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Some interesting features of the coast range massif of British Columbia Patmore, William Henry 1936

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U'3 &y> fir- l°7 5 £ §OME INTERESTING FEATURES OP THE COAST RANGE' MASSIF OF BRITISH COLUMBIA BY jWilliam Henry Patmore A Thesis Submitted for the Degree of MASTER OF ARTS i n the Department of Geology JThe University of B r i t i s h September, 1936 Columbia, C O N T E N T S Page Foreword Introduction I Purpose of Thesis .1 Acknowledgments II Early Work I l l Later Surveys IV Theses of Interest XI Chapter I Vulcanism i n B r i t i s h Columbia Relations to Mountain Building ,1 The Igneous Cycle 2 Relation to Isostasy 3 Energy and Thrust Transmission .4 A c t i v i t y 5 Tseaux River Flows 5 Blue River 7 Garibaldi 7 Milbank Area 10 Bardswell and Price 11 Basalt Dyke Relations 11 Clearwater Flows 12 Ruby Creek Flows 13 Mann Creek 14 Volcanic ash - Bridge River ...15 Iskut River 15 Description of Hoodoo 16 Other Flows 17 Pleistocene Flows 18 Tuya Lake 19 Be l l a Coola Area 20 Koshin River 20 pearce Island 21 Relation to Hot Springs 21 Mount Waddington 22 Alaska 23 Yukon 24 Summary 25 Page Chapter II F i o r d System of B r i t i s h Columbia Introduction • 28 Conclusions 28 Description 30 G-eomorphic Development 47 Summary 57 Submerged Valleys 59 Chapter III Fracture. System of B r i t i s h Columbia F i r s t Observations .64 Schofield 1 s Work 64 Comparisons 65 Cairnes Work . . 66 A. Gold-Silver 67 B. Antimony-Silver 68 Lees - Yukon 71 peacock's Systems 72 Lord - Schofield 73 L e i t h 76 Comparisons - beams ...84 peacock's Assumptions 85 Summary 88 underlying Causes 90 Bibliography L i s t of Writers Used to Best Others Mentioned Where Used. Advantage. CONTENTS(continued) Number Page. #1 .4a. #2 ....50a. #3 35a. #4 36a. #5. 38a. #6 ...52a. #7 ...62a. #8 63a. #9 72a. #10 74a. Illustrations. Number. Page. #1 14. #2 33. #3 38. #4 41. #5 42. #6 43. #7 44.. #8 .45 . #9 85. #10 49. #11 67. #12 ..68. #13 .70. #14 78. #15 82. #16 83. #17 85. #18 ....86. #19 86a . Photographs. F r o n t i s p i e c e — : Inside cover. . Numbed. Page. #1 17a. #2 22a . #3 24a. #4 24a. #5. 27a. #6 27a. #7 27a. #8 31a. #9 32a. #10 54a. CONTENTS(cotinued). Photographs.(cotinued). Number. Page. #11 37a. #12 ....40a. #13 41a. #14 43a. #15. 43a. #16 56a. ; #17 57a. #18. 57a. #19. 60a. #20 60a. #21. 65a. #22 .68a. #23 i 76a. #24 83a. Added Notes. Concerning hanging valleys and the gouging power of ice P.63b. 63c. I FOREWORD. The Coast Range Batholith, i t s s a t e l l i t e s , s t o c k s and apophyses,are a g e n e t i c a l l y related mass of intrusive rocks composing a petrographical province of no meanrextent along the western margin of B r i t i s h Columbia. This much denuded igneous complex: rears a broad zone of towering peaks to the sky-line, assuming as dominant a role now as i t d i d through f o r t y m i l l i o n years of magmatic upwelling and associ-ated mineralization. Another hundred m i l l i o n years of gene-rous carving and etching by the u n t i r i n g agencies of erosion have done much to expose the core of that immense range to our view. With i t s mighty length of one thousand odd miles, i t s breadth of aa much as three hundred miles and i t s host of rock types and phases, the Coast Range Batholith presents many d i f f i c u l t but engaging problems. However, because of the lack of f i e l d data, most of these w i l l remain unsolved for many years to come. The following B t u d y i s in i t s e l f only a means of sorting and compiling the relevant material written to date. The writer has attempted to set f o r t h c l e a r l y the sal i e n t problems and the f a c t s necessary for t h e i r solution. Such a preparation w i l l undoubtedly allow for a sound attack on some of the questions now unanswered -an attack which the author hopes to take up in the near future. II With this idea i n mind d i f f e r e n t theories have been brought f o r t h and t h e i r r e l a t i v e merits compared, while actual f i e l d occurrences.noted during eight years of work in the b a t h o l i t h or on i t s margins, were used to sway opinion one way or the other. To a large extent, however, this thesis i s a compendium of important facts and p a r t i a l l y accepted ideas. Area The Coast Range granodioritic complex comes to a remarkably clear cut termination i n southern B r i t i s h Columbia, although related masses, arranged en echelon, are to be seen i n Washington State. A northward extension passes well through into the Yukon and Panhandle of Alaska. That portion l y i n g within B r i t i s h Columbia w i l l be given main consideration, butjbecause of the extensive work of Dr. A. P. Buddington i n the northern section, many outside references must be made. Acknowledgments Many thanks are due to Dr. S. J. Schofield who advised and aided the writer i n this task. I t i s with pleas-ure that the considerate help of Dr. J . T. Mandy i s r e c a l l e d , for he has done much during the past few years to arouse a s p i r i t of enquiry concerning b a t h o l i t h i c problems. To him further thanks' i s necessary f o r the use of his excellent photographic plates which have been coll e c t e d over a large number of years. I l l The work of Dr. A. P. Buddington has also been used to the f u l l e s t extent, and a word of gratitude i s only too l i t t l e return f o r the vast fund of data he has published i n reference to intrusive questions. In conclusion, thanks i s tendered to a l l those who supplied information and are, therefore, mentioned i n the accompnaying bibliography. Early Maps and Reports The f i r s t map on record which makes any attempt to show the geology of the Coast Range i s that by A. K. I s b i s t e r ^ i n 1851. I t represents the mountainous tract as a composite of granites, gneisses, traps etc. The year 1850 saw publication of a valuable paper on the geography and geology of S-E Alaska by Dr. C. Grewingk from data supplied by a Russian naval o f f i c e r . Cushing drew up a geological map of the v i c i n i t y of Glacier Bay i n 1891. p This work was followed by a reconnaissance paper by Brooks" i n 1901 wherein the e s s e n t i a l s t r u c t u r a l and stratigraphic features of S-E Alaska were substantially outlined. More detailed surveys were i n s t i t u t e d In the next few years with the production of many remarkable maps of the area. In 1884 the Geological Survey of Canada produced a map i n v/hich the Intrusive, rocks and t h e i r surrounding aureole 1. I s b i s t e r , A.K., Q.J.G.S., London, 1851, p 497. 2. Brooks, A.H. Prelim. Rep. on Ketchikan Mining Dis., Ala., U.S.G.S., Prof. Paper 1, 1902. IV of sedimentaries, mostly metamorphosed, were coloured similar and named gneissic and schistose rocks of probable Palaeozoic age intruded by large masses of granite. These early maps were, ho¥/ever, only rough guesses concerning areas merely touched "upon and were accordingly considered as such. I t was not u n t i l the early Twentieth Century that the Canadian government issued an approximately correct map of the Coast section. This map, published i n 1913, shows the b a t h o l i t h i c areas to be composed mainly of granite but, as i t i s now generally understood, the error was la r g e l y one of omission of important pendant areas. 1 Dr. Camsell's traverse of the Coast Range i n 1920 along the P. G. E. Railway goes a long way i n eradicating false ideas of the s o l e l y g r a n i t i c masses making up that province. Some Early Ideas It must be remembered that the time has.just passed when l i t t l e was known about the close relations existing be-tween orogenesis, intruding magmas and zoned ore deposits. Large g r a n i t i c areas were just accepted as fa c t s , rather mysterious perhaps, but nevertheless quite unimportant eco-nomically. Yet, i n the l i g h t of present day knowledge, a close study of Igneous bodies and t h e i r associated mineral 1. Camsell, C. Geol. Survey of Can., Summ. Report, 1920. V zones i s leading to new discoveries of ore and commercially planned attacks on old ones. ; i t i s only necessary to refer to one of the early .reports issued by the Department of Mines-. Bancroft, i n 1913, makes a statement of theory too well accepted to-day to be repeated. "Heated waters and vapours emanating from the vast batholiths of the Coast Range have been the chief source of mineralization."-'- Later, In 1922, Dolmage writes, "The Coast Range Batholite i s of great economic importance, i t Is well known that most of the mineral deposits of the coast region had t h e i r o r i g i n i n the magma which formed this b a t h o l i t h , B a n c r o f t ' s coastal work was the beginning of a much more detailed period of mapping of large batho-l i t h i c areas. Generalizations of Dr. S. J . Schofield Dr. Schofield's early start and close acquaintance with the area covered by this work has placed him i n a position that has allowed him to make a c r i t i c a l survey of the f i e l d facts discovered and apply sound generalizations which have i n t h e i r main structure withstood the acid test of time. Those generalizations and r e l a t i v e implied theories are now being expanded and added to by l a t e r research, T O Schofield geology i s Indebted, amongst other work, for a 1. Bancroft, J.A. Geol. of Coast & Is. bet. s t r a i t of Georgia & Queen Charlotte Sound, B.C., Mem. 23, pl23 2. Dolmage, V. Summary Report, 1922, r a r t A, p 17A. VI study of the broader s t r u c t u r a l relations of the Coast Range, for his system of horizontal zoning of ore bodies peripherally to the b a t h o l i t h and for his well founded geological history. Much of his work was i n collaboration v/ith Dr. Hansen whose results are used to advantage i n this thesis. Summary by Dr. A. F. Buddington A long series of exceptionally c r i t i c a l surveys was undertaken by Dr. Buddington who began work i n south-eastern Alaska i n 1921 with the collaboration of T. Chapin. Their report, published i n 1929^ contains much valuable reconnaissance data, including an important section concerning the intrusive rocks of the Coast Range. Buddington was able to use a valuable c o l l e c t i o n of rock sections v/hich had been obtained by F. E. Wright across the Batholith along the Stikine River. Chapin and Buddington put together a very interesting rock column f o r south-eastern Alaska, showing rocks as old as the Ordovician on the western contact area of the b a t h o l i t h . A s t r i k i n g feature i s the discovery of S i l u r i a n beds of conglomerates containing cobbles of granite and d i o r i t e . The results of work by Buddington and his associates have shown that variations i n broader generaliz-ations such as Schofield's are e n t i r e l y possible north of rortland Canal. Although, as Buddington states i t , "the 1. Buddington, A . F . & Chapin, T. Geol. & Min. Deposits of South-eastern Alaska, U.S.G.S., B u l l . 