s south of Bullmoose Mountain. The non-marine area extends from the southern l i m i t of the t r a n s i t i o n a l a rea, near 245 BULLMOOSE MTN. Limit of outcrop of the Gates Formation NON-MARINE DUMB GOAT MTN. A MOUNT BELCOURT 50 kilometres SAXON AREA-. F i gure 9_4. G e n e r a l i s e d paleogeography of the Gates Formation. T h i s f i g u r e was c o n s t r u c t e d u s i n g the data on the r e g i o n a l c r o s s s e c t i o n s from t h i s study ( F i g u r e s 5,6 and 7) together with i n f o r m a t i o n on c r o s s s e c t i o n s by Duff and G i l c h r i s t (1981), L e c k i e (unpublished) and i n S t o t t (1968, 1982) f o r the region north of the study a r e a . 246 Kinuseo Creek, to the A l b e r t a / B r i t i s h Columbia border." In t h i s area, sediments i n the Gates Formation above the Torrens Member are e n t i r e l y non-marine, with the exception of some marginal marine ( l a g o o n - t i d a l f l a t ? ) d e p o s i t s near the southern pinchout of the Babcock and S h e r i f f members. Thick c o a l s are present i n t h i s area, mainly i n the lower and middle part of the Gates Formation. By comparing the data on F i g u r e 93 with the paleogeographic map of the Gates Formation (Figure 94), i t i s apparent that the maximum c o a l development (28 m t o t a l c o a l and 6 seams over 1.5 m t h i c k ) occurs near the boundary between the t r a n s i t i o n a l and non-marine a r e a s . 3.6 DEPOSITIONAL SETTING OF COAL SEAMS IN THE GATES FORMATION. With the exception of a few very t h i n seams, the Gates c o a l s appear to be e n t i r e l y autochthonous and to have accumulated as peat i n swamps in a c o a s t a l p l a i n d e p o s i t i o n a l s e t t i n g . F a c i e s a s s o c i a t i o n s and the s t r a t i g r a p h i c p o s i t i o n of-the c o a l s i n d i c a t e s that the swamps were l o c a t e d i n 4 p r i n c i p a l a reas: 1. Along the margins of lagoons i n the lower c o a s t a l p l a i n . 2. Immediately landward of beach b a r r i e r s i n the lower c o a s t a l p l a i n . 3. Marginal to e s t u a r i e s and t i d a l f l a t s i n the lower c o a s t a l p l a i n . 4. In i n t e r c h a n n e l areas i n the upper c o a s t a l p l a i n . P r e v i o u s l y , t h i c k c o a l s i n the lower Gates Formation were i n t e r p r e t e d as having formed i n swamps on a lower c o a s t a l p l a i n , 247 while g e n e r a l l y t h i n n e r seams i n the middle Gates Formation were i n t e r p r e t e d as upper c o a s t a l p l a i n i n o r i g i n (Carmichael, 1982;1983). Based on the f o l l o w i n g evidence, i t i s now thought that t h i s i n t e r p r e t a t i o n was i n c o r r e c t and that many of the swamps extended i n l a n d f o r l a r g e d i s t a n c e s , spanning both the lower and upper c o a s t a l p l a i n s . 1. The J seam on the Q u i n t e t t e Property (Figure 5), and i t s e q u i v a l e n t s i n other areas, i s the most important c o a l seam in the Gates Formation. T h i s seam i s up to 10m t h i c k and can be c o r r e l a t e d from Bullmoose Mountain (where i t s e q u i v a l e n t i s the B seam) southeast as f a r as Denison Mines B e l c o u r t Property, (where the e q u i v a l e n t seam i s #5), a d i s t a n c e of over 100 km. At the McConkey P i t , J r e s t s d i r e c t l y on top of the S h e r i f f member ( F i g u r e 15) i n d i c a t i n g that the c o a l at the base of J must have accumulated i n swamps immediately landward of the backshore. S e v e n t y - f i v e k i l o m e t r e s southeast i n borehole BD 7802, the e q u i v a l e n t seam, #5, o v e r l i e s 55 m of non-marine d e p o s i t s above the Torrens Member (Figure 5). I t i s reasonable to assume t h a t , s i n c e the J/#5 seam i s very t h i c k , p a r t of the #5 seam i s time e q u i v a l e n t to the base of the J seam i n the McConkey P i t . I f t h i s i s the case then #5 was d e p o s i t e d i n swamps at l e a s t 75 km from the s h o r e l i n e i n an upper c o a s t a l p l a i n s e t t i n g . Based on t h i s reasoning i t i s concluded that the t h i c k l a t e r a l l y continuous c o a l seams i n the lower Gates Formation were d e p o s i t e d i n very e x t e n s i v e swamps which covered p a r t s of both the lower and upper c o a s t a l p l a i n s . 248 2. The importance of the F a l h e r C marine u n i t was not p r e v i o u s l y recognised. As shown on F i g u r e 8 the southern l i m i t of the F a l h e r C i s l o c a t e d approximately 6 km northeast of the Babcock area. The G/l seam at Babcock i s present i n the i n t e r v a l e q u i v a l e n t to the F a l h e r C. T h i s suggests that at one time the G/I seam was d e p o s i t e d i n swamps approximately 6 km from the s h o r e l i n e i n a lower c o a s t a l p l a i n s e t t i n g and not upper c o a s t a l p l a i n as p r e v i o u s l y i n t e r p r e t e d . F i g u r e 95 i s a d e p o s i t i o n a l model to i l l u s t r a t e the s e t t i n g of the c o a l forming environments through time d u r i n g d e p o s i t i o n of the Gates Formation. The primary o b j e c t i v e of - t h i s F i g u r e i s to show how major r e g r e s s i o n s and t r a n s g r e s s i o n s of the Gates s h o r e l i n e s a f f e c t the a r e a l d i s t r i b u t i o n of the c o a l swamps. Each panel .represents a schematic paleogeographic map of the study area at a d i f f e r e n t time i n t e r v a l . Panel 1 i s the o l d e s t and panel 9 the youngest. The l a t i t u d e s of some of the l o c a l i t i e s are shown on the l e f t hand s i d e . In the study area, Gates sediments were d e p o s i t e d d u r i n g four major r e g r e s s i v e / t r a n s g r e s s i v e c y c l e s . (Note: