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On the origin of the small moraines of Upper Hat Creek Valley Aylsworth, Janice Margaret 1975

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ON THE ORIGIN OF THE SMALL MORAINES OF UPPER HAT CREEK VALLEY by JANICE MARGARET AYLSWORTH B.A., U n i v e r s i t y of Western O n t a r i o , 1971 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n the Department of Geography We accept t h i s t h e s i s as conforming to the r e q u i r e d s t andard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1975 In presenting t h i s t h e s i s in 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 at the U n i v e r s i t y of B r i t i s h Columbia, I agree that 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 reference and study. I f u r t h e r agree that permission for extensive copying of 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 r e p r e s e n t a t i v e s . It i s understood that 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 gain s h a l 1 not be allowed without my w r i t t e n permission. Depa rtment The U n i v e r s i t y of B r i t i s h Columbia Vancouver 8, Canada Date ABSTRACT Numerous small l i n e a r moraines occur i n Upper Hat Creek v a l l e y , B r i t i s h Columbia. The r i d g e s l i e t r a n s v e r s e to the a x i s o f the v a l l e y . They are, upon average, 1000 f e e t (305 m.) l o n g , 8 f e e t (2.4 m.) h i g h , and spaced 130 f e e t (40 m.) a p a r t . T h e i r p r o f i l e i s asymmetrical, w i t h a s t e e p e r proximal s l o p e . The a l i g n -ment o f a-axes o f pebbles i n the t i l l i s t r a n s v e r s e to the moraine c r e s t , r e g a r d l e s s of the o r i e n t a t i o n o f the c r e s t with r e s p e c t to the d i r e c t i o n o f r e g i o n a l i c e movement. The dip o f the pebbles i s i n the d i r e c t i o n o f the s u r f a c e s l o p e , however, i t i s l e s s than the s l o p e on the proximal s i d e and g r e a t e r than the s l o p e on the d i s t a l s i d e . The Hat Creek moraines form an e x t e n s i v e system o f push moraines, d e p o s i t e d d u r i n g the r e t r e a t o f the l a s t i c e sh e e t . During the w i n t e r , a s l i g h t readvance o f the g l a c i e r pushed the a b l a t i o n moraine o f the p r e v i o u s summer i n t o a r i d g e along the i c e f r o n t . The r i d g e was not o v e r r i d d e n by the i c e . T h e r e f o r e , the asymmetry o f a simple push moraine was maintained. During the subsequent a b l a t i o n season the moraine was i s o l a t e d from the r e t r e a t i n g i c e margin. The next w i n t e r ' s readvance r a r e l y e x t e nded 1 as f a r as the p r e v i o u s r i d g e , thereby p r e s e r v i n g the moraines. i i i PREFACE The G e o l o g i c a l Survey o f Canada has sponsored the mapping of the s u r f i c i a l geology o f B r i t i s h Columbia f o r over s i x t y y e a r s . In the summer o f 1972 I was a s s i g n e d t o a f i e l d p a r t y mapping the t e r r a i n and s u r f i c i a l d e p o s i t s o f the A s h c r o f t map-area (92 l/NW; 1:126,720 s c a l e ) . T h i s area i n c l u d e s a s m a l l segment o f the Coast Mountains and p a r t o f the rugged western edge o f the I n t e r i o r P l a t e a u . One o f the major b a s i n s o f the map-area i s Upper Hat Creek v a l l e y , a broad upland v a l l e y on the e a s t e r n s i d e o f the C l e a r Range. I t i s c e n t r e d on approximately 50° 40' 15" n o r t h l a t i t u d e and 121° 36* 00" west l o n g i t u d e . (See F i g . 1) While engaged i n the mapping p r o j e c t I was a b l e to spend over two and one h a l f months s t u d y i n g the g l a c i a l landforms and d e p o s i t s o f Upper Hat Creek v a l l e y as the b a s i s o f t h i s master's t h e s i s . i v TABLE OF CONTENTS ABSTRACT , i i PREFACE i i i TABLE OF CONTENTS i v LIST OF TABLES v i LIST OF FIGURES v i i ACKNOWLEDGEMENTS v i i i INTRODUCTION 1 Chapter 1. THE PHYSICAL ENVIRONMENT OF HAT CREEK VALLEY 3 1.1 I n t r o d u c t i o n 3 1.2 The P h y s i c a l S e t t i n g 3 1.3 P l e i s t o c e n e H i s t o r y 7 1.3.1 Re g i o n a l P l e i s t o c e n e chronology 7 1.3.2 P l e i s t o c e n e h i s t o r y o f the study area 10 1.3.2.a G l a c i a t i o n 10 1.3.2.D D e g l a c i a t i o n 14 1.4 S u r f i c i a l Geology o f Upper Hat Creek V a l l e y 16 1.4.1 I n t r o d u c t i o n 16 1.4.2 The b u r i e d d e p o s i t s 18 1.4.3 The t i l l d e p o s i t s 19 1.4.4 The p o s t g l a c i a l d e p o s i t s 26 1.5 Summary 27 2. REVIEW OF THE LITERATURE ON SMALL MORAINES 29 2.1 I n t r o d u c t i o n 29 2.2 The Review o f the L i t e r a t u r e 31 2.2.1 Moraines formed du r i n g advancing i c e c o n d i t i o n s . 31 2.2.2 Moraines formed during r e t r e a t i n g i c e c o n d i t i o n s 33 2.2.3 Moraines formed du r i n g stagnant i c e c o n d i t i o n s . 40 2.2.4 Summary 43 2.3 Other L o c a t i o n s o f Small Moraines i n B r i t i s h Columbia . 44 3. RELATIONSHIP BETWEEN LOCAL TOPOGRAPHY AND SMALL MORAINES IN UPPER HAT CREEK VALLEY 46 3.1 I n t r o d u c t i o n ^6 3.2 Upper Hat Creek V a l l e y 46 V 3.3 The Small Moraine Areas 47 3.3.1 Area A: between Cashmere and Hat Creeks 47 3.3.2 Area B: between McCormick and McDonald Creeks. 51 3.3.3 Area C: south o f McDonald Creek 51 3.3.4 Area D: between Parke and P h i l Creeks 53 3.3.5 Area E: south o f P h i l Creek 54 3.3.6 S c a t t e r e d areas to the south 54 3.3.7 Crevasse f i l l i n g s south o f White Rock Creek ... 55 3.3.8 Summary 55 4. EXTERNAL MORPHOLOGY OF THE HAT CREEK MORAINES 59 4.1 I n t r o d u c t i o n 59 4.2 Study Design 59 4.3 The E x t e r n a l Morphology o f the Moraines 65 4.3.1 D e s c r i p t i o n 65 4.3.2 R e l a t i o n s h i p s between the v a r i a b l e s 67 4.4 Comparison w i t h Other Moraines 73 5. INTERNAL CHARACTERISTICS OF THE HAT CREEK MORAINES 75 5.1 I n t r o d u c t i o n 75 5.2 Study Design 75 5.3 The I n t e r n a l C h a r a c t e r i s t i c s o f the Moraines 80 5.3.1 T e x t u r a l a n a l y s i s 80 5.3.2 Pebble a n a l y s i s 82 5.3*3 T i l l f a b r i c a n a l y s i s 82 5.4 Comparison with Other Moraines 84 6. ORIGIN OF THE HAT CREEK MORAINES 87 6.1 I n t r o d u c t i o n 87 6.2 Summary o f the P h y s i c a l C h a r a c t e r i s t i c s 87 6.3 D i s c u s s i o n o f A l t e r n a t i v e Hypotheses o f O r i g i n 88 6.4 C o n c l u s i o n s 92 BIBLIOGRAPHY 94 v i LIST OF TABLES T a b l e page I. L i t h o l o g i e s o f T i l l Pebbles (percentage) 13 I I . Small Moraines D e s c r i b e d i n the L i t e r a t u r e 30 I I I . F i e l d Techniques 6 0 IV. A i r Photograph Techniques 1^ V. Height and Slope Measurements by Area °2 V I . Other E x t e r n a l Measurements by Area 63 V I I . C o r r e l a t i o n s o f F a c t o r s w i t h V a r i a b l e s 68 V I I I . Pebble A n a l y s i s 8 1 IX. T i l l F a b r i c A n a l y s i s 83 X. Comparison o f S i m i l a r C h a r a c t e r i s t i c s o f Hat Creek Moraines and Other Small Moraines 89 v i i LIST OF FIGURES Figure Page 1. Location Map of Study Area and Physiographic Subdivisions . 2 2. Geological Map of Upper Hat Creek Valley and Environs ... 3 3. Late G l a c i a l Chronology of Southern B r i t i s h Columbia .... 8 4. G l a c i a l Lineations and Generalized Contours 11 5. S u r f i c i a l Geology of Upper Hat Creek Valley 17 6. Photographs of Topography 2 1 7. Closeup of Moraines i n Area D 22 8. View Along Moraine Crests 23 9. Location Map of the Small Moraines : Area A 48 10. Location Map of the Small Moraines : Area B 50 11. Location Map of the Small Moraines : Areas C, D, E 52 12. Diagram Demonstrating the Influence of Southerly Slope on the Height of Moraines i n Area A (slope) 66 13. Correlations of Variables Between and Among Factors 69 14. Relationship Between Position of Ice Front and Length of Moraines; Example: Area C ? 2 15. Textural Analysis ~ 8 16. Cumulative Curves: Granule and Sand Sizes 79 v i i i ACKNOWLEDGEMENTS I wish t o thank my a d v i s o r , Dr. June Ryder, f o r her v a l u a b l e comments, guidance, and support during the r e s e a r c h i n g and w r i t i n g of t h i s t h e s i s . I a l s o acknowledge t h e c o n t r i b u t i o n t o t h i s t h e s i s of those who ai d e d me i n the f i e l d : my f i e l d a s s i s t a n t , M a r i l y n n Rodes; and f r i e n d s , Jim Aylsworth, Rob B l a i r , Don Howes, and Jim Johnstone. F i n a l l y , I wish t o thank the G e o l o g i c a l Survey o f Canada f o r s u p p o r t i n g t h i s r e s e a r c h i n t h e f i e l d . 1 INTRODUCTION The landscape o f the I n t e r i o r P l a t e a u o f B r i t i s h Columbia bears the i n d i s p u t a b l e mark o f the g l a c i e r s . W i t h i n t h i s r e g i o n many o f the landforms have been c r e a t e d or m o d i f i e d as a r e s u l t o f the l a s t advance and r e t r e a t o f i c e sheets over the l a n d . However, much o f the P l e i s t o c e n e h i s t o r y o f the area and the exact o r i g i n o f many o f the landforms i s s t i l l u n r e s o l v e d . Q Upper Hat Creek v a l l e y was s e l e c t e d as the r e s e a r c h area with t h i s l a t t e r problem i n mind. Outstanding amongst the g l a c i a l landforms o f the area are numerous sma l l l i n e a r moraines which t r e n d t r a n s v e r s e to the a x i s o f the v a l l e y . These f e a t u r e s bear s u p e r f i c i a l resemblance to many known v a r i e t i e s o f sma l l moraines. T h i s t h e s i s c o n s i d e r s the o r i g i n o f the moraines o f Upper Hat Creek v a l l e y . Using f i e l d techniques and a i r photograph i n t e r p r e t a t i o n , t h i s t h e s i s d i s c u s s e s the r e l a t i o n s h i p between the moraines and l o c a l topography, and examines e x t e r n a l and i n t e r n a l c h a r a c t e r i s t i c s o f the r i d g e s . These r e s u l t s are compared w i t h the morphology o f moraines reviewed i n the l i t e r a t u r e . Some a l t e r n a t i v e modes o f o r i g i n f o r the Hat Creek moraines are present e d . 2 FIG. 1: Location Map of Study Area and Physiographic Subdivisions 3 1. THE PHYSICAL ENVIRONMENT OF HAT CREEK VALLEY 1.1 I n t r o d u c t i o n Chapter I examines the p h y s i c a l environment o f the study a r e a . The p h y s i c a l s e t t i n g ( i n c l u d i n g physiography, geology, and g e o l o g i c h i s t o r y ) o f the are a , r e g i o n a l P l e i s t o c e n e h i s t o r y , and s u r f i c i a l geology o f Upper Hat Creek v a l l e y are d i s c u s s e d . The small moraines, t h a t are the s u b j e c t o f t h i s t h e s i s , are i n t r o d u c e d . 1.2 The P h y s i c a l S e t t i n g Upper Hat Creek v a l l e y l i e s i n the ruggedly d i s s e c t e d western zone o f the I n t e r i o r P l a t e a u system, i n the t r a n s i t i o n zone between the s u b u n i t s - - F r a s e r and Thompson P l a t e a u s ( H o l l a n d , 1964) ( F i g . 1). Vest and northwest o f the v a l l e y r i s e the broad rounded summits o f the C l e a r and Marble Ranges o f the F r a s e r P l a t e a u . These peaks reach e l e v a t i o n s g r e a t e r than 7000 f e e t (2135 m.) (eg. C a i r n Peak, 7650 f e e t (2332 m.)). East o f the v a l l e y are the f l a t topped h i l l s o f the d i s s e c t e d edge o f the Thompson P l a t e a u , r e a c h i n g approximately 5500 f e e t (1575 m.) e l e v a t i o n . A few o f these h i l l s , u n d e r l a i n by more r e s i s t a n t s t r a t a , are h i g h e r (eg. Cornwall H i l l s , 6684 f e e t (2037 m.)). The d i f f e r e n t i a t i o n o f p h y s i o g r a p h i c s u b d i v i s i o n s i s based upon the d i s t r i b u t i o n o f v a r i o u s types o f landforms, which, i n t u r n , are i n f l u e n c e d by the g e o l o g i c c h a r a c t e r and h i s t o r y o f the (otter Duffel I a n d M c T a g g a r t , 1952 ) TERTIARY KAML00PS GROUP: dark c o l o u r e d v o l c a n i c s : b a s a l t ; a n d c s i t e ; r h y o l i t e ; a s s o c i a t e d ••• t u f f s & b r e c c i a s Coldwater Beds: sandstone; shale & conglomerate; c o a l CRETACEOUS SPENCES BRIDGE GROUP: m u l t i - c o l o u r , l i g h t shade v o l c a n i c s : a n d e s i t e , • • ••• d a c i t e , b a s a l t , r h y o l i t e ; t u f f , b r e c c i a , agglomerate; c o n g l o ->os>vvvv iterate, sandstone, greyvacke & arkose $$$$^JACKASS MOUNTAIN AND LILLOOET GROUPS: gieywacke, a r g i l l i t e , c o n g l o -! - — _ merate, arkose, s i l t s t o n e , t u f f a c e o u s sandstone BREW GROUP a r g i l l i t e , q u a r t z i t e , conglomerate CRETACEOUS OR JURASSIC X X A X g r a n o d i o r i t e X XXBXMOUNT LYTT0N BATHOLITH: g r a n o d i o r i t e , q u a r t z d i o r i t e , d i o r i t e TRIASSIC OR EARLIER •SsrsHS' a r g i l l i t e , s l a t e , p h y l l i t e , q u a r t z i t e , greywacke, c h e r t , l i m e s t o n e ; riHHK greenstone; s c h i s t PERMIAN AND EARLIER CACHE CREEK GROUP: greenstone; c h e r t , a r g i l l i t e , minor l i m e s t o n e & q u a r t z i t e ; c h l o r i t e & qua r t z - m i c a s c h i s t Marble Canyon Formation: limestone C? ) h e a v i l y d r i f t covered area <D@ pebble sample s i t e s FIG. 2: Geological Map of Upper Hat Creek Valley and Environs 5 a r e a . A wide d i v e r s i t y o f rock types occur w i t h i n a r e l a t i v e l y s m a l l r e g i o n surrounding the study area ( F i g . 2). V o l c a n i c and sedimentary rocks predominate, o f t e n c o e x i s t i n g i n the same group, along w i t h t h e i r metamorphic e q u i v a l e n t s . Igneous i n t r u s i v e s are l e s s common. The formation o f these rock groups took p l a c e d u r i n g a number o f oro g e n i c and e r o s i o n a l c y c l e s which e v e n t u a l l y formed the general t o p o g r a p h i c p a t t e r n o f the p r e s e n t . D e t a i l s o f the r e g i o n a l geology presented below are summarized from D u f f e l l and McTaggart, 1952. The o l d e s t r o c k s , d e p o s i t e d d u r i n g the Permian p e r i o d , belong to the Cache Creek Group. I t c o n s i s t s o f a t h i c k assemblage o f c h e r t s , a r g i l l i t e s , minor limestones and q u a r t z i t e s , a n d e s i t e flows, agglomerates and t u f f s , and t h e i r metamorphic d e r i v a t i v e s . . . . I t a l s o i n c l u d e s the massive, r e c r y s t a l l i z e d l imestones t y p i c a l l y exposed i n the Marble Canyon ( D u f f e l l and McTaggart, 1952, p. 15)« T h i s Marble Canyon Formation a l s o outcrops on the western and southern s i d e s o f Cornwall H i l l s , where, i n many p l a c e s , i t stands i n steep c l i f f s . Such c l i f f s form the e a s t e r n w a l l o f Upper Hat Creek v a l l e y . The J u r a s s i c p e r i o d was a time o f u p l i f t and igneous i n t r u s i o n s . A q u a r t z - d i o r i t e stock t h a t was i n t r u d e d as an o u t l i e r o f the Mount L y t t o n B a t h o l i t h , now forms Mount Ma r t l e y i n the no r t h e r n C l e a r Range. Increased e r o s i o n f o l l o w i n g t h i s u p l i f t r e s u l t e d i n d e p o s i t i o n of sediments along F r a s e r R i v e r d u r i n g the Cretaceous p e r i o d . During Cretaceous time a widespread v o l c a n i c group 6 (Spences B r i d g e Group), c o n s i s t i n g mainly o f l i g h t , m u l t i - c o l o u r e d a n d e s i t e s and d a c i t e s , was d e p o s i t e d i n t h e area which i s now t h e C l e a r Range. These l a v a s have proven very s u s c e p t i b l e t o weathering, f a c i l i t a t i n g t h e great d i s s e c t i o n o f t h e C l e a r Range. The l a t e Cretaceous was a time o f e r o s i o n d u r i n g which the o u t l i n e s o f present topography began t o emerge. Hat Creek v a l l e y was at l e a s t p a r t i a l l y eroded then, as T e r t i a r y sediments ( C o l d -water Beds) occur w i t h i n t h e present b a s i n . During the Eocene, t h e s e Coldwater Beds were d e p o s i t e d i n the downstream p o r t i o n o f Upper Hat Creek b a s i n (where th e y i n c l u d e an e x t e n s i v e c o a l d e p o s i t ) . These sandstones and conglomerates are now deeply weathered and are u n s t a b l e i n p l a c e s , t e n d i n g t o s l i d e or flow downslope. One such s l i d e i s l o c a t e d along t h e northwestern s i d e o f the v a l l e y , where i t has formed a landscape s i m i l a r t o t h a t of hummocky t i l l d e p o s i t s i n other p a r t s o f t h e v a l l e y . The l a s t rocks formed were t h e Kamloops Group o f T e r t i a r y v o l c a n i c s , a t h i c k assemblage o f dark c o l o u r e d , dense b a s a l t s , a n d e s i t e s , and minor t u f f s . T h i s group u n d e r l i e s much o f t h e f l o o r o f Upper Hat Creek v a l l e y , where i t produces a f a i n t s t e p -l i k e topography along the v a l l e y s i d e s . Another p e r i o d o f u p l i f t o c c u r r e d a f t e r l a t e Miocene time (Mathews and Rouse, 1963). T h i s r e s u l t e d i n i n c r e a s e d d i s s e c t i o n o f t h e p l a t e a u s u r f a c e , a c c e n t u a t i n g the rugged western edge o f the P l a t e a u . ( L o c a l r e l i e f here i s 5000 f e e t (1525 m.).) Thus, by the end o f t h e T e r t i a r y , t h e form o f t h e present landscape was e s t a b l i s h e d . The s u r f a c e d e t a i l s were added l a t e r by t h e i c e 7 sheets and meltwater o f t h e P l e i s t o c e n e . 