800, 1929. VII phenomena, are too complex and the data at hand are insuf-f i c i e n t for an evaluation" of the many problems i n Alaska , he has done much, to summarize the facts already on hand, and to commence an attack on problems of d i f f e r e n t i a t i o n i n the batholith, of o r i g i n of structure, of genetic relationship of various metals to varied rock types and of application of recognized•theories. Furthermore, Buddington has shown c r i t i c a l i nterest i n any attempt to study these conditions i n B r i t i s h Columbia or Alaska , belonging, as lie does, to the Committee on Batholith Problems, National Research Council of the U.S. Reconnaissance of Southern B. C. - Dr. Dolmage Most of Dolmage's energetic survey work has been confined to the southern h a l f .of B r i t i s h Columbia, much of i t coastal- reconnaissance and shore-line mapping. Here he has had a remarkably f i n e chance to consider the types of ba t h o l i t h i c intrusions over large f i o r d sections and to com-pare the m e t a l l i z a t i o n of the eastern and western contact areas. Thus we f i n d Dolmage being repeatedly quoted i n papers concerning suoh questions,since i t Is only by amassing a great quantity of f i e l d data-'that generalizations may be arrived at. The differences Impartially brought out by Bud-dington i n the northern and southern sections are accentuated by Dolmage's conclusions. He says, "Quartz-diorite i s the most abundant variety, not only of this d i s t r i c t but of VIII the whole batholith." Of course the l a s t part of the state-ment i s weak, due to the lack of facts covering large sections of the i n t r u s i v e rocks, xn addition to his valuable study of the Coast Range petrography, Dolmage has collected data on a great many mineral deposits on both contact margins i n southern B r i t i s h Columbia. Reconnaissance of Northern B. C. - Dr. Kerr Dr. Forrest A. Kerr has probably done more to enlighten the minds of geologists concerning the north-eastern b a t h o l i t h i c areas than any other single man. His work i n this respect checks with that of Dr. Buddington and i s i t s e l f corroborated by information c o l l e c t e d by Dr. Cock-f i e l d at numerous points along the eastern contact. Kerr's t e r r i t o r y has been mainly along the larger "antecedent" rings i n northern B r i t i s h Columbia such as the iskut, a t i k i n e , Whiting and Taku Rivers. He has become exceptionally well acquainted with the c r i t e r i a of age re-lations of marginal phases of the i n t r u s i v e s , mainly because of his vinflagging energy i n reconnaissance work. The results of his survey-are to be bad i n the Summary Reports of the Canadian Geological Survey, m 1935 he published a very inter e s t i n g summary on the s t r u c t u r a l relationships of mineral 1. Dolmage, V. Coast & Islands of B. C. bet. Douglas Channel and the alaskan Boundary, C. G. S., Summary Rep, 1922, r a r t A, p 16A. IX deposits along the C. N. R. Here he points out-that conditions have been f a r too complex to employ the zoning c h a r a c t e r i s t i c s noted elsewhere. In accordance v/ith Budding-ton, he notes that much of the eastern contact i s exceedingly i r r e g u l a r . "The b a t h o l i t h assumed a very i r r e g u l a r shape, so that throughout the area there i s a considerable i n t e r -mingling of intrusives and non-intrusives." This and other facts relative- to the problems under consideration w i l l be advanced i n the following review of theories presented to date, always allowing for possible discordance between the northern and southern halves of the Coast Range. Work by Dr. J. T. Mandy Dr. Mandy, who i s a graduate M. E. of two German un i v e r s i t i e s and a geologist with sound t h e o r e t i c a l capa-b i l i t i e s , has done much, to open up new trends of thought i n connection with solution of b a t h o l i t h i c phenomena. He i s fortunate enough to have gained a broad outlook on the facts involved, due to the extensive areal size of the North-western Mineral Survey D i s t r i c t No. 1 which he oversees annually. Although his interests for the government are substantially p r a c t i c a l , he has been gathering and considering more t h e o r e t i c a l data at his own expense of energy. His 1. Kerr, P.A. Struct. Relationships of Min. Dep. along the N. Route of C. N. R. Miner, Sept. 1935, Vol. 8, p 20. 2. Kerr, P.A. Prelim. Rep. on Iskut R. Area, B. C , Summ. Rep. 1929, Part A, p 48a. X ideas are n a t u r a l l y very enlightening to the writer, who has spent much, valuable time with, him on coastal f i e l d t r i p s . These ideas vary i n many ways from those of the geologists already reviewed, but here also the reason may be a marked difference between the center and the ends of the batholith. The writer has received much aid and encouragement i n his study of the central coastal section through the g e n i a l i t y of Dr. Mandy, Besides t h i s , the many reports issued by the B. C. Mines Branch and those describing mineral deposits i n Mandy's area have done a great deal to give insight into problems of fracturing and mineralization. Dr. Mandy's theo r e t i c a l cross-section of the b a t h o l i t h - well checked over by the author - has been reproduced with his kind permission. 1. Mandy, J.T. Lode Gold Deposits of B. C , B. G. Dept. of Mines, B u l l . 1, 1932, pp 16-20. XI Theses at U.B.C. Pertaining to the Coast Range Batholith 1. Geology and Ore Deposits of the Coast Range of Northern B. C. and S-E Alaska, J . Y. Smith, 1933."'" 2". The Physiography of the Coast Range of B. C. and S-E Alaska, C. S. Lord,- 1929. 3'.' A Thesis on the Lode Gold Deposits i n B. C , R. Maconachie, 1934. 4,; Ore Deposits Associated with the Coast Range Batholith, P. D. Paterson, 1927. 5'.' Geography and Geology of Vancouver, Ivan Alexis Lopatin, 1929. 6. Coastal Erosion near V i c t o r i a , B. C , J. R. Maconachie, 1933. 7'.' Gla c i a t i o n In an Area Bordering Stikine River, B. C., C. S. Lord, 1928. 8. Survey of the Stikine River Valley, B. C , C. S. Lord, 1927. 9'.' The Geology of the Queen Charlotte Islands, J. E. Armstrong, 1934. 10>Y Changes of the Coast of B. C , C. E. Rayner, 1930. 11. Geology of Britannia Map Area with Reference to the Coast Range Batholith, E. J. Lees, 1925. 12. Geology and Mining i n the Salmon River D i s t r i c t , E. G. L a n g i l l e , 1935. 13. Topography and Geology of Big Salmon Map Area, Yukon, J. S. Stevenson,, 1929. 14. A Reconnaissance Geological Survey In a Portion of the Stikine Map Area, T. Warden, 1928. 15. A Reconnaissance i n the Whitesail Lake D i s t r i c t , H. V. Warren, 1924. 16. Geology and Ore Deposits of Taku River D i s t r i c t , J.Y. Smith, 1932. -«- Of special i n t e r e s t . XII 17. .A Reconnaissance i n Southern Yukon, C. H. Stockwell, 1924. 18. A General Account of Iskut River Area, S. S. Holland, 1929. 19. The Geology and Mineralogy of the West ern Contact of the Coast Range Batholith, J . E. A. Kania, 1928. 20? Geology ofthe Queen Charlotte Islands, A. I. E. Gordon, 1955. 2l'.< The Geology of Vancouver Island, V. J. Dalton, 1932. 22. The Whitesail - Eutsuk Lakes Map Area, C. P. Barton, 1935. 23. - A Br i e f Reconnaissance Between Prince Rxxpert and Smithers, B. C , C. F. Barton, 1924. 24. A t l i n Ruffner Lead S i l v e r Mine - Physiography, Geology and Mineralogy, V. J. Okulitch, 1931. 25. The Ore Deposits of the Eastern Side of the Coast Range Batholith, V. J. Okulitch, 1932. 26. The Stratigraphy, Structure and Ore Deposits of the Southern Yukon, J . E. Armstrong, 1935. 27'i The Ore Deposits of the Eastern Contact of the Coast Range Batholith, J . Black, 1936. 28'.' Vulcanism and Recent Extravasation i n B. C , E. G. L a n g i l l e , 1936. 29V Notes on the Coast Range Batholith - Its Ore Deposits and Zoning, S. C. Robinson, 1936. 30V Ore Deposits of Alaska and Yukon, W. Snow, 1936. 3l'.' T e l l u r i d e s i n B. G., S. C. Robinson, 1936. Note: Lord gives an extremely concise and inter e s t i n g synopsis of the general physiography of the Coast Range with special reference to g l a c i a t i o n and the fracture system. Two compilations that present a clear picture of opposite sides of the ba t h o l i t h are those by Kania (Western Contact) v Of special i n t e r e s t . XIII and Black (Eastern Contact). Snow's tr e a t i s e on Alaska gives a b r i e f consideration of the northern extremity of the batho-l i t h with a detailed rock table and summaries of various reports concerning the ore deposits. Armstrong and Gordon completed a comparatively concise summary of the geology done to date on the Queen Charlottes, while Dalton covered In an excellent manner the southern portion of the Insular Ranges, namely Vancouver Island. I t i s noteworthy that Langille's i n t e r e s t i n g treatment of recent vulcanism i n B. C. i s the f i r s t written by a student at U. B. C. -1-Chapter 1  VULCANISM IN BRITISH COLUMBIA Relations to Mountain Building It i s common knowledge that vulcanism, seismic out-bursts and mountain building are c l o s e l y related. Naturally British. Columbia, being an exceedingly mountainous t r a c t , has i t s volcanic representatives, but they are i n such a state of quiescence that so f a r l i t t l e notice has been taken of them. It i s only recently that actual "cones" have been c a l l e d to the attention of observers and received close scrutiny. Trie t h e o r e t i c a l considerations of vulcanism are beyond the scope of this work, and therefore they receive l i t t l e attention other than mere mention. I t has long been a matter of i n -terest that seismic and volcanic belts l i e c l o s e l y adjacent to deep crustal embayments}or downwarps, such as that beyond the continental shelf of B r i t i s h Columbia. Actual causes of volcanoes are as yet highly contested hypotheses, thereby showing lack of s u f f i c i e n t confining data. The lack of volcanic a c t i v i t y i n the centers of continental masses, and the r e l a t i v e abundance of Islands born of vulcanism (appearing and disappearing) proves conclusively that there Is a close relationship between these outbursts of molten magma and subsiding continental margins. Mountain chains, with t h e i r attendant f a u l t i n g , are the agencies that produce l o c a l -2-pressure release and allow conditions that consummate i n extravasation. There i s l i t t l e doubt as to the permanence of ocean basins and continents, mainly because of the lack of abyssal types of sediments on present land masses, although the marginal areas are of an o s c i l l a t i n g nature. The Igneous Cycle A study of the geological h i s t o r y of B r i t i s h Colum-bia tends to show that magmatic extrusion i s as prolonged as 1 the orogenic disturbances themselves. Quoting Clapp, "In general the Mesozoic igneous rocks conform to the general eruptive cycle of (1) the volcanic phase (2) the ba t h o l i t h i c phase, and (3) the phase of minor int r u s i v e s . The volcanics are composed almost e n t i r e l y of basalts and andesites of a remarkably uniform character. The batholiths are made up of a number of rocks erupted i n a general sequence from basic to acid; and the minor intrusives consist of a few rocks erupted i n a general sequence from acid to basic. The volcanics may have resulted from the eruption, through deep vents, of a but s l i g h t l y d i f f e r e n t i a t e d , primary b a s a l t i c magma. The composite batholiths may have been formed by the more complete d i f f e r e n t i a t i o n of the primary magma i n cham-bers of various s i z e s , the older and smaller and hence more 1. Clapp, C. H. Sooke and Duncan Map Areas V I, G. S. C. mem. 96, 1917, p 14 -3-q u i c k l y c r y s t a l l i z e d and l e s s d i f f e r e n t i a t e d p o r t i o n s s o l i -d i f y i n g t o f o r m t h e more b a s i c r o c k s . The m i n o r i n t r u s i v e s , on t h e o t h e r