these diagrams do not show three other r e g r e s s i v e / t r a n s g r e s s i v e c y c l e s recognised by Cant and L e c k i e (1983), the FalherA,B and D c y c l e s , north of the study a r e a ) . During the r e g r e s s i o n s , the s h o r e l i n e prograded i n a n o r t h e r l y d i r e c t o n and the c o a r s e n i n g -upward marine sequences i n the Torrens, S h e r i f f , F a l h e r C and Babcock Members were d e p o s i t e d . During t r a n s g r e s s i o n s the s h o r e l i n e r e t r e a t e d i n a s o u t h e r l y d i r e c t i o n . T r a n s g r e s s i v e d e p o s i t s are g e n e r a l l y t h i n i n the Gates marine u n i t s . D e t a i l s of the types of s h o r e l i n e and non-marine f a c i e s i l l u s t r a t e d on 249 B u l l m o o s e M t n . H W o l v e r i n e R. - | B a b c o c k Mtn. K l n u s e o C r e e k D u m b G o a t M t n . 4 S a x o n T o r r e n s M e m b e r S\ S h e r i f f M e m b e r ' / > B u l l m o o s e M t n . 4—^5: W o l v e r i n e R. B a b c o c k M t n . K l n u s e o C r e e k " p - ^ • -c^^' D u m b G o a t M t n . S a x o n B u l l m o o s e M t n . -I W o l v e r i n e R. 4 B a b c o c k M t n . K l n u s e o C r e e k D u m b G o a t Mtn.H S a x o n 8 H u l c r o s s T r a n s g r e s s i o n F i g u r e 95. Models to i l l u s t r a t e the d e p o s i t i o n a l s e t t i n g of the c o a l forming environments i n the Gates Formation. 250 F i g u r e 95 area given i n Parts I and II of the t h e s i s . The f o l l o w i n g i s a summary of some of the main p o i n t s : 1. The Torrens and S h e r i f f Member s h o r e l i n e s were wave dominated and c h a r a c t e r i s e d by l a t e r a l l y e x t e n s i v e b e a c h - b a r r i e r s o r i e n t e d east-west. 2. The c h a r a c t e r i s t i c s of the F a l h e r C are u n c e r t a i n as t h i s u n i t i s recognised only from logs i n the northern part of the study area. Based on work by Cant and L e c k i e (1983) and Cant (1983, i n press) i t appears to be b a s i c a l l y s i m i l a r to the Torrens and S h e r i f f Member s h o r e l i n e f a c i e s . 3. The Babcock member s h o r e l i n e s are more s t r o n g l y t i d a l l y i n f l u e n c e d than lower Gates s h o r e l i n e s and c h a r a c t e r i s e d by e s t u a r i e s and mesotidal b a r r i e r i s l a n d s . 4. F l u v i a l channels i n the Gates are predominantly high bedload, b r a i d e d r i v e r types. 5. Thick and coarse f l u v i a l conglomerates near Dumb Goat Mountain i n d i c a t e t h i s area was l o c a t e d c l o s e to the source area, probably at a major r e - e n t r a n t i n the mountain b e l t to the west from which l a r g e r i v e r s flowed out on to the Gates c o a s t a l p l a i n . 6. Low s i n u o s i t y (non-braided) or anastomosing r i v e r s are recognised i n a lower c o a s t a l p l a i n s e t t i n g adjacent to the F a l h e r C s h o r e l i n e . 7. Meandering r i v e r d e p o s i t s are present i n the upper Gates Formation i n the southern p a r t of the study area. 8. Other environments i n the overbank areas, i n a d d i t i o n to swamps, i n c l u d e l e v e e s , l a k e s and crevasse splay -l a c u s t r i n e d e l t a s . 251 During the Torrens r e g r e s s i v e c y c l e , the s h o r e l i n e prograded no r t h as f a r as the Wolverine River (Panels 1 and 2 ) . Thick c o a l s accumulated i n l a t e r a l l y e n tensive swamps south of Kinuseo Creek (eg., B1 seam i n the Duke Mountain a r e a ) . A r i s e of r e l a t i v e base l e v e l r e s u l t e d i n a marine t r a n s g r e s s i o n and the submergence of the c o a s t a l p l a i n to j u s t south of Kinuseo Creek(Panels 2 and 3). I n i t i a l l y , e x t e n s i v e lagoons formed on the c o a s t a l p l a i n south of the Wolverine R i v e r . Thin c o a l s (e.g., #1 seam at Babcock) formed i n swamps along the lagoon margins while t h i c k e r c o a l c o n t i n u e d to form i n c o a s t a l p l a i n swamps south of Kinuseo Creek. The next major r e g r e s s i v e c y c l e (Panels 3 and 4) r e s u l t e d i n the d e p o s i t i o n of the S h e r i f f member. During the r e g r e s s i o n , the s h o r e l i n e prograded northward at l e a s t as f a r as Bullmoose Mountain. In some areas two coarsening-upward c y c l e s are present i n the S h e r i f f member, i n d i c a t i n g that more than one t r a n s g r e s s i v e / r e g r e s s i v e c y c l e i s i n v o l v e d and not a s i n g l e r e g r e s s i v e phase as shown on panels 3 and 4. During thi's time (panel 4) the t h i c k e s t and l a t e r a l l y most e x t e n s i v e c o a l seam i n the Gates Formation (the J seam on the Q u i n t e t t e Property and i t s e q u i v a l e n t s i n other areas) was d e p o s i t e d . Swamps covered very l a r g e areas of the c o a s t a l p l a i n , extending i n l a n d f o r at l e a s t 75 km from the s h o r e l i n e . The next marine t r a n s g r e s s i o n of the study area o c c u r r e d only i n the northeast (Panel 5) and d i d not extend i n t o the F o o t h i l l s south of the Wolverine R i v e r . T h i s was f o l l o w e d by the Fa l h e r C r e g r e s s i v e c y c l e (Panel 6 ) . Coals d e p o s i t e d d u r i n g t h i s time are not as t h i c k g e n e r a l l y as those which formed duri n g the 252 e a r l i e r S h e r i f f r e g r e s s i v e c y c l e . In the time i n t e r v a l between Panels 6 and 7, the sea t r a n s g r e s s e d south as f a r as the Babcock area. F a r t h e r south, i n the Duke Mountain area, t h i s t r a n s g r e s s i o n i s represented by l a g o o n - i n t e r t i d a l d e p o s i t s above the B9 seam. T h i s was f o l l o w e d by the Babcock member r e g