1.3 P l e i s t o c e n e H i s t o r y 1.3 1 Reg i o n a l P l e i s t o c e n e chronology During t h e P l e i s t o c e n e most o f B r i t i s h Columbia was covered by i c e sheets at l e a s t once. In t h e F r a s e r and Puget Lowlands four g l a c i a t i o n s , separated by t h r e e i n t e r g l a c i a t i o n s , have been r e c o g n i z e d . The l a s t o f t h e s e , t h e F r a s e r G l a c i a t i o n , has been s u b d i v i d e d i n t o stades (Armstrong et a l . , 1965; Easterbrook et a l . , 1967; Easterbrook, 1969). However, i n c e n t r a l B r i t i s h Columbia, sediments which represent g l a c i a t i o n s p r e c e d i n g t h e l a s t i n t e r -g l a c i a t i o n are ve r y uncommon and, at p r e s e n t , none o f t h e sub-d i v i s i o n s of t h e F r a s e r G l a c i a t i o n have been f o r m a l l y r e c o g n i z e d ( F u l t o n , 1971)• F i g u r e 3 summarizes t h e l a t e P l e i s t o c e n e sequence i n southern B r i t i s h Columbia. During t h e e a r l y s tages o f each g l a c i a t i o n , i c e b u i l t up i n t h e Coast and Columbia Mountains. Subsequently, g l a c i e r s flowed onto t h e I n t e r i o r P l a t e a u , c o a l e s c i n g t o form l a r g e i c e sh e e t s . The next stage o f development depended upon t h e i n t e n s i t y and d u r a t i o n o f each g l a c i a t i o n . The i c e sheets may have met and d i v e r t e d northward and southward or they may have b u i l t up t o form an i c e dome, over t h e I n t e r i o r , from which r a d i a l flow o c c u r r e d . An i c e dome would have been h i g h e r than t h e r e g i o n a l snowline and, t h e r e f o r e , independently n o u r i s h e d . Two opposing t h e o r i e s o f t h e p a t t e r n o f r e g i o n a l i c e movement ac r o s s t h e I n t e r i o r P l a t e a u d u r i n g t h e F r a s e r G l a c i a t i o n 8 1— 1 0 0 0 0 — — — — JEVERSON INTERSTADE VASHON STADE FRASER GLACIATION 1_ 2 0 0 0 0 — — — — — — — — — — — — — — 3 0 0 0 0 — — — OLY/APIA INTERGLACIATION l_ 4 0 0 0 0 — — — — — — — — — — — — — — — — — — oldest . dote ' d n c o v e r ed Vancouver Island Fraser Lowland Coast Mts. Interior Plateau position of Hat Creek Columbia Mountians Physiographic Subdivisions on 49 th Para l le l FIG. 3: L a t e G l a c i a l Chronology o f Southern B r i t i s h Columbia ( a f t e r F u l t o n , 1971, F i g . It Mathewes et a l . , 1972; Ryder, p e r s o n a l communication, 197^) 9 have been proposed ( F u l t o n , 19^7i and T i p p e r , 1971). An i c e dome t h e o r y was p r e s e n t e d by R. J . F u l t o n . He suggested t h a t v a l l e y g l a c i e r s from t h e Coast, C a r i b o o , and Monashee Mountains fed piedmont g l a c i e r s i n t h e I n t e r i o r P l a t e a u . Piedmont g l a c i e r s from the rimming mountains j o i n e d i n a s i n g l e sheet t h a t u l t i m a t e l y overrode t h e I n t e r i o r P l a t e a u . The i n t e r i o r i c e sheet, hemmed i n by the mountain chains t o t h e east and west, flowed north and south from a c e n t r a l dome formed i n t h e v i c i n i t y o f t h e 52nd p a r a l l e l ( F u l t o n , 1967), p. l ) . H. W. T i p p e r (1971) suggested t h a t the l a s t g l a c i a t i o n reached merely the i n i t i a l c o n t i n e n t a l i c e sheet stage ( K e r r , 193^), although i c e domes may have e x i s t e d d u r i n g e a r l i e r g l a c i a t i o n s . In h i s o p i n i o n , d u r i n g t h e F r a s e r G l a c i a t i o n , i c e flowed e a s t e r l y and s o u t h e a s t e r l y from the Coast Mountains and w e s t e r l y and southwesterly from t h e Cariboo Mountains, c o a l e s c i n g and d i v e r g i n g northwards and southwards. F o l l o w i n g a p a r t i a l r e t r e a t o f i c e , a l a t e readvance o c c u r r e d d u r i n g which i c e from the Cariboo Mountains p e n e t r a t e d westward as f a r as t h e F r a s e r R i v e r . N e i t h e r t h e o r y of r e g i o n a l i c e movement has been c o n c l u s i v e l y proven. At t h e maximum of t h e F r a s e r G l a c i a t i o n the i c e was at l e a s t 2000 f e e t (610 m.) t h i c k over the P l a t e a u ( i c e s u r f a c e was 7000 t o 8000 f e e t (2135-2440 m.) above sea l e v e l ) and reached t h i c k n e s s e s o f 6000 f e e t (1830 m.) over t h e deep v a l l e y s (Wilson et a l . , 1 9 5 8 ) . At t h e end o f the F r a s e r g l a c i a t i o n , r e t r e a t was accomplished by downwasting and by withdrawal o f t h e f r o n t toward t h e northwest ( F u l t o n , 1 9 6 7 ) . As t h e i c e t h i n n e d , mountains emerged from beneath the s u r f a c e , d i v i d i n g t h e sheet i n t o tongues which r e t r e a t e d along t h e v a l l e y s . Many o f th e s e tongues were g r a d u a l l y cut o f f 10 from t h e i r sources and l e f t t o stagnate i n the v a l l e y s . At t h i s time ice-dammed l a k e s dominated th e I n t e r i o r b a s i n s . A date, determined from a sample which was c o l l e c t e d from t h e m i d - s e c t i o n o f Lochore Creek fan i n the F r a s e r v a l l e y , i n d i c a t e s t h a t t h e L y t t o n - L i l l o o e t s e c t i o n o f the F r a s e r v a l l e y was i c e f r e e b e f o r e 11285 - 1000 years BP (Sample no. GX2612; Geochron L a b o r a t o r i e s , Cambridge, Mass.) ( J . M. Ryder, p e r s o n a l communication, 1974). F u l t o n (1971, p. 17) estimates t h a t t h e I n t e r i o r P l a t e a u was i c e f r e e by approximately 9500 years ago. 1.3.2 P l e i s t o c e n e h i s t o r y o f the study area 1.3.2.a G l a c i a t i o n During t h e F r a s e r G l a c i a t i o n , t h e whole o f t h e I n t e r i o r P l a t e a u was covered by g l a c i a l i c e . Features s t r e a m l i n e d by i c e on t h e broad t o p s o f the C l e a r Range and unweathered e r r a t i c s and s t r i a e on B l u s t r y Mountain are i n d i s p u t a b l e evidence t h a t t h i s range ( e l e v a t i o n s r e a c h i n g 7650 f e e t (2332 m.)) was b u r i e d . D u f f e l l and McTaggart (1952, p. 69) found e r r a t i c s and s t r i a e on the Coast Mountains up t o 83OO f e e t (2530 m.). The G l a c i a l Map o f Canada (Wilson et a l . , 1958) suggests t h a t i c e reached a hei g h t o f at l e a s t 8000 f e e t (2440 m.) above sea l e v e l over t h e study a r e a . Thus the i c e t h i c k n e s s over Upper Hat Creek v a l l e y and the surrounding mountains would have been 4800 f e e t (1463 m.) and at l e a s t 1300 fe e t (395 m.) r e s p e c t i v e l y . The l i n e a r f e a t u r e s on summits and r i d g e c r e s t s i n d i c a t e 11 12 t h a t i c e movement was e a s t e r l y from the Coast Mountains a c r o s s t h e Marble and C l e a r Ranges, changing t o s o u t h e a s t e r l y and s o u t h e r l y i n t h e Bonaparte and Thompson R i v e r v a l l e y s . These west-east l i n e a t i o n s occur at e l e v a t i o n s g e n e r a l l y over 4500 f e e t (1370 m.). F l u t i n g s and a few d r u m l i n o i d f e a t u r e s on t h e f l o o r o f Upper Hat Creek v a l l e y , however, r e v e a l a s o u t h e r l y movement p a r a l l e l t o the a x i s o f t h e v a l l e y . (See F i g . 4) The s o u t h e r l y l i n e a t i o n s suggest t h a t t h e r e was a d i r e c t i o n a l change i n t h e l a t e phases o f i c e movement. These f e a t u r e s , which are at and below 4200 f e e t (1280 m.) probably r e f l e c t t h e d i r e c t i o n o f flow o f the l a s t i c e i n t h e area; i c e which d i d not cover the surrounding uplands. It i s l i k e l y t h a t the l a t e i c e came from the n o r t h e a s t , as a l e s s r e s t r i c t e d passage e x i s t s f o r i c e v i a Bonaparte and Lower Hat Creek v a l l e y s , than by the a l t e r n a t i v e r o u te through t h e narrow Marble Canyon. (See F i g . 4) An a n a l y s i s o f l i t h o l o g i e s o f t i l l pebbles p r o v i d e s some s l i g h t a d d i t i o n a l evidence o f a movement of i c e from t h e n o r t h e a s t . A l l sample s i t e s are from t i l l o v e r l y i n g Kamp'loops v o l c a n i c rocks ( F i g . 2). The s i t e s are p l o t t e d on F i g u r e 2 and the r e s u l t s presented i n T a b l e I . In g e n e r a l , t h e s i m i l a r d i s t r i b u t i o n o f most l i t h o l o g i e s o f bedrock on both e a s t e r n and western margins of t h e b a s i n does not enable an easy i n t e r p r e t a t i o n o f l o c a l i c e movement. In a l l samples v o l c a n i c l i t h o l o g i e s predominate with b u l k percentages i n c r e a s i n g with d i s t a n c e up t h e b a s i n . Occurrences o f i n t r u s i v e e r r a t i c s fade q u i c k l y with d i s t a n c e east and south from t h e Mt. M a r t l e y s t o c k . Cache Creek l i t h o l o g i e s 13 TABLE I Lithologies of T i l l Pebbles (percentage) SITES* PEBBLE LITHOLOGIES Area Area Area Area A C D F 1 2 3 Mt. Martley; intrusives 4 3 1 2 2 2 20 Kamloops; basalt 39 59 58 61 42 36 30 Spences Bridge; other volcanics 14 23 21 31 32 16 28 Marble Canyon; limestone 8 3 3 0 6 16 4 Coldwater; sandstone, shale, conglomerate 4 2 1 0 2 0 0 Cache Creek; chert, a r g i l l i t e , quartzite 22 6 15 4 16 28 8 Other; Unknown; Weathered 6 4 1 2 0 2 10 •Areas A, C, D: average of 6 s i t e s per area Area F: average of 4 s i t e s per area 1, 2, 3: individual s i t e s 14 e x i s t s i g n i f i c a n t l y i n t h e n o r t h e a s t e r n s i t e s and are l e s s common i n t h e extreme northwestern s i t e . T h i s would be i n accord with i c e flow from t h e n o r t h e a s t . In summary, d u r i n g the F r a s e r G l a c i a t i o n , l a r g e volumes o f i c e entered the I n t e r i o r P l a t e a u from t h e surrounding mountains and c o a l e s c e d i n t o l a r g e sheets which met and d i v e r g e d northwards and southwards. I t i s not known whether an i c e dome stage was reached. However, l i n e a t i o n s i n Hat Creek b a s i n and t h e surrounding uplands suggest t h a t t h e main movement o f i c e over the study area was e a s t e r l y from t h e Coast Mountains. T h i s evidence may be i n t e r p r e t e d as support f o r T i p p e r ' s t h e o r y or may simply r e p r e s e n t i c e flow d u r i n g a r e l a t i v e l y l a t e , post-ice-dome phase of g l a c i a t i o n . As the end o f t h e i c e age approached, t h e i c e began t o withdraw and, with t h e s h r i n k i n g sheets, l o c a l i c e flow began t o change. Some p a r t s , i n c l u d i n g Upper Hat Creek v a l l e y , became i c e - f r e e f o r a p e r i o d (See 1.3.2.b). During t h e l a t e phase o f i c e movement, a lobe r e - e n t e r e d Upper Hat Creek v a l l e y from t h e n o r t h e a s t . G l a c i a l l i n e a t i o n s which r e p r e s e n t t h i s l a s t movement occur at e l e v a t i o n s below 4200 f e e t (1280 m.). l.'3.2.b D e g l a c i a t i o n The d e g l a c i a t i o n o f t h e r e g i o n was i n two p a r t s ; t h e main withdrawal o f F r a s e r i c e and the l a t e r m e l t i n g o f the l a s t i c e . The main F r a s e r r e t r e a t was accomplished by downwasting o f t h e 15 s u r f a c e o f the i c e sheet. T h i s would f i r s t r e s u l t i n the emergence o f the summits o f the C l e a r Range. Meltwater channels, from west to e a s t , c r o s s i n g the d i v i d e support t h i s view. The c i r q u e s o f the C l e a r Range were never r e o c c u p i e d by i c e f o l l o w i n g t h i s s t a g e . The emergence o f the summits would cause a change i n the p a t t e r n o f i c e flow; i n t h i s case, the movement o f i c e from the n o r t h e a s t . Drainage from i c e m e l t i n g i n Upper Hat Creek b a s i n and the C l e a r Range would probably have escaped eastward a c r o s s the low d i v i d e (3850 f e e t , 1174 m.) i n the Cornwall H i l l s at the head o f Oregon Jack Creek. An esker on the western s i d e o f t h i s d i v i d e i n d i c a t e s t h a t t h i s r o u t e was used at one time by s u b - g l a c i a l d rainage. Hat Creek v a l l e y was l i k e l y i c e - f r e e f o r a p e r i o d f o l l o w i n g the main withdrawal o f F r a s e r i c e . Some f l u v i a l g r a v e l s and s i l t s , whose unweathered and r e l a t i v e l y u n d i s t u r b e d appearances suggest a v e r y r e c e n t o r i g i n , are l o c a t e d at the n o r t h e r n end o f the v a l l e y (See 1 .4.2). They were probably d e p o s i t e d f o l l o w i n g the main withdrawal. The f l u v i a l d e p o s i t s are o v e r l a i n by t i l l which r e p r e s e n t s the l a t e i c e readvance from the n o r t h e a s t . The f i n a l d e g l a c i a t i o n i n v o l v e d r a p i d r e t r e a t o f the i c e f r o n t from Upper Hat Creek v a l l e y . Stagnant i c e d e p o s i t s are s c a r c e . Small moraines, the t o p i c o f t h i s t h e s i s , r e p r e s e n t a complex end moraine system of the l a t e i c e . Meltwater may have o r i g i n a l l y d r a i n e d south and east v i a Oregon Jack Creek v a l l e y or northward over the i c e . There i s no evidence o f a ponded la k e o f long d u r a t i o n or great s i z e i n the b a s i n . Northward f l o w i n g meltwater may have flowed west a c r o s s the Marble Canyon d i v i d e (2750 f e e t , 838 m.) u n t i l Lower Hat Creek and Bonaparte R i v e r v a l l e y s were c l e a r . 1.4 S u r f i c i a l Geology o f Upper Hat Creek V a l l e y 1.4.1 I n t r o d u c t i o n A mantle o f u n c o n s o l i d a t e d sediments covers most o f the b a s i n o f Upper Hat Creek (See F i g . 5) The t h i c k n e s s of t h i s mantle ranges from a few inches over bedrock to at l e a s t 100 f e e t (30 m.), as exposed i n s e c t i o n s at the n o r t h end o f the v a l l e y . The mantle i s composed c h i e f l y o f t i l l , however, f l u v i a l and c o l l u v i a l 1 sediments a l s o e x i s t , both on the s u r f a c e and exposed beneath the t i l l i n r i v e r bank s e c t i o n s . The d i s t r i b u t i o n and t o p o g r a p h i c appearance o f the s u r f i c i a l d e p o s i t s which comprise the mantle are p r e s e n t e d i n F i g u r e 5» The s u r f i c i a l e x p r e s s i o n of the t i l l v a r i e s g r e a t l y . "Veneers" ( l e s s than 6 f e e t (1.8 m.))and " b l a n k e t s " ( g r e a t e r than 6 f e e t (1.8 m.)) are covers which d e r i v e t h e i r t o p o g r a p h i c appear-ance from the c h a r a c t e r o f the u n d e r l y i n g u n i t . Other forms o f d e p o s i t s completely d i s g u i s e the nature o f the u n d e r l y i n g u n i t s . "Hummocky" r e f e r s to a t e r r a i n o f s m a l l steep s i d e s hummocks and h o l l o w s . " U n d u l a t i n g " r e f e r s to a r o l l i n g p l a i n w i t h l o c a l s l o p e s of l e s s than t e n degrees. C o l l u v i a l sediments are d e f i n e d as m a t e r i a l which has been moved downslope by the f o r c e o f g r a v i t y , w i t h or without a water l u b r i c a n t . 0 1 2 3 Miles 4 I ' » ' ° o o v 0 oo o| o 0 o o o ©o Mh, Dh Mm, Dm Mb, Mv, Mr, Db, Dv, Dr fLp.gAp, *At, gAQt gAf, dCf, dCa, Cb Hllll||||lll\^ Rs,R other; specified by letter code small morainic ridge esker LETTER KEY M : morainal (till) : D : undifferentiated Quaternary sediments L : lacustrine : A : alluvial : ( A G : fluvio - glacial ) R : bedrock : C : colluvial : E : aeolian : f : fine (fL) : g : gravel (gA) : s : steep slope ( 25°) d : diamicton : r : rubble : $Ev : sandy aeolian veneer ^ b : blanket v : veneer h : hummocky m : undulating r : ridged fan terrace plain f t P f : fan h : hummocky b : blanket a : apron (coalescing fans, sheet) compound terms : Mb/Cb (approximately 2 : 1 proportions) Mb:Cb (approximately equal proportions) FIG. 5: S u r f i c i a l Geology of Upper Hat Creek Valley LEAF 17. OMITTED IN PAGE NUMBERING. 18 1.4.2 The b u r i e d d e p o s i t s In the lower t h r e e m i l e s (4.8 km.) o f the v a l l e y t h e r e are outcrops o f d e p o s i t s which predate the l a s t i c e advance i n t o the v a l l e y . The o l d e s t d e p o s i t c o n s i s t s o f 30 f e e t (9 "»•) o f laminated s i l t , w ith c l a y and f i n e sand, exposed i n a road cut at the n o r t h e r n end o f the v a l l e y . The d e p o s i t i s l a c u s t r i n e i n o r i g i n . The sediments are very compact and h i g h l y f r a c t u r e d , with beds upheaved and numerous c o n t o r t i o n s . H o r i z o n t a l l y bedded cobble g r a v e l s and s i l t s o f f l u v i a l o r i g i n abut onto the n o r t h e r n s i d e o f the c o n t o r t e d s i l t s . The l a c u s t r i n e s i l t s are much more -f r a c t u r e d , compacted, and weathered i n appearance than the f l u v i a l sediments, s u g g e s t i n g t h a t the former are o l d e r . Both bear s t r u c t u r a l evidences o f having been o v e r r i d d e n by a g l a c i e r , although t i l l does not occur a t the top o f the exposure. In the next two m i l e s (3^2 km.) southward i n t o the v a l l e y , numerous s e c t i o n s o f w e l l s o r t e d , s t r a t i f i e d s i l t s , sands, and g r a v e l s o f f l u v i a l o r i g i n are exposed beneath t i l l along the entrenched s i d e s o f Hat Creek. The unweathered appearance o f the sediments and the r e l a t i v e s c a r c i t y of f r a c t u r i n g , c o n v o l u t i o n s , e t c . , as compared to the o l d e r s i l t at the n o r t h e r n end o f the v a l l e y , suggests t h a t these sediments were much younger. However, they may be contemporaneous wi t h the f l u v i a l d e p o s i t a b u t t i n g the o l d e r s i l t . A s e r i e s o f exposures around a l a r g e g r a v e l p i t r e v e a l a depth o f more than 100 f e e t (30 m.) o f these f l u v i a l d e p o s i t s . Very t h i c k pebble g r a v e l s (30 to 60 f e e t (9 to 18 m.)) top the s e c t i o n . An exposure about one h a l f m i l e (0.8 km.) south 19 o f the p r e v i o u s s e c t i o n , along the creek, r e v e a l s 20 f e e t (6 m.) (base not seen) o f w e l l s o r t e d , s t r a t i f i e d g r a v e l s and s i l t s d i p p i n g from 10° to 25° northward. A smooth h o r i z o n t a l d i s c o n -f o r m i t y e x i s t s between the f l u v i a l d e p o s i t s and an o v e r l y i n g 40 f e e t o f compact t i l l . I t i s probable t h a t the o l d e r , l a c u s t r i n e s i l t s are o f p r e - F r a s e r G l a c i a t i o n age. However, the f l u v i a l sediments may have been d e p o s i t e d d u r i n g the main withdrawal o f the F r a s e r i c e . The unweathered and r e l a t i v e l y u n d i s t u r b e d appearance o f the f l u v i a l sediments supports t h i s t h e o r y . 1.4.3 The t i l l d e p o s i t s The g l a c i a l d e p o s i t s i n the c e n t r a l p a r t o f the v a l l e y are predominantly t i l l . These vary from a t h i n veneer t o a mantle f o r t y f e e t deep. The t e x t u r e o f the t i l l depends upon the c h a r a c t e r i s t i c s o f the l o c a l bedrock. In the extreme northwest t i l l has a v e r y sandy matrix and commonly i n c l u d e s g r a n i t i c e r r a t i c s , i n d i c a t i n g the i n f l u e n c e o f the nearby Mount M a r t l e y s t o c k . On the v o l c a n i c rock, the t i l l has a f i n e r matrix and the e r r a t i c s are o f v a r y i n g l i t h o l o g i e s . In some areas two t i l l l a y e r s can be d i s t i n g u i s h e d . Along Medicine Creek, one q u a r t e r m i l e (0.4 km.) from the mouth, t h e r e i s an exposure o f t h r e e f e e t (0.9 m.) o f g r a v e l l y t i l l o v e r l y i n g a more compact t i l l . An i r r e g u l a r boundary separates them. Another i n d i c a t i o n o f two t i l l s o ccurs i n a s e c t i o n along Parke Creek. A g r i t t y t i l l o v e r l i e s a c l a y t i l l w ith a s t r o n g l y u n d u l a t i n g 20 boundary between them. The c l a y t i l l i s s l i g h t l y c o n v o l u t e d i n t o the upper t i l l . These l i m i t e d exposures make i t i m p o s s i b l e to determine whether the two l a y e r s r e p r e s e n t two separate events or an a b l a t i o n t i l l over a lodgement t i l l . D e t a i l e d d e s c r i p t i o n s o f the c h a r a c t e r o f the t i l l sheet are p o s s i b l e i n the a x i a l p a r t o f the v a l l e y because o f the presence o f unobstructed views and the ready access to exposures along g u l l i e s and r o a d c u t s . However, the f l a n k s o f the b a s i n are f o r e s t e d and l e s s a c c e s s i b l e , thus the d e s c r i p t i o n o f the s u r f a c e must r e l y on i n t e r p r e t a t i o n o f a i r photographs. Due to these d i f f i c u l t i e s , the d e p o s i t s along the v a l l e y f l a n k s are simply r e f e r r e d to as u n d i f f e r e n t i a t e d d r i f t and the to p o g r a p h i c e x p r e s s i o n i s u s u a l l y r e s t r i c t e d to veneer or b l a n k e t . The d i s t i n c t i o n be-tween veneer and b l a n k e t i s based upon the l o c a l s l o p e , extent o f bedrock o u t c r o p s , v e g e t a t i o n p a t t e r n s , and v i s i b i l i t y o f bedrock l i n e a t i o n s . For d e s c r i p t i v e purposes the a x i a l p a r t o f the v a l l e y i s d i v i d e d i n t o two r e g i o n s . The topography of the n o r t h e r n p a r t of the v a l l e y i s predominantly hummocky, with s m a l l i r r e g u l a r h i l l s o f four to twelve f e e t (1.2 to 3.7 m.) l o c a l r e l i e f , some shor t i r r e g u l a r r i d g e s , and many swales c o n t a i n i n g ponds or marshes. (See F i g . 