hand, p r o d u c e d b y t h e i n j e c t i o n o f r e s i d u a l l i q u i d s , w o u l d be drawn s u c c e s s i v e l y f r o m , l o w e r and l o w e r l e v e l s as c r y s t a l l i z a t i o n o f t h e b a t h o l i t h i c masses p r o g r e s s e d downwards, and f o r t h a t r e a s o n t h e y a p p e a r t o have b e e n more b a s i c . " Of c o u r s e i t must be r e c o g n i z e d t h a t e x t r a v a s a t i o n i n B r i t i s h C o l u m b i a has p r o c e e d e d i n t e r m i t t e n t l y s i n c e C r e -t a c e o u s t i m e s , due t o t h e c y c l i c n a t u r e o f i t s d i a s t r o p h i s m and t h e y o u n g e r s a t e l l i t i c i n t r u s i o n s d u r i n g O l i g o c e n e and M i o c e n e t i m e s . R e l a t i o n t o I s o s t a s y G r a v i t y p endulum t e s t s have f i r m l y e s t a b l i s h e d t h e h i g h e r s p e c i f i c g r a v i t y o f o c e a n beds as compared w i t h c o n -t i n e n t a l m a s s e s . Prom t h i s f a c t s p r a n g t h e t h e o r y o f " i s o -s t a t i c A d j u s t m e n t " , o r t h e a t t e m p t o f e a r t h masses o f d i f f e r e n t s p e c i f i c g r a v i t i e s and v a r y i n g v e r t i c a l e l o n g a t i o n t o s e e k an e q u i l i b r i u m on t h e u n d e r l y i n g b a s a l t i c s u b - s t r a t a . J o l y 1 r e f e r s t h e p r o b a b l e l i q u e f a c t i o n l o c a l l y t o r e l i e f o f p r e s s u r e t h r o u g h t e n s i o n s t r e s s e s s e t up i n t h e c r u s t . The t e n s i o n i s a r e s u l t o f u n e q u a l e x p a n s i o n o f t h e s u b s t r a t a due t o i n -s u f f i c i e n t r a d i a t i o n o f h e a t p r o d u c e d b y r a d i o a c t i v e e l e m e n t s . 2 A c c o r d i n g t o L a n g i l l e , "Upon t h e r e l e a s e o f t h e s e h i g h o r d e r 1. J o l y , J . R a d i o a c t i v i t y and t h e S u r f a c e H i s t o r y o f - t h e E a r t h 2. L a n g i l l e , E . G. V u l c a n i s m and R e c e n t E x t r a v a s a t i o n i n B r i t i s h C o l u m b i a B.A.Sc. T h e s i s , U. B. C , 1936, p 14. -4-compression forces on continents through f a u l t i n g and over-thrusting, i s o s t a t i c action causes upthrust sections to sub-side, carrying down adjacent lands. Those bordering lands on the ocean side of the mountain tract sink farther below the sea, while those continental lands bordering the other side of the u p l i f t e d mountain tr a c t also sink below sea-l e v e l . They form long s y n c l i n a l seas, and usher i n an era of volcanic a c t i v i t y . " Energy and Thrust Transmission The dynamic energy that i s able to raise huge columns of lava and cause immense outbursts may be referred to that l a s t residium of mineralizers l e f t over from any magma during d i f f e r e n t i a t i o n - sudden release of pressure on water, for example, would do much to explain independent eruption of c l o s e l y situated vents. L e i t h believes that "The great pressures i n the zone of rock flowage may Impart a high degree of r i g i d i t y to the mass, capable of transmitting thrusts, i n spite of the fact that rock flows.""'" Here, then, i s a theory that allows for transmittal of topographical features over great distances, such as i s required by both Isostasy and vulcanism. 1. L e i t h , C. K. Structural Geology, 1923. 136" 136° 134° 132° 130° 188° 126° IS* - (S2 - ISO" 118" 116" 114" 132* 130° 128" 126° 124" 12" 120'  IIS" '16° 14" Mop * A c t i v i t y Although i t occupies about one - t h i r t i e t h of the P a c i f i c volcanic r i n g , B r i t i s h Columbia i s i n a state of decreasing a c t i v i t y . There were numerous explosive craters during the Pleistocene, whereas at present there i s r e l a t i v e quiescence. No volcanoes are active i n B r i t i s h Columbia now, although Edgecomb to the north and Baker to the south have evinced s l i g h t disturbances recently. The accompanying map # /. of the province shows the approximate locations of recent eruptions so f a r discovered. These are Ruby Creek, Blue River (tributary of the Unuk), Hoodoo Mt., Nass River (Tseaux River), Milbank Sound (Lady I s . ) , Mann Creek, Gun Creek, L i l l o o e t , Garibaldi and Mt. Waddington. I t appears highly probable that Crater Mt., just north of Ashnola River near Keremeos, southern B r i t i s h Columbia, belongs to this Recent group. This l a s t example has had very l i t t l e geo-l o g i c a l study, but i t s lavas show extreme youth and freshness. Tseaux River Flows As shown by tree growth, the flow of Tseaux River i s probably the youngest. Hanson states the age of the oldest tree rooted on the flow i s less than 180 years. Since lavas r e a d i l y and quickly form f e r t i l e s o i l , the age l i m i t of the Tseaux flow must be less than 300 years. Quoting Hanson^ , 7 " 1. Hanson, G. Reconnaissance between K i t s a u l t R. and Skeena R., B. C. Summ. Report, 1922, Part A, p 44A -6-"This i s a lava flow 20 miles long covering an area of 20 to 25 square miles, and i s the youngest lava flow so f a r . recognized i n B. C." This statement i s backed by McEvoy 1 (1893). Interrupted drainage i s one of the most outstanding features of Recent vulcanism i n the province. The Tseaux flow came from one large and several smaller cones and flowed across and down a creek v a l l e y into the Tseaux River, follow-ing t h i s channel to the Nass. In so doing i t dammed the small creek and Tseaux River, thus forming two lakes. I t was s u f f i c i e n t l y unconfined when i t reached the Nass to do l i t t l e more than force the water to the f a r side and create a canyon. Scoria was erupted to form a small cone around the crater. The flow i s extremely fragmental, probably due, as 2 Hanson thinks, to "explosions from saper-heated steam", much water having been present. The lava i s an enstatite-andesite with a more basic facies of basalt. I t might be noted that Hanson examined other enstatite-andesite flows a few- miles S E of Ali c e Arm, that were of probable Late Te r t i a r y or Pleistocene age. These are several hundred feet thick, and b a s a l t i c dykes with the appearance of "feeders" occur nearby. This i s a s t r i k i n g l y i n t e r e s t i n g proof of the intermittency of eruption of lavas of similar composition. 1. McEvoy G. S. C , 1893, Part A, p 14. 2. Hanson, G. Reconnaissance between K i t s a u l t R. and Skeena R., B. G. Summ. Report, 1922, Part A, p 44A. -7-Blue River Unuk River vulcanism of Recent age i s so f a r con-fined to i t s tr i b u t a r y , the Blue River. Wright"'"states that the source of these eruptions has not yet been determined, but the flows came down Canyon Creek and the Blue River from the north, forming three narrow canyons by forcing the water to the south wall of the Unuk. A lake resulted from the damming of the Blue River near i t s confluence with the Unuk. These flov/s are exceedingly porous and cause spouts of water along the north bank of the main r i v e r . Volcanic ash present i n the Unuk River basin has probably come from the same vents that supplied the flows, but at a l a t e r date. Its presence was noted by Wright. "Volcanic ash can s t i l l be seen as black patches on g l a c i e r peaks eight to ten miles distant.""'' Garibaldi Garibaldi has also had i t s drainage interrupted by flows of varying ages - some Post-Pleistocene and some Pre-Pleistocene. A flow of reddish-brown andesite from the western crater of Red Mountain, just f i v e miles to the north of G a r i b a l d i , dammed the Cheakamus River v a l l e y , forming a lake. An examination by Burwash, of a dissected portion of the flow, showed that i t rests "upon a g l a c i a l t i l l and 1. Wright G. S. C. Summ. Rep., 1905, p 50. -8-upon r o c k s u r f a c e s w h i c h b e a r s t r i a e b e l o n g i n g t o b o t h p e r i o d s of g l a c i a t i o n . These l a t e r l a v a streams are t h e r e -f o r e u n d o u b t e d l y p o s t - g l a c i a l . 1 , 1 Burwash's r e p o r t i n d i c a t e s o t h e r p r o b a b l e v o l c a n i c cones on d i s t a n t peaks t o the n o r t h , w h i c h presages the thought t h a t many o t h e r c e n t e r s of Recent e x t r a v a s a t i o n are y e t t o be f o u n d i n B r i t i s h Columbia. 2 Burwash d e s c r i b e s G a r i b a l d i as the l a r g e s t of i t s group and the h i g h e s t peak i n the a r e a , w i t h a summit 8,700 f e e t above s e a - l e v e l and 3,500 f e e t above the s u r r o u n d i n g p l a t e a u . I t l i e s 12 m i l e s f r o m t i d e w a t e r , and i s so com-p l e t e l y c o v e r e d by snow and i c e t h a t l i t t l e o f i t s f i e l d r e l a t i o n s can be d e c i p h e r e d . The W a l l s of the c i r q u e s , w h i c h have been gouged i n t o i t s s i d e s , a f f o r d e x c e l l e n t s e c t i o n s of the cone i t s e l f , showing t h a t i t i s l a r g e l y f r a g m e n t a l and composed of r e d d i s h l a v a . The l a t t e r extends down i n t o the Cheakamus V a l l e y . D i s s e c t i o n has been d i s t i n c t l y r a p i d , c a u s i n g the l o s s of c o n i c a l symmetry and ease of I d e n t i -f i c a t i o n of the c r a t e r . A l p i n e g l a c i a t i o n has r e n d e r e d e x c e e d i n g l y d i f f i c u l t any a c c u r a t e d e t e r m i n a t i o n of the age of the G a r i b a l d i o u t b u r s t , i t s e f f e c t s b e i n g superimposed upon, and p a r t l y removing, t h o s e of the l a s t advance of the c o n t i n e n t a l i c e - s h e e t . Burwash made a s t u d y of g l a c i a l t i l l i n C a p i l a n o V a l l e y ( n e c e s s a r i l y a P l e i s t o c e n e p r o d u c t ) , and 1. Burwash, E. M. P l e i s t o c e n e V u l c a n i s m of the Coast Range of B. C., p 262. 