r e s s i v e c y c l e (Panels 7 and 8). During t h i s time the s h o r e l i n e prograded north of the study area. Coals which formed d u r i n g t h i s r e g r e s s i v e phase a r t h i n ( g e n e r a l l y l e s s than 1 m). The next marine t r a n s g r e s s i o n (Panel 9) f l o o d e d the c o a s t a l p l a i n as f a r south as the A l b e r t a / B r i t i s h Columbia border ( i n the F o o t h i l l s ) and marks the f i n a l event i n the Gates d e p o s i t i o n a l r e c o r d . In the southern p a r t of the study area the upper Gates Formation i s c h a r a c t e r i s e d by numerous t h i n c o a l s interbedded with overbank and channel d e p o s i t s . The c h a r a c t e r i s t i c s of the channel d e p o s i t s suggest that r i v e r s were mainly small meandering types. These sediments accumulated on the c o a s t a l p l a i n during the southward advance of the H u l c r o s s .. seaway (Panel 9). 253 PART IV SANDSTONE PETROGRAPHY 4.1 DATA AND METHODS Thin s e c t i o n s were made of 137 s e l e c t e d samples. A l l t h i n s e c t i o n s were etched i n h y d r o f l u o r i c a c i d vapour and s t a i n e d with sodium c o b a l t i n i t r i t e to i d e n t i f y potassium f e l d s p a r . Attempts to s t a i n p l a g i o c l a s e f e l d s p a r with barium c h l o r i d e and amaranth (Laniz et a l . , 1964) were u n s u c c e s s f u l . Untwinned p l a g i o c l a s e was d i s t i n g u i s h e d from quartz mainly by i t s higher r e l i e f due to the e t c h i n g . Thin s e c t i o n s were a l s o s t a i n e d with A l i z a r i n Red S or equal volumes of A l i z a r i n Red S and Sodium hydroxide (Friedman, 1959) to d i s t i n g u i s h between c a l c i t e and dolomite. 62 t h i n s e c t i o n s were p o i n t counted to determine composition. The po i n t counted samples were taken from the borehole and outcrop s e c t i o n s shown on F i g u r e 96. A g r i d of at l e a s t 200 p o i n t s was counted on.each t h i n s e c t i o n . Estimates were a l s o made of g r a i n - s i z e and s o r t i n g . Reference photographs (Beard and Weyl, 1973) were used to v i s u a l l y estimate s o r t i n g . Of the p o i n t counted s e c t i o n s , 8 were from sandstones i n the Torrens Member, 5 from sandstones i n the S h e r i f f member, 21 from f l u v i a l channel and crevasse s p l a y sandstones i n the non-marine part of the Gates Formation and 28 from sandstones i n the Babcock member. Tables 3 and 4 l i s t the data o b t a i n e d from the poi n t counted s e c t i o n s . 4.2 FRAMEWORK GRAINS Quartz and ch e r t are the p r i n c i p a l d e t r i t a l components of 254 F i g u r e 9_6. Map showing the l o c a t i o n of boreholes and outcrop s e c t i o n s from which samples were p o i n t counted to determine compo s i t i o n . 255 the sandstones with s i l i c e o u s rock fragments, c l a s t i c sedimentary and metasedimentary rock fragments, carbonate rock fragments, igneous rock fragments and f e l d s p a r present i n l e s s e r amounts. M o n o c r y s t a l l i n e quartz forms 16-76% of the framework g r a i n s . Quartz overgrowths are present on many d e t r i t a l q u a r t z g r a i n s . Because there i s often no c l e a r boundary between the d e t r i t a l g r a i n and the quartz overgrowth, a l l of the q u a r t z present was counted as " d e t r i t a l . " Consequently i n some cases the d e t r i t a l quartz content has been s l i g h t l y overestimated and the other d e t r i t a l components l i g h t l y underestimated. Most of the g r a i n s are common ( p l u t o n i c ) q u a r t z types with s t r a i g h t to s l i g h t l y undulose e x t i n c t i o n and r e l a t i v e l y few i n c l u s i o n s . A few g r a i n s show s t r o n g l y undulose e x t i n c t i o n . P o l y c r y s t a l l i n e q uartz forms 0-16% of the framework g r a i n s . I n t e r n a l l y these g r a i n s range from uniformly s i z e d c r y s t a l s with mostly s t r a i g h t c o n t a c t s to elongate c r y s t a l s with s l i g h t l y sutured c o n t a c t s . S t r o n g l y elongate quartz c r y s t a l s , c h a r a c t e r i s t i c of s t r e t c h e d metamorphic quartz types are rare and were observed i n only a fewthin s e c t i o n s . Chert forms 2-49% of the framework g r a i n s and i s more abundant i n the c o a r s e r sandstones. The c h e r t s e x h i b i t a v a r i e t y of c o l o u r s i n c l u d i n g v a r i o u s shades of grey, l i g h t to dark brown, black and green. In a few pebbles, green c o l o u r e d c h e r t occurs as a r i n d (due to weathering?) around a core of brown c h e r t . Under the microscope most c h e r t s are c l e a r or l i g h t grey and e x h i b i t a u n i f o r m l y f i n e m i c r o c r y s t a l l i n e t e x t u r e . Some g r a i n s are c r y p t r o c r y s t a l l i n e and almostopaque under c r o s s 256 p o l a r i z e r s . G rains may c o n t a i n v a r i a b l e amounts of d e t r i t a l q u a r t z , a r g i l l a c e o u s m a t e r i a l , i r o n oxides and euhedral dolomite rhombs. F o s s i l i f e r o u s or replacement c h e r t s are f a i r l y common. The r e p l a c e d f o s s i l d e b r i s i n c l u d e s sponge s p i c u l e s , r a d i o l a r i a , bryozoans, e c h i n o i d p l a t e s and c r i n o i d ? fragments. S i l i c e o u s rock fragments ( a r g i l l i t e or c r y p t o c r y s t a l l i n e , impure c h e r t s ) comprise 0-12% of the framework g r a i n s . They vary in c o l o u r from l i g h t to dark brown and are n e a r l y opaque under c r o s s p o l a r i s e r s . Some g r a i n s are laminated, and appear to c o n s i s t mainly of dark, organic? r i c h c l a y s . With i n c r e a s i n g s i l i c a