6) Among the few exposures of these d e p o s i t s , most r e v e a l a compact t i l l . However, a small number o f outcrops i n the hummocks approximately o n e - h a l f t o one mi l e (0.8 to 1.6 km.) southwest o f Goose Lake, do r e v e a l some d i f f e r e n t sediments. One s e c t i o n shows a t i l l w ith very g r a v e l l y l e n s e s and i n c o r p o r a t e d c l a y - s i l t l a y e r s . A second s e c t i o n exposes s t r a t i f i e d d i r t y T y p i c a l hummocky moraine topography. C l e a r Range i s i n background Area o f small moraines (Area D, F i g . 11) seen from o p p o s i t e s i d e o f v a l l e y . Angle o f view i s o b l i q u e to t r e n d o f c r e s t s FIG. 6: Photographs o f Topography View along c r e s t s o f two sinuous moraines. Note asymmetrical p r o f i l e . Ridges terminate a g a i n s t hummocky h i l l at top o f photo. View along d i s t a l s i d e o f sinuous moraine, boulders on moraine c r e s t . Note FIG. 8: View Along Moraine C r e s t s 24 g r a v e l s and sand, however the s t r u c t u r e i s obscured by slumping. S t r a t i f i e d f i n e sands and g r a v e l s , d i p p i n g approximately 30° south-westward, are exposed i n a r i d g e . A very p o o r l y s o r t e d pebble to b o u l d e r g r a v e l i s exposed i n yet another l o c 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 kames a s s o c i a t e d with s t a g n a t i n g i c e . However, most of the hummocks c o n s i s t o f t i l l . These hummocky moraine d e p o s i t s are e x t e n s i v e throughout the n o r t h e r n p a r t o f the v a l l e y (See F i g . 6), w i t h the e x c e p t i o n o f the s t e e p e r s l o p e s o f the e a s t e r n s i d e , which are covered by moraine b l a n k e t s or veneers. Hummocky moraine i s much l e s s common i n the southern p a r t of the v a l l e y , although i t i s s t i l l found i n the low areas, and i t i s s t i l l composed o f t i l l . The s t e e p e r s l o p e s and h i g h areas of the e a s t e r n s i d e o f the v a l l e y are covered by a t i l l b l a n k e t . F a i n t n o r t h - s o u t h f l u t i n g s are apparent i n the t i l l . On the more g e n t l e western s l o p e s an u n d u l a t i n g t i l l s u r f a c e i s common. Small t r a n s v e r s e moraines, which are the s u b j e c t of t h i s t h e s i s , occur on these u n d u l a t i n g or b l a n k e t t i l l s u r f a c e s . (See F i g . 6, 7, 8) There are s i x d i s c e r n i b l e areas o f s m a l l moraines i n the v a l l e y ( d i s c u s s e d i n Chapter 3)« In g e n e r a l , the moraines are v e r y d i s t i n c t , s u b p a r a l l e l r i d g e s which t r e n d approximately east-west, t r a n s v e r s e to the a x i s of the v a l l e y . These f e a t u r e s are u s u a l l y l e s s than o n e - h a l f m i l e (0.8 km.) long and l e s s than 25 f e e t (7.5m.) h i g h ; averaging 8 f e e t (2.4 m.) h i g h . T h e i r p r o f i l e s are s t r o n g l y asymmetric. The average s l o p e o f the n o r t h e r n or proximal s i d e i s 24° and the d i s t a l s i d e i s 11°. The r i d g e c r e s t s are u s u a l l y sinuous and u n d u l a t i n g . In some areas the proximal s l o p e s have a s c a l l o p e d appearance. A few 25 r i d g e s have a b r a i d e d appearance. The r i d g e s c o n s i s t o f a coarse compact t i l l w i t h a sandy-s i l t m a t r i x . Boulders l i n e the r i d g e c r e s t s and may be c o n c e n t r a t e d on the h i g h e r p a r t s o f the r i d g e . The ground moraine between the r i d g e s i s a p p a r e n t l y f i n e r , but, t h i s may be due to s u p e r f i c i a l slopewash d e b r i s accumulating i n the lower a r e a s . An e x c e p t i o n to the g e n e r a l l y m o r a i n i c nature o f these r i d g e s e x i s t s i n an area on the s t e e p e r e a s t e r n s l o p e s south o f White Rock Creek. S t r a t i f i e d sands and g r a v e l s , w i t h beds d i p p i n g away from the c r e s t , are exposed i n road cuts through the l a r g e r r i d g e s . In t h i s area, the l a r g e s t r i d g e s , at l e a s t , are i n t e r p r e t e d as g l a c i o f l u v i a l f e a t u r e s , l i k e l y c r e v a s s e f i l l i n g s . These r i d g e s are a l s o d i f f e r e n t i n appearance. They are more i r r e g u l a r i n h e i g h t and s i n u o s i t y than m o r a i n i c r i d g e s i n o t h e r p a r t s o f the v a l l e y . However, the asymmetry o f t h e i r p r o f i l e i s s i m i l a r t o t h a t o f the o t h e r moraines. The m o r a i n i c r i d g e s are found normally at e l e v a t i o n s between 3600 and 4200 f e e t (1100 and 1280 m.) and normally occur at h i g h e r e l e v a t i o n s i n the n o r t h e r n a r e a s . No moraine extends h i g h e r than 4500 f e e t (1370 m.). T h i s may be near the upper l i m i t t h a t the l a s t g l a c i a l i c e reached along the s i d e s o f the v a l l e y . ( E a s t -west l i n e a t i o n s are p r e s e r v e d above 4500 f e e t (1370 m.) e l e v a t i o n . ) In many p l a c e s the moraines appear to be a s s o c i a t e d w i t h l o c a l breaks o f s l o p e . Commonly a r i d g e w i l l end a b r u p t l y at the break o f s l o p e , r e g a r d l e s s of the c o n v e x i t y or c o n c a v i t y o f the break. The areas o f s m a l l moraines may have been more e x t e n s i v e at one time, and subsequently have been destroyed by f l u v i a l and 26 c o l l u v i a l processes i n the v a l l e y . T h i s appears to be p a r t i c u l a r l y t r u e along the western s i d e where a l l u v i a l fans have b u r i e d areas of moraines. 1.4.4 The p o s t g l a c i a l d e p o s i t s P o s t g l a c i a l d e p o s i t s r e s u l t from f l u v i a l and c o l l u v i a l a c t i o n which has c o n s i d e r a b l y m o d i f i e d the g l a c i a l landscape i n the v a l l e y . T a l u s i s r e l a t i v e l y r a r e , o c c u r r i n g only at the base o f the limestone c l i f f s n o r th of Oregon Jack Creek. However, c o l l u v i a l slopewash m a t e r i a l i s v e r y common, p a r t i c u l a r i l y on the ste e p e r s l o p e s o f the e a s t e r n v a l l e y s i d e . I t c o l l e c t s i n small d e p r e s s i o n s , i n c l u d i n g the low areas between moraines. I t forms sm a l l fans at the base o f s l o p e s . In some areas very l a r g e , hummocky complexes of mudflows occu r . S e c t i o n s through one o f these mudflow complexes are r e v e a l e d i n the g u l l i e s two m i l e s (3.2 km.) north of White Rock Creek. Here t h e r e are 7 to 9 f e e t (2.1 to 2.8 m.) o f b u r i e d s o i l s , c a l i c h e s t r i n g e r s , and s i l t o v e r l y i n g a Mazama ash bed. Beneath the ash th e r e are interbedded pebble g r a v e l s and s i l t s , and a m a t e r i a l which may be e i t h e r a t i l l w ith limestone e r r a t i c s or a ve r y weathered limestone at the base. A l a r g e area o f moraines occurs to the immediate n o r t h of t h i s mudflow complex and i t i s l i k e l y t h a t many moraines were destroyed when the mudflow commenced. The White Rock Creek area, i t s e l f , i s a l a r g e mudflow complex. T i l l humps are surrounded and sometimes b u r i e d by g e n e r a l l y coarse mudflow l a y e r s . The ash i s not v i s i b l e here. A 27 v e r y weathered sandstone near the s u r f a c e at the upper end o f the flow p r o v i d e d some of the d e b r i s . L o c a l t i l l was the source o f the r e s t . A s e c t i o n along Parke Creek r e v e a l e d a l e s s obvious mudflow fan , 3% f e e t ( l . l m.) deep, o v e r l y i n g t i l l . The fan c o n s i s t e d o f l a y e r s of b u r i e d s o i l s , c a l i c h e , marl, and reworked s i l t s , over a s i l t / l i m e s t o n e d e b r i s , which may have flowed from a bed o f v e r y weathered limestone exposed f u r t h e r up the creek. During t h i s post g l a c i a l p e r i o d Hat Creek has c r e a t e d a wide g r a v e l l y f l o o d p l a i n i n the southern p a r t o f the v a l l e y and has become entrenched i n t o the s u r f i c i a l d e p o s i t s o f the n o r t h e r n p a r t . F l u v i a l a l l u v i a l fans are common at v a r i o u s e l e v a t i o n s i n the v a l l e y . There are some h i g h l e v e l fans on the western s i d e at Anderson, McCormick and McDonald Creeks, at a break o f s l o p e . They spread out over the t i l l d e p o s i t s at e l e v a t i o n s o f 360O to 3900 f e e t (1100 to 1190 m.). Some of the small moraines are p a r t i a l l y b u r i e d by these fan d e p o s i t s and i t i s l i k e l y t h a t o t h e r s have been completely obscured. Other fans, c l o s e t o Hat Creek, have had streams entrenched i n t o them as base l e v e l lowered, and new fans are forming a t the edges o f the modern f l o o d p l a i n . There are t h r e e l e v e l s o f fans at the mouth o f Medicine Creek and two l e v e l s at Pocock and Yet Creeks. 1.5 Summary Near the c l o s e of the l a s t g l a c i a t i o n , i c e moved i n t o 28 Upper Hat Creek v a l l e y from the northeast, depositing a layer of t i l l at elevations below 4500 feet (1370 m.). Probably the most interesting features formed during the subsequent retreat of the glac i e r are the small moraines i n the southern part of the v a l l e y . 29 2. REVIEW OF THE LITERATURE ON SMALL MORAINES 2.1 I n t r o d u c t i o n Many types o f small moraines, s i m i l a r to those i n the Hat Creek v a l l e y , have been d e s c r i b e d i n the l i t e r a t u r e . These moraines are s u b p a r a l l e l among themselves and g e n e r a l l y t r a n s v e r s e to the l a s t r e g i o n a l i c e movement. I n i t i a l l y , much o v e r l a p p i n g terminology e x i s t e d ; the same name was a p p l i e d to d i f f e r e n t f e a t u r e s and s i m i l a r f e a t u r e s were known under a v a r i e t y o f names--annual, De Geer, washboard, minor, s m a l l , r i b b e d , Rogen, r i p p l e d , i c e - c r a c k , push, c r o s s - v a l l e y , and r i b b e d a b l a t i o n moraines. However, as more i n f o r m a t i o n about t h e i r l o c a t i o n and t h e i r e x t e r n a l and i n t e r n a l morphology became a v a i l a b l e , the moraines were grouped a c c o r d i n g t o s p e c i f i c p r o c e s s e s . In many cases the o r i g i n a l l y suggested o r i g i n s , a b l a t i o n - f i l l e d c r e v a s s e s and i c e pushed r i d g e s , were r e p l a c e d by hypotheses o f lodgement ( E l s o n , 1957), p l a s t i c deformation (Hoppe, 1957; Andrews, 1963), push and o v e r r i d i n g (Andrews and Smithson, 1966; Cowan, 1968), and f l o w t i l l ( B o u l ton, 1968; Mackay, i960). These hypotheses have been f u r t h e r r e f i n e d , j u s t i f i e d , or e l i m i n a t e d i n the l i g h t o f r e c e n t l y a c q u i r e d knowledge o f pro c e s s e s a c t i v e at the base or margin o f pr e s e n t A r c t i c or A l p i n e g l a c i e r s ( B o u l t o n , 1970, 1971)* In s p i t e o f many common c h a r a c t e r i s t i c s , enough d i s s i m i l a r -i t i e s e x i s t between the small moraines o f Upper Hat Creek v a l l e y / TABLE II S m a l l M o r a i n e s D e s c r i b e d i n t h e L i t e r a t u r e I c e M o r a i n e c o n d i t i o n name A u t h o r i t v H e i g h t W i d t h L e n g t h S pac i na P r o f i l e F a b r i c S i t u a t i o n ADVANCE R i b b e d M o r a i n e Cowan ( 1 968 ) 1 0 - 3 0 ' 3 0 0 - 1 0 0 0 ' " i r r e g u l a r " 1 0 0 0 ' -1 m i l e 3 0 0 - 1 0 0 0 ' r o u n d e d 2 - 1 5 ° p a r a l l e l t o i c e movement p l a i n s , g e n t l y s l o p i n g u p l a n d s Hughes ( 1 964 ) 3 0-90' 51 m i l e 3 0 0 - 1 0 0 0 ' s h o r t - l i v e d , s h a l l o w g l a -c i a l l a k e s H e n d e r s o n ( 1959 ) * 1 0 - 2 5 ' - 2 0 0 - 5 0 0 ' . 1 0 0 0 ' -1 m i l e 6 0 0-1400' RETREAT De Geer Mora i ne Hoppe ( 1 9 5 2 . 1957, 1959) < 2 p ' 2 5 - 1 3 0 ' < 0 . 6 m i l e s t e e p e r d i s t a l t r a n s v e r s e t o m o r a i n e c r e s t g l a c i a l marine bas i ns C r o s s - V a l l e y Mora i ne Andrews (X 9&3) " & S m i t h s o n ( 1966 ) S 5 0 ' 8 0 - 4 9 5 ' X= l 6 5 ' d i s t a l = 3'*" p r o x i m a l = 1 8-24° ", d i p i n d i r e c t i o n o f s l o p e g l a c i a l l a k e bas i n s S m a l l M o r a i n e L ^ k e n & L e a h y ( 1 9 6 4 ) < 2 0 ' 1 0 0 - 3 2 5 ' i r r e g u l a r 11 M o r a l n e R i d g e s P r i c e ( 1 9 7 3 ) 3 - 1 3 ' 1 3 - 3 3 ' d i s t a l = 2 5 - 3 5 ° p r o x i m a l = 2 0 - 2 5 " " , d i p up-g l a c i e r on b o t h s i d e s P u s h M o r a i n e H e w i t t ( 1 9 6 7 ) 5 1 3 ' " n a r r o w " <330' s y m m e t r i c a l , g e n t l e S u b - l a c u s t -r i n e M o r a i n e s B a r n e t t & H o l t i s w o r t h (197'*) <115' X=35' £ 3 - 7 m i l e s d i s t a l = l 8 - 2 2 ° p r o x i m a l = 13-14* " , a l s o p a r a l -l e i t o i c e movement STAGNANT Washboard M o r a i ne E l s o n ( 1 9 5 7 ) <15' <1 m i l e 3 0 0 - 5 0 0 ' r o u n d e d p a r a l l e l t o i c e movement plains & u p l a n d s sloping upglacier L i n e a r D i s i In-t e g r a t i o n R i d g o s G r a v e n o r & K u p s c h ( 1 9 5 9 ) 3 - 3 5 " 2 5 - 3 0 0 - < 8 m i l e s r o u n d e d p l a i n s & uplands s l o p i n g down-g l a c i e r A b l a t i on S l i d e M o r a i n e Mackay ( i 9 6 0 ) "few f e e t " 5 0 ' 7 0 - 1 1 0 ' s t e e p e r p r o x i m a l s t a g n a n t i c e d e p r e s s i ons C o n t r o l l e d B o u l t o n M o r a i n e ( f l o v t i l l ) ( 1 9 6 8 ) p a r a l l e l t o f l o w o f , t i l l O and the sma l l moraines d e s c r i b e d i n the l i t e r a t u r e t h a t i t i s i n i t i a l l y i m p o s s i b l e to a s s o c i a t e the moraines o f Hat Creek w i t h any p a r t i c u l a r moraine type. Because o f t h i s o b s c u r i t y r e g a r d i n g a d e f i n i t e mode o f o r i g i n , an e x t e n s i v e review o f the l i t e r a t u r e on small moraines i s presented here. Comparisons can then be made with r e s u l t s o f ana l y s e s i n subsequent c h a p t e r s , and p o s s i b l e modes of o r i g i n can be i n f e r r e d . The f o l l o w i n g s e c t i o n s o f t h i s chapter d i s c u s s the morphology and probable o r i g i n o f sma l l moraines which were formed d u r i n g i c e c o n d i t i o n s o f a c t i v e advance, r e t r e a t , or s t a g n a t i o n . A d e s c r i p t i o n o f each type i s summarized i n T a b l e I I . L o c a t i o n s o f other areas o f smal l moraines i n B r i t i s h Columbia are a l s o g i v e n . 2.2 The Review o f the L i t e r a t u r e on Small Moraines 2.2.1 Moraines formed d u r i n g advancing i c e c o n d i t i o n s F e a tures p r e v i o u s l y r e f e r r e d t o as r i b b e d moraine (Cowan, I9685 Hughes, 1964), Rogen moraine (Hoppe, 1957), and r i p p l e d t i l l ( I v e s , 1956) are a l l r e f e r r e d to as r i b b e d moraine i n t h i s review. Ribbed moraine forms a f i e l d o f s u b p a r a l l e l r i d g e s which are com-monly a r c u a t e , convex downglacier, and t r a n s v e r s e to the d i r e c t i o n o f i c e movement. I n d i v i d u a l r i d g e s are ve r y i r r e g u l a r . H e i ghts v a r y between 10 and 90 f e e t (3 and 27.5 m.) and widths may reach 1000 f e e t (305 m.). The p r o f i l e i s g e n e r a l l y symmetrical and con-vex, although i r r e g u l a r i n d e t a i l . S l opes vary between 2° and 15°• F l u t i n g s , p a r a l l e l to the i c e flow, may occur on the s i d e s and c r e s t s and they grade l a t e r a l l y i n t o d r u m l i n s . Ribbed moraine i s found on p l a i n s and g e n t l y s l o p i n g uplands which may have p r o v i d e d 32 temporary, shallow l a k e b a s i n s . The p r e f e r r e d o r i e n t a t i o n o f the t i l l pebbles i s p a r a l l e l t o the i c e movement, which i s commonly, although not n e c e s s a r i l y , t r a n s v e r s e to the r i d g e c r e s t . A s i g n i f i c a n t u p g l a c i e r dip o c c u r s on the proximal s l o p e s ; the dip o f the top and d i s t a l s l o p e s i s g e n e r a l l y conformable wi t h the s l o p e . (Cowan, 1968) Hoppe (1959) suggested t h a t these f e a t u r e s were formed by water s a t u r a t e d t i l l extruded out from under the i c e f r o n t . Henderson (1959) suggested t h a t they were annual moraines c o n s i s t i n g o f lodgement t i l l . I ce o v e r l o a d e d with d e b r i s would d e p o s i t a morainal r i d g e near the edge o f a r e t r e a t i n g i c e sheet. S l i g h t w i n t e r advances would p a r t l y o v e r r i d e the moraine, im p a r t i n g an observed h o r i z o n t a l f i s s i l i t y t o the t i l l . However, Hughes (1964) d i s a g r e e d , p o s t u l a t i n g t h a t they were molded s u b g l a c i a l l y by a c t i v e l y advancing i c e , but the exact mechanism remained unknown. Cowan ( I 9 6 8 ) c i t e d the compactness, f i s s i l i t y , and p a r a l l e l f a b r i c o f the t i l l as evidence o f a s u b g l a c i a l o r i g i n . He suggested a mechanism f o r the s u b g l a c i a l molding o f d e p o s i t s i n t o r i b b e d moraine, as f o l l o w s . Advancing i c e would push up m a t e r i a l at i t s l e a d i n g edge u n t i l the r e s i s t a n c e p r o v i d e d by t h i s moraine was s u f f i c i e n t t o cause the i c e to o v e r r i d e the moraine. The f r o n t would then continue advancing, r e p e a t i n g the process and c o n s t r u c t i n g a f i e l d o f r i b b e d moraine. An o r i g i n o f push and o v e r r i d i n g by a c t i v e l y advancing i c e , (Cowan, 1968), i s most prob a b l e f o r r i b b e d moraine. However, t h i s p rocess i s dependent upon the s u b g l a c i a l thermal c o n d i t i o n s . Although most o f the s o l e o f the g l a c i e r would be at the p r e s s u r e 33 m e l t i n g p o i n t , and the substratum unfrozen, an o u t e r zone o f the i c e - b a s e w i l l be s e a s o n a l l y subzero. That zone may become f r o z e n to the bed. I f the p r o g l a c i a l area i s unfrozen below a super-f i c i a l depth, the m a t e r i a l w i l l be weak, and shoving o f the m a t e r i a l and formation o f a moraine w i l l o c c u r . I f , however, a t h i c k l a y e r o f permafrost l i e s i n f r o n t o f the i c e , the m a t e r i a l w i l l be very r e s i s t a n t to the above process and no moraines w i l l be formed. T h e r e f o r e the p r o g l a c i a l area must be kept u n f r o z e n . The e x i s t e n c e o f a shallow p r o g l a c i a l l a k e w i l l s a t i s f y t h i s c o n d i t i o n . The s p a c i n g between the moraines i s r e l a t e d to the i c e t h i c k n e s s , o r , i n other words, the volume o f moraine r e q u i r e d to p r o v i d e the necessary r e s i s t a n c e to i n i t i a t e the o v e r r i d i n g p r o c e s s . (Cowan, 1968) In c o n c l u s i o n , r i b b e d moraine was probably molded s u b g l a c i a l l y by a c t i v e l y advancing i c e which pushed and then overrode the r i d g e . F o l l o w i n g d e g l a c i a t i o n o f the area the f i e l d s o f r i b b e d moraine would be exposed. 