2. Burwash, E. M. J o u r n a l of G e o l . , V o l X X I I , No. 3, 1914. -9-discovered there much lava c h a r a c t e r i s t i c of Garibaldi's e a r l i e r flows. Since intervening high ridges form a bar r i e r that could not be surmounted by Recent f l u v i a l transportation, the lava must have been part of a pre-rleistocene or early Pleistocene extrusion. This lava could not have come from the other much lower cones due to th e i r p o s i t i o n . Two un-glaciated cones l i e upon glaciated surfaces of Red Mountain, f i v e miles north of Garibaldi. An older cone on the same mountain shows effects of the intense ice action which carved out those cirques containing the la t e r cones. The conclusion to be drawn i s a corroboration of that from other f i e l d evidence - vulcanism i s , and has been, i n a stage of com-parative intermittency i n B r i t i s h Columbia since the l a s t minor diastrophism of Miocene age when immense floods of lava covered the surface of both flanking areas of the batho-l i t h . Most of this l a t e r extravasation has been centered either i n the b a t h o l i t h i c areas or close to the margins, and can be expected to recur i n the not distant future with infrequent but explosive outbursts. The fact that most of the cones l i e i n cirques i n the Garibaldi center may be attributed to r e l a t i v e l o c i of c r u s t a l weakness created by ice gouging. -10-M l l b a n k A r e a DoImage"'"made a d e c i d e d l y I n t e r e s t i n g s t u d y of the M i l b a n k Sound cones and f l o w s w h i l e s u r v e y i n g the c o a s t a l a r e a between Burke and Douglas C h a n n e l s . T h i s c e n t e r o f a c t i v i t y l i e s 340 m i l e s N W of G a r i b a l d i and 160 m i l e s s o u t h of t h e Nass R i v e r f l o w s , and i s p a r t of the I s l a n d F r i n g e or Western Pendant a r e a . Most of the s u r r o u n d i n g r o c k s are q u a r t z - d i o r i t e - a m a r g i n a l phase of the g r a n o d i o r i t i c b a t h o l i t h c o r e w h i c h d i s a p p e a r s s l i g h t l y t o the e a s t i n a g r a d u a l embayment. Here i t might be n o t e d t h a t most of the c e n t e r s of e x t r a v a s a t i o n are l o c a t e d i n c l o s e p r o x i m i t y t o the a n c i e n t r o o f h o r i z o n of the main J u r a - C r e t a c e o u s b a t h o -l i t h , and t h a t t h e y a r e o f t e n accompanied by n e i g h b o r i n g hot s p r i n g s . These c e n t e r s p r o b a b l y r e p r e s e n t a g r a d u a l c o o l i n g of the g r a n o d i o r i t e c o r e by means of p r e s s u r e r e l i e f t h r o u g h c r u s t a l d i s p l a c e m e n t . The M i l b a n k Sound e r u p t i v e s a r e s c a t t e r e d a l o n g a N W - S E l i n e , or p a r a l l e l t h e " g r a i n " of the f i o r d - l a n d . Dolmage l o c a t e d t e n e x t r u s i o n s ( b a s i c or t u f f a c e o u s ) of l i m i t e d s i z e , but d i s c o v e r e d o n l y two v e n t s . One cone formed a steep t u f f a c e o u s mound about 1,000 f e e t h i g h on Lake I s l a n d , w h i l e the o t h e r , composed m a i n l y o f l a v a , was a cone 600 f e e t h i g h on S w i n d l e I s l a n d . Ample e v i d e n c e of p o s t g l a c i a l age was o b s e r v e d i n f o u r d i f f e r e n t p l a c e s . Quoting Dolmage, "At another l o c a l i t y the t u f f s r e s t on what 1. Dolmage, V. P o s t P l e i s t o c e n e V o l c a n i c s o f the B. C. C o a s t . -11-appeared t o be a bed of t i l l . I n many o t h e r p l a c e s , where the base of the t u f f s i s exposed, l a r g e b o u l d e r s up t o s i x f e e t i n d i a m e t e r were found r e s t i n g upon the u n d e r l y i n g q u a r t z - d i o r i t e , and b u r i e d i n the t u f f s . Some of these showed a s t r o n g tendency t o e x f o l i a t e . A l l these phenomena i n d i c a t e t h a t the t u f f s a r e of p o s t - p l e i s t o c e n e age." B a r d s w e l l and P r i c e The o c c u r r e n c e s on B a r d s w e l l and P r i c e I s l a n d s c o n s i s t of f l o w s w i t h o u t t u f f s , and t h e i r r e l a t i o n t o the g l a c i a t e d s t i r f a c e was n o t d i s c o v e r e d , a l t h o u g h they do not conform t o the p r e s e n t topography. The Lake I s l a n d t u f f s are of a b r o w n i s h c o l o u r and c o n t a i n numerous fragments o f q u a r t z d i o r i t e . Those on Lady I s l a n d c o n s i s t of r o c k f r a g -ments ( p r o d u c t s of e x p l o s i o n ) , and a l a r g e amount o f spher-u l i t i c and pumaceous v o l c a n i c g l a s s w h i c h g i v e s the brown c o l o r t o the r o c k . Much c l e a n a m b e r - c o l o r e d a u g i t e , u s u a l l y s h a t t e r e d and g l a s s - c o a t e d , accompanies the q u a r t z , h o r n -b l e n d e and rounded p h e n o c r y s t s of y e l l o w l a b r a d o r i t e , The l a t t e r i s a c h a r a c t e r i s t i c m i n e r a l i n t h i s a r e a . Some of the f l o w s are much b l a c k e r due t o l a r g e amounts of f i n e m a g n e t i t e . B a s a l t Dyke R e l a t i o n s The c o a s t a l s e c t i o n i s a l s o e x t e n s i v e l y f i s s u r e d by young dykes of a c h a r a c t e r i s t i c v e s i c u l a r l a v a - l i k e 1. Dolmage, V. P o s t Pleistocene V o l c a n i c s of the B. C. C o a s t , p 43. -12-appearance. They show sudden c h i l l i n g which points to con-ditions of low temperature and pressure.' According to Dolmage "Many of them contain glass, and some of them, up to 12 feet i n width, are composed e n t i r e l y of volcanic glass with a few spherulites and mi c r o l i t e s . " Furthermore, these dykes exhibit other features common to lavas such as columnar j o i n t i n g , amygdules, p e r l i t i c , nodular and flow structures. It would appear that they were feeders to the flows and now exposed by erosion of the overlying lava. Some of them are undoubtedly pre-Pleistocene, pointing to a period of ex-trusion l a s t i n g from the Pliocene to the Recent. Clearwater Flows The Ray Mountain flows i n the Clearwater Lake area 2 were f i r s t reported by Davis as late as 1929. They are unglaciated and unusually fresh i n appearance. No crater i s present, but one f i v e - f o o t dyke of olivine-basalt has been exposed by erosion of the overlying lava. This dyke may be a vent, and i s probably accompanied by others s t i l l buried by the flows.- A ten-foot waterfall was formed at the foot of Clearwater Lake by a stream of lava flowing down from Ray Mountain. The flow was a quarter of a mile wide, eight miles long, and extended one and a half miles down Clearwater 1. Dolmage, V. Journal of Geology, Vol. XXXII, Jan. Feb., 1924, p47. 2. Davis, N. F. G. Summ. Report 1929, G. S. C , p 290. -13-Valley. The thickest section i s right at the peak, where i t has the appearance of having come from a long f i s s u r e opening now buried by lava. The rock i s mainly a dark, blocky-weathering, olivine-basalt with phenocrysts o f . o l i v i n e and augite. Much magnetite i s present and often occurs as inclusions i n the augite. Above this predominating type l i e s a reddish, scoriaceous t u f f which weathers to a fine red dust, coloring Ray Mountain. The flow presents t y p i c a l ropy or "pahoehoe" structure, elongated vesicules and flow banding. According to Davis "The surface of the flow at the foot of Clearwater Lake i s generally f l a t but rough and un-grooved v/ith no e r r a t i c s on i t , and i s i n marked contrast with the g l a c i a l ridge to the west upon which the lava over-laps."^ The presence of g l a c i a l d r i f t beneath the lava at other points removes a l l p o s s i b i l i t y of i t s being pre-Pleisto-cene. Ruby Creek Flows 2 Gwillim recorded Recent flows 16 miles northeast of A t l i n where the lava, a grey basalt, has floored Ruby Creek and confined i t to a narrow canyon. At thi s l o c a l i t y a cone was b u i l t 2,000 feet above the surrounding terrane. 1. Davis, N. F. G. Clearwater Lake Area, B. C. Summ. Report; 1929, part A. 2. Gwillim, "fl\ C. A t l i n Mining D i s t r i c t , B. C. Vol XII, 1899, G. S. C. -14-Mann Greek Another Recent flow was reported by Uglow i n 1921 when he was surveying the North Thompson River area. Two ten-foot lava beds are exposed on one side of Mann Creek. They are separated by ten feet of cinders and overlie an unconsolidated assortment of coarse stream gravels. The flows interrupted the drainage of Mann Creek^and formed a canyon by forcing the water to one side of the channel. This lava i s andesitic and of a highly vesicular texture. i n . = t H . Note:-T h e gorge is poof-glacial. 1. Uglow G-. S. G. Summ. Rep., 1921, p 88. Volcanic Ash. - Bridge River The Bridge River area has a widespread occurrence of volcanic ash which reaches a depth of 22 inches In the South Fork. This i s according to Bateman1 who suggests that the originating vent l i e s between the headwaters of Bridge River and L i l l o o e t River. The material Is i n three separate beds, probably from d i f f e r e n t vents, and i s a white, pulverulent, scoriaceous material which varies i n size from powder to two-inch fragments. These ash beds cover an area of approximately 1,500 square miles and usually overly very Recent gravels. .Their extreme lightness and non-resistance to erosion are i n d i r e c t proof of th e i r Recent age. So far the ash has proven of l i t t l e commercial value and has, therefore,received very l i t t l e attention from the Geological Survey. Iskut River The Hoodoo Mountain group of Recent volcanics l i e s about 30 miles upstream from the mouth of the Iskut River, a tr i b u t a r y of the S t i k i n e . There are six d i s t i n c t lava beds that make up a thickness of about 4,000 feet. Flow breccias separate the flows, and the basal member rests on an old erosion surface - a conglomerate containing pebbles of meta-morphosed sediments, older volcanics and Coast Range g r a n i t i c 1. Bateman G. S. C. Summ. Rep., 1912, p 188. -16-rocks. The flows show columnar jo i n t i n g and are a l l very much a l i k e , being composed of white, basic feldspar pheno-crysts i n a dense, black or dark brown groundmass. Quoting Kerr, "North of the confluence of Craig and Iskut Rivers there r i s e s one of the most magnificent and interesting mountains i n northern B. C : a volcano which probably began erupting i n the late Pleistocene and v/hich has continued intermittently to such recent times that i t seems reasonable to expect that the volcano may s t i l l be active and capable of further eruptions." 1 The mountain i s not rugged, but has gentle slopes with a f l a t top at an elevation of over 6,500 feet. I ts horizontal cross section i s roughly c i r c u l a r . Occasional pyramid-like forms, or "hoodoos", project from the steeper slopes, r e s u l t i n g i n the weird appearance that has given the mountain i t s name. The old crater i s now f i l l e d with i c e which projects i n tongues. Erupted i n the center of an old v a l l e y , Mt. Hoodoo has dammed the two main t r i b u -taries of the old drainage system and created two ice lakes from which magnificent g l a c i e r s extend and encircle the base of the mountain. Description of Hoodoo There are delta deposits, p i s o l i t i c mud and con-solidated d r i f t interbedded i n the lava which make up a 1. Kerr;,:E. A. Preliminary Report on the Iskut R. Area, B. C. Summ. Report, 1929, part A, p 52A. -17-thickness as great as 200 feet. Some of the interflow breccias are consolidated talus and others are simple due to v i s c o s i t y of flow. The upper surface flows are badly broken up due-to v e s i c u l a r i t y and "aa" character. Dykes intrude the lava i n a l l directions and, although composed of material similar to the lava, they are more resistant to weathering. Kerr states thattthere i s much evidence to support the b e l i e f that the f i r s t eruptions took place when the area was ice covered i n the late Pleistocene. Many-thin flows show only s l i g h t downcutting by stream action, and would therefore appear exceedingly recent i n age. Other Flows A considerable extent of the Iskut Valley i s covered with lava flows of an appearance similar to those of Hoodoo Mountain. They constitute the western l i m i t of a series that has blocked the Iskut River and i s now i n c i s e d by the canyon water. Pleistocene Flows The Eagle River area of Dease Lake D i s t r i c t con-tains many volcanic flows of probable early Pleistocene and Late Te r t i a r y age. There are several volcanic cinder cones i n the Eagle River country that are over 1,000 feet high. They are steep-sloped, f r i a b l e and e a s i l y eroded. E r r a t i c s occur on the summits and slopes, but the lack of erosion would seem to indicate a late Pleistocene age for the flows. Lava flows underlain by gravels on the west bank of the Tahltan river at the t r a i l cross-ing. Cassiar d i s t r i c t of British Columbia. -18-Elongation i s i n the d i r e c t i o n of the flow of i c e . Gravels overlain by lava occur i n many places on the' north side of the Stikine as f a r as Tahltan. Thus the series of flows (at least four as determined by Dawson"*") has confined the Stikine to a canyon-like course i n i t s upper reaches, although the v a l l e y i t s e l f i s very broad. The can-yons average about 300 feet deep, mainly In the lava, but i n some instances i n the older rocks where the flows have f i l l e d the former v a l l e y and forced the stream to re-entrench along-side. Sometimes the upper flows f i l l channels cut i n the lower ones. The gravels i n the higher, lava-buried channels were probably derived from g l a c i a l d r i f t , f or they contain many boulders of g r a n i t i c rock up to one foot i n diameter, which are foreign to the l o c a l i t y and must have been derived from some source at a considerable distance. According to Johnston i t i s probable, therefore, that some of the l a t e r , If not a l l the lava flows,are Pleistocene i n age. The lowest gravels are s l i g h t l y d i f f e r e n t from the highest, being less unconsolidated and f i n e r . I t v/ould appear that the lava overlying these i s late T e r t i a r y . Gravels overlain by volcanic t u f f s occur i n the bed of a small creek flowing into L i t t l e Eagle River. The tuffs contain numerous glaciated boulders of g r a n i t i c rock. 1. Dawson, G. M. G. S. G. Pub. No. 629, pp 67-70. 