content these grade i n t o a r g i l l a c e o u s c h e r t . Some g r a i n s c o n t a i n small c i r c u l a r c h e r t fragments ( r e p l a c e d f o s s i l s ? ) i n a dark brown, a r g i l l a c e o u s matrix. C l a s t i c sedimentary and metasedimentary rock fragments ( s h a l e s , s i l t s t o n e s , sandstones and p h y l l i t e s ) comprise 0-16% of the framework g r a i n s . Brown sh a l e s and p h y l l i t e fragments are most common. In t h i n s e c t i o n s these fragments are s i m i l a r . The p h y l l i t e fragments were i d e n t i f i e d on the b a s i s of their' c o a r s e r and more s t r o n g l y o r i e n t e d c l a y minerals compared to the s h a l e s . The sandstone rock fragments are quartzose. Some of the sandstone rock fragments are c h e r t cemented. D e t r i t a l carbonate g r a i n s comprise 0-28% of the framework g r a i n s but i n most t h i n s e c t i o n s are l e s s than 10%. S t a i n i n g i n d i c a t e s that most of the d e t r i t a l carbonate i s dolomite. D e t r i t a l carbonate g r a i n s c o n s i s t of rounded p o l y c r y s t a l l i n e aggregates or s i n g l e rhombic c r y s t a l s of a s i m i l a r s i z e to the a s s o c i a t e d quartz g r a i n s . Many g r a i n s e x h i b i t i r o n s t a i n i n g along the edges and along cleavage pl a n e s . Abraded edges pr o v i d e 257 the best evidence of t r a n s p o r t a t i o n but i t i s o f t e n very d i f f i c u l t to d i s t i n g u i s h between d e t r i t a l carbonate g r a i n s and secondary carbonate cements. Consequently, the f i g u r e s f o r d e t r i t a l carbonate i n some s e c t i o n s may be overestimated. F e l d s p a r s were recognised i n only 23 of the 62 t h i n s e c t i o n s which were p o i n t counted. 6 of the t h i n s e c t i o n s were of sandstones i n the Torrens Member.and con t a i n e d 0.5-19.6% p l a g i o c l a s e f e l d s p a r i n the framework. The remaining 17 t h i n s e c t i o n s which co n t a i n e d f e l d s p a r were of upper Gates ( f a c i e s 3A, 3B, 3C and 5B) sandstones from the Babcock area. In these samples, f e l d s p a r comprises 0.3-22.6% of the framework g r a i n s and incudes both potassium and p l a g i o c l a s e f e l d s p a r . Potassium f e l d s p a r i s s l i g h t l y more abundant than the p l a g i o c l a s e f e l d s p a r and shows v a r y i n g amounts of a l t e r a t i o n ranging from h i g h l y a l t e r e d to f r e s h . Most g r a i n s are.untwinned. M i c r o c l i n e i s f a i r l y common. P e r t h i t i c f e l d s p a r i s present i n small amounts. The p l a g i o c l a s e f e l d s p a r s are- a f f e c t e d by a l t e r a t i o n i n v a r y i n g amounts. Some g r a i n s are- f a i r l y f r e s h i n appearance. The e x t i n c t i o n angle of a l b i t e twins i s unif o r m l y low suggesting the p l a g i o c l a s e s are sodic i n composition. Igneous rock fragments are absent i n most t h i n s e c t i o n s but were i d e n t i f i e d i n some of the more f e l d s p a t h i c sandstones i n the upper Gates where they form up to 4.6% of the framework g r a i n s . Most g r a i n s c o n s i s t of m i c r o c r y s t a l l i n e quartz and f e l d s p a r suggesting they were d e r i v e d from g r a n i t i c r o c k s . Accessory d e t r i t a l m i n e r a l s i n c l u d e micas and heavy m i n e r a l s . Micas are absent i n most samples but form up to 7% of the d e t r i t a l g r a i n s i n some of the f i n e r - g r a i n e d sandstones. 258 Heavy minerals are rare i n most samples. The hi g h e s t c o n c e n t r a t i o n of heavy minerals (up to 3.5% of the framework g r a i n s ) occurs near the top of f a c i e s 2A marine sandstones i n the upper Gates. Most of the heavy m i n e r a l s are z i r c o n s . Reddish brown p e l l e t s of s i d e r i t e or s i d e r i t e r i c h c l a y averaging 1 mm or more i n diameter are common i n marginal marine sandstones i n the upper Gates. They are a l s o present i n some marine sandstones lower i n the s e c t i o n but are very r a r e i n the non-marine sandstones. The p e l l e t s are s t r o n g l y deformed by compaction i n d i c a t i n g they were s o f t d u r i n g d e p o s i t i o n . T h i s together with t h e i r s i z e shows that they have a l o c a l o r i g i n . 4.3 MATRIX AND CEMENTS A r g i l l a c e o u s matrix c o n s i s t s predominantly of c l a y with minor amounts of s i l t s i z e d d e t r i t u s , forming an i n t e r s t i t i a l f i l l i n g between the framework g r a i n s . The c l a y matrix i n the sandstones i s both d e t r i t a l a n d.diagenetic i n o r i g i n and may a l s o be d e r i v e d , i n p a r t , from squashed sedimentary rock fragments and mudstone r i p - u p c l a s t s . Well formed "books" of k a o l i n i t e are a common " l a t e " a u t h i g e n i c c l a y m i n e r a l forming up to 2.7% of the t o t a l rock. A u t h i g e n i c g l a u c o n i t e occurs i n very small amounts (0.5%) i n some of the marine sandstones. The t o t a l amount of a r g i l l a c e o u s matrix i n any one sample ranges between 0-32%. In general the amount of matrix i n c r e a s e s with d e c r e a s i n g g r a i n - s i z e but there are exc e p t i o n s ; examples of these i n c l u d e some f i n e - to very f i n e - g r a i n e d , w e l l s o r t e d sandstones i n the upper Gates ( e s t u a r i n e f a c i e s 1A and marine sandstones of f a c i e s 2A) which t y p i c a l l y have l e s s than 5% a r g i l l a c e o u s matrix. 