2.2.2 Moraines formed d u r i n g r e t r e a t i n g i c e c o n d i t i o n s When the i c e f r o n t i s r e t r e a t i n g moraines may be formed by deformation o f lodgement t i l l beneath the i c e f r o n t or by pushing o f m a t e r i a l at the f r o n t o f the i c e du r i n g a seasonal advance. Hoppe (1952, 1957, 1959) d e s c r i b e d s m a l l s u b p a r a l l e l r i d g e s , t r a n s v e r s e t o i c e movement, i n N o r r b o t t e n , Sweden, which he named De Geer moraines. These moraines reach 0.6 m i l e ( l km.) l e n g t h , 20 to 23 f e e t (6 to 7 mj h e i g h t , and 13 to 26 f e e t (4 to 8 m.) 34 w i d t h . T h e i r most n o t i c a b l e f e a t u r e i s marked asymmetry, w i t h a ste e p e r d i s t a l s l o p e . The p r e f e r r e d o r i e n t a t i o n o f t i l l pebbles w i t h i n the moraine i s t r a n s v e r s e to the t r e n d o f the r i d g e c r e s t and independent of the d i r e c t i o n o f r e g i o n a l i c e movement. In Norbotten, De Geer moraines are o n l y found below the l e v e l o f the h i g h e s t marine s h o r e l i n e s , which suggests t h a t they are formed i n subaqueous environments. Hoppe (1952) p o s t u l a t e d an o r i g i n due to b a s a l squeezing o f water soaked t i l l . I f the g l a c i e r terminated i n a body o f water, a h i g h e r h y d r o s t a t i c head should e x i s t i n the g l a c i e r than would e x i s t i n the water. Thus flow o f meltwater would be towards the i c e f r o n t and excess p r e s s u r e would r e s u l t i n seepage through the b a s a l t i l l . A c r i t i c a l h y d r a u l i c g r a d i e n t i s reached when the seepage p r e s s u r e equals the submerged weight o f the t i l l . A weight r e s t i n g on t h i s m a t e r i a l would then s i n k , e f f e c t i v e l y r e s u l t i n g i n flow o f t i l l i n t o b a s a l c r e v a s s e s near the i c e f r o n t , or out from under the i c e c l i f f . T h i s h y p o t h e s i s i s compatible with the d i s t i n c t i v e t i l l f a b r i c observed i n these moraines. The f a b r i c would be p a r a l l e l to the t i l l flow and, t h e r e f o r e , t r a n s v e r s e to the r i d g e c r e s t . I r r e g u l a r i t i e s i n the spacing p a t t e r n o f the moraines r e f l e c t the c a l v i n g p a t t e r n , as i c e r e t r e a t i s f a s t e r where water i s deeper. Andrews (1963a, b) d e s c r i b e d a s e r i e s o f small s u b p a r a l l e l moraines which he named c r o s s - v a l l e y moraines. These moraines are l i n e a r or g e n t l y sinuous r i d g e s t h a t are a l i g n e d t r a n s v e r s e to the axes o f v a l l e y s i n which they occur, and a l s o t r a n s v e r s e t o i c e 35 movement. The p a t t e r n o f the moraine i s concave downglacier, w i t h approximately 55 y a r d (50 m.) i n t e r v a l s between adjacent r i d g e s . The moraines are l a r g e s t (9«9 to 66 f e e t (3 to 20 m.) high) at i n t e r m e d i a t e e l e v a t i o n s on the v a l l e y s i d e , becoming p r o g r e s s i v e l y s m a l l e r (3»3 to 9^ 9 f e e t (1 to 3«n.)) both upslope and a l s o down-sl o p e , toward the c e n t r e o f the v a l l e y , where they grade i n t o a s e r i e s o f i n t e r c o n n e c t e d r i d g e s and h o l l o w s . L i k e the De Geer moraines, c r o s s - v a l l e y moraines are asymmetric with a s t e e p e r d i s t a l s i d e . The s l o p e o f the d i s t a l s i d e averages 34°, and the s l o p e o f the proximal s i d e averages 18* to 24°. The t i l l f a b r i c i n the c r o s s - v a l l e y moraines i s v e r y d i s -t i n c t l y De Geer moraine type. I n s t e a d o f being p a r a l l e l to the l a s t d i r e c t i o n o f i c e movement, the p r e f e r r e d o r i e n t a t i o n i n the c r o s s - v a l l e y moraines i s t r a n s v e r s e to the c r e s t o f the r i d g e . T h i s o ccurs r e g a r d l e s s o f the o r i e n t a t i o n o f the c r e s t . A s t r o n g up-g l a c i e r i m b r i c a t i o n , g r e a t e r than the angle o f the s l o p e , e x i s t s i n the proximal s i d e , whereas a much weaker downglacier d i p , l e s s than the angle o f the s l o p e , e x i s t s i n t h e d i s t a l s i d e . The proximal f a b r i c s have a s t r o n g e r o r i e n t a t i o n . (Andrews and Smithson, 1966) L i k e the De Geer moraines, the c r o s s - v a l l e y moraines do not occur above the h i g h e s t s t r a n d l i n e o f a p r o g l a c i a l l a k e . Andrews concluded t h a t a s t r o n g c o r r e l a t i o n must e x i s t between d i s t a n c e from the watershed and the e f f e c t i v e s t r e s s at the base o f a g l a c i e r ending i n a ponded l a k e , as an i n v e r s e r e l a t i o n s h i p between s p a c i n g o f moraines and d i s t a n c e from the d i v i d e was observed (Andrews, 1963b). 36 I n i t i a l l y (1963b), Andrews accepted the theory t h a t the c r o s s - v a l l e y moraines were formed by squeezing o f t i l l i n t o b a s a l c r e v a s s e s . In order f o r b a s a l squeezing to occur, the t i l l near the i c e margin, (which i s normally f r o z e n i n the A r c t i c case,) must become thawed, b a s a l c r e v a s s e s must form, and a squeeze mech-anism must e x i s t . A g l a c i e r c a l v i n g i n t o a deep p r o g l a c i a l l a k e would p r o v i d e these c o n d i t i o n s . I f the depth o f the l a k e i s e q u i v a l e n t to the depth o f the i c e , h y d r o s t a t i c p r e s s u r e i n the water i s g r e a t e r than the s t a t i c p r e s s u r e a c t i n g on the i c e . T h e r e f o r e , the h o r i z o n t a l f o r c e exceeds the v e r t i c a l f o r c e , a r e v e r s e p r e s s u r e g r a d i e n t e x i s t s , and water w i l l seep under the i c e f r o n t and melt the t i l l . Adhesion between the i c e and the now unfrozen ground ceases, and the i c e becomes buoyant, c r e a t i n g b a s a l c r e v a s s e s . T h i s a l s o s h i f t s con-d i t i o n s toward those proposed by Hoppe (1952, I957). When the c r i t i c a l h y d r a u l i c g r a d i e n t i s reached, s t a t i c p r e s s u r e on the t i l l i s much g r e a t e r than the maximum b e a r i n g p r e s s u r e o f s o f t c l a y and wet sand. At the p o i n t o f buoyancy the i c e can bear down and squeeze the s a t u r a t e d t i l l i n t o the b a s a l c r e v a s s e s . (Andrews, 1963b) The above h y p o t h e s i s i s r e s t r i c t e d to deep water c o n d i t i o n s i n which seepage, thaw, and buoyancy can e x i s t because o f an i n i t i a l r e v e r s e g r a d i e n t . However, Andrews l a t e r d i s c o v e r e d areas i n which p r o g l a c i a l l a k e s were too shallow f o r buoyancy (Andrews and Smithson, 1966). A b a s a l squeeze mechanism c o u l d a l s o work s e a s o n a l l y , at the i c e f r o n t , i n a manner s i m i l a r to t h a t suggested by Hoppe (1952). In t h i s case the t r i g g e r would be the summer i n f l u x o f meltwater 37 (Andrews and Smithson, 1966). I f a c o n s i d e r a b l e i n f l u x o f water under h y d r o s t a t i c p r e s s u r e reached the i c e base through a s e r i e s o f c r e v a s s e s , the ground water seepage would a l t e r and the squeezing process c o u l d o c c u r . The presence o f kames and eskers a s s o c i a t e d with the c r o s s - v a l l e y moraines t e s t i f i e s to an abundance o f a v a i l a b l e meltwater. The steep d i s t a l s l o p e o f the moraine would be due to a subsequent o v e r r i d i n g . Any f l u c t u a t i o n i n the shape and o r i e n t a t i o n o f the moraines would be due to l o c a l i r r e g u l a r i t i e s i n the c a l v i n g bay. (Andrews and Smithson, 1966) Squeezing of t i l l i n t o b a s a l c r e v a s s e s can s t i l l o ccur under these c o n d i t i o n s i f some mechanism to form c r e v a s s e s e x i s t s other than buoyancy i n deep water. Small , s u b p a r a l l e l r i d g e s i n other p a r t s o f the g l a c i a t e d r world have a l s o been a t t r i b u t e d to the b a s a l squeezing o f water soaked sediments e i t h e r i n t o c r e v a s s e s or out from under the i c e f r o n t ( B o ulton, 1971; L0ken and Leahy, 1964; P r i c e , 1969, 1973)-The suspected annual formation o f some sma l l moraines c o u l d a l s o be a t t r i b u t e d to a f r o n t a l push th e o r y . In w i n t e r , when accumulation exceeds a b l a t i o n the g l a c i e r advances s l i g h t l y , pushing the a b l a t i o n moraine o f the p r e v i o u s summer ahead o f i t . During the subsequent a b l a t i o n season the i c e f r o n t withdraws, l e a v i n g the push moraine. F l i n t (19711 P- 203) d e f i n e s a push moraine as a narrow, s t e e p - s i d e d r i d g e not known to exceed 9 m. /^ 30 f t _ 7 i n h e i g h t , made by b u l l d o z i n g by an advancing terminus. Push moraines are s m a l l , a p p a r e n t l y because a more massive heap o f d r i f t would cause the i c e to f a i l and o v e r r i d e i t , t h e r e a f t e r d e p o s i t i n g d r i f t mainly by lodgement. I f i t were o n l y a simple push forward the proximal s l o p e would be s t e e p e s t and the d i s t a l s l o p e weaker, reduced by movement o f ma-38 t e r i a l downslope. I f the i c e l a t e r overrode the r i d g e , the p r o f i l e would be r e v e r s e d . (Andrews and Smithson, I966). Formation o f these f r o n t a l push moraines was observed by Hewitt (1967) at the B i a f o g l a c i e r . During the a b l a t i o n season, d e b r i s i s r e l e a s e d from the r e t r e a t i n g i c e , forming an u n s t r u c t u r e d moraine. During the c o l d season the i c e c l i f f steepens, as h i g h e r i c e l a y e r s o v e r r i d e the base, and the a b l a t i o n moraine i s reworked. T i l l i s pushed forward t h i c k e n i n g the d e p o s i t outward and s p i l l i n g down the d i s t a l s l o p e . The i c e o v e r r i d e s the moraine forming a t h i c k e n i n g wedge o f t i l l beneath the terminus. The r e s u l t i n g moraine i s an ar c u a t e , narrow r i d g e , up to 13 f e e t (4 m.) h i g h and 330 f e e t (100 m.) lo n g , w i t h symmetrical, g e n t l e s l o p e s . A problem e x i s t s r e c o n c i l l i n g the t h e o r e t i c a l f a b r i c o f a push moraine, - - p a r a l l e l w i t h the c r e s t and t r a n s v e r s e to the d i r e c t i o n o f push, wi t h the a c t u a l f a b r i c s observed by Andrews (1963b). He suggests t h a t the pebbles were r e o r i e n t e d during the p e r i o d o f o v e r r i d i n g , becoming t r a n s v e r s e to the moraine c r e s t . However, t h i s can not e x p l a i n the f a b r i c s o f those moraines wi t h the steep proximal s l o p e s which he f e l t were formed by a simple forward push. U n f o r t u n a t e l y Hewitt d i d not p u b l i s h any t i l l f a b r i c data on h i s push moraines. I t i s p o s s i b l e t h a t the push mechanism c o u l d s t i l l o perate i n deep water c o n d i t i o n s where buoyancy would normally negate f r o n t a l push. During the w i n t e r , t i l l at the buoyancy l i n e c o u l d be pushed and o v e r r i d d e n by advancing i c e . With the i n f l u x o f summer meltwater, la k e l e v e l s would i n c r e a s e , i c e would l i f t o f f the push moraine, and the i c e f r o n t would r e t r e a t . T h e r e f o r e next 39 w i n t e r ' s push, at t h e buoyancy l i n e , would occur f u r t h e r back. Thus two p o s s i b l e o r i g i n s f o r thes e moraines e x i s t ; b a s a l squeezing or push (with or without o v e r r i d i n g ) , or p o s s i b l y a combination o f both. I f t h i s were t h e case, t h e d i f f e r e n t p a t t e r n s o f moraines found by Andrews c o u l d be e x p l a i n e d i n terms o f d i f f e r e n t p r o c e s s e s or d i f f e r i n g i n t e n s i t i e s o f p r o c e s s . (Andrews & Smithson, 1966, p. 286-289) The most common, a "simple l i n e a r moraine" would be formed by push or squeeze at the i c e f r o n t or buoyance l i n e . "S-shaped moraines" would be due t o b a s a l squeezing i n t o s u b g l a c i a l meltwater channels. Moraines which are o r i e n t e d t r a n s v e r s e t o t h e i c e f r o n t would be due t o squeezing i n t o l o n g i -t u d i n a l c r e v a s s e s . A "hooked moraine" would be formed by a push under g r e a t e r p r e s s u r e o f a more r a p i d l y advancing s e c t i o n o f the i c e f r o n t . "Asymmetrical moraines" with a ve r y long, g e n t l e , proximal ramp would be caused by push and o v e r r i d i n g . "Asymmetrical moraines" with a steep proximal s i d e would be due t o a simple push. A recent study on moraines, s i m i l a r t o c r o s s - v a l l e y moraines, at Generator Lake, B a f f i n I s l a n d , has been completed by Bar n e t t and Holdsworth (1974). The moraines, t o which they r e f e r as s u b l a c u s t r i n e moraines, are s i m i l a r i n a l l r e s p e c t s t o Andrews' c r o s s - v a l l e y moraines save f o r t h e i r more g e n t l e s l o p e s . These moraines have average d i s t a l s l o p e s o f 18° t o 22* and average proximal s l o p e s o f 13° t o 14°. T i l l pebbles are t r a n s v e r s e t o t h e c r e s t , and p a r a l l e l t o flow, and t h e s t r o n g e s t o r i e n t a t i o n s are on t h e proximal s l o p e s . The d i p s p a r a l l e l t h e proximal and d i s t a l s l o p e s . They suggest t h a t the moraines formed beneath buoyant i c e ramps by t i l l m e l t i n g out o f t h e bottom o f the ramp and f i l l i n g 40 the wedge shaped space below. The f i n a l shape i s determined by-subsequent movement at the buoyancy l i n e or by r o t a t i o n o f the i c e ramp when i t breaks o f f . In areas i n which buoyancy c o u l d not occur, moraines were observed to be s m a l l e r and l e s s asymmetric. These moraines were formed when melt undercut the i c e c l i f f , c r e a t i n g a space i n the shallow water f o r t i l l t o accumulate. They c o n s i d e r t h a t the s u b l a c u s t r i n e moraines are not annual, t h a t they may average ten years per moraine, and no moraine w i l l form i f r e t r e a t o f the f r o n t i s r a p i d . ( B a r n e t t and Holdsworth, 1974) However the t i l l f a b r i c and t e x t u r e o f the d e p o s i t are not compatible w i t h those expected from a t i l l which f e l l through water. I f m a t e r i a l melted from the bottom o f a ramp and f e l l through water b e f o r e being d e p o s i t e d , the p r e f e r r e d o r i e n t a t i o n o f the pebbles would probably be weak or n o n - e x i s t e n t and the dips would be p a r a l l e l to the d e p o s i t i o n a l p l a n e . T h i s does not match the p u b l i s h e d r e s u l t s , u n l e s s the d e p o s i t was subsequently over-r i d d e n and r e o r i e n t e d . Some s o r t i n g might occur as the t i l l f e l l to the bottom o f the l a k e . 2.2J Moraines formed d u r i n g stagnant i c e c o n d i t i o n s Two types o f moraines may be found i n areas where i c e stagnated and d i s i n t e g r a t e d r a t h e r than r e t r e a t e d along a w e l l d e f i n e d i c e f r o n t . Washboard moraine ( E l s o n , 1957) was formed s u b g l a c i a l l y but owes i t s co n t i n u e d e x i s t e n c e to the d i s i n t e g r a t i o n o f i c e i n s i t u . C o n t r o l l e d a b l a t i o n r i d g e s ( B oulton, I968; Gravenor & Kupsch, 1959; Mackay, i960) were formed d u r i n g i c e 41 d i s i n t e g r a t i o n . E l s o n (1957) d e s c r i b e d washboard moraines as s u b p a r a l l e l , d i s c o n t i n u o u s r i d g e s , r e a c h i n g a h e i g h t o f 15 f e e t (4.5 m.) and l e n g t h o f 1 m i l e (1.6 km.), w i t h 300 to 500 f e e t (92 to 152 m.) spacing between them. The r i d g e s are e i t h e r s t r a i g h t or a r c u a t e , convex downglacier. They possess a rounded p r o f i l e . The p r e f e r r e d o r i e n t a t i o n o f pebbles i n the t i l l i s p a r a l l e l t o the general d i r e c t i o n o f i c e movement which may not n e c e s s a r i l y be t r a n s v e r s e to the r i d g e c r e s t . The washboard moraines are found on p l a i n s or uplands which s l o p e towards the g l a c i e r s l i g h t l y , c r e a t i n g areas of compressive flow. E l s o n (1957) p o s t u l a t e d t h a t the moraines were d e p o s i t e d s u b g l a c i a l l y at the zone where b r i t t l e upper i c e extends down to the s o l e and t h r u s t s a g a i n s t and over a marginal apron o f stagnant i c e . T h e r e f o r e t i l l i s lodged a g a i n s t the stagnant i c e and along the t r a n s v e r s e t h r u s t planes by squeezing. These moraines are p r e s e r v e d because the i c e stagnated and d i s i n t e g r a t e d along the t h r u s t p l a n e s . The spacing i n t e r v a l s may be due to the r e t r e a t o f the t h r u s t zone and inward widening o f the stagnant i c e due to annual g l a c i e r t h i n n i n g . The d i s c o n t i n u i t y may be due to i r r e g u l a r i t i e s i n the f l o o r and i n the amount o f e n t r a i n e d d e b r i s . ( E l s o n , 1957) Gravenor and Kupsch (1959) d e s c r i b e d a s e r i e s o f " l i n e a r d i s i n t e g r a t i o n r i d g e s . " T h e i r l e n g t h may vary from a few yards (metres) to 8 m i l e s (13 km.), and the r i d g e s are g e n e r a l l y s t r a i g h t or s l i g h t l y a r c u a t e , becoming more i r r e g u l a r i n areas of h i g h r e l i e f . There are commonly two s e t s o f r i d g e s i n t e r s e c t i n g each 42 o t h e r , and, i n some cases, they are superimposed at the j u n c t i o n . The most prominent r i d g e s may be t r a n s v e r s e , p a r a l l e l , or o b l i q u e to the d i r e c t i o n o f i c e movement. The r i d g e s are composed c h i e f l y o f t i l l , although they may c o n t a i n s t r a t i f i e d d r i f t pockets, and they commonly have a t h i n g r a v e l veneer on top. L i n e a r d i s i n t e -g r a t i o n r i d g e s are found i n areas which s l o p e d away from the i c e f r o n t , and thereby c r e a t e d a s i t u a t i o n o f extending flow. Two p o s s i b l e o r i g i n s f o r the l i n e a r r i d g e s have been suggested by Gravenor and Kupsch; b a s a l squeezing or a b l a t i o n . T h e i r b a s a l squeezing h y p o t h e s i s i s based upon Hoppe's theory o f p l a s t i c deformation o f s a t u r a t e d t i l l under p r e s s u r e . In t h i s case flow would be i n t o i n t e r s e c t i n g c r e v a s s e s . However i t i s u n l i k e l y t h a t p l a s t i c deformation would have o c c u r r e d . In t h i s example the l a n d s l o p e d away from the g l a c i e r , e n a b l i n g f r e e d r a i n -age from the i c e f r o n t . B o u l t o n (1970) commented upon the r e a c t i o n of t i l l to p r e s s u r e i n open and c l o s e d systems o f d r a i n a g e . I t i s important to note t h