2. Johnston, W. A. G. S. C. Summ. Rep., 1925, part A. Gold Placers of Dease L. Area, Cassiar D i s t r i c t , B. C. -19-The l a s t f l o w nearby shows s i g n s of some g l a c i a t i o n . There-f o r e the v o l c a n i c a c t i v i t y must have been d u r i n g an i n t e r -g l a c i a l p e r i o d . . Tuya Lake K e r r ^ r e p o r t s the e x i s t e n c e of a huge a r e a of p r ob-a b l e P l e i s t o c e n e v u l c a n i s m i n the Tuya Lake p l a t e a u r e g i o n . Much of the a r e a i s capped by f l o w s and p r e s e n t s a r e m a r k a b l y f l a t appearance except f o r a number of huge b l a c k v o l c a n i c cones. The a r e a a d j a c e n t t o Dease Lake i s a l s o i n t e n s e l y c u t by young b a s a l t i c d y k e s . The f l o w i n the v a l l e y of Canyon Creek i s about 40 f e e t t h i c k , a n d , due t o i t s narrow-ness and l e n g t h , p o i n t s t o g r e a t l i q u i d i t y of the m o l t e n l a v a . I t i s c e r t a i n t h a t the f l o w s d i d not come from one s i n g l e f i s s u r e , b u t f r o m numerous s m a l l cones and s m a l l f r a c t u r e s . K e r r s t a t e s t h a t a l l the cones he examined have the f e e d i n g p i p e s t i l l apparent near the c e n t e r . S l o u g h Mountain i s made up almost e n t i r e l y of e x t r u d e d l a v a s c u t by d y kes. The Canyon Creek l a v a i s f i n e l y c r y s t a l l i n e and c o n t a i n s a l i t t l e g r e e n g l a s s y o l i v i n e . The base of the f l o w i s somewhat s c o r i a c e o u s . Most of the dykes are more compact and c o a r s e l y g r a n u l a r w i t h w h i t e f e l d s p a r and g reen hornblende p h e n o c r y s t s . K e r r s a y s , " A l l the specimens examined m i c r o s c o p i c a l l y are b a s a l t s . The Canyon Creek l a v a 1. K e r r , P. A. Dease Lake A r e a , C a s s i a r D i s t r i c t , B. C. Summ. R e p o r t , 1925, p a r t A, page 94A. -20-consists of: augite 10-15%, ol i v i n e 20-30fo, bytownite 60-70% and magnetite 3-5%. Associated v/ith the lavas are many t u f f s , breccias and agglomerates. Hot springs are common around the base of some of the cones i n the Dease Lake area. B e l l a Coola Area 2 Dolmage found a large section of Tert i a r y lavas, with some indications of a few Pleistocene flows, i n the Tatl a - B e l l a Coola d i s t r i c t . The small ranges (Rainbow, Ilgachuz and Itcha) adjoining the eastern flank of the Coast Range are composed large l y of these rocks. Three small bodies of fresh lavas (thought to be late T e r t i a r y or early Pleistocene i n age) were found - one at the base of Kappan Mountains, another i n West Homathko Valley, and a third' on the west side of Middle Lake. The f i r s t two are b a s a l t i c , as are'the T e r t i a r y lavas, but the l a s t i s a coarse porphyritic r h y o l i t e . Koshin River Cockfield made a study of the flows between Koshin River and Tahltan River but found no evidence of Recent or Pleistocene flov/s away from the Tahltan area described above. 1. Kerr, P. A. Dease Lake Area,.-Cassiar D i s t r i c t , B. C. Summ. Report 1925, part A, p96A. 2. Dolmage, V. Tat l a - B e l l a Coola Area, Coast D i s t r i c t , B. C. Summ, Report 1925, part A, p 155. 3. Cockfield, W. E. Explorations between A t l i n and Telegraph Creek, B. C. G-. S. C. Summ. Rep. 1925, part A, p 25. -21-He states that the amcaint of erosion, since the formation of the upper flows i n the d i s t r i c t studied, i s very great, for canyons 1,500 feet or more deep have been cut through these rocks. Pearce Island While examining the coastal area between Douglas Channel and the Alaskan Boundary, Dolmage^found a single area of Recent or Pleistocene vulcanism on Pearce Island. A thickness of 20 feet of volcanic breccia occupies a few hundred square yards on the most northern point of the i s l a n d . The rock i s fragmental, consisting of pebbles of a l l sizes of gneiss, s c h i s t , t u f f , porphyrite, granodiorite and quartz d i o r i t e with a l i g h t greyish-green, fine-grained matrix including quartz, oligoclase,•andesine, orthoclase, hornblende, c h l o r i t e , u r a l i t e , s e r i c i t e , c a l c i t e and micropegmatite. Relation to Hot Springs I t i s i n t e r e s t i n g to note that Dolmage's study of the hot springs scattered along the coast, and often right in the heart of the Coast Range, has shown a great proportion of them to be issuing from fissures i n the quartz-diorite of the batholith.. The presence of schist i s not a prere-q u i s i t e , and Dolmage believes that the springs are not 1. Dolmage, V. Coast and Islands of B. C. between Douglas Channel and the Alaskan Boundary Summ. Rep., 1922A, p 18A -22-related to Recent vulcanism but are just another cooling phase of the s t i l l warm g r a n i t i c magmas. "The absence of boron i s a further i n d i c a t i o n that they (the springs) are not related to the Recent vulcanism." 1 Most of the springs occur i n l o c a l i t i e s widely separated from volcanic flows, but they are usually associated v/ith great f a u l t s or shear zones. It appears that these would explain the o r i g i n of the heated waters (being a means of-ascent from great depths). Most-of the springs are sulphate waters (sodium v/ith some calcium). A few are sodium chloride (Surf I n l e t ) . The rocks through which the springs pass are r i c h i n calcium and sodium, but the sulphate and chlorine can not be accounted 2 f o r . A l f r e d H. Brooks and Gerald A.' Warring made a similar study of the springs on the Alaskan side, and attribute them to the fact that they occur i n a region of repeated defor-mation and f i s s u r i n g , some of which took place i n Te r t i a r y time. Mount Waddington A recent f i e l d t r i p has shown Mt. Waddington (one of the highest mountains i n B. C.) to be capped by acid volcanic t u f f s . L i t t l e i s known concerning the age of the 1. Dolmage, V. Geol. of Coast and Islands of B. C. between Burke and Douglas Channels Summ.' Rep., 1921A, p 41A. 2. Brooks, A. H. and Warring, G. A. Mineral Springs of Alaska , Water Supply Paper 418, U. S. G. S., 1917.. 3. Brock, R. W. Personal Communication. HE R E is the highest summit of Mount Waddington (Mystery Mountain), 13,260 feet, ieen under good conditions. About 400 feet of the unclimbablc peak is shown, "I took this photograph from the northwest peak, which is about s'«xty feet lower, an d so plunder a between my feet," Mrs. Don Munday says. The rock* appear anow-c with what m a y be called a gigantic form of hoarfrost. ragile that blue light shone up >ut are encased, many feet thick, -23-r o c k s , but t h e i r f r e s h n e s s and l o c a t i o n a l o n g the a x i s of the Coast Range would p o i n t t o a v e r y r e c e n t o u t b u r s t . T h i s i s p r o b a b l y one o f t h e reasons why the mountain i s so g r a n d l y e l e v a t e d (13,260 f e e t ) . I t i s o n l y r e a s o n a b l e t b expect t h a t o t h e r s of the major peaks w i l l be found t o have s i m i l a r v o l -c a n i c caps. N a t u r a l l y t h a t of Mt. Waddington i s h e a v i l y g l a c i a t e d , s i n c e i t i s s t i l l under an immense i c e sheet w h i c h extends f a r down the v a l l e y . A l a s k a ' " • ' • < Bu d d i n g t o n 1 r e p o r t s . m a n y s m a l l areas of Q u a t e r n a r y b a s a l t i c l a v a a l o n g the m a i n l a n d of s o u t h - e a s t e r n A l a s k a and 2 on R e v i l l a g i g e d o I s l a n d . The v o l c a n i c cone of Mt. Edgecombe on K r u z o f I s l a n d , i n the S i l k a d i s t r i c t , i s formed o f Qua-t e r n a r y l a v a and t u f f - m a i n l y b a s i c a n d e s i t e and b a s a l t . A c c o r d i n g t o Westgate, "Lava, c h i e f l y b a s a l t and a s s o c i a t e d t u f f , i s found a t s e v e r a l p o i n t s a l o n g the shore of Belm C a n a l n o r t h o f Smeatori Bay. The l a r g e s t a r e a , 3 m i l e s l o n g , i s a t P o i n t T r o l l o p , a l o n g s i d e t h e e n t r a n c e t o Smeaton Bay. Two s m a l l areas are found on the west s i d e . o f Belm C a n a l and another a t t h e s o u t h end of the Punchbowl - Rudyerd Bay. Oh the e a s t shore t h e r e i s a s m a l l mass a t E d i t h P o i n t and another two m i l e s n o r t h . These may have been c o n t i n u o u s once w i t h the b a s a l t o f some of the a d j a c e n t s m a l l i s l a n d s , 1. B u d d i n g t o n , A. P.- G e o l . & M i n . D e p o s i t s of S o u t h e a s t e r n A l a s k a B u l l . 800, U. S. G. S. p 278. 2. Knopf, A. The S i t k a M i n i n g D i s . , A l a s k a U. S. G. S. B u l l . 004, p 14 -24-1 including .New Eddy^tone Rock." They are f l a t - l y i n g flows which are confined to the lowlands. At some l o c a l i t i e s they are intensely wave truncated and inc i s e d . Although they are very black when fresh, the Point Trollop lavas are b a s a l t i c and weather to a reddish, color. Winstanley Island has a l i g h t gray augite-andesite which i s extremely fine-grained, but i t contains scattered phenocrysts up to 3 mm. i n length.. Westgate thinks stream erosion, at a time of greater elevation than the present, has had much to do v/ith carving these flows into t h e i r present shape. I f so, the lava must have been either i n t e r g l a c i a l or early Pleistocene i n formation, since u p l i f t i s now going on, and has been since the l a s t advance of the ice-sheet. Yukon • 2 Cairnes states that the southern Yukon i s covered over an area of at least 25,000 square miles by a layer of r v volcanic ash as much as two feet thick. This points to extensive volcanic outbursts of an eruptive nature i n Recent times. 3 Cockfield records numerous volcanics i n the White-horse D i s t r i c t , Yukon. These he c a l l s "Newer Volcanics" and questions t h e i r age - probably late T e r t i a r y or Pleistocene. 1. Westgate, L. G. Geol. and Min. Resources of the Area East of Belm Canal. Unpublished. 