259 S i l i c a i s the most common cement p a r t i c u l a r l y i n the quartzose sandstones where i t occurs as an overgrowth on d e t r i t a l quartz g r a i n s . In some of the more a r g i l l a c e o u s sandstones, c h e r t and chalcedony cements are common. Often these cements occur intermixed with a r g i l l a c e o u s matrix. Chert a l s o r e p l a c e s other d e t r i t a l g r a i n s . Carbonate cements, which i n c l u d e dolomite, c a l c i t e and s i d e r i t e , are present in v a r i a b l e amounts. The carbonates occur as overgrowths on d e t r i t a l carbonate g r a i n s , as replacements of d e t r i t a l g r a i n s , as l a r g e c r y s t a l s p o i k i l o t o p i c a l l y e n c l o s i n g d e t r i t a l g r a i n s and as s m a l l e r c r y s t a l s i n the a r g i l l a c e o u s matrix. The highest content of carbonate cement (42%) occurs i n a sandstone sample from the Torrens Member. S i d e r i t e i s a common carbonate cement i n marine sandstones of f a c i e s 2A i n the upper Gates. I t s d i s t r i b u t i o n i s very i r r e g u l a r and i s o f t e n r e s t r i c t e d to d i s t i n c t brown s t a i n e d bands and patches. 4.4 MISCELLANEOUS CONSTITUENTS C o n s t i t u e n t s which are d i f f i c u l t to c l a s s i f y under the c a t e g o r i e s d e s c r i b e d above i n c l u d e organic matter ( c o a l spar and f i n e l y laminated carbonaceous d e b r i s ) which ranges from 0-16% of the t o t a l sample and i r o n oxides (0-5.5%). 4.5 TEXTURE The sandstones show c o n s i d e r a b l e v a r i a t i o n i n g r a i n - s i z e (very f i n e to very coarse) and s o r t i n g ( p o o r l y s o r t e d to extremely w e l l s o r t e d ) . The marine sandstones are t y p i c a l l y f i n e - to medium-grained and very w e l l s o r t e d while the channel 260 sandstones are o f t e n c o a r s e r - g r a i n e d and l e s s w e l l s o r t e d . F i n e -g r a i n e d sandstones of f a c i e s 1A ( e s t u a r i n e d e p o s i t s ) and f a c i e s 2A ( s h e l f - s h a l l o w marine) i n the upper Gates show the best s o r t i n g (very w e l l to extremely w e l l s o r t e d ) . Most quartz g r a i n s are subangular to subrounded. Some of the sandstones c o n t a i n w e l l rounded qu a r t z g r a i n s with d e t r i t a l quartz overgrowths which have been c l e a r l y r e c y c l e d . 4.6 SANDSTONE CLASSIFICATION Using F o l k ' s (1969) c l a s s i f i c a t i o n , 53 of the p o i n t counted s e c t i o n s are l i t h a r e n i t e s , 5 are f e l d s p a t h i c l i t h a r e n i t e s and 4 are quartz a r e n i t e s (Figure 97). I f the l i t h a r e n i t e s are f u r t h e r c l a s s i f i e d , a c c o r d i n g to the dominant type of rock p a r t i c l e , approximately 85% would be c l a s s i f i e d as chert a r e n i t e s and 15% as c a l c - l i t h i t e s . Sandstones i n the upper part c o n t a i n , i n ge n e r a l , more f e l d s p a r than those i n the lower-middle p a r t s of the Gates Formation as shown on F i g u r e 98. 4.7 SOURCE AREA Numerous other s t u d i e s (e.g., G l a i s t e r , 1959; W i l l i a m s , V963; Mellon, 1967; S t o t t , 1968; Jansa, 1972; S c h u l t h e i s and Mountjoy, 1978) have shown that the Canadian C o r d i l l e r a i s the main source area f o r uppermost J u r a s s i c and E a r l y Cretaceous sediments i n the western p a r t of the f o r e l a n d b a s i n . The pe t r o g r a p h i c data from t h i s study, i n a d d i t i o n to the pa l e o c u r r e n t evidence which i n d i c a t e s r i v e r s flowed mainly from a south-southwesterly d i r e c t i o n , a l s o suggests that the Canadian C o r d i l l e r a was the main source area f o r the d e t r i t a l components 261 Figure 97. A triangular diagram i l l u s t r a t i n g the composition of the framework grains in the Gates sandstones. Quartz Q.M.R.F. Feldspar 2 5 50 25 R 0 C k Fragments Chert F i g u r e 98. Comparison of framework g r a i n composition of sandstones in the lower-middle Gates and upper Gates. 263 Table 3. Compos i t Ion of point counted t h i n sect ions.  (Lower-middle Gates) 5 0 If S°3 (go if u gu 3 b r r 1 "3 S£ -J ."5 "5 r i i i r a SAXON 470' 7726 chan-nel crsSL-C P S S U 6.2 SAXON 495' 7726 chan-nel SAXON 967' Chan- mS 7726 nel WS 24.4 2.9 24.8 7.0 8.5 SAXON 1030' Chan- IBS 7726 nel 47.0 11.7 12.3 — 4.1 2.3 MWO 218.5ni chen-7830 nel 9.2 3.2 5.0 18.8 18.8 MWO 296.8m Chan- mS- W- 36.7 1.0 — " 23.9 4.5 8.5 — 13.9 3.0 -- 1.0 -- 6.0 — — 1.5 7830 nel craSL VW MWO 7830 303.0m chan-nel mSU-crsSL MW-(W) 24 .3 1.3 21.6 7.6 9.5 8.6 2.2 20.3 4.5 MXD . 7827 127m chan-nel fSU-mSL w 45.9 2.4 14.9 3.3 5.3 9.6 3.8 14.8 MOD 76-6 357' chan-nel ms w-vw 24 .4 2.9 41.4 3.3 5.8 4.0 2.2 0.4 14.5 1 . 1 MDD 7801 42.4m chan-nel f SL-(fSU) VW ' 35 .7 10.5 1.9 10.0 12.9 5.7 0.5 22.5 0.5 MDD 7801 46.3m chan-nel mSU w 31 .2 2.8 24.6 8.4 6.0 5. 1 7.4 1.9 12.6 MOD 7823 224.9m chan-nel mS-crsSL MW-(W) 22 .0 4.3 39.7 6.7 10.6 5.2 4.3 1.0 6.2 MOO 7822 182.3m chan-nel mS-(»SU) w-vw 36 .4 4.4 21.8 2.9 6.5 8.4 12.3 0.7 6.6 MDD 7822 224.5m chan-nel f -c r s MW 30 . 1 4.6 26.8 3.7 11.1 6.9 5.2 11.6 MOD 7752 123.5m chan-nel mS-crsSL w 17 .8 14.9 26.1 8.7 9.8 14.9 1.9 1.3 3.6 1 .0 OBD 7714 174.7m c r e -vasse splay fSU w-MW 30. .7 8.2 13.6 2.6 5.9 12.8 1.3 18. 1 6.6 OBD 7714 180.35m c r e -vasse splay fSU-(mSL) w 30. .7 4.5 9.6 4.2 9.6 12. 1 0.3 28.4 0.3 0.3 OBO 7306 1569' c r e -vasse splay fSU-(mSL) w 23.7 15.3 10.3 3.5 12.2 11.0 3.8 2.6 14.0 0.9 2.7 OBD 7306 1613.5' c r e -vasse splay fSU w-MW 24. .2 11.5 8.2 1 .0 3.9 17.8 13.4 3.6 12.5 1.4 2.5 MDD 7822 349.6m d l s t r . chan. FSU VW-(W) 31 . 6 6.2 12.4 3.6 9.3 16.0 10.8 10.2 MOD 7806 217.05m d l s t r . Chan. CrsSL-(mSU) w-(VW) 34. .4 5.5 23.4 7.8 4.6 2.3 11.9 0.5 9.6 MDD 7806 248.2m d l s t r . chan. MS MW 18. 3 1 .0 19.0 8.7 7.2 5.8 20.3 0.5 9.2 MDD 7806 263.7m d l s t r . chan. MSU VW 37, .8 0.9 37.8 8.5 7.2 1.8 1.8 0.9 1.3 0.5 MOD 7918 44.75m d l s t r . chan. CrsSL-(mSU) w-(MW) 25. .2 5.5 0.5 32.6 10. 