a t t h e i r / t i l l / 7 response t o i c e l o a d i n g and shear i s water e x p u l s i o n , compaction, and b r i t t l e f r a c t u r e r a t h e r than f l u i d flow to zones o f lower p r e s s u r e . . . . I t i s c o n c e i v a b l e t h a t , i f s u b g l a c i a l t i l l l i e s i n a c l o s e d system i n which water i s made a v a i l a b l e but unable to escape, s u b g l a c i a l pore p r e s s u r e s w i l l b u i l d up and the t i l l w i l l become f l u i d ( B o u l ton, 1970, p. 244). T h e r e f o r e the squeeze theory can be a p p l i e d i n the case o f De Geer moraines as the p r o g l a c i a l l a k e would p r o v i d e such a c l o s e d system. However, i t can not be a p p l i e d to these l i n e a r d i s i n t e g r a t i o n r i d g e s which l i e i n an open system. An a b l a t i o n o r i g i n (Gravenor and Kupsch, 1959) i s the most l i k e l y h y p o t h e s i s f o r these f e a t u r e s . Extending i c e flow i n t h i s area would have r e s u l t e d i n many open c r e v a s s e s . T h e r e f o r e , d e b r i s 43 was l e t down from the s u r f a c e i n t o these open c r e v a s s e s . T h i s h y p o t h e s i s can e x p l a i n the superimposed j u n c t i o n s between s e t s o f i n t e r s e c t i n g r i d g e s and the e x i s t e n c e o f r i d g e s on bare r o c k . The authors q u e s t i o n e d whether t h i s o r i g i n c o u l d e x p l a i n the l a c k o f sediment s o r t i n g , a d i s t i n c t t i l l f a b r i c and the compact nature of the t i l l . However, these q u e s t i o n s have been l a r g e l y r e s o l v e d by other r e s e a r c h e r s ( B o u l t o n , 1968; Mackay, i960). Mackay (i960) d e s c r i b e d a s e r i e s o f r i d g e s which he termed a b l a t i o n s l i d e moraines, e x p l a i n i n g t h e i r o r i g i n as the c h u t i n g , slumping, and s l i d i n g o f a b l a t i o n m a t e r i a l downslope o f stagnant i c e b l o c k s w i t h minimal reworking by water. The f o r m a t i o n o f some c o n t r o l l e d a b l a t i o n moraines was observed by Boulton (1968). T h i c k e n g l a c i a l d e b r i s bands, o u t -cropping on the i c e s u r f a c e , were d i f f e r e n t i a l l y melted, producing a s e r i e s o f r i d g e s and furrows. F l o w t i l l accumulated i n these furrows. When the i c e melted the d e p o s i t s i n the furrows would remain as l i n e a r r i d g e s . These c o n t r o l l e d moraines tend to have an upper p a r t i n which f i n e s may be washed out and a lower compact, u n s t r a t i f i e d p a r t . (Gravenor and Kupsch (1959) found g r a v e l veneers on t h e i r r i d g e s . ) The t i l l pebbles i n the f l o w t i l l moraines tend to l i e p a r a l l e l or t r a n s v e r s e to g l a c i e r movement, as the i n i t i a l d e b r i s o utcrops were p a r a l l e l to the i c e f r o n t ( B o u lton, 1971). Boulton's c o n t r o l l e d a b l a t i o n moraines can be formed during a r e t r e a t i n g i c e phase as w e l l as i n a stagnant phase. 2.2.4 Summary From the preceeding review i t appears t h a t small moraines 44 can be formed d u r i n g a l l t h r e e types o f i c e c o n d i t i o n s ; advance, r e t r e a t , and s t a g n a t i o n . Each o f these i c e c o n d i t i o n s r e s u l t s i n p a r t i c u l a r processes which produce d i s t i n g u i s h a b l e moraine t y p e s . Moraines which r e f l e c t a c t i v e l y advancing i c e c o n d i t i o n s can only be formed by push and o v e r r i d i n g . (Cowan's r i b b e d moraine) In the case o f a r e t r e a t i n g g l a c i e r , moraines may be formed d u r i n g the winter accumulation season by a seasonal push forward, producing Hewitt's and at l e a s t some o f Andrews' moraines. Moraines may a l s o be formed by p l a s t i c deformation (squeezing) o f b a s a l t i l l , pro-ducing De Geer type moraines. F i n a l l y , i n the case of stagnant i c e , i c e - d i s i n t e g r a t i o n r i d g e s are formed by a b l a t i o n along t h r u s t planes or accumulations o f s u p r a g l a c i a l f l o w t i l l i n c r e v a s s e s . Only these processes which depend on a seasonal t r i g g e r , such as the s h o r t w i n t e r advance o f a r e t r e a t i n g g l a c i e r , or the i n f l u x o f summer meltwater, may produce annual moraines. 2.3 Small Moraines i n B r i t i s h Columbia Very l i t t l e mention o f sma l l moraines has been made i n the l i t e r a t u r e on the s u r f i c i a l geology o f B r i t i s h Columbia. It F u l t o n (1967, p. 33) mentioned "ice-squeeze r i d g e s " as " s t r a i g h t , round-topped r i d g e s g e n e r a l l y composed o f compact t i l l . " He d i d not name any l o c a l i t i e s , however, he s t a t e d t h a t these f e a t u r e s are common near small rock h i l l s and other o b s t r u c t i o n s t h a t c o u l d have d i s r u p t e d the flow o f i c e and caused c r e v a s s e s to form. T i p p e r (1971) observed numerous small r i d g e s i n the Taseko Lakes, Anahim Lake, Quesnel, and Bonaparte Lake map-areas. They are low, p a r a l l e l , f a i r l y s t r a i g h t r i d g e s , l e s s than 15 f e e t (4.5 m. 45 h i g h , 2 to 3 m i l e s (3*2 to 4 .8 km.) long, and spaced a few hundred yards a p a r t . They have very g e n t l e s l o p e s which g i v e the whole landscape a f a i n t r i p p l e d e f f e c t . He s t a t e d t h a t they were not obvious on the ground, but appear on a i r photographs as c o r r u g a t i o n s on the t i l l s u r f a c e , o r i e n t e d mainly at r i g h t angles to the d i r e c t i o n o f i c e movement. He d i d not suggest a mode of o r i g i n f o r these f e a t u r e s , but s t a t e d t h a t they seemed s i m i l a r to De Geer moraines or r i b b e d moraine. Examination o f T i p p e r ' s maps do not r e v e a l any g e n e r a l i t i e s i n the s i t e s o f these r i d g e a r e a s . They may be on s l o p e s f a c i n g up or downglacier; they are sometimes on l o c a l h e i g h t s o f l a n d r a t h e r than nearby low areas; and they are not always t r a n s v e r s e to the i c e flow d i r e c t i o n . Probably t h e r e i s a wide v a r i e t y o f moraine types grouped here, i n c l u d i n g r i b b e d moraine, f l o w t i l l r i d g e s , c r e v a s s e f i l l i n g s and even f l u t i n g s . The d e s c r i p t i o n and l o c a t i o n s e l i m i n a t e the p o s s i b i l i t y t h a t these r i d g e s may be De Geer moraines. Small moraines o f unknown o r i g i n a l s o occur i n the McLean Lake and Veasy Lake areas o f the A s h c r o f t map-area. 46 3. RELATIONSHIP BETWEEN LOCAL TOPOGRAPHY AND SMALL MORAINES IN UPPER HAT CREEK VALLEY 3.1 I n t r o d u c t i o n T h i s chapter d i s c u s s e s the r e l a t i o n s h i p s between the occurrence o f moraines and the l o c a l s u r f a c e c o n f i g u r a t i o n s i n the s i x areas i n which c l u s t e r s o f small moraines e x i s t . I t i s p o s s i b l e t h a t some c h a r a c t e r i s t i c o f l o c a l topography may have a c t e d as a t r i g g e r mechanism, i n i t i a t i n g and l o c a l i z i n g the process by which the moraines were formed. Thus an examination o f the topography may suggest an o r i g i n f o r these f e a t u r e s . The t o p o g r a p h i c c h a r a c t e r i s t i c s may a l s o i n f l u e n c e the p h y s i c a l appearance o f the moraines i n an a r e a . Chapter I I I addresses these problems on two s c a l e s : the v a l l e y as a whole and the l o c a l a r e a s . 3.2 Upper Hat Creek V a l l e y Upper Hat Creek v a l l e y s l o p e s g e n t l y northwards. Thus the i c e t h a t e n t e r e d the v a l l e y from the n o r t h flowed upslope. The e f f e c t o f upslope movement was probably f u r t h e r augmented by a general narrowing o f the v a l l e y toward the south. These c o n d i t i o n s would r e s u l t i n a s t a t e o f compressive flow and i t i s u n l i k e l y t h a t widespread zones o f c r e v a s s e s would form. However, a c r e v a s s e o r i g i n f o r the s m a l l moraines can not be d i s c o u n t e d immediately. C o n v e x i t i e s i n the c o n f i g u r a t i o n o f the bedrock f l o o r may have c r e a t e d l o c a l areas o f extending flow; 4 7 thus l o c a l areas o f c r e v a s s e s . The presence o f a deep ponded l a k e during d e g l a c i a t i o n would have r e s u l t e d i n buoyancy o f the i c e f r o n t , a l l o w i n g the formation o f b a s a l c r e v a s s e s . S i n c e the drainage would have been s o u t h e r l y , away from the i c e which b l o c k e d the v a l l e y to the n o r t h , i t i s l i k e l y t h a t water was ponded south o f the i c e f r o n t . However, no evidence o f a deep p r o g l a c i a l l a k e o f long d u r a t i o n has been f o u n d - - n e i t h e r beaches, wavecut c l i f f s , l a c u s t r i n e sediments, nor d e l t a s . Nor i s t h e r e c l e a r evidence o f l a k e o u t l e t flow through the low c o l at the head o f Oregon Jack Creek v a l l e y . T h i s c o l between Upper Hat Creek and Oregon Jack Creek v a l l e y s i s very low (3850 f e e t , 1175 metres), thus the depth o f a p o s s i b l e p r o g l a c i a l l a k e ranges from o n l y 150 f e e t (46 m.) near the o u t l e t v a l l e y to 500 f e e t (153 m.) near the northernmost occurrence o f moraines. Most o f the moraine areas are at e l e v a t i o n s h i g h e r than t h i s o u t l e t l e v e l . I t i s p o s s i b l e t h a t Oregon Jack Creek v a l l e y was b l o c k e d by i c e from the e a s t , thereby r a i s i n g l a k e l e v e l s , however, t h e r e i s no p h y s i c a l evidence t h a t such a l a k e d i d e x i s t i n the v a l l e y . There-f o r e , a c r e v a s s e o r i g i n due to i c e buoyancy i n a deep p r o g l a c i a l l a k e can be d i s c o u n t e d . 3•3 The Small Moraine Areas 3.3.I Area A: between Cashmere and Hat Creeks T h i s area d i v i d e s n a t u r a l l y i n t o two u n i t s , the western s l o p e and the h i g h e r , more l e v e l area ( F i g . 9 ) , which are d e s c r i b e d s e p a r a t e l y . On the s l o p i n g area the moraines are found at e l e v a t i o n s 48 FIG. 9: L o c a t i o n Map of the Small Moraines: Area A 49 between 3700 and 4000 f e e t (1130 and 1220 m.), and t r e n d t r a n s v e r s e to g e n t l e n o r t h e a s t e r l y and s o u t h w e s t e r l y s l o p e s . The area i s bounded by e r o s i o n s c a r p s to the south and west ( F i g . 9)« The moraines fade out at a very s l i g h t concave break o f s l o p e to t h e e a s t , although t h e r e are f a i n t t r a c e s o f r i d g e s , v i s i b l e o n l y on the a i r photographs, which seem to c r o s s t h i s break and c o n t i n u e i n t o the h i g h e r , more l e v e l a r e a . Toward the n o r t h , the r i d g e s a b r u p t l y become more sinuous and cut a c r o s s the p r e v i o u s t r e n d (See F i g . 9). The cause o f t h i s change i s not c l e a r , although i t appears to be a s s o c i a t e d w i t h a low c o l and rock knob to the northwest. The l o n g e s t r i d g e i s an e s k e r , which may have c a r r i e d meltwater through the c o l when the narrow gorge o f Ambusten Creek was plugged by i c e . On the h i g h e r , more l e v e l area the moraines occur at e l e v a t i o n s r a n g i n g from 38OO to 4500 f e e t (ll60 t o 1370 m.) w i t h the m a j o r i t y at approximately 4200 f e e t (1280 m.). They are u s u a l l y t r a n s v e r s e to a g e n t l e n o r t h e r l y s l o p e . Again, the area o f moraines i s bounded by breaks o f s l o p e , convex and concave. I t i s s i g n i f i c a n t t h a t the moraines occur at much hi g h e r e l e v a t i o n s i n t h i s area than any o t h e r l o c a t i o n , and the appearance o f the r i d g e s i s d i f f e r e n t . They are much s t r a i g h t e r , have lower r e l i e f , and are more d i s c o n t i n u o u s . They have a general tendency to s w e l l and s i n k which makes them very d i f f i c u l t to t r a c e f o r any d i s t a n c e . D i f f e r e n t p r o c e s s e s or i n t e n s i t i e s o f processes must have e x i s t e d d u r i n g the formation o f moraines i n t h i s area. Most o f Area A has a g e n t l e n o r t h e r l y s l o p e . B a s a l i c e would have been moving a g a i n s t the s l o p e , a c o n d i t i o n o f compressive 50 FIG. 10: L o c a t i o n Map o f the Small Moraines : Area B 51 flow. I t i s u n l i k e l y t h a t c r e v a s s e s formed here. 3.3«2 Area B: between McCormick and McDonald Creeks A s m a l l area o f moraines occurs between McCormick and McDonald Creeks, a t e l e v a t i o n s o f 3650 to 3850 f e e t (1115 to 1175 m.) ( F i g . 10). T h e i r t r e n d i s p a r a l l e l to a v e r y g e n t l e e a s t e r l y s l o p e . The western edge o f the moraines i s c l o s e l y a s s o c i a t e d w i t h a v e r y marked, concave break o f s l o p e . The moraines u s u a l l y end b e f o r e r e a c h i n g the break o f s l o p e to the e a s t . Some seem t o be b u r i e d by fans to the n o r t h and south. The moraines i n t h i s area are v e r y sinuous, s h o r t and d i s c o n t i n u o u s , w i t h a great v a r i e t y o f h e i g h t s . The flow o f i c e would have been compressive. A steep bedrock p r o t r u s i o n on the e a s t e r n s l o p e o f the v a l l e y would have d e f l e c t e d a g r e a t amount o f i c e westward through a c o n s t r i c t e d passage over t h i s a r e a . The e x i s t e n c e o f c r e v a s s e s would be u n l i k e l y . 3.3.3 Area C: south o f McDonald Creek Small moraines occur south o f McDonald Creek between e l e v a t i o n s o f 3750 to 4100 f e e t (1145 to 1250 m.), c l u s t e r i n g at approximately 3850 f e e t (1175 m.) ( F i g . 11). The t r e n d o f the r i d g e c r e s t s i s g e n e r a l l y o b l i q u e or t r a n s v e r s e to the n o r t h e a s t e r l y s l o p e . The spacing between moraines and the s i n u o s i t y o f the f e a t u r e s i n c r e a s e toward the n o r t h . The ends o f the moraines are obscured by f o r e s t cover i n the n o r t h e r n h a l f o f the area, however, i n the southern p o r t i o n , the moraines end at prominent breaks o f 52 FIG. 11: L o c a t i o n Map o f the Small Moraines : Areas C, D, E 53 s l o p e , concave to the west and convex to the e a s t . Only f a i n t i r r e g u l a r f e a t u r e s occur beyond these breaks o f s l o p e . A few i n d i s t i n c t r i d g e s continue eastward toward Area D. The p h y s i c a l appearance, as w e l l as the occurrence, o f moraines seems t o be c l o s e l y a s s o c i a t e d w i t h changes o f s l o p e . The moraines are s t r a i g h t and p a r a l l e l i n the western p o r t i o n o f the area, changing to a more i r r e g u l a r mass o f r i d g e s i n the e a s t . A much more i r r e g u l a r p a t t e r n of branching r i d g e s occurs i n the c e n t r a l d e p r e s s i o n ( F i g . 11). 3«3«4 Area D: between Parke and P h i l Creeks In the area between Parke and P h i l Creeks, s m a l l moraines occur at e l e v a t i o n s from 3600 to 3750 f e e t (1095 to 1145 m.) and they t r e n d o b l i q u e l y a c r o s s the e a s t e r l y s l o p e ( F i g . 11). The r i d g e s t e r m i n a t e a g a i n s t a prominent, hummocky break o f s l o p e to the west. A convex break o f s l o p e forms most o f the e a s t e r n border o f the a r e a . Below t h i s s l o p e the moraines d i s i n t e g r a t e i n t o a s e r i e s o f low, i n t e r c o n n e c t e d r i d g e s and h o l l o w s . The t r e n d o f the moraines i n Area D p a r a l l e l s the o r i e n t a -t i o n o f the r i d g e s i n Area C, however, the moraines are more i r r e g u l a r i l y sinuous and more c l o s e l y spaced than those i n Area C. Ice movement across the area would be s i m i l a r f o r Areas C and D. The narrow b o t t l e n e c k over Area B has widened out con-s i d e r a b l y , which may have p e r m i t t e d a s h i f t to extending flow as the i c e spreads out a g a i n . 54 3.3-5 Area E: south of P h i l Creek Area E i s a l e v e l area (4050 to 4100 f e e t (1235 to 1250 m.) e l e v a t i o n ) , w i t h a s l i g h t n o r t h e r l y s l o p e . Although the moraines are s i m i l a r to r i d g e s i n those areas t o the n o r t h , the t r e n d o f these moraines i s approximately 50° away from the p r e v i o u s one, and t r a n s v e r s e to the s l o p e ( F i g . l l ) . Although i t i s d i f f i c u l t to t r a c e these moraines f o r any d i s t a n c e through the f o r e s t , Area E i s a p p a r e n t l y bounded on the east and west by nearby concave breaks o f s l o p e , s i m i l a r to those bounding the more s o u t h e r l y p a r t s o f Area C. South o f Area E another c l u s t e r o f moraines occurs between two breaks o f s l o p e . C o n d i t i o n s o f i c e flow would be s i m i l a r i n Areas C, D, and E. 3.3*6 Area F: s c a t t e r e d areas to the south To the south o f Area E t h e r e are s c a t t e r e d areas o f moraines; a l l at e l e v a t i o n s between 3750 and 4150 f e e t (1145 to 1265 m.). There are fewer r i d g e s i n these areas, and, compared to the p r e v i o u s areas, t h e i r c r e s t t r e n d i s more i r r e g u l a r , although s t i l l r o u g hly p a r a l l e l to the e a s t e r l y s l o p e . T h e i r shape i s a l s o more i r r e g u l a r , w i t h s m a l l , s h o r t , sinuous r i d g e s and o c c a s i o n a l l a r g e r s t r a i g h t e r r i d g e s . With the e x c e p t i o n o f some o f these l a r g e moraines, the areas o f r i d g e s appear to be roughly bounded by breaks o f s l o p e . Although the c l u s t e r s o f moraines occur at d i f f e r e n t l e v e l s , o n l y two v e r y prominent, s t r a i g h t moraines c r o s s the i n t e r v e n i n g breaks o f s l o p e . The v a l l e y i s narrowing toward the south and i t i s probable t h a t the i c e flow c o n d i t i o n s would have been compressive. 