2. Cairnes, D. D. Portions of A t l i n Dis., B. C. . G. S. C Mem. 37Q, 1913, p 39. 3. Cockfield, W. E. Whitehorse Dis., Yukon, Mem. 150, G. S. C. 1926, p 33. ^ 3 . Slough mountain,a volcanic cone,Cassiar district,B.,C.. Most of the volcanic c-ones of B.,C. are of this type and can be seen from distant points. Miles canyon,Lewes river. The river is cutt-ing its way down into the basaltic flows which are very fresh in appearance and show their jointing quite clearly. -25-Many of the andesites and basalts are dark and much weathered. Some are d i s t i n c t l y red. The t u f f s present are white to l i g h t pink. I t i s certain that at least some of the flows are f a i r l y recent, because i n the case of Miles Canyon the Lewes River has cut through basalt i n the v a l l e y to a depth of probably less than 100 feet. Some acid volcanics (porphyritic rhyolites) are present i n the eastern h a l f of the Whitehorse D i s t r i c t . These have widely spaced jointing and contain small dykes of acid aporhyolites. Most of the rock i s of a f l i n t y appearance and gives a conchoidal fracture. In places the flows vary to t u f f s (with an appearance similar to the former) which sometimes contain foreign fragments such as granodiorite. The age i s i n d e f i n i t e but i s probably early Pleistocene and i s placed above the "Newer Volcanics" i n the rock column. A summary of Quaternary vulcanism i n B r i t i s h Co-lumbia gives the following interesting points: 1) Much of the extravasation i n B. C. i n the past has been quiet. 2) An increase i n the explosive type was shown i n the early Quaternary (volcanic ash). 3) No active volcanoes i n B. C. at present, although some are very recent (Hoodoo Mt. and Lava Lake). 4) Active volcanoes l i e just north and just south of B. C. (Edgecomb). -26-5) Most of the Quaternary vulcanism l i e s along the eastern contact margin of the batholith. i n areas of sediments. 6) Some a c t i v i t y on the western margin or "pendant zone" and some along the Coast Range axis d i r e c t l y from the intrusive g r a n i t i c rocks (Lake I s . , G a r i b a l d i ) . 7) Therefore d i r e c t l y connected with these g r a n i t i c rocks which must be under tremendous, pressure and at high temperature. 8) The release of pressure i s l o c a l - by f a u l t i n g (under tensional or compr.essional stress as proven by the past geological h i s t o r y of B. C.) r e s u l t i n g i n l i q u i d a t i o n . 9) Source of magma must be f a i r l y deep but from d i f f e r e n t -i a t i o n chamber because both acid and basic flows occur i n the same v i c i n i t y . 10) Deep source because usually basic basalts and andesites. 11) This l a s t idea leads to the perception of a b a s a l t i c or medium composition layer below the acid g r a n i t i c rocks. 12) The Inte r i o r Plateau was a scene of great extravasation i n Miocene and Pliocene times due to a general u p l i f t or upwarp of the area. In some l o c a l i t i e s this a c t i v i t y lasted u n t i l Recent times (Tuya Lake area). 13) Although a c t i v i t y was greatest i n Miocene times, i n the I n t e r i o r Plateau, i t has since become greatest along the b a t h o l i t h i c margins. The Coast Range i s d e f i n i t e l y r i s i n g . I s o s t a t i c adjustment must set i n with resultant stresses, s t r a i n s , rock f a i l u r e and vulcanism. -27-The average composition i s andesitic to b a s a l t i c , with rare variations to r h y o l i t e . This agrees c l o s e l y with Miocene vulcanism. Pre-Miocene extravasation tended to be more andesitic ( T r i a s s i c ) and more explosive with r e s u l t i n g t u f f s i n abundance. Unbelievable thicknesse's of volcanic rocks accumulated. Volcanic a c t i v i t y i s to be expected i n the not distant future i n B. C. because of i t s c r u s t a l movements, but i t should not be intense or prolonged, just explosive. Huge cones may then be b u i l t up similar to those of Alaska and the northern U. S. A c t i v i t y has been intermittent since Eocene times -including the Pl e i s t o c e n e ( I n t e r g l a c i a l ) . B. C. i s lagging f a r behind her southern neighbor as far as elevation i s considered. The Si e r r a Nevadas were u p l i f t e d 5,000-7,000 feet i n the early Pleistocene and late Pliocene and are s t i l l going up. This i s shown by the even coast-line. The Miocene flows (lying unconformably on d e f i n i t e Oligocene conglomerates) are 9,000-10,000 feet thick, and may be traced from the northern States into the Yukon. This immense thickness i s c e r t a i n l y related to diastrophism which folded Oligocene beds. Volcanic accumulations i n Eocene times on Vancouver Island amounted to 8,000 feet i n thickness (basalts). Oligocene flows were also of a great thickness (Tulameen) Chilco lake(a fiord valley lake). Looking south from Mt. Tullin. Note the cranked pattern. Such lakes of many miles in length are charact-eristic of B.,C. along the eastern margin of the Coast Range. There is no doubt that some downfaulting has occurred along this disturbed belt but the drainage is mainly controlled by the fractures. pounded top of a mountain below the level representing the upper limit of Pleistocene continental glaciation. Tracy Arm of Holkam bay. The elevation is 4000 feet. Often such mountains are cut away on top by ice action and are then known as scarred domes. Tracy Arm,a fiord in south-eastern Alaska. View looking east. The valley is three-fifths of a mile wide at sea level,one thousand to twelve hundred feet deep and its walls are more than a mile high. -28-C h apter I I  FIORD SYSTEM OF BRITISH COLUMBIA I n t r o d u c t i o n B r i t i s h Columbia's m a g n i f i c e n t f i o r d - c o a s t r a n k s h i g h i n comparison w i t h the g r a n d e s t i n the w o r l d . I t s d e e p l y i n d e n t e d , i s l a n d - s t u d d e d m argin may be t r a v e r s e d t h r o u g h u s u a l l y narrow, b o l d l y s c u l p t u r e d c h a n n e l s f o r a d i s t a n c e of almost 1,000 m i l e s . I n t h i s d i s t a n c e t h e r e i s an i n t e n s e p h y s i c a l change. The snow l i n e descends from 6,000 f e e t i n the s o u t h t o about 3,000 f e e t i n the n o r t h , r e s u l t i n g i n a f l o w of g l a c i e r i c e d i r e c t l y t o the sea i n Taku I n l e t . C o n c l u s i o n s The o r i g i n of f i o r d s has g i v e n r i s e t o two opposed t h e o r i e s , the t e c t o n i c and the g l a c i a l e r o s i o n t h e o r i e s , which, have enough i n common t o suggest r e c o n c i l i a t i o n . R e p r e s e n t a t i v e s u p p o r t e r s of the two views are J . W. Gregory ( t e c t o n i c ) and W. M. D a v i s i g l a c i a l e r o s i o n ) . D a v i s m a i n t a i n s ur_at a f i o r d system i s the n t i c u r a l r e s - I t of v a l l e y g l a c i u o i o n of a s t a b l e , d i s s e c t e d c o a s t a l h i g h l a n d , a l t h o u g h he a l l o w s t h a t the p r e - G l a c i a l d r a i n a g e may have been f r a c t u r e c o n t r o l l e d . He does, however, r e g a r d t e c t o n i c c o n t r o l as n o n - e s s e n t i a l t o the f o r m a t i o n of f i o r d s . -29-Gregory continually emphasizes earth movements as the cause of present levels of the f i o r d v a l l e y f l o o r s be-neath the sea, but he does not claim that favilting i s a general cause of these forms. He places t h e i r o r i g i n i n f l u v i a l erosion of fractured and u p l i f t e d table-lands of hard rock bordering the sea. Here i t seems only natural that, due to the intense system of fracturing which has undoubtedly controlled the coast l i n e , much greater erosion along these directions i n an otherwise tough g r a n i t i c rock would produce f i o r d forms such as are found. Gl a c i a t i o n has, without question, moderat-ed a l l u v i a l action by widening the v a l l e y walls and disrupting l a t e r drainage with i t s debris. Probably, i f i t be assumed that the weight of ice played a major part i n subsidence of the coast-line, i t can be said that g l a c i a t i o n did produce our "drowned" v a l l e y s , but through, action of gravity and not of erosion. M. A. Peacock^has found that earth movements, stream erosion and g l a c i a l erosion have a l l played important parts i n the physical evolution of the f i o r d s of B. C. Tectonically, the continental margin i s a fractured and u p l i f t e d plateau that was deeply dissected before Pleistocene time. Longitudinal f a u l t i n g contributed to the formation of the Island Fringe and regional subsidence was responsible for 1. Peacock, M. A. Fiord-land of B. G. B u l l , of Geol. Soc. of America, Vol. 46, No. 4, p 693. -30-the drowned nature of the f i o r d basins. G l a c i a l l y the pre-rleistocene valleys were troughed ana bu^ined with the pro-duction of many minor physiographic forms such as truncated spurs. Description The main c o r d i l l e r a n trend i s generally one of arcs curving towards the P a c i f i c and connected by rounded cusps heading inland. The area being considered i s made up of one such arc. This Western B e l t ^ i s composed of two main mountainous t r a c t s , an Island Range and a Mainland Range, which are separated by an inland waterway of probable orogenic down-folding. In general plan the coast land i s crescent-shaped and convex toward the P a c i f i c . I t l o c a l l y resolves i t s e l f into a series of variously curved reaches which are repeated i n the s i m i l a r l y curved margins of Vancouver and Queen Charlotte Islands. The Coast Range i s mainly granodiorite with large, probably thin, cooling margins of quartz-diorite varying l o c a l l y to u l t r a b a s i c s . The plutonics have been much denuded, leaving scattered roof-pendants and inclusions of various sizes - a l l v/ith a remarkable SE-NW alignment. I t i s to be noted that such areas of schisted rock must have been eroded at a much more rapid rate than the surrounding g r a n i t i c 1. Geographic Board of Canada. Nomenclature of the Mts. of Western Canada, Ottawa, 1918. FRONTISPIECE This i s a view of the North shore of Burrjard Inlet one of B.C.'s f i o r d s . The mts shown average between"6'000,-5000l whereas just a few miles north they approximate 7000'-8000'. They are composed mainly of granodiorite of the Coast Range b a t h o l i t h . A few remnants or pendant areas of schistoce rocks scattered along the shores of Howe Sound and Burrard Inlet(Capilttno Canyon rocks f o r example)mark the aacient roof horizon of the b a t h o l i t h where i t appears to plunge f a i r l y steeply in an embayment marked by the Eocene and Oligocene sediments of the Puget Sound and Eraser Delta areas.It may be that the end of the Coast Range of B.C. i s located here e i t h e r because of erosion across i t by the Eraser River as an "antecedent" stream or because there was no u p l i f t and orogeny here (south of Busrard I n l e t ) i n the Jura-CtBt- Disturbance-the ac t u a l southern extension l i e s further ea3t "en echelon. Probably both factors are worthy of consideration -Some down f a u l t i n g has occurred but i s of l i t t l e consequence i n explaining the o r i g i n of the trough. The rounded contours of g l a c i a t i o n may be seen as high as 5000' on Grouse and Crown Mts. ro 0) 0) Q O III I ' l , , , ' ! " O-DI o 'ill III o o o o o o o 0 o 0> o o o 1 1 1 ' I ' I I i |U I In 3 •As. Quao.n Cho r/otle Is/crnds. nzidG Ch