1 .9.6 4.1 5.5 5.5 MW 7830 363.7m d l s t . chan. MSU ws 22. . 1 3.7 " " 35. 1 10.2 6.9 6.5 9.5 6.0 MXD 7827 431.9m marine mS ws 20. .7 6.6 46.0 9.4 10.3 0.9 5.6 0.5 MDD 7823 385.3m marine fSU-(mSL) VW 20 .9 5.8 4.9 27. 1 0.4 3.6 0.4 2.2 1.4 32.0 1.3 MOO 7823 388m marine fSU-(mSL) vw-(w) 24 .8 2.4 5.8 16.0 2.4 5.3 0.5 8.7 11.2 21.9 MOD 7801 197.9m marine fSU VW 34 .5 7.7 22.5 5.2 5.7 9.6 3.3 10.5 1.0 MOD 7801 214.5m marine fSL-tsu VW 23 .3 1.9 0.5 9.2 2.9 4.8 6.3 43.8 5.8 1.5 MDD 7918 S3.65m marine f SL-(fSU) VW 23 -(EW) .5 2.8 0.5 7.0 0.9 5.2 1.5 27.2 0.5 20.2 4.7 SH-82-1 marine fSL w-(MW) 25. 4 0.5 9.0 6.9 1.1 3.2 0.5 1 . 1 4.2 40.2 3.7 4.2 264 Compos 11 Ion of point counted thin sect long. (Upper GatesT" 0 _<J 7714 e Vi i k 3S 3| i 4 r ^ ^  ^  s r v i f f * * & •o £ u opt H V 5 t i _a_ i 0 0 o o •J 3' 2 2 2 2 S 145.73m 1A fSU-(fSL) VW 54.3 5.0 0.3 15.1 4.0 QBD 7219 788m 1A fSU-(fSL) VW 59.0 4.7 OBD 7219 803m 1A fSU-(fSL) VW- 75.3 EW 6.7 1.0 SHER-IFF S6-2 f SU-(mSL) W- 52.3 8.2 (VW) 34.5 1.3 1.0 SHER-IFF S6-5 fSU-(mSL) VW 66.2 5.0 OBD 7753 OBO 7218 OBD 7219 OBD 7219 OBD 7219 93.15m 2A VW- 54.7 1.8 EW 761' 2A 744' 2A f SL-(fSU) VW 33.3 2.0 5.9 3.0 fSL-(fSU) VW- 59.4 (EW) 736' 2A fSL-(fSU) W- 40.0 VW 5.5 2.0 4.9 0.5 37.7 0.5 -- 4.2 722' 2A VW- 37.7 EW OBO 7307 900' 2A f S L -U S U ) EW- 60.9 VW OBD 7307 888' 2A fSL-(fSU) EW 63. -VW OBD 7306 1162' 3A fSU-(mSL) W- 40.0 (MW) 2.3 0.5 5.6 1.7 1.0 6.5 -- 18.6 OBD 7307 823' 3A W 31.0 1. 1.8 7.0 3.5 0.6 5.2 2.3 2.3 11.7 0.6 OBD 7306 1192' 3A f SU-(mSU) W 32.5 3.3 1.0 10.2 2.0 2.7 12.6 2.0 -- 12.4 OBD 7306 1195.5' 3A fSU-(mSL) W 48.4 2.8 9.0 1.5 1.2 5.6 — 10.2 OBO 7306 1229' 3A fSU-(fSL) W 24.2 5.2 3.5 21.5 1.0 1.4 10.0 — 23.8 -- 0.9 7.0 OBD 7306 1225' 3A VW- 51.7 5.2 21.2 3.0 2.8 7.1 2.8 -- 3.8 -- 1.9 -- 0.5 OBD 7306 1276' 3» W- 14.7 (MW) 3.3 3.9 3.1 20.7 2.5 2.7 2.4 4.2 — 7.9 10.8 15.2 — — 8.2 OBD 7219 646' 3A fSL B i t o t W- 17.5 6.6 2.4 1.6 21.1 4.0 1.4 1.4 0.5 -- 8.5 -- 29.8 1.0 — 3.8 OBD 7219 655' 3A mS-craSL 3.1 1.9 34.7 6.0 5.0 0.9 1.9 0.5 6.0 -- 5.8 QBD 7219 672' 3A mSL-(fSU) W- 21.6 VW 13.0 4.0 4.0 23.6 7.6 4.9 1.0 0.5 -- 7.6 3.5 8.4 OBO 7219 694' 3* fSU-(mSL) W' 10.4 12.3 4.0 4.0 21.1 4.0 5.0 0.5 1.0 10.2 9.9 16. 1 OBD 7219 fSU-(«SL) W 17.0 10.4 4.8 3.2 31.1 6.9 3.0 0.5 3.3 10.8 6.6 OBD 7201 fSL-(fSU) 0.3 4.0 13.5 0.5 1.0 1.2 1.8 — 14.2 — 18.0 OBD 7201 fSL-(fSU) W 23.2 5.7 4.14.411.1 1.2 -- 28.0 0.6 0.3 18. OBD 7201 229.5 38 VW 26.3 3.3 6.0 7.7 12.3 2.3 1.7 0.7 0.7 — 7.7 — 26.0 — — 5.3 OBO 7754 138m 3B MW 24.3 6.5 4.1 6.3 12.1 0.2 1.2 1.0 2.2 — 10.9 2.5 21.9 1.4 — 5.1 OBD. 7711 94.55m 3C MW 23.9 -(W) 7.0 5.1.6.4 15.31.3 3.5 8.0 0.6 4.4 — 17.6 0.3 — 4.7 OBD 7203 258.5' SB OBD 7203 270' 5B mSU-(fSU) WS 25.2 4.6 3.4 0.6 32.2 2.0 0.9 10.1 0.6 -- 4.3 mSL WS 16.3 3.7 3.0 — 16.0 1.2 1.2 4.6 32.9 — 2.8 — 11.0 -- — 7.2 265 i n the Gates Formation. The composition of d e t r i t a l g r a i n s i n the Gates Formation i n d i c a t e s d e r i v a t i o n from sedimentary, metamorphic and igneous t e r r a i n s . Sedimentary rocks formed the p r i n c i p a l source based on the presence of abundant c h e r t , d e t r i t a l carbonate and smaller amounts of f i n e - g r a i n e d sedimentary rock fragments and w e l l rounded, reworked quartz g r a i n s . A metamorphic source i s i n d i c a t e d by the presence of p h y l l i t e , r e c r y s t a l l i s e d metamorphic and s t r e t c h e d metamorphic quartz g r a i n s . An igneous source i s i n f e r r e d from the presence of igneous rock fragments. The c o n t r i b u t i o n from igneous rocks i s , however, s m a l l and appears to be r e s t r i c t e d mainly to the upper Gates. Mesozoic to Cambrian sedimentary rocks i n the Rocky Mountain Front and Main Ranges c o n t a i n abundant quartzose sandstones, carbonates, c h e r t and shales and are a probable source of much of the d e t r i t u s i n the Gates Formation. Some of the c h e r t and carbonate .rock fragments may have been d e r i v e d from P a l e o z o i c e u g e o s y n c l i n a l r o c k s , west of the Rocky Mountain Trench. The Omineca b e l t west of the Rocky Mountain Trench i s the probable source of the metamorphic rock fragments. The source of the igneous rock fragments and f e l d s p a r i s u n c e r t a i n . The f e l d s p a r may have been d e r i v e d from metamorphic or igneous rocks or reworked from sedimentary rocks. The occurrence of f e l d s p a r i n sandstones which a l s o c o n t a i n igneous rock fragments suggests an igneous source f o r at l e a s t some of the f e l d s p a r . Mid J u r a s s i c to E a r l y Cretaceous i n t r u s i v e igneous recks i n the Omineca B e l t i n southeastern B r i t i s h Columbia are c o n s i d e r e d the most l i k e l y source of the igneous d e t r i t u s . 266 SUMMARY AND CONCLUSIONS The Lower Cretaceous Gates and Moosebar Formations of nor t h e a s t e r n B r i t i s h Columbia comprise a 350-450 m t h i c k i n t e r v a l of marine and non-marine c l a s t i c sediments which were de p o s i t e d i n the Rocky Mountain F o r e l a n d B a s i n . The Gates Formation i s the main c o a l - b e a r i n g u n i t i n the Northeast C o a l f i e l d s of B r i t i s h Columbia. S e d i m e n t o l o g i c a l s t u d i e s of the Gates-Moosebar i n t e r v a l were c a r r i e d out using outcrop and subsurface data i n a study area l o c a t e d i n the Rocky Mountain F o o t h i l l s between the A l b e r t a / B r i t i s h Columbia border and the Wolverine R i v e r and adjacent p a r t s of the P l a i n s . The Moosebar Formation and lowermost u n i t of the Gates Formation (the Torrens Member) c o n s i s t of between 2 and 4 coarsening-upward r e g r e s s i v e marine c y c l e s . In the northern part of the study area, non-marine