55 3.3*7 Crevasse f i l l i n g s south o f White Rock Creek Another area o f r i d g e s occur south o f White Rock Creek on the steeper s l o p e s o f the e a s t e r n s i d e o f the v a l l e y . E l e v a t i o n o f t h i s area ranges from 3650 to 4100 f e e t (1115 to 1250 m.), and the t r e n d o f the r i d g e c r e s t s i s p a r a l l e l to the s l o p e . L o c a l breaks o f s l o p e a p p a r e n t l y do not i n f l u e n c e the occurrence or c o n t i n u a t i o n o f the r i d g e s . Such was not the case i n the m o r a i n i c r i d g e a r e a s . These r i d g e s d i f f e r from the moraines i n the p r e v i o u s areas and have been i n t e r p r e t e d as g l a c i o f l u v i a l f e a t u r e s (See 1.4.3)• Ice p r o b a b l y moved down across t h i s area from the h i g h l a n d to the n o r t h and was d e f l e c t e d westward by high c l i f f s , which form the e a s t e r n w a l l o f the v a l l e y , so t h a t i c e moved down the w e s t e r l y s l o p e . (These c l i f f s p r o t r u d e westward i n t o the v a l l e y and are h i g h e r than the upper l i m i t o f l a t e i c e . ) T h e r e f o r e , i t i s l i k e l y t h a t the e a s t e r n s l o p e o f the v a l l e y , i n t h i s area, experienced extending i c e flow and c o n d i t i o n s were s u i t a b l e f o r the formation o f l a t e r a l c r e v a s s e s i n the t h i n n i n g i c e . Meltwater would have kept the c r e v a s s e s open. 3.3.8 Summary Although i c e flow i n the v a l l e y would g e n e r a l l y be compressive, l o c a l i r r e g u l a r i t i e s i n the e a s t e r n s i d e o f the v a l l e y c o u l d have r e s u l t e d i n l o c a l i z e d areas o f extending flow. However t h e r e i s no c o r r e l a t i o n between areas o f moraines and areas o f p o s s i b l e extending flow. I t i s s i g n i f i c a n t t h a t g l a c i o f l u v i a l f e a t u r e s , not moraines, occur i n the one area i n which extending flow c o n d i t i o n s were most l i k e l y . T h e r e f o r e an o r i g i n dependent upon the c r e a t i o n o f c r e v a s s e s 56 can be d i s c o u n t e d f o r the m a j o r i t y o f the moraines, and a f r o n t a l theory w i l l be c o n s i d e r e d . The moraines occur at e l e v a t i o n s up t o 4500 f e e t (1370 m.). T h i s f i g u r e i s i n t e r p r e t e d t o r e p r e s e n t the upper l i m i t o f l a t e i c e i n the v a l l e y (See 1.3.2.a). T h e r e f o r e , the process which c r e a t e d the moraines must be o p e r a b l e along the e n t i r e l e n g t h o f the i c e f r o n t . L o c a l s l o p e does not seem to e x e r t any i n f l u e n c e upon the moraines. There i s no r e l a t i o n s h i p between the d i r e c t i o n o f s l o p e and the t r e n d o f the r i d g e , which may l i e p a r a l l e l , t r a n s v e r s e , or o b l i q u e to the s l o p e . There i s a l s o no c o n s i s t e n t r e l a t i o n s h i p between the degree o f s l o p e and the s p a c i n g of the moraines. For example, as s l o p e i n c r e a s e s toward the n o r t h i n Area C, the s p a c i n g decreases; whereas the r e v e r s e occurs i n Area E. A d e f i n i t e r e l a t i o n s h i p has been found between the c o n t i n u i t y o f a moraine (and, t h e r e f o r e , width o f the moraine area) and the occurrence o f breaks o f s l o p e . In almost a l l cases, the end o f the moraine i s a g a i n s t , or near, a break o f s l o p e , r e g a r d l e s s o f how s l i g h t . T h i s r e l a t i o n s h i p e x i s t s whether the break o f s l o p e i s convex or concave. (However, the converse does not always h o l d t r u e . ) T h i s must s i g n i f y some change i n the c r i t i c a l c o n d i t i o n s which r e s u l t i n the formation o f moraines along the i c e f r o n t . Whether t h i s c r i t i c a l change c o u l d p o s s i b l y be a r e l e a s e o f p r e s s u r e , a change i n meltwater seepage, a d i f f e r e n t i a l movement along the f r o n t , or some other c o n d i t i o n i s u n r e s o l v e d . 57 3.4 D i s c u s s i o n The areas o f m o r a i n i c r i d g e s were probably more e x t e n s i v e i n the southern p a r t o f Upper Hat Creek v a l l e y at one time, and have been reduced subsequently by p o s t g l a c i a l p r o c e s s e s . The c l o s e p r o x i m i t y o f Areas B, C, D, E and F and the s i m i l a r i t y o f c r e s t t r e n d s among these areas i n d i c a t e t h a t they probably o r i g i n a t e d as one area o f continuous r i d g e f o r m a t i o n . The moraines o f Area F were d e p o s i t e d f i r s t and are much more s p o r a d i c . The sequence o f f r o n t a l r e t r e a t and moraine formation continued northward to the v i c i n i t y o f P h i l Creek. A major change i n the i c e f r o n t p a t t e r n , r e f l e c t e d i n the abrupt realignment o f c r e s t trends between Areas E and C, o c c u r r e d at P h i l Creek (See F i g . 11). The sequence o f r e t r e a t and moraine formation then continued northward to McCormick Creek without another s i g n i f i c a n t change i n the p a t t e r n o f the i c e f r o n t . At the same time c r e v a s s e f i l l i n g s were being formed i n the t h i n i c e on the steep e a s t e r n s l o p e s . Some a l t e r n a t i o n i n g l a c i a l c o n d i t i o n s ; p o s s i b l y a more r a p i d and i r r e g u l a r r e t r e a t o f the i c e f r o n t , which may have i s o l a t e d areas o f stagnant i c e , caused a t r a n s i t i o n from m o r a i n i c r i d g e to hummocky moraine d e p o s i t i o n northward from McCormick Creek. T h i s change o c c u r r e d f i r s t i n the c e n t r a l p a r t o f the v a l l e y , whereas the moraine forming process continued to operate near the v a l l e y s i d e s f o r another m i l e . (See F i g . 5) During the p o s t g l a c i a l i n t e r v a l t h i s e x t e n s i v e moraine area was reduced by creek e r o s i o n and fan d e p o s i t i o n u n t i l i t was s u b d i v i d e d i n t o the present a r e a s . Although i t i s d i f f i c u l t to p i e c e t o g e t h e r the o v e r a l l alignment o f moraines i n the v a l l e y , the p a t t e r n appears to be l o b a t e , 58 convex downglacier. However, the alignment o f the moraines i n Area A does not match t h i s p a t t e r n . These moraines may have been d e p o s i t e d by the p o r t i o n o f the i c e lobe which was f l o w i n g along a broad t o p o g r a p h i c bench on the e a s t e r n s i d e o f the v a l l e y . In t h a t case, the i c e would approach Area A from the n o r t h e a s t , t r a n s v e r s e to the t r e n d o f the r i d g e s . T h i s bench i s between 3800 and 4500 f e e t ( l l 6 0 and 1370 t n . ) ; the same e l e v a t i o n as t h a t o f Area A. 59 4. EXTERNAL MORPHOLOGY OF THE HAT CREEK MORAINES 4.1 I n t r o d u c t i o n Measurement o f the moraines was undertaken i n order to p r o v i d e a d e t a i l e d d e s c r i p t i o n o f the e x t e r n a l c h a r a c t e r i s t i c s o f the Hat Creek moraines. The moraines can then be compared to small moraines reviewed i n the l i t e r a t u r e (Chapter 2 ) . In a d d i t i o n , the e x t e r n a l morphology o f the Hat Creek moraines w i l l shed some l i g h t upon t h e i r o r i g i n . A r e a l d i f f e r e n c e s between these moraines are i n v e s t i g a t e d a l s o . P o s s i b l e r e l a t i o n s h i p s between v a r i a b l e s or between a v a r i a b l e and some other f e a t u r e o f t h e i r environment, which might e x p l a i n the a r e a l d i f f e r e n c e s , are examined. 4.2 Study Design Measurement o f the e x t e r n a l morphology o f the s m a l l moraines was made i n s e l e c t e d areas (Areas A ( s l o p e ) , C, D, and E; F i g s . 9 & 11). The areas chosen were those i n which there are a great number o f moraines and the m a j o r i t y o f these moraines are very d i s t i n c t and easy t o i d e n t i f y . The h e i g h t , angle, and aspect o f the proximal and d i s t a l s l o p e s , the o r i e n t a t i o n o f the c r e s t , and the l e v e l n e s s o f the c r e s t s u r f a c e were measured i n the f i e l d . Length, s i n u o s i t y , s p a c i n g , and number of branches were measured from l a r g e s c a l e a i r photographs. These v a r i a b l e s are d e f i n e d and the method o f measurement i s d i s c u s s e d i n T a b l e s I I I and IV. The measurements were performed on a l l the TABLE I I I F i e l d Techniques FIELD TECHNIQUE DEFINITION METHOD OF MEASUREMENT S i t e s : on proximal and d i s t a l s l o p e s at 5 evenly spaced s i t e s along the moraine, i n c l u d i n g the p o i n t s a t maximum and minimum h e i g h t s o f the proximal s i d e HEIGHT heigh t from trough between l e v e l i n g r o d and cl i n o m e t e r used as l e v e l moraines to c r e s t ANGLE OF SLOPE angle from the h o r i z o n t a l o f the s t e e p e s t p a r t o f the slope ASPECT OF SLOPE d i r e c t i o n f a c e d by s l o p e CREST ORIENTATION o r i e n t a t i o n o f l o c a l p a r t of c r e s t o f moraine CREST SURFACE u n d u l a t i o n s i n c r e s t h e i g h t LEVELNESS l e v e l i n g rod l a i d on slope and angle o f rod measured wit h c l i n o m e t e r compass d i r e c t i o n to nearest 5° compass d i r e c t i o n t o nearest 5° walked along c r e s t and made v i s u a l assessment o f s u r f a c e i r r e g u l a r i t y based upon f o l l o w i n g c r i t e r i a : 1. - " I r r e g u l a r " - - r i s e s more than 3 f t . per 10 f t . d i s t a n c e 2. - " F a i r l y I r r e g u l a r " — r i s e s 2.25 - 3.0 f t . per 10 f t . d i s t a n c e 3. - " F a i r l y L e v e l " - - r i s e s 1.5 - 2.25 f t . per 10 f t . d i s t a n c e 4. - " L e v e l " - - r i s e s O.75 - 1.5 f t . per 10 f t . d i s t a n c e 5. - "Very L e v e l " - - r i s e s l e s s than 0.75 f t . per 10 f t . d i s t a n c e TABLE IV A i r Photograph Techniques AIR PHOTOGRAPH TECHNIQUE DEFINITION METHOD OF MEASUREMENT Measured from a i r photos: BC7222-222, BC7222-274, BC72222-276, BC7224-045; enlargements LENGTH SINUOSITY SPACING NUMBER OF BRANCHES Length along c r e s t o f ; c o n t i n u o u s moraines r e l a t i v e f i g u r e r e p r e s e n t i n g number o f bends i n moraine f o r the purpose o f comparison between moraines or moraine areas d i s t a n c e between adj a c e n t moraine c r e s t s number o f apparent branches i n moraine c r e s t . U s u a l l y o n l y one o f branches con-t i n u e s more than 10 yards t r a c e d c r e s t w i t h map measurer Sum o f angles o f c r e s t bends l e n g t h o f moraine = a + b + c + d + e le n g t h R e l a t i v e s i n u o s i t y i n c r e a s e s as S i n c r e a s e s , whereas l i n e a r i t y approaches 0 measured d i s t a n c e from p r e -ceeding s o u t h e r n ( o l d e r ) moraine along a s t r a i g h t l i n e t r a n s v e r s e to the general t r e n d o f the moraines. The l i n e i s a d j u s t e d i f a general change i n t r e n d occurs counted 62 TABLE V Height and Slope Measurements by Area PROXIMAL SIDE OF MORAINES AREA Average Maximum Minimum h e i g h t * s l o p e * h e i g h t s l o p e h e i g h t s l o p e A ( s l o p e ) mean range 6.0 1.7-14.3 18 8-27 9.5 2.6-23.5 26 14-40 2.7 0-9-0 9 0-23 C mean range 7.8 5.3-10.3 24 19-27 11.1 7.6-15-3 27 17-40 5.1 3.3-8.2 22 11-33 D mean range 8.6 4.9-13.0 25 18-28 13.0 7.3-25.5 27 20-33 4.2 2.3-6.8 19 11-36 E mean range 7.8 4.6-12.6 26 20-31 11.1 5.5-16.2 32 16-45 4.4 1.1-10.5 21 13-38 DISTAL SIDE OF MORAINES Average Maximum Minimum h e i g h t * s l o p e * h e i g h t s l o p e h e i g h t s l o p e A ( s l o p e ) mean range 9.3 0.6-14.8 12 3-17 12.7 1.2-25.3 14 3-20 5.5 0-11.8 9 0-16 C mean range 4.2 2.1-6.9 11 9-16 6.0 3.7-9.3 15 10-24 2.4 0.5-5.5 8 4-11 D mean range 4.3 1.5-5.9 9 4-11 7.5 2.6-13.2 13 8-21 2.0 0-3.3 5 0-10 E mean range 4.3 1.4-6.5 11 6-16 6.8 3.3-10.8 16 10-22 2.2 0-4.7 8 0-13 • h e i g h t i n f e e t , s l o p e i n degrees 63 TABLE VI Other E x t e r n a l Measurements by Area AREA l e n g t h s p a c i n g s i n u o s i t y no. o f l e v e l -( f t . ) ( f t . ) branches ness A ( s l o p e ) mean 919-0 126 .2036 0.5 3.4 range 348-1588 54-358 .043-.413 0-2 1-5 C mean 2679.7 195 .2196 1.9 -range 1979-3893 36-335 .097-.280 0-7 — D mean 1176.8 89 .4924 1.8 2.4 range 392-1501 36-I63 .211-.666 0,6 1-5 E mean 961.5 111 .2487 2.4 3.4 range 718-1240 41-199 .101-.402 0-6 3-4 64 d i s t i n g u i s h a b l e moraines i n an a r e a . The r e s u l t s are summarized i n T a b l e s V and V I . The average angle o f s l o p e and the average, maximum, and minimum h e i g h t s o f the proximal and the d i s t a l s l o p e s were c a l -c u l a t e d f o r each moraine. The angle o f s l o p e at the s i t e s o f maximum and minimum h e i g h t s was a l s o r e c o r d e d . Thus, t h e r e are twenty-one v a r i a b l e s which d e s c r i b e the e x t e r n a l morphology o f the moraines ( l i s t e d i n Table V I I ) . A f a c t o r a n a l y s i s was performed upon the v a r i a b l e s , u s i n g the computer program, UBC Fan. The b e n e f i t o f performing a f a c t o r a n a l y s i s r a t h e r than a simple c o r r e l a t i o n a n a l y s i s i s , t h a t not o n l y are the i n t e r r e l a t i o n s h i p s between a l l v a r i a b l e s analyzed, but t h a t c l u s t e r s o f h i g h l y r e l a t e d v a r i a b l e s are d e r i v e d from a l a r g e s e t o f v a r i a b l e s . These r e s u l t s may not have been i n i t i a l l y e v i d e n t . A f a c t o r i s a c l u s t e r o f c o - v a r y i n g v a r i a b l e s . A f a c t o r l o a d i n g i s the amount o f c o r r e l a t i o n o f a v a r i a b l e w i t h a f a c t o r . V a r i a b l e s w i t h h i g h l o a d i n g s l i e c l o s e to the f a c t o r a x i s and are h i g h l y i n t e r c o r r e l a t e d . T h e i r v a r i a t i o n t o g e t h e r e x p l a i n s the v a r i a b i l i t y among area s . The f a c t o r l o a d i n g s upon the second and subsequent f a c t o r s w i l l be d i f f e r e n t , and d i f f e r e n t v a r i a b l e s w i l l c l u s t e r around these f a c t o r s . T h i s procedure was a p p l i e d to data f o r each i n d i v i d u a l area and f o r the t o t a l moraine a r e a . P o s s i b l e r e l a t i o n s h i p s between v a r i a b l e s and p o s s i b l e a r e a l d i f f e r e n c e s were sought. 65 4 . 3 The E x t e r n a l Morphology o f the Moraines 4 . 3 . 1 D e s c r i p t i o n From i n i t i a l i n s p e c t i o n of the data, the e x t e r n a l morphology o f the moraines seems to be s i m i l a r i n a l l o f the areas s t u d i e d . (See T a b l e s V and VI.) The average h e i g h t i s approximately 8 f e e t ( 2 . 4 m . ) and the maximum h e i g h t may be as much as 25 f e e t (7*6 m.). The moraines are n o t i c e a b l y asymmetric, wi t h a st e e p e r p r o x i m a l , or northern, s l o p e . The average proximal s l o p e i s 24° (maximum 4 5 ° ) and the average d i s t a l s l o p e i s l l 4 (maximum 24 ° ) . The moraines are l e s s than 4000 f e e t (1220 m.) long and are commonly much s h o r t e r . A t y p i c a l l e n g t h i s 1000 f e e t (305 m.). Spacing between adjacent moraines i s t y p i c a l l y 130 f e e t (40 m.), and v a r i e s between 36 and 358 f e e t (11-109 m.) a p a r t . There are u s u a l l y l e s s than two branches on a moraine. The l e v e l n e s s of the c r e s t s u r f a c e v a r i e s g r e a t l y ; from "very l e v e l " to " i r r e g u l a r " (Table I I I ) . When these r e s u l t s are compared wit h Table I I , s i m i l a r i t i e s between the Hat Creek moraines and many of the push, squeeze, and c o n t r o l l e d a b l a t i o n moraines, d e s c r i b e d i n the l i t e r a t u r e , are obvio u s . A n o t a b l e e x c e p t i o n i s the d i r e c t i o n o f asymmetry o f Hat Creek moraines. T h i s w i l l be d i s c u s s e d l a t e r . Some d i f f e r e n c e s i n e x t e r n a l morphology e x i s t between the areas s t u d i e d . A study o f h e i g h t s and s l o p e s r e v e a l s t h a t Area A ( s l o p e ) i s d i s t i n c t . H e i ghts and angles o f proximal s l o p e s are lower, whereas h e i g h t s and angles o f d i s t a l s l o p e s are g r e a t e r than i n o t h e r r e g i o n s . As w e l l , the h e i g h t o f the d i s t a l s i d e i s g r e a t e r than t h a t o f the proximal s i d e , although asymmetry remains s i m i l a r 66 X • height o l p r o x i m a l side Y • height of distal side south north FIG. 12: Diagram Demonstrating the I n f l u e n c e o f S o u t h e r l y Slope on the Height o f Moraines i n Area A ( s l o p e ) 67 to o t h e r areas (See F i g . 12). The d i f f e r e n c e s i n Area A ( s l o p e ) are probably due to the l o c a l ground s u r f a c e which s l o p e s downglacier, t h e r e f o r e emphasizing the h e i g h t o f the d i s t a l s l o p e . The o n l y o t h e r d i f f e r e n c e between areas i s the g r e a t l y i n c r e a s e d s i n u o s i t y and c l o s e r s p a c i n g o f moraines i n Area D. T h i s suggests t h a t an i n v e r s e r e l a t i o n s h i p may e x i s t between these two v a r i a b l e s . 4.3.2 R e l a t i o n s h i p s between the v a r i a b l e s A f a c t o r a n a l y s i s o f the twenty-one v a r i a b l e s f o r the t o t a l moraine area d e f i n e d four f a c t o r s , which tog e t h e r account f o r 70% o f the t o t a l v a r i a n c e o f the d a t a . A d e s c r i p t i o n o f each o f these f a c t o r s and the c o r r e l a t i o n s o f the f a c t o r s with the v a r i a b l e s i s p r e s e n t e d i n T a b l e V I I . The i n t e r c o r r e l a t i o n o f the v a r i a b l e s , which c l e a r l y i l l u s t r a t e s the f a c t o r s , i s demonstrated i n F i g . 13. A number o f these r e l a t i o n s h i p s were not obvious b e f o r e the data was s u b j e c t e d to f a c t o r a n a l y s i s ( i e . F a c t o r 4, d i s c u s s e d l a t e r ) . The amount o f the t o t a l v a r i a n c e e x p l a i n e d i s g r e a t e r when the f a c t o r a n a l y s i s i s performed on data from i n d i v i d u a l areas, however the f a c t o r s are not always as c l e a r , and some o f the c o r r e l a t i o n s are d i f f i c u l t to e x p l a i n . F a c t o r s 1 and 2 are v e r y s i g n i f i c a n t f o r the i n t e r p r e t a t i o n o f asymmetry. The angle o f the s l o p e v a r i e s d i r e c t l y w i t h the h e i g h t , f o r both the proximal and d i s t a l s i d e s . As h e i g h t i n c r e a s e s , the angle o f s l o p e does a l s o . There i s l i t t l e c o r r e l a t i o n between the steepness o f the s l o p e and the aspect o f t h a t s l o p e ; o t h e r than the f a c t t h a t s l o p e s on the p r o x i m a l , or n o r t h f a c i n g , s i d e 68 TABLE VII C o r r e l a t i o n s o f F a c t o r s w i t h V a r i a b l e s VARIABLE CORRELATION FACTOR % EXi PLAINED No. o f branches Proximal max. s l o p e min. s l o p e max. h e i g h t min. h e i g h t average s l o p e average h e i g h t D i s t a l min. s l o p e max. s l o p e min. h e i g h t max. h e i g h t average s l o p e average h e i g h t Proximal average aspect " max. aspect " min. aspect D i s t a l average aspect Spacing L e v e l n e s s Length S i n u o s i t y .3981 .5833 .7025 .7891 • 7904 .8388 .8541 .5686 .5992 .8469 .8528 .8740 .9491 .7265 .6391 .5772 .8802 .6352 .3823 .3291 .5981 FACTOR 1: 3296 "Height and angle o f s l o p e o f proximal s i d e " FACTOR 2: 32% "Height and angle o f s l o p e o f d i s t a l s i d e " FACTOR 3: 24% "Aspect o f s l o p e " FACTOR 4: 12% "Plane measurements" D 5 aspect 3 \ ^ P • slope | I m " I P • height I I I / ' I | Branches | . Sinuosity D ^ Levelness | [ S p a c i n g p - i 1 1 - -\ Length | P - aspect 1 2 3 4 : Factors C o r r e l a t i o n s : ( 9 5 % significance) 0.290 - 0.4 00 0.401 - 0.500 0.501 - 0.600 . 