a n ne:/• I a rial. side Channel. /fo m Trincess Royal Or Prjrcner Is. — Inside Channef. - As in BanKs or 'Pitt Is. Inside Channel. fi»'.'l j li-Ti —Mineralized pendant" as in Hidden Cree* mine. Glacier: Glacier: I111'I ' ' I'M i 1 • « • , • i • i • 111 i 0) o o 0 O 0) Of o §• 0) (J) 3 Q s. Q P> v. Y 51 •2 i a o o o s > .1 U 5 1 i 5 -31-t e r r i t o r y and must, t h e r e f o r e , h a v e h a d much, t o do with, t h e l o c a t i o n o f d r a i n a g e l i n e s d u r i n g t h a t p e r i o d when t h e r o o f was b e i n g s t r i p p e d . N a t u r a l l y t h e p o s i t i o n o f t h e l o w e s t p e n d a n t s was d e p e n d e n t on f o l d i n g and t h e h o r i z o n t a l com-p r e s s i o n t h r u s t s p r o d u c i n g B r i t i s h C o l u m b i a ' s f r a c t u r e s y s t e m . O b v i o u s l y most o f our waterways s t r i k e i n t h i s SE-NW d i r e c t i o n and a r e f l o o r e d b y s c h i s t r e m n a n t s . F o r p r o o f o f t h e o u t -s t a n d i n g o r i e n t a t i o n o f t h e s e r o o f p e n d a n t s i t i s o n l y n e c e s s a r y t o t r a v e r s e one o f t h e c o a s t a l i s l a n d s s u c h as P i t t o r P r i n c e s s R o y a l I s l a n d . Here t h e v a r i a t i o n s f r o m s c h i s t t o g r a n o d i o r i t e may be l i k e n e d t o t h e c o r r u g a t i o n s o f a t i n r o o f . I n t h e t w e l v e - m i l e w i d t h s o f P i t t I s l a n d t h e r e a r e a t l e a s t t e n n a r r o w bands o f h o r n e b l e n d e , m i c a , g a r n e t s c h i s t s and metamorphosed l i m e s t o n e s s e p a r a t e d b y g e n t l e u n d u l a t i o n s , m a i n l y o f q u a r t z - d i o r i t e . The m a j o r , p r e v i o u s l y l o c a t e d v a l l e y s on t h e s e i s l a n d s a r e n o t d e p e n d e n t on t h e p e n d a n t s , b u t y o u n g e r d r a i n a g e i s l a r g e l y c o n t r o l l e d b y t h e s e numerous c o n t a c t s i n a " t r e l l i s " p a t t e r n . An a e r i a l v i e w o f t h e o t h e r w i s e r u g g e d a p p e a r i n g C o a s t Range imbues t h e o n l o o k e r w i t h t h o u g h t s o f e a s i l y t r a v e l l e d r i d g e s b e c a u s e o f t h e a v e r a g e h e i g h t m a i n -t a i n e d . T h i s may be an u p l i f t e d and d i s s e c t e d p e n e p l a i n , p r o d u c t o f C r e t a c e o u s e r o s i o n . The w r i t e r h as p e r c e i v e d t h i s many t i m e s i n r e c o n n a i s s a n c e t r i p s f r o m Dean t o G a r d n e r C h a n n e l s . H e r e f l a t - t o p p e d r i d g e s , a f f o r d i n g t h e e a s i e s t o f t r a v e l , e x t e n d f o r c o u n t l e s s m i l e s , b r o k e n o n l y b y s l i g h t -l y h i g h e r p e a k s and y o u n g e r s t r e a m v a l l e y s . O r i g i n a l l y t h e n , — 3 I d .— A youthful and r a p i d l y incised post - Pleistocene stream valley of the "box canyon" type. Former drain-age outlet disrupted by g l a c i a l debris f i l l i n g the channel. -32-the plateau was about 8,000 feet high, with, a smooth gradation to the I n t e r i o r Belt and a "step-down" to the Island Fringe. This i s apparent i f sections are drawn across the Range. I t i s noteworthy that the Mainland Range i s highest where i t approaches closest to the Insular Range and i s lowest at the breach. The residuals of the ancient peneplain take the form of sharp peaks and comb ridges i n the higher parts and simple domes, broad-sided pyramids and obtuse-angled ridges i n the lower areas. Its apparent ruggedness, then, i s due to intense d i s s e c t i o n , with the major drainage cutting across the general trend of the Range and the valleys forming "through-corridors". In this category belong the Fraser, Dean, Nass, Stikine, Iskut and Taku Rivers. Others, such as the Homathko, flow eastward from the Coast Range and then cut back i n a semi-circle to re-enter the mountains by a through v a l l e y , flowing thence to the P a c i f i c . A l l these are, therefore, antecedent streams that have been.able to keep abreast of orogenesis. Peacock finds that these through valleys are not antecedent, but are the product of scouring by transverse g l a c i a l tongues from the I n t e r i o r Belt, with a resultant disappearance of divides that worked headwards close to the inner margin of the Mainland Range. Some of the old Cretaceous r i v e r s must have had t h e i r backs broken by the r i s i n g land mass and were thus divided into two streams, one flowing east and becoming tri b u t a r y to some antecedent outlet, the other flowing west from the heart of the Range and empty-ing into the P a c i f i c Ocean. I t i s notable that even these - 3 Z C L -r This is a view looking northerly along the fiord channel of Indian Arm(Burrard Inlet). Note the typically rounded headlands and the scarred dome to the lef t . It is interesting to see that the small islands of less resistant roof rock lying in the center of the channel were not greatly eroded by ice action which was fairly pronounced in the area as a whole. It would point to a not too extensive down-cutting power of the ice mass as i t journeyed seaward. -33-sinaller water courses are able to continue transverse to the mountain trend because t h e i r valleys were so well incised before- being severed. The r i v e r s exhibit a strong t r e l l i s pattern under control of structure, commonly showing straight reaches and sharp elbows. There i s no apparent connection between the size of a stream and the size of the f i o r d i t enters. Gardner Channel, for instance, i s the outlet to a very i n s i g n i f i c a n t waterway, whereas Dean Channel i s fed by a healthy stream. ' This i s mainly a res u l t of "stream piracy", as i n the case of the Skeena capturing most of the Kitsum-•gallum Valley drainage of the Nass and f i n a l l y leaving the old outlet of the l a t t e r (Douglas Channel) almost dry. — I /lustration ^2.. '—• The Island Fringe Is a maze of thousands' of closely set iislands and peninsulas of a l l sizes, tending to rec-tangular patterns. They are commonly extended coastwise, but sometimes transversely. The elevations of the larger ones, such as P i t t , are approximations to those of the mainland; but Banks I s . and most of the smaller ones show a decided drop i n a l t i t u d e , For example, Mt. Noble on the west -34-coast of P i t t Island i s 3,200 feet, whereas Banks and McAulay Islands, just a half mile westward, ra r e l y attain an ele-vation of more than 500 feet. The islan d topography i s correspondingly a subdued one, with such exceptions as steep-sided A n v i l Island i n Howe Sound. The Intermont Valley Belt of B r i t i s h Columbia comprises Georgia Basin, Hecate Basin and, i n Alaska, the Alexander Basinl The Georgia Basin reaches a maximum depth of 245 fathoms but averages 100 fathoms. Most of the Hecate Basin i s a l e v e l p l a i n less than 100 fathoms deep, and the narrow channel connecting the two basins shoals to 19 fathoms at Seymour Narrows. An up-l i f t of 600 feet would be enough to convert the Intermontane Valley Belt of B. C. into a consecutive pair of great valleys surrounded almost completely by mountains. The main d i f f e r -ence noted between the insular and Mainland Ranges i s the much smaller area of g r a n i t i c rocks exposed on the former. The general elevation of the Queen Charlottes and Vancouver Island i s well below that of the Mainland Range, but both, are highest i n the south-east where the Vancouver i s l a n d Range l i e s closest to the mainland. Both are lowest i n the elabo-rately dissected portion of the mainland facing seaward across the Southern Hecate Basin. A subdued topography characterizes the ins u l a r System where there are many i n d e f i n i t e , f l a t -topped, residual mountains. Areas such as Queen Charlotte 1. A. P. Buddington & T. Chapin, Geol. and Min. Deposits of South-eastern A l a s k a , U. S. G. s., B u l l . 800, p 19. r i This spur has received r e l a t i v e l y l i t t l e truncation although the i c e mass was t r a v e l l i n g a t 90 degrees to i t s axis and should have r e -moved i t quite e a s i l y had overdeepening and sid e c u t t i n g by the a c t i o n of i c e been as great as some geologists would b e l i e v e . I t may be seen that the i c e d i d override the spur. The l o c a t i o n i s ju s t north of Bri t a n n i a beach(Howe Sound). At t h i s point the f i o r d makes a short 90 degree turn. Such examples go to prove that the established drainage systems p r a c t i -c a l l y c o n t r o l l e d the flow of i c e e s p e c i a l l y at the lower elevations here the narrow channels must have acted as a rudder to the main i c e mass i n the mountainous areas. This c o n t r o l was probably l o s t when the i c e l e f t the higher mountains. Arrows show the bearing changes i n the channel. -35-Sound must have been great dumping grounds fo r the ice which was i n the form of a piedmont g l a c i e r over th i s r e l a t i v e l y plane section. This would account f o r the average greater height over the f i o r d bottoms where the ice was confined to thicker columns and eroding rather than depositing. An example i s the average depth of Fitzhugh Sound which i s 80 to 90 fathoms and that of i t s junction with Queen Charlotte Sound which i s 65 fathoms. The Continental Margin varies tremendously i n i t s width (2 miles along Graham Island and 60 miles along the S t r a i t of Juan de Fuca) with a steep slope replacing the shelf at an average depth of 100 fathoms or 600 feet. The valleys'continue seaward as submarine troughs of d e f i n i t e pattern. Here they are joined by other submarine depressions such as the one p a r a l l e l i n g the coast of Vancouver Island at about 30 miles distance. These extensions generally do not follow the s t r i k e of t h e i r upper parts. Beyond the Marginal Shelf the gradient becomes about 300-500 feet to the mile up to 2,000 fathoms. A cursory map examination of the simplest f i o r d s impresses the student with the straightness of these water-ways. Changes of course are by abrupt deflections at high o angles, usually approximating 90 , so that two dominating directions are perceived. 'The resultant channel i s termed a "cranked" f i o r d . These are often j o i n e d by streams f o l l o w -ing the same general pattern. A l t h o u g h the cause of the t o t a l e f f e c t i s not as apparent, l o c a l l y i t i s c l e a r l y due -36-to new p r i n c i p a l directions dominating i n other sections of the coast. The accompanying diagram i s made up of straight lines drawn p a r a l l e l to a l l straight-edged islands and channels, from which, there are few exceptions. Examination at f i r s t suggests a general mix-up of d i r e c t i o n a l l i n e s , but clo'ser scrutiny reveals two sets of regular elements. One of these has a major st r i k e p a r a l l e l to the grain of the coast and i s therefore designated as "concordant". The other i s an oblique pattern and consequently "discordant". Accord-1 ing to Peacock, the f i o r d pattern i s complex, consisting of a dominant concordant system of longitudinal (concentric) and transverse (radial) l i n e s whose mean trends are respec-t i v e l y N50°W and N45°E, with considerable range due to repeated curving of the pattern In accord v/ith the compound, curved plan of the coast land; and a subordinate discordant system which i s strongest i n the north and weakest i n the south, and i s composed of lines whose trends d i f f e r l i t t l e o o from the mean directions N7 W and N84 E. That there i s a close relationship existing between the f i o r d pattern and s t r u c t u r a l conditions can not be denied. 