sediments i n the Gates Formation occur interbedded with 3 major marine tongues (the S h e r i f f member, F a l h e r C and Babcock member) which pinch out towards the south. In the study area south of Duke Mountain, sediments i n the Gates Formation above the Torrens Member are e n t i r e l y non-marine. The coarsening-upward marine c y c l e s i n the Moosebar-lower Gates are comprised of up to 3 main f a c i e s (mudstone f a c i e s , t r a n s i t i o n a l f a c i e s and sheet sandstone f a c i e s ) . The mudstone f a c i e s occurs mainly i n the Moosebar Formation and c o n s i s t s of b i o t u r b a t e d mudstones and t h i n s i l t s t o n e s i n t e r p r e t e d as o f f s h o r e d e p o s i t s . The t r a n s i t i o n a l f a c i e s c o n s i s t s of interbedded mudstones, s i l t s t o n e s and t h i n very f i n e - g r a i n e d sandstones i n t e r p r e t e d as forming i n the t r a n s i t i o n zone between 267 the o f f s h o r e and shoreface. Sedimentary s t r u c t u r e s i n the s i l t s t o n e s and sandstones i n c l u d e hummocky c r o s s - s t r a t i f i c a t i o n which i n d i c a t e that storms were important along the Moosebar-lower Gates s h o r e l i n e s . The sheet sandstone f a c i e s c o n s i s t of l a t e r a l l y e x t e n s i v e u n i t s of sandstone 12 to 32 m t h i c k . Thin conglomerates are present l o c a l l y . T h i s f a c i e s i s i n t e r p r e t e d as shoreface-beach d e p o s i t s with channel d e p o s i t s present i n the upper part of a few s e c t i o n s . Thin t r a n s g r e s s i v e d e p o s i t s occur at the base of the S h e r i f f member. The presence of s h o r e l i n e conglomerates and the t h i c k n e s s and l a t e r a l extent of the shoreface-beach d e p o s i t s together with the absence of numerous t i d a l i n l e t d e p o s i t s suggest that the lower Gates s h o r e l i n e s were high energy and wave dominated. Pal e o c u r r e n t data and mapping of the landward pinchout of the marine tongues i n d i c a t e s that the Torrens, S h e r i f f and Babcock Member s h o r e l i n e s were o r i e n t e d approximately E-W and the F a l h e r C s h o r e l i n e approximately NW-SE. Non-marine d e p o s i t s above the marine u n i t s are i n t e r p r e t e d as forming i n lagoons, f l u v i a l channels and overbank environments w i t h i n a c o a s t a l p l a i n s e t t i n g . F l u v i a l channel d e p o s i t s c o n s i s t mainly of sandstones and conglomerates up to 42 m t h i c k . S e v e r a l types of f l u v i a l systems are re c o g n i s e d i n c l u d i n g b r a i d e d , anastomosing or s t r a i g h t (non-braided) and meandering r i v e r s . Braided r i v e r types are most common. Paleo c u r r e n t data and mapping of channel d e p o s i t s show that the r i v e r s flowed towards the northwest, n o r t h , northeast and eas t , with n o r t h e a s t e r l y d i r e c t i o n s most common. Three separate u n i t s of very coarse f l u v i a l conglomerate are present i n the Gates 268 Formation near Mount B e l c o u r t . These conglomerates are i n t e r p r e t e d as forming i n the proximal p a r t s of b r a i d e d r i v e r s p o s s i b l y w i t h i n an a l l u v i a l fan. Overbank l i t h o l o g i e s c o n s i s t of mudstones, s i l t s t o n e s , sandstones and c o a l s . These d e p o s i t s are i n t e r p r e t e d as forming in l e v e e , crevasse s p l a y , l a c u s t r i n e and w e l l to p o o r l y d r a i n e d swamp environments. D e t a i l e d s t u d i e s of the upper Gates marine u n i t (Babcock member) were c a r r i e d out using outcrop and c l o s e l y spaced borehole data. The upper Gates marine t r a n s g r e s s i o n i s recorded by 3 d i s t i n c t types of d e p o s i t s : 1. Thick (maximum 40 m) estuary mouth (shoal r e t r e a t massif) sandstones and congomerates ( f a c i e s 1A) preserved i n l i n e a r b e l t s approximately 0.4-2 km wide t r e n d i n g NW-SE and N-S. 2. A t h i n (<90 cm) but l a t e r a l l y e x t e n s i v e marine l a g ( f a c i e s 1B) . 3. L a g o o n - i n t e r t i d a l d e p o s i t s ( f a c i e s 4) preserved at the southern l i m i t of the upper Gates marine t r a n s g r e s s i o n i n the Duke Mountain area. During the p e r i o d of s t i l l s t a n d and e a r l y stages of c o a s t a l r e g r e s s i o n , shallow marine and channel f i l l conglomerates ( f a c i e s 2B) were d e p o s i t e d south of Babcock Mountain. F a r t h e r north, upper Gates r e g r e s s i v e d e p o s i t s are represented by l a t e r a l l y e x t e n s i v e s h e l f to shallow marine sandstones, s i l t s t o n e s and mudstones ( f a c i e s 2A), o v e r l a i n by s u b t i d a l channel ( f a c i e s 3A) and shoal ( f a c i e s 3B) d e p o s i t s . These i n turn are o v e r l a i n l o c a l l y by t i d a l f l a t ( f a c i e s 3C) and c o a s t a l p l a i n ( f a c i e s 5) d e p o s i t s with t h i n c o a l seams. In c o n t r a s t to 269 the lower Gates s h o r e l i n e s which were high energy and wave dominated, the upper Gates s h o r e l i n e s appear to have been r e l a t i v e l y low energy with a str o n g t i d a l i n f l u e n c e . Thick (maximum 10m), l a t e r a l l y e x t e n s i v e c o a l seams occur i n the lower p a r t of the Gates Formation above the Torrens and S h e r i f f Members. Coal seams i n the upper Gates are t h i n ( g e n e r a l l y <1.0 m). C r o s s - s e c t i o n s based on c l o s e l y spaced borehole and outcrop s e c t i o n s i l l u s t r a t e the occurrence and d i s t r i b u t i o n of c o a l seams i n the Duke, Honeymoon, Babcock, Frame and McConkey P i t s . Most of the major c o a l seams are continuous w i t