0.601 - 0.700 mm^mm 0.701 P i u s x : average P : proximal side + : maximum D ' distal side - : minimum FIG. 13: C o r r e l a t i o n s o f V a r i a b l e s Between and Among F a c t o r s 70 are s t e e p e r than those on the d i s t a l s i d e . I t i s p o s s i b l e t h a t the asymmetry o f the moraine p r o f i l e c o u l d be a p o s t - d e p o s i t i o n a l , and not a primary d e p o s i t i o n a l , f e a t u r e . Snowbanks remain much longer on the n o r t h f a c i n g s i d e s o f the moraines than on the r e s t of the area i n the s p r i n g . T h i s causes the n o r t h e r n s i d e t o be extremely moist when the r e s t o f the area has become dry. Under these c o n d i t i o n s i t i s p o s s i b l e t h a t the process o f n i v a t i o n w i l l a c t to steepen the backwall of the snow patch (Lewis, 1939). Thus the asymmetry might a c t u a l l y be due to p o s t - d e p o s i t i o n a l m o d i f i c a t i o n s . T h i s c o u l d e x p l a i n the s i m i l a r i t y o f the asymmetry o f the g l a c i o f l u v i a l f e a t u r e s south o f White Rock Creek (See 1.4.3) and the moraines i n o t h e r a r e a s . However, a c l o s e r c o r r e l a t i o n between angle o f s l o p e and aspect would be expected i f t h i s were the o n l y cause o f asymmetry. Yet moraines which tend away from an east-west o r i e n t a t i o n a l s o have marked asymmetry, whether the proximal s i d e i s toward the east or the west. The l a t t e r f a c t a l s o d i s c o u n t s the p o s s i b i l i t y o f wind blown snow d r i f t s having an i n f l u e n c e . Hence, the asymmetry o f the moraines must be the r e s u l t o f primary p r o c e s s e s , although snow-bank m o d i f i c a t i o n may have some e f f e c t on the s c a l l o p e d shapes o f the n o r t h e r n s i d e s i n some areas. The " s i z e " v a r i a b l e s o f average, maximum, and minimum h e i g h t (and, i n some cases, length) c o r r e l a t e w i t h a number o f "plane measurements" ( i e . s i n u o s i t y , l e v e l n e s s , s p a c i n g , and number o f b r a n c h e s ) . The h e i g h t i s the most important s i z e v a r i a b l e . I t may be a f u n c t i o n o f the i n t e n s i t y o f the formation p r o c e s s , the l e n g t h of time during which the p r o c e s s operated, 71 or the amount o f m a t e r i a l a v a i l a b l e . However, the l a t t e r i s u n l i k e l y to vary g r e a t l y over a sm a l l a r e a . On the other hand, as the i n t e n s i t y or d u r a t i o n o f d e p o s i t i o n i n c r e a s e d , so sh o u l d the s i z e o f the moraine. Thus, the formation o f a l a r g e r moraine would a l s o present the g r e a t e s t o p p o r t u n i t y f o r development o f a more i r r e g u l a r s u r f a c e . S i m i l a r i l y , a l a r g e r moraine may have more branches which may r e s u l t from a s l i g h t change i n the p o s i t i o n o f the i c e f r o n t over a p e r i o d o f time or the i n c o r p o r a t i o n o f p a r t o f a p r e v i o u s l y d e p o s i t e d moraine. The r e l a t x o n s h i p o f h e i g h t wxth s i n u o s i t y , a v a r i a b l e which must r e f l e c t the shape o f the i c e f r o n t , i s u n r e s o l v e d . A p o s i t i v e c o r r e l a t i o n e x i s t s between s p a c i n g and l e n g t h . I f the moraines are c l o s e l y spaced, t h e r e may be a g r e a t e r chance t h a t the formation o f one moraine w i l l d e s t r o y or i n c o r p o r a t e p a r t s o f a former moraine. I f the i c e f r o n t remains p a r t i a l l y s t a t i o n a r y , p a r t s o f former moraines are i n c o r p o r a t e d i n t o the l a t e s t moraine. Depending on the l o c a l s l o p e , meltwater may erode through the p r e v i o u s moraines. The r e s u l t i n g p a t t e r n w i l l c o n s i s t o f a s e r i e s o f s h o r t moraines and a few longer ones. I t i s l i k e l y t h a t t h i s sequence o f d e p o s i t i o n and e r o s i o n produced the moraine p a t t e r n found i n Area C. (See F i g . 14) An i n v e r s e r e l a t i o n s h i p e x i s t s between s p a c i n g and s i n u o s i t y , as was observed i n Area D (See 3«3«4), but i t does not h o l d t r u e i n a l l a r e a s . T h i s r e l a t i o n s h i p may be merely c o i n c i d e n t a l , o r , p o s s i b l y , both o f these v a r i a b l e s depend upon some undetermined f a c t o r . The v a r i a b l e s were a l s o analyzed by l o c a t i o n . The areas were coded from south to n o r t h , and the f a c t o r a n a l y s i s was per-72 flow of meltwatei a) Retreat of the ice front, showing the positions of the margin from 1 to 1) .5 miles b) Present moraine pattern FIG, 14: R e l a t i o n s h i p Between P o s i t i o n o f I c e F r o n t and Length o f Moraines; Example: Area C 73 formed a g a i n . The r e s u l t s are as f o l l o w s . Toward the n o r t h , s i n u o s i t y and the number o f branches decreased and s u r f a c e l e v e l n e s s and s p a c i n g i n c r e a s e d . Heights and g r a d i e n t s o f the proximal s l o p e s decreased and those o f the d i s t a l s l o p e s i n c r e a s e d . The l a t t e r i s pro b a b l y due to the s o u t h e r l y s l o p e o f Area A ( s l o p e ) (See F i g . 12). The i n c r e a s e d spacing probably i n d i c a t e s a f a s t e r r e t r e a t o f the i c e f r o n t , which would r e s u l t i n c r e a t i o n o f s m a l l e r moraines. The s i z e o f the moraines would e x p l a i n the trends i n the other v a r i a b l e s . 4.4 Comparison wi t h Other Moraines Many s i m i l a r i t i e s e x i s t between the Hat Creek moraines and those d e s c r i b e d i n the l i t e r a t u r e ( T a ble I I ) . I t i s i m p o s s i b l e , on the b a s i s o f e x t e r n a l morphology alone, t o determine whether the Hat Creek r i d g e s were formed from f l o w t i l l moving o f f o f the i c e or from m a t e r i a l shoved forward d u r i n g a s h o r t w i n t e r readvance, or from wet t i l l squeezed out from beneath the i c e f r o n t ; (a c r e v a s s e o r i g i n i s d i s c o u n t e d i n Chapter 3). However, the prominent shape o f the moraines, and, i n p a r t i c u l a r , the steepness o f the proximal s l o p e s deny the l i k e l i h o o d o f formation by o v e r r i d i n g i c e . The d i r e c t i o n o f asymmetry o f the p r o f i l e o f the Hat Creek moraines i s a n o t a b l e e x c e p t i o n t o these s i m i l a r i t i e s . The steep proximal s l o p e i s o n l y comparable to the a b l a t i o n s l i d e moraines o f Mackay (i960) and a few o f Andrews* c r o s s - v a l l e y moraines, which he named simple push moraines (Andrews and Smithson, 1966). (The s l o p e s o f the m a j o r i t y o f the c r o s s - v a l l e y moraines are s t e e p e s t on the d i s t a l s i d e . ) The p o s s i b i l i t y o f a f l o w t i l l or push moraine 74 o r i g i n f o r the Hat Creek moraines w i l l be d i s c u s s e d i n Chapter 75 5. INTERNAL CHARACTERISTICS OF THE HAT CREEK MORAINES 5.1 I n t r o d u c t i o n The i n v e s t i g a t i o n o f the i n t e r n a l c h a r a c t e r i s t i c s o f the moraines i n v o l v e s the f o l l o w i n g a n a l y s e s : t e x t u r e , shape and l i t h o l o g y o f t i l l pebbles, compaction, and t i l l f a b r i c . 5.2 Study Design The areas i n which measurements o f the i n t e r n a l c h a r a c t e r -i s t i c s o f the moraines were made were chosen on the b a s i s o f a c c e s s i b i l i t y by v e h i c l e . Areas A, C, D, and F were chosen. Three moraines were s e l e c t e d i n each o f Areas A, C, and D, and the two l a r g e s t moraines chosen i n Area F. The sample s i t e s were s e l e c t e d on the h i g h , s t e e p e r p a r t s o f each moraine. Trenches from 2.5 f e e t to 3.0 f e e t (.8 to 1.0 m.) deep were dug i n t o the proximal and d i s t a l s l o p e s i n order to expose and measure m a t e r i a l t h a t had not undergone p o s t - d e p o s i t i o n a l m o d i f i c a t i o n by f r o s t a c t i o n . A sample o f t i l l was c o l l e c t e d from near the base o f the t r e n c h and t r e a t e d a c c o r d i n g t o standard laboratory procedures o f s i e v e and hydrometer a n a l y s i s . These procedures were undertaken to determine whether d i f f e r e n c e s e x i s t i n the composition and s o r t i n g o f sediment from the proximal and d i s t a l s i d e s of the moraines and whether t e x t u r e has any i n f l u e n c e upon compaction. F i f t y pebbles were s p l i t from each t i l l sample and analyzed 76 f o r shape and l i t h o l o g y . The l e n g t h o f the a, b, and c axes and the l e a s t r a d i u s o f c u r v a t u r e ( r ) i n the p r i n c i p a l plane o f the pebble were measured. Roundness, f l a t n e s s , and s p h e r i c i t y o f each pebble were c a l c u l a t e d ( a f t e r C a i l l e u x , 1 9 4 5 ) . roundness = 2 r/a f l a t n e s s = 2 c / ( a + b) s p h e r i c i t y = ^ a b c / f ^ a 3 ) Zingg shapes were computed (Zingg, 1 9 3 5 ) . The l i t h o l o g i e s o f the pebbles were examined and the r e s u l t s are presented and d i s c u s s e d i n T a b l e I (See 1 . 3 . 2 . a ) . The l i t h o l o g i e s are a l s o r e l a t e d to the Zingg shapes. The compaction o f the t i l l was measured u s i n g a m o d i f i e d v e r s i o n o f the i n s i t u d e t e r m i n a t i o n o f bulk d e n s i t i e s p r e s e n t e d by Spangler and Wallace ( 1 9 7 0 ) . T i l l was c a r e f u l l y dug from the f l o o r o f the t r e n c h , l e a v i n g a s m a l l h o l e . Because o f the compact nature of the t i l l , the s i d e s would not cave i n , t h e r e f o r e the h o l e c o u l d be kept f r e e o f l o o s e sediment. A measured volume (V) o f f i n e granules ( 2 . 0 to 2.83 mm s i z e ) was poured i n t o the h o l e u n t i l f u l l . In the l a b , the t i l l was d r i e d and weighed (M) and the mass (Mp) and volume (Vp) o f a l l the pebbles i n the sample were measured. The bu l k d e n s i t y o f the sample was c a l c u l a t e d t o be (M-Mp)/(V-Vp) A t t e n t i o n was focused upon the r e l a t i v e compaction o f proximal and d i s t a l s i d e s . The compaction r e s u l t s , u s i n g the m o d i f i e d b u l k d e n s i t y method were o b v i o u s l y i n c o n s i s t e n t . The problem was probably due to the m o d i f i e d technique o f volume e s t i m a t i o n . F i n e granules must be too coarse a sediment t o permit uniform s e t t l i n g or packing when poured i n t o the h o l e . Spangler and Wallace (1970) used f i n e r sand s i z e s ( 0 . 1 to 1 .0 mm.). 77 Measurements o f the o r i e n t a t i o n and dip o f t i l l pebbles were made at depths from 2.5 to 3.0 f e e t (.8 to 1.0 m) below the s u r f a c e i n each t r e n c h . I t was hoped t h a t the r e s u l t s o f the f a b r i c a n a l y s i s , when compared wit h f a b r i c s o f other s m a l l moraines d e s c r i b e d i n the l i t e r a t u r e , would shed l i g h t on the o r i g i n o f the Hat Creek moraines. F i f t y pebbles w i t h a to b a x i s r a t i o s g r e a t e r than 1.5 were measured f o r o r i e n t a t i o n and dip o f the long a x i s . The o r i e n t a t i o n o f the c r e s t and the angle o f s l o p e o f the proximal and d i s t a l s i d e s o f the moraines at each s i t e were measured f o r comparison wi t h the f a b r i c r e s u l t s . The data were analyzed u s i n g the eigenvalue method f o r the a n a l y s i s o f a x i a l o r i e n t a t i o n data (Mark, 1973). T h i s method r e l i e s upon a s p h e r i c a l p r o b a b i l i t y d e n s i t y d i s t r i b u t i o n , i n which t h r e e mutually orthogonal e i g e n v e c t o r s and t h e i r e i g e n v a l u e s c h a r a c t e r i z e the data d i s t r i b u t i o n . (An ei g e n v e c t o r i s the a x i s o f best f i t through a n-dimensional s c a t t e r of p o i n t s and the ei g e n v a l u e i s the l e n g t h o f the a x i s . ) The l a r g e s t e i g e n v a l u e i n d i c a t e s the maximum e i g e n v e c t o r , which p a r a l l e l s the a x i s o f maximum c l u s t e r i n g o f data p o i n t s . The minimum e i g e n -v e c t o r , a s s o c i a t e d w i t h the s m a l l e s t e i g e n v a l u e , i s orthogonal to the plane o f b e s t f i t through the data; a plane which i n c l u d e s the maximum e i g e n v e c t o r . In a t i l l f a b r i c , the maximum e i g e n v e c t o r r e p r e s e n t s the p r e f e r r e d o r i e n t a t i o n of the long axes o f the pebbles and the d i r e c t i o n o f d i p o f the p r e f e r r e d plane i s d e r i v e d from the minimum e i g e n v e c t o r . The angle between these two eigenv e c t o i n d i c a t e s the p a r a l l e l or t r a n s v e r s e nature of the f a b r i c . An angle of l e s s than 30° i n d i c a t e s a p a r a l l e l f a b r i c , whereas an angle o f over 60° i n d i c a t e s a t r a n s v e r s e f a b r i c . (Mark, 1973) 78 sand 1 0 0 % fine sand 100 % fine AREA A AREA C 100' sand 1 0 0 % fine sand 1 0 0 % fine AREA D AREA F c o a r s e : > 2.0 mm. sand : 2 . 0 - 0 . 0 6 2 5 mm. f i n e : < 0 . 0 6 2 5 mm. <§) s a m p l e f r o m p r o x i m a l s ide rg s a m p l e f r o m d i s t a l s i de FIG. 15: T e x t u r a l A n a l y s i s 79 AREA A AREA C A R E A D A R E A F • Proximal tide ~ s Distal tide Cumulative Curves: G r a n u l e and Sand S i z e s 80 5.3 The I n t e r n a l C h a r a c t e r i s t i c s o f the Moraines 5.3.1 T e x t u r a l a n a l y s i s The moraines have a g e n e r a l l y coarse t e x t u r e . Percentage weight o f pebbles ranges from 5% to 60% o f the t o t a l sample; the mean i s 35%- Twenty to 50% o f the sediment i n the samples c o n s i s t s o f sand; the mean being 35%- Because o f the g e n e r a l l y small p r o p o r t i o n o f f i n e r f r a c t i o n s and the d i f f i c u l t y o f matching hydrometer and s i e v e curves, hydrometer r e s u l t s w i l l not be co n s i d e r e d i n d e t a i l . S u f f i c e to say that percentage s i l t i s g r e a t e r than percentage c l a y , and t h e r e were no great d i f f e r e n c e s between samples. The r e s u l t s o f the completed t e x t u r a l a n a l y s i s are pr e -sented i n F i g u r e s 15 and 16. As can be seen on.these diagrams, some a r e a l d i f f e r e n c e s e x i s t i n the s i z e and s o r t i n g o f p a r t i c l e s i n the t i l l . The t e x t u r e o f t i l l i n Area F i s s l i g h t l y f i n e r and the t e x t u r e o f t i l l i n Area D i s c o a r s e r than i n other a r e a s . P o s s i b l y t h i s can be a t t r i b u t e d to the l i t h o l o g i c c h a r a c t e r i s t i c s of the sediment c a r r i e d by the i c e at t h a t l o c a t i o n . A g r e a t e r range o f t e x t u r e and s o r t i n g e x i s t s among the samples from Areas A and C, as opposed to samples from Areas D and F. T h i s p a t t e r n i s p o s s i b l y due to the wide sp a c i n g o f sample moraines i n the former areas and the c l u s t e r -in g o f s i t e s i n the l a t t e r a r e a s . No c o n s i s t e n t p a t t e r n of t e x t u r a l d i f f e r e n c e s between t i l l from proximal and d i s t a l s i d e s o f a moraine e x i s t s . In p a r t i c u l a r the presence o f f i n e p a r t i c l e s i n the t i l l o f the d i s t a l s i d e i m p l i e s t h a t the s l o p e o f the d i s t a l s i d e was not m o d i f i e d by the 81 TABLE V I I I Pebble A n a l y s i s Mean Mean Mean Mean ZINGG SHAPE T o t a l - 100% Sample B- a x i s roundness f l a t - Spher- Spher-(mm) ness i c i t y Blade R o l l e r o i d D i s c F - l - P 14 .177 .562 .723 2 18 30 50 -D 13 .149 • 570 .715 12 12 32 44 -2-P 14 .173 • 555 .721 10 10 26 54 -D 15 .194 .593 .728 12 16 38 34 D-l-P 13 .192 .567 .714 12 16 32 40 -D 14 .205 .548 .707 8 16 24 52 -2-P 14 .180 .601 .749 2 14 52 32 -D 13 .201 .601 .740 4 18 38 40 -3-P 13 .161 .588 .716 10 28 34 28 -D 14 .225 .608 .744 4 22 42 32 C-l- P 13 .186 .557 .716 10 8 32 50 -D 13 .166 .533 .691 20 14 22 44 -2-P 15 .217 .558 .716 8 8 30 54 -D 13 .189 • 597 .729 2 20 42 36 -3-P 13 .167 .580 .727 12 18 32 38 -D 13 .166 .575 .718 10 14 30 46 A-l-P 13 .199 .574 .726 10 12 32 46 -D 14 .209 .567 .728 14 6 38 42 -2-P 13 .179 .573 .722 8 16 24 52 -D 14 .188 .598 .738 4 18 36 42 -3-P 12 .204 .593 .719 2 28 36 34 -D 13 .202 .565 • 710 12 12 36 40 Sample F - l - P : Area F-moraine 1-proximal s i d e 82 a c t i o n o f meltwater, s i n c e such an a c t i o n would have r e s u l t e d i n the removal o f f i n e sediments from the s u r f a c e o f the moraine. 5«3«2 Pebble a n a l y s i s A summary of the pebble a n a l y s i s i s presented i n T a b l e V I I I . The t i l l pebbles are v e r y angular; a v e r a g i n g 0.19 on a s c a l e from 0 to 1.0. There i s a s l i g h t tendency away from f l a t n e s s (O.58 on a s c a l e from 1.0 to 0) and a tendency toward s p h e r i c i t y (O.72 on a s c a l e from 0 to 1.0). There are many more d i s c s and s p h e r o i d s than r o l l e r s o r b l a d e s , a c c o r d i n g to the Zingg c l a s s i f i c a t i o n . A breakdown o f l i t h o l o g i c types i s presented and d i s c u s s e d i n Chapter I . V o l c a n i c l i t h o l o g i e s predominate. When Zingg shape i s compared with l i t h o l o g y a t r e n d i s apparent. V o l c a n i c pebbles are more angular, f l a t t e r , and l e s s s p h e r o i d than other l i t h o l o g i e s . The v a r i a t i o n i n pebble shapes between areas i s probably due to the d i s t r i b u t i o n o f v o l c a n i c p e b b l e s . 5.3.3 T i l l f a b r i c a n a l y s i s The r e s u l t s o f the t i l l f a b r i c a n a l y s i s , u s i n g the e i g e n -v a l u e method (Mark, 1973)? are summarized i n T a b l e IX. A l l f a b r i c s are s i g n i f i c a n t at the 95% c o n f i d e n c e l e v e l . The p r e f e r r e d o r i e n t a t i o n o f the long axes o f t i l l pebbles i s u s u a l l y t r a n s v e r s e to the moraine c r e s t , r e g a r d l e s s o f the o r i e n t a t i o n of the c r e s t . Of 22 s i t e s ; 13 are t r a n s v e r s e , 4 o b l i q u e , and 5 p a r a l l e l to the c r e s t . The average d i p on the proximal s i d e i s 24°, i n the d i r e c t i o n of the s l o p e , but l e s s than 83 TABLE IX T i l l F a b r i c A n a l y s i s Sample C r e s t Trend Angle Slope o f F l Dip 1 F3 Dip 3 P/T SI S3 F - l - P 1 0 0 ° 2 0 ° 2 5 ° 3 6 0 42° 380 P 5 9 4 122 F-l-D 1 0 0 5 217 11 138 X 4 7 T 585 193 F - 2-P 160 2 0 321 7 44 51 T 5 2 0 196 F -2-D 160 2 0 342 36 282 55 601 181 D-l-P 85 34 253 38 167 8 6 T 559 1 3 0 D-l-D 85 14 56 23 354 44 T 5 0 9 166 D-2-P 1 0 0 29 18 22 9 23 P 5 9 0 125 D-2-D 1 0 0 12 154 19 126 21 P 613 078 D-3-P 115 32 355 24 3 3 6 25 P 601 0 9 7 D-3-D 1 2 0 12 195 25 194 25 P 603 071 C - l - P 140 - 63 19 29 X 2 3 X 4 3 0 151 C-l-D 140 - 218 36 242 38 P 6 0 7 0 9 6 C - 2-P 140 28 53 2 6 31 28 P 5 2 5 122 C-2-D 140 24 219 19 248 22 P 550 107 C - 3-P 1 6 0 _ 91 1 0 9 8 X 1 0 P 5 2 2 1 0 8 C-3-D l6o _ 242 6 315 X20 T 4 8 9 138 A - l - P 90 30 350 2 6 11 28 P 709 0 6 0 A-l-D 85 9 164 14 90 42 T 651 0 8 0 A -2-P 95 25 75 5 354 31 T 4 9 0 058 A-2-D 95 12 172 32 151 34 P 487 144 A -3-P 105 30 5 23 355 24 P 573 132 A-3-D 105 15 146 34 138 35 P 504 195 X: n o n - s i g n i f i c a n t Sample F - l - P : Area F-moraine 1-proximal s i d e F l : p r e f e r r e d o r i e n t a t i o n o f long axes Dip 1: dip o f long axes F3: dip d i r e c t i o n o f p r e f e r r e d p lane Dip 3' dip o f p r e f e r r e d plane P/T: p a r a l l e l or t r a n s v e r s e f a b r i c S i : l a r g e s t e i g e n v a l u e . ( s t r e n g t h o f F l i n c r e a s e s , as SI i n c r e a s e s ) S3: s m a l l e s t e i g e n v a l u e ( s t r e n g t h o f F3 i n c r e a s e s , as S3 decreases) 84 t h e s l o p e . The average d i p on t h e d i s t a l s i d e i s 22° i n the d i r e c t i o n o f t h e s l o p e and g r e a t e r than t h e s l o p e . The dip d i r e c t i o n o f t h e p r e f e r r e d plane i s a l s o t r a n s v e r s e t o t h e c r e s t , although t h e r e i s g r e a t e r v a r i a t i o n i n t h e f a b r i c s on the d i s t a l s i d e s . Of t h e 11 f a b r i c s from t h e proximal s i d e ; 8 have p r e f e r r e d p l a n e s t r a n s v e r s e t o the c r e s t and d i p p i n g u p g l a c i e r , 1 i s t r a n s v e r s e and d i p p i n g v e r t i c a l l y , and 2 are diago n a l t o t h e c r e s t . On the other hand, o f t h e 11 f a b r i c s from the d i s t a l s i d e s ; 3 have p r e f e r r e d planes t r a n s v e r s e t o the c r e s t and d i p p i n g downglacier, 1 i s t r a n s v e r s e and d i p p i n g u p g l a c i e r , 3 are p a r a l l e l t o t h e c r e s t , and 4 are o b l i q u e t o t h e c r e s t . A s e r i e s o f p a i r e d t - t e s t s r e v e a l no s i g n i f i c a n t d i f f e r e n c e s between proximal and d i s t a l f a b r i c s f o r any o f t h e parameters (D.M. Mark, p e r s o n a l communication, 1974) except f o r t h e sense o f the d i p . 