2 F o r instance, s c h o f i e l d points out that the ore deposits of the b a t h o l i t h , when bedded veins are ignored, may be grouped Into a "shear zone" type, s t r i k i n g p a r a l l e l to the grain of 1. reacock, M. A. Fiord-land of B. C. 1935 B u l l , of Geol. Soc. of America, Vol. 46, p 656. 2. Schofield, S. J . Fissure System of B. C. C . I . k-. M. B u l l . , V o l . 159, 1925, pp 759-764. — Page * 3 6 « . -L E G E N D T I M P S IE A N ¥ j jf 1"^ h — M I ' -Quartz cii or tie. B-nnery I5LA 111) Schists. 0/iow<5 contact Grots ion Tidal flak QUARRY Con tourjs — /OO ' Tir-awn by :- YXfttZ* /Vote:— This map shows a -fiord -fo/fowing a line of weakness c/e/er-min&cf by et cjeo/ojjt'ca/ contact. -37-the coast, and a "vein" system, intersecting at ri g h t angles and conforming to the "concordant" f i o r d d i r e c t i o n s . S i m i l a r l y i t has been the writer's experience to cross l i t e r -a l l y hundreds of roof-pendants whose major axes s t r i k e approximately p a r a l l e l to such large channels as Grenville which i s twenty-five miles south of Prince Rupert. Many of the contacts between g r a n i t i c and schistose rocks are the actual boxxndaries of f i o r d s , usually of the longitudinal type. Therefore i t would appear that the main s t r u c t u r a l l i n e , i n so far as the western contact of the ba t h o l i t h i s concerned, i s NW-SE, p a r a l l e l i n g shear zones and pendant areas. Although heavy vegetation prevents easy inspection of the f i o r d walls, close scrutiny at low tide brings to view the same system of fractures that has undoubtedly controlled location of th i s drainage system. The Island Fringe shows th i s to perfection because of heavier wave and tide action. Here many "goes" are formed. An intensive study of these coastal fractures and "goes" was undertaken by Peacock, who found unending r e p e t i t i o n of p a r a l l e l i s m to the f i o r d pattern. This cannot be an accidental occurrence. Step-faulting of the tension type has been determined from physiographic evidence only. . Detailed f i e l d work i s lacking. Downthrow i s to the seaward, and the st r i k e i s p a r a l l e l to the shear zone. The following sketch i l l u s t r a t e s t h i s structure c l e a r l y . - 7 a -Shows angular inclusions of(black) host rock i n a large acid dyke rock(white). These dykes are very common i n the area and point to close proximity to the roof of the bathol i t h i c rocks. Note the var-ious d i f f e r e n t sized inclusions. They do not appear to show absorption although some of the fragments are decidedly small. Very l i t t l e schlleren or streaking i s to be seen. This could possibly be explained by the minor size of the intrusive which i s a p l i t i c and pegmatitic. This area l i e s j u st north of Horse-shoe bay on Howe Sound. -38-11/us. — CASCADE INLET f Looking NW along a straight and remarkably steep-sided f i o r d branching from Dean Channel. Surrounded by granodiorite rocks of the bat h o l i t h . Note the marked difference i n the elevations of the mountains on either side - suggests f a u l t i n g along the l i n e of the f i o r d . The stepped surface of Kaien Island (Prince Rupert) may be a transverse representative of the same structure. Generally, the stepped-down appearance of the Island Fringe may be due to such a cause. Chatham S t r a i t and Lynn Canal, 1 according to the Wrights, make up an immense f i o r d 250 miles long, eroded along a faulted zone belonging to the discordant 1. Wright, F. E. & C.-W. The Ketchikan and Wrangell Mining D i s t r i c t s , Alaska. U. S. G. S. B u l l . 347, 1906 pp 21-22. — Page 3*3CZ: Map* 5. -39-system. The o r i g i n a l location of the f i o r d s must be con-sidered, then, a r e s u l t of s t r u c t u r a l control and not of glac-.i a t i o n . G r e n v i l l e Channel i s a longitudinal reach. Obser-vatory Inle t i s transverse, whereas Fitzhugh Sound belongs to the wholly oblique type. Repeated deflections r e s u l t i n tremendously long f i o r d s such as Fisher Channel, Dean Channel and Fitzhugh Sound, a t o t a l lengtih of 121 miles. The f i o r d s of B. C. are r e l a t i v e l y p a r a l l e l - s i d e d , many of them exhibiting s t r i c t u r e d entrances with numerous t i d a l lakes such as Hevenor Lagoon on P i t t Island. Banks Island and i t s neighbors are l i t e r a l l y dotted v/ith large transverse lakes, up to 10 miles i n length, whose outlets are within 100 yards of the seaways and are p r a c t i c a l l y at sea-level. Red Bluff Lake ?across from Lowe Inlet Cannery; on P i t t Island i s a t y p i c a l example. The average width of the fi o r d s of B r i t i s h Columbia i s from 1 to 1§ miles, giving an exceedingly high r a t i o / o f length to breadth. Since most of the projecting spurs have suffered truncation by ice action, the f i o r d walls show straight edges. Although some of the smaller f i o r d s converge rapidl y inland, they customarily continue f o r great lengths. Many of them cross the entire Coast Range, and show no out-standing v a r i a t i o n from the drowned portion, except for the deep a l l u v i a l f l o o r s b u i l t up by "aggrading streams" working under the disconcerting load of g l a c i a l debris. Some writers -40-such as Lord and Bancroft believe that many of the submerged fi o r d s immediately become constricted, and show a decided change i n l e v e l where they j o i n the f i o r d valleys or the extensions above water. I t must be remembered that, i f any u p l i f t has occurred recently, i t i s not very long since tidewater extended many miles further across the Coast Range and, therefore, the lower reaches of these r i v e r v a l l e y s now exposed are almost exact p a r a l l e l s of sections s t i l l l y i n g beneath the sea. The only difference i s that of t i d a l and f l u v i a l aggrading. Why should there be any l o c a l i z a t i o n of c o n s t r i c t i o n and change i n l e v e l at the present submerged v a l l e y heads? I t has not been the writer's good fortune to see any such phenomena, although four years of prospecting this coastal section have given many opportunities. A further point may be noticed. The exposed sections of the f i o r d valleys show a f a i r gradient, while the plane surface of the t i d a l waters has p r a c t i c a l l y none. Therefore, any observa-ti o n i n the drowned portions becomes progressively higher on the v a l l e y walls towards the channel entrance. This would create an i l l u s i o n of a •faik&hrs& v a l l e y i n the submerged fi o r d s than t h e i r landward continuation. Delta formation would further accentuate t h i s . Usually the steep, symmetrical walls of the channels are convex towards the water, giving a plunging 1. Lord, C. S. Physiography of the Coast Range of B. C. & S.E. Alaska, B.A.Sc. Thesis at U. B. C , 1929, p 82. 2. Bancroft, J . A. G. S. C. Mem. 23, 1913, p 46. r ^ Side view of truncated spur at head of Howe Sound Note the gouging and polishing action of the ice about one third of the distance up the bluff marked X. Such bluffs with steep preci-pitous slopes and overhanging cl i f f s are to be seen almost anywhere along the fiordland coast. Most of them are practically barren of vegetation as in the above photograph. This bluff flanks the head of the fiord channel and its base is accompanied by the usual mud flat which extends out into the water for some distance at a very small gradient and then drops off steeply. The delta mud is being carried down by the river which is labouring under the tremendous burden of glacial debris deposited in its upper reaches and is s t i l l in a period of aggradation. The mud deposits may be seen as much as fi f t y miles up this small river from which point bedrock is exposed. A consider-able amount of finer s i l t works its way out in front of the delta and is spread over the floor of the deep fiord. Here the tidal and current influences are brought into play and aid in distributing the material over the rest of the channel floor. -41-effect that i s s t r i k i n g l y revealed to p i l o t s of coastal boats by the lack of rocks only a short distance from shore. The only dangerous points are those composed of pendant schists which form s l i d e s and terraces due to t h e i r i n a b i l i t y to hold round contours under erosion. This happens i n the case of granodiorite. An average of the wall slope of the majority of these channels approximates 40° over a v e r t i c a l distance of 4,500 feet. Extreme grooving by g l a c i a t i o n with c e r t a i n j o i n t plane strikes has resulted i n nearly v e r t i c a l precipices up to 2,000 feet i n height as observed by Bancroft^in Knight I n l e t . Where peaks are situated f a i r l y close to the f i o r d s , the walls of the l a t t e r soon lose d e f i n i t i o n and more than average^is obtained. The slopes are commonly interrupted by bench forms. An average trans-verse p r o f i l e would be as follows: jset? /eve/. IV/7IAS. -Illus.#4: -1. Bancroft, A. J. Geol. of the Coast and Islands between S t r a i t of Georgia and Queen Charlotte Sound, B. C. G. S. C. Mem. 23, 1913, p 22. -4-1 a.-r ^ Front view of the granodiorite bluff 2000 feet high standing at the head of Howe Sound fiord channel— at Squamish B.C.. This sound penetrates the Coast Range massif for a distance of 25 miles in a northerly direct-ion. The bluff shows distinctly the action of the ice first as an undercutting then as a caving or sapping action resulting in the precipitous c l i f f s . The mud flats seen in front of the ice carved bluffs belong to the extensive fluvio-glacial deposits that the streams are now busy working towards the sea. The fiord walls here show no sign of constriction where they leave tidewater except for that narrowing to be expected where a flat plain of water and mud approach closer to the rising valley bottom. Note the lamprophyre dyke marked X. -42-Only recently have soundings been made of the f i o r d s , and these are not extensive. Comparisons of the f i o r d v a l l e y f l o o r s (evenly decreasing) with the channel -. f l o o r s show extreme i r r e g u l a r i t i e s i n the l a t t e r , producing deep basins with shallow, p r a c t i c a l l y clos-ed outlet's. See below. « / ' c / e fiorct -r£i main T W transverse ctianne/. Longitudinal section showing side f i o r d v a l l e y with continuation as a f i o r d channel entering transverse main f i o r d channel. I t i s to be noted that the average difference between depths of f i o r d channels and the depth of the continental shelf i s nearly 1,000 feet, and i s as much-as -2,000 feet. Normally, the greatest depth may be anywhere along the length of the channel. Even 'the f i o r d s t r a i t s , open at both ends, show signs of thresholds. A consideration of the oblique and transverse f i o r d s shows the depth and width to be d i r e c t l y r e l a t e d . A divergence of the walls i s a sign of increasing depth, but t h i s r e l a t i o n f a i l s , or i s reversed, i n many of the longitudinal channels such as Principe. Peacock says, "The greatest depths are frequently' found