h i n the p i t s . Some c o a l seams e x h i b i t t h i c k n e s s v a r i a t i o n s r e l a t e d to d e p o s i t i o n a l f a c t o r s . Examples of t h i s i n c l u d e the E seam and G/I2 and G/I3 seams i n the Babcock area which t h i n and pinch out adjacent to f l u v i a l channel and crevasse splay d e p o s i t s . D e p o s i t i o n a l t h i n n i n g adjacent to channel d e p o s i t s a l s o occurs i n the B1 seam south of the Duke P i t . In the northern part of the Duke Mountain area the B2 seam t h i n s and i s r e p l a c e d by s h o r e l i n e sandstones of the S h e r i f f member. Draping of c o a l seams over f l u v i a l channel d e p o s i t s (e.g., the G/I1 seam at Babcock and the B5 seam i n the Honeymoon P i t ) causes r a p i d v a r i a t i o n s i n interseam t h i c k n e s s which may lea d to c o r r e l a t i o n problems i n the e a r l y stages of e x p l o r a t i o n and a f f e c t the p o t e n t i a l m i n e a b i l i t y of c o a l seams. Within the study area the t o t a l c o a l t h i c k n e s s i n the Gates Formation v a r i e s between 10 and 28 m and the number of seams t h i c k e r than 1.5 m i n any one s e c t i o n v a r i e s between 2 and 6. The maximum c o a l development (28 m t o t a l c o a l and 6 seams >1.5 m t h i c k ) occurs i n the Duke Mountain area and B e l c o u r t P roperty, 270 south of Kinuseo Creek. In terms of regional paleogeography th i s area i s located near the boundary between t r a n s i t i o n a l marine and non-marine facies b e l t s . North of Bullmoose Mountain the number of thick seams and t o t a l coal thickness in the Gates Formation decreases rapidly as the non-marine intervals in the Gates are replaced by marine s t r a t a . With the exception of a few very thin seams, the Gates coals appear to be e n t i r e l y autochthonous and to have accumulated as peat in swamps in a coastal p l a i n depositional setting. Flora within the swamps include conifers, cycads, gingkos, ferns and sub-aquatic plants. Coal seams in the lower Gates accumulated as peat in swamps which were located along the margins of lagoons, immediately landward of beach barriers and in interchannel areas on the coastal p l a i n . Some of the swamps (e.g., those of the J seam) were very extensive, extending inland for at least 75 km from the shoreline. Coal seams in upper Gates accumulated as peat in swamps which were located inland from lagoons, estuaries, t i d a l f l a t s and in interchannel areas on the coastal p l a i n . The main d e t r i t a l components in the Gates sandstones (based on point counts of 62 thin sections) are quartz and chert with s i l i c e o u s rock fragments, carbonate rock fragments, c l a s t i c sedimentary and metasedimentary rock fragments, igneous rock fragments and feldspar present in lesser amounts. Igneous rock fragments and feldspar are more abundant in the upper Gates. Using Folk's (1969) c l a s s i f i c a t i o n , ,53 of the point counted sections are c l a s s i f i e d as l i t h a r e n i t e s , 5 are feldspathic l i t h a r e n i t e s and 4 are quartz arenites. The Mesozoic to Cambrian 271 sedimentary rocks of the Rocky Mountain Front and Main Ranges are i n t e r p r e t e d as the p r i n c i p a l source of the d e t r i t a l components i n the Gates sandstones. 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Youn, S.H., 1982, Conglomerate s h o r e l i n e d e p o s i t s i n the Elmworth area, A l b e r t a , Canada, ( a b s t r a c t ) : I n t e r n a t i o n a l A s s o c i a t i o n of S e d i m e n t o l o g i s t s , Hamilton, O n t a r i o , p. 105. Yurko, J.R., 1976, Deep Cretaceous c o a l resources of the A l b e r t a P l a i n s : A l b e r t a Research C o u n c i l Report 75-4, 47p. Northwest N o r t h w e s t F r a m e Q M D 7 6 2 0 O u t c r o p Q M D 7 6 1 8 Q B D 7 3 0 6 * • Q F D 7 2 2 0 / 7 2 2 1 Q u i n t e t t * # 2 Composite M O D 7 6 - 6 8 W D 7 6 - 6 M W D 7 6 3 0 B S D 7 6 - 3 Formation Regional Cross Section of the Gates and bns. Foothills of Northeastern British Columbia Northwest WOLVERINE QWD 7115 Southeast McCONKEY PIT QMD 7705/7701 McConkey Road Cut Composite QBD 8106 BABCOCK MTN Syncline Extension QBD 7510 Outcrop Section QBD 7219 QBD 7217 ROMAN MTN. QBD 7513 HONEYMOON PITS EAST WEST MDD 7908/7912 MDD 7914/7918 Composite Composite MDD7823 DUKE MTN MDD 7811/7905 Composite MDD 7822 DUCHESS MTN MUD 7704 WAPITI RIVER BD 7915 RED DEER Red Deer Road Cut BD 7802 Hulcross Formation - / Torrens Member *8B *8A x. A Gates Formation Location Map 100-. metres Moosebar Formation 50 H Gething Formation sltst. I fine s st. medium &st. coarse sst.l granular sst. conglomerate Legend Surface of marine transgression —^- Cross-bedding l^ r^ J Conglomerate —v- Low angle cross-bedding Trough cross-bedding Sandstone Tabular cross-bedding Hummocky cross-stratification | | Siltstone/Mudstone Ripples --«<\c Climbing ripples ^1 Coal ~<^ * Flaser bedding Wavy bedding Bent Bentonfte Lenticular bedding Burrows Parallel bedding L Roots ar> Soft sediment deformation — Sltet/Mdst pebble. "•"'Cture. and rlp-up clasts Pebble imbrication Cross Section 1 - Regional Cross Section of the Gates and Moosebar Formations, Foothills of Northeastern British Columbia 2$X ^ N o r t h w e s t b60A93P02 C76D93P02 d57093P02 C20CS3P02 d89K93l15 085093118 • 74Q93I1S b62Q93M6 849H93I1S 83A93I15 S o u t h e a s t C88F93M5 | . ' . ' . j M a r i n e D e p o s i t s 2. Logs indicate apparent thickness - not corrected tor structural dip. 3. 'Foothills' nomenclature used. C r o s s S e c t i o n 3 Q a m m a R a y L o g C o r r e l a t i o n o f S t r a t a E q u i v a l e n t t o t h e G a t e s a n d M o o s e b a r F o r m a t i o n s in t h e P l a i n s Fiawre 7 

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