5.4 Comparison with Other Moraines When compared wit h p u b l i s h e d r e p o r t s o f t i l l f a b r i c s o f other small moraines, many modes o f formation f o r t h e Hat Creek moraines can be d i s c a r d e d . The f a b r i c s o f t h e Hat Creek moraines are • c l e a r l y o r i e n t e d w i t h r e s p e c t t o t h e moraine c r e s t . The long axes o f the pebbles are commonly t r a n s v e r s e t o t h e r i d g e c r e s t , r e g a r d l e s s o f the o r i e n t a t i o n of t h e c r e s t with r e s p e c t t o t h e apparent so u t h e r -l y d i r e c t i o n o f i c e flow. Thus an o r i g i n under c o n d i t i o n s o f a c t i v e l y advancing i c e can be e l i m i n a t e d , as moraines formed under those c o n d i t i o n s possess a f a b r i c o r i e n t e d w i t h r e s p e c t t o t h e d i r e c t i o n o f i c e movement. T h e o r e t i c a l l y , a push mechanism should produce f a b r i c s t r a n s v e r s e t o the d i r e c t i o n o f movement, and, th u s , p a r a l l e l 85 to the r i d g e c r e s t . T h e r e f o r e i t appears u n l i k e l y t h a t the Hat Creek moraines are push f e a t u r e s . The Hat Creek f a b r i c s appear to be most s i m i l a r t o those o f the i c e squeezed moraines o f Hoppe (1952) and Andrews (1963b). A comparison o f the Hat Creek t i l l f a b r i c s and Andrews' c r o s s - v a l l e y moraine f a b r i c s , analyzed u s i n g the e i g e n v a l u e method, was made by D.M. Mark. The r e s u l t s o f p a i r e d t - t e s t s r e v e a l t h a t the two groups o f f a b r i c s are s i g n i f i c a n t l y d i f f e r e n t . The Hat Creek moraine f a b r i c s have weaker p r e f e r r e d o r i e n t a t i o n s , more s t e e p l y d i p p i n g p r e f e r r e d p l a n e s , and on the proximal s i d e s , s t r o n g e r p r e f e r r e d planes than have the B a f f i n c r o s s -v a l l e y moraine f a b r i c s . Proximal and d i s t a l f a b r i c s do not d i f f e r s i g n i f i c a n t l y f o r any parameter w i t h i n e i t h e r a r e a (D.M. Mark, p e r s o n a l communication, 1974). However, some q u e s t i o n of the importance o f such a s t a t i s t i c a l d i f f e r e n c e may be r a i s e d . The two groups appear more s i m i l a r t o each other than to any othe r type o f moraine f a b r i c . I t i s u n l i k e l y t h a t moraines formed i n a b a s i c a l l y s i m i l a r manner under d i f f e r e n t g l a c i a l c o n d i t i o n s i n w i d e l y s e p a r a t e d areas w i l l be s t a t i s t i c a l l y i d e n t i c a l . I t must be remembered t h a t Andrews' moraines were formed by an a r c t i c g l a c i e r i n a permafrost zone, and are a s s o c i a t e d w i t h ponded l a k e s o f v a r i o u s depths. They depended upon an i n f l u x o f summer meltwater to thaw the b a s a l t i l l , a l l o w i n g the i c e c l i f f to s e t t l e , or upon buoyancy i n deep water. Such c o n d i t i o n s are not necessary to achieve movement o f water s a t u r a t e d b a s a l t i l l under a temperate g l a c i e r . Some o f the c h a r a c t e r i s t i c s o f the t i l l pebbles are a l s o d i f f e r e n t between the two groups, and these may i n f l u e n c e the nature o f the f a b r i c . The m a j o r i t y o f the pebbles i n the c r o s s - v a l l e y moraines have g n e i s s i c l i t h o l o g i e s and i r r e g u l a r shapes ("wedge-shaped" and " v a r i h e d r o i d " a f t e r Holmes (l94l) 86 (Andrews, 1963b, p. 87 and 95))* Andrews a l s o adopted a more s t r i n g e n t axes r a t i o (2:1) f o r h i s r e s e a r c h . F a b r i c s i n a f l o w t i l l are p a r a l l e l to the d i r e c t i o n o f flow ( B o u l t o n , 1968). I f flow o f f o f the i c e produced a l i n e a r r i d g e along the i c e f r o n t , i t i s l i k e l y t h a t f a b r i c s would be t r a n s v e r s e to the moraine c r e s t . However, i t i s probable t h a t the proximal s i d e would slump when the i c e support melted away, and the proximal f a b r i c would be c o n t o r t e d . T h e r e f o r e , i t i s u n l i k e l y t h a t the Hat Creek moraines are c o n t r o l l e d a b l a t i o n moraines a f t e r B o u l t o n (1968). F u r t h e r d i s c u s s i o n o f a l t e r n a t i v e modes o f o r i g i n , u t i l i z i n g the r e s u l t s o f the a nalyses o f i n t e r n a l c h a r a c t e r i s t i c s and e x t e r n a l morphology, i s p r e s e n t e d i n Chapter 6. 87 6. ORIGIN OF THE HAT CREEK MORAINES 6.1 I n t r o d u c t i o n Chapter 6 reviews the important p h y s i c a l c h a r a c t e r i s t i c s o f the Hat Creek moraines and then d i s c u s s e s t h r e e p o s s i b l e modes o f o r i g i n - - b a s a l squeezing, i c e push, and c o n t r o l l e d a b l a t i o n or f l o w t i l l . 6.2 Summary o f the P h y s i c a l C h a r a c t e r i s t i c s The s m a l l moraines o f Upper Hat Creek v a l l e y are d i s t i n c t , s u b p a r a l l e l r i d g e s , which t r e n d a c r o s s the a x i s o f the v a l l e y , forming a s l i g h t l y convex downglacier p a t t e r n . T h e i r average l e n g t h i s 1000 f e e t (305 m.) and they are spaced approximately 130 f e e t (40 m.) a p a r t . The average h e i g h t i s 8 f e e t (2.4 m.), although they reach h e i g h t s o f 25 f e e t (7.6 m.). One of the most dominant f e a t u r e s i s the marked asymmetry o f t h e i r p r o f i l e . The average angle o f s l o p e o f t h e i r proximal and d i s t a l s i d e s i s 24° and 11° (maximum i s 45* and 24*) r e s p e c t i v e l y . The moraine i s composed o f a coarse compact t i l l w i t h a s a n d y - s i l t m a t r i x . The t i l l pebbles are mostly v o l c a n i c , v e r y angular and predominantly d i s c and s p h e r o i d shapes. The p r e f e r r e d o r i e n t a t i o n o f the long axes o f t i l l pebbles i s t r a n s v e r s e t o the t r e n d o f the c r e s t , r e g a r d l e s s o f the o r i e n t a t i o n o f the c r e s t w i t h r e s p e c t to the d i r e c t i o n o f i c e movement. The dip o f the long axes i s i n the d i r e c t i o n o f the s u r f a c e s l o p e : 24° and l e s s than the 88 s l o p e on the proximal s i d e , and 22° and g r e a t e r than the s l o p e on the d i s t a l s i d e . Although the d i r e c t i o n and steepness of the l o c a l s l o p e does not seem t o e x e r t an i n f l u e n c e upon the moraines, an u n r e s o l v e d r e l a t i o n s h i p between c o n t i n u i t y o f a moraine and breaks o f s l o p e , whether concave or convex, has been found. 6.3 D i s c u s s i o n o f A l t e r n a t i v e Hypotheses o f O r i g i n The s m a l l moraines o f Upper Hat Creek are found mainly i n areas which experienced compressive flow c o n d i t i o n s . Under such c o n d i t i o n s c r e v a s s e s would not form. Thus a p o s s i b l e c r e v a s s e o r i g i n , i n which the t i l l was d e p o s i t e d i n a system o f c r e v a s s e s , can be d i s c o u n t e d . A f r o n t a l o r i g i n , i n which t i l l was d e p o s i t e d i n a r i d g e along the i c e f r o n t , i s c o n s i d e r e d to be the most l i k e l y a l t e r n a t i v e . The Hat Creek moraines have c h a r a c t e r i s t i c s which are s i m i l a r to sma l l moraines formed by t h r e e f r o n t a l p r o c esses: b a s a l squeezing (Andrews and Smithson, 1966), f r o n t a l push (Andrews and Smithson, 1966), and a b l a t i o n f l o w t i l l ( B o u l ton, 1971). S i g n i f i c a n t c h a r a c t e r -i s t i c s o f each o f these moraine types are summarized i n T a b l e X f o r comparison w i t h the f e a t u r e s o f the Hat Creek moraines. The t i l l f a b r i c o f the Hat Creek moraines d i f f e r s somewhat from the t h e o r e t i c a l f a b r i c o f a l l t h r e e moraine types--push, squeeze, and f l o w t i l l . The g r e a t e s t c o n t r a s t i s between the f a b r i c o f the Hat Creek moraines and the t h e o r e t i c a l f a b r i c o f a push moraine (Table X ) . Although the o r i e n t a t i o n o f the f a b r i c o f squeeze and f l o w t i l l moraines ressembles t h a t o f the study r i d g e s , d i s c r e p a n c e s 89 TABLE X Comparison o f S i m i l a r C h a r a c t e r i s t i c s o f Hat Creek Moraines and Other Small Moraines Moraine Type T i l l F a b r i c Hat Creek O r i e n t a t i o n t r a n s v e r s e to r i d g e c r e s t P r o x i m a l : d i p l e s s than s l o p e D i s t a l : d i p g r e a t e r than s l o p e Squeeze O r i e n t a t i o n t r a n s v e r s e to r i d g e c r e s t P r o x i m a l : dip g r e a t e r than s l o p e D i s t a l : d i p l e s s than s l o p e Push ^ O r i e n t a t i o n p a r a l l e l to r i d g e c r e s t F l o w t i l l O r i e n t a t i o n t r a n s v e r s e t o r i d g e c r e s t Upslope i m b r i c a t i o n ( d i p l e s s than s l o p e ) Moraine Type Asymmetry Other C h a r a c t e r i s t i c s Hat Creek st e e p e r proximal Squeeze ste e p e r d i s t a l Push ste e p e r proximal t e c t o n i c d i s t u r b a n c e s F l o w t i l l s t e e p e r proximal g r a v e l l y veneer 90 e x i s t between the t y p i c a l d i p s o f these f e a t u r e s (Table X ) . The asymmetry o f p r o f i l e o f Hat Creek moraines i s s i m i l a r to the p r o f i l e o f push and f l o w t i l l moraines, and the r e v e r s e o f the p r o f i l e o f squeeze moraines. I f the p r o f i l e o f Hat Creek moraines i s a primary f e a t u r e , the squeeze h y p o t h e s i s can be d i s c o u n t e d . I t i s probable t h a t the p r o f i l e o f Hat Creek moraines i s o f primary n a t u r e . In Chapter 4 i t i s demonstrated t h a t the proximal s i d e s were not oversteepened p o s t g l a c i a l l y . I t i s a l s o u n l i k e l y t h a t the d i s t a l s l o p e s have been reduced f o l l o w i n g d e p o s i t i o n , s i n c e evidence o f m o d i f i c a t i o n by l o c a l ponding i s l a c k i n g . The s l o p e s are uniform; f i n e sediments are present on the d i s t a l s i d e ; and the i n t e r m o r a i n a l areas do not have a veneer o f pond s i l t s . A p p a rently the p r o f i l e i s a primary f e a t u r e , thus a squeeze o r i g i n i s improbable. Although a push moraine i s g e n e r a l l y c o n s i d e r e d t o have a s t e e p e r proximal s l o p e (Andrews and Smithson, I966), the asymmetry o f the push moraines o f the Athabasca g l a c i e r i s r e v e r s e d (D.M. Mark, w r i t t e n communication, 1974) and P r i c e (1973, p. 85) suggests t h a t push moraines have s t e e p e r d i s t a l s i d e s . I t i s probable t h a t the moraines i n the l a t t e r two cases have been a l t e r e d by s l i g h t o v e r r i d i n g f o l l o w i n g the push. Andrews and Smithson (1966) a t t r i b u t e a simple push o r i g i n t o moraines wi t h steep proximal s i d e s , and a push with o v e r r i d i n g o r i g i n to moraines w i t h s t e e p e r d i s t a l s i d e s and long proximal ramps. Hewitt (1967) witnessed the formation o f moraines w i t h symmetrical s l o p e s by the process o f push and over-r i d i n g . 91 S e v e r a l arguments a g a i n s t a f l o w t i l l o r i g i n e x i s t . F i r s t l y , the shape o f the r i d g e s o f f l o w t i l l i s expected to be l e s s uniform, w i t h more l o b a t e f e a t u r e s , than t h a t o f Hat Creek moraines. Secondly, i f the moraine was formed o f f l o w t i l l along the i c e margin, i t would be l i k e l y t h a t slumping would occur along the proximal s i d e as the i c e support melted away. T h i s would probably d i s t u r b the f a b r i c , yet the t i l l f a b r i c o f Hat Creek moraines i s s t r o n g e s t on the proximal s i d e . The argument f o r a f l o w t i l l o r i g i n i s a l s o weakened by the d i s c r e p a n c y i n the dip o f pebbles between the two moraine t y p e s . F i n a l l y , a g r a v e l l y veneer, o f t e n a s s o c i a t e d w i t h f l o w t i l l s ( B o u l t on, 1971)i occurs i n o n l y a few exposures i n the moraines o f Upper Hat Creek v a l l e y . Thus o f the t h r e e suggested modes o f o r i g i n , a b a s a l squeeze process can be d i s c o u n t e d due to the primary nature o f the moraine asymmetry and a f l o w t i l l o r i g i n i s d o u b t f u l on the b a s i s o f shape, f a b r i c , and t e x t u r e d i s c r e p a n c i e s . T h e r e f o r e , i t i s i m p l i e d t h a t the t r u e mode o f o r i g i n i s i c e push. Problems, however, e x i s t with the acceptance o f a push o r i g i n . The major d i s c r e p a n c y l i e s w i t h the r e c o n c i l i a t i o n o f the t h e o r e t i c a l t i l l f a b r i c produced by a push wi t h the a c t u a l f a b r i c o f the Hat Creek moraines. I t i s p o s s i b l e t h a t the g e n e r a l l y assumed f a b r i c o f a push moraine, which seems t o r e s t upon t h e o r e t i c a l r e a s o n i n g , unsupported by p u b l i s h e d f a b r i c r e s u l t s , may be i n c o r r e c t . A l t e r n a t i v e l y , i t i s l i k e l y t h a t the push d i d not r e o r i e n t the o r i g i n a l f a b r i c o f the t i l l . I f the push was i n t o f r o z e n ground, the i n d i v i d u a l pebbles would not be r e o r i e n t e d . I n s t e a d b l o c k s o f f r o z e n t i l l would be shoved. I f t h i s were the case, a shear plane 92 s h o u l d e x i s t at the base o f the moraine. T e c t o n i c d i s t u r b a n c e s such as f o l d i n g and f a u l t i n g which are o f t e n a s s o c i a t e d with push moraines were not observed, i n t h e few exposures a v a i l a b l e . In c o n c l u s i o n , o f the t h r e e p o s s i b l e hypotheses; push, squeeze, and f l o w t i l l , i t i s most probable t h a t the sma l l moraines o f Upper Hat Creek v a l l e y are push moraines or a combination o f push moraines and c o n t r o l l e d a b l a t i o n moraines ( f l o w t i l l ) . The l a t t e r may e x p l a i n the shape o f a few, very i r r e g u l a r moraines, but i s c o n s i d e r e d t o be a minor i n f l u e n c e i n the t o t a l area o f moraines. The push mechanism, a c t i v e over the e n t i r e b a s i n , may e x p l a i n the asymmetrical p r o f i l e o f the crev a s s e f i l l i n g s south o f White Rock Creek (See 3.3.5). A s l i g h t push forward might a l t e r the shape o f the crev a s s e d e p o s i t , steepening the proximal s i d e . U n f o r t u n a t e l y , the l a c k o f good s e c t i o n s prevented any p o s s i b l e o b s e r v a t i o n o f t e c t o n i c c o n t o r t i o n s which might be expected from a push o f s t r a t i f i e d d e p o s i t s . 6.4 C o n c l u s i o n s Many types o f sma l l moraines occur i n the g l a c i a t e d r e g i o n s o f the world and have been d e s c r i b e d i n the l i t e r a t u r e . A great v a r i a t i o n i n i n t e r n a l c h a r a c t e r i s t i c s and e x t e r n a l morphology e x i s t s between them, and they have been a t t r i b u t e d t o a v a r i e t y o f o r i g i n s , i n c l u d i n g b a s a l squeezing, i c e push, and c o n t r o l l e d a b l a t i o n ( f l o w -t i l l ) . The s m a l l moraines o f Upper Hat Creek v a l l e y possess a d i s t i n c t t i l l f a b r i c , t e x t u r e , and c r o s s p r o f i l e , which, when 93 c o n s i d e r e d i n combination, d i f f e r s from the t y p i c a l c h a r a c t e r i s t i c s o f a l l s m a l l moraines p r e v i o u s l y d e s c r i b e d . Of the h y p o t h e s i z e d o r i g i n s f o r the small moraines o f Upper Hat Creek v a l l e y , an i c e push i s the most l i k e l y . The h y p o t h e s i s o f b a s a l squeezing i s d e s c r e d i t e d due to the primary nature o f the asymmetry o f Hat Creek moraines. The h y p o t h e s i s o f c o n t r o l l e d a b l a t i o n i s d i s c o u n t e d because o f d i s c r e p a n c i e s which e x i s t between the t i l l f a b r i c , t e x t u r e , and shape o f f l o w t i l l r i d g e s and Hat Creek moraines. Each w i n t e r the a b l a t i o n t i l l o f the p r e v i o u s summer was pushed i n t o a r i d g e during a s l i g h t readvance o f the i c e f r o n t . However, the forward motion ceased b e f o r e the accumulation o f t i l l would f o r c e the i c e to o v e r r i d e the r i d g e . Thus, the s t e e p e r proximal s l o p e , c r e a t e d by the simple push, was not a l t e r e d by o v e r r i d i n g i c e . The i c e margin would then melt back, i s o l a t i n g the moraine. Subsequent push moraines were c o n s t r u c t e d behind the p r e v i o u s one. O c c a s i o n a l l y , l a t e r readvances extended f a r enough to i n c o r p o r a t e or d e s t r o y p r e v i o u s moraines ( F i g . 14). The push must have been i n s u f f i c i e n t to r e o r i e n t the pebbles i n the t i l l , thereby r e s o l v i n g the v a r i a n c e between the observed and t h e o r e t i c a l t i l l f a b r i c s of these push moraines. Although i m p l i e d by the push o r i g i n , an annual formation can not be proven f o r the moraines o f Upper Hat Creek v a l l e y . 94 BIBLIOGRAPHY Andrews, J.T. 1963a. C r o s s - v a l l e y moraines o f the Rimrock and I s o r t o q R i v e r V a l l e y s , B a f f i n I s l a n d , N.W.T. Geog. B u l l . , 19, PP. 49-77. . 1963b. The c r o s s - v a l l e y moraines o f N o r t h - c e n t r a l B a f f i n I s l a n d : A q u a n t i t a t i v e a n a l y s i s . Geog. B u l l . , 20, pp. 82-129. . and Smithson, B.B. 1966. T i l l f a b r i c s o f the c r o s s -v a l l e y moraines o f N o r t h - c e n t r a l B a f f i n I s l a n d , N.W.T., Canada. G.S.A. B u l l . , 77, pp. 271-290. Armstrong, J.E., C r a n d e l l , D.R., Easterbrook, D.J., and Noble, J.B. 1965. Lat e P l e i s t o c e n e s t r a t i g r a p h y and chronology i n southwestern B r i t i s h Columbia and northwestern Washington. G.S.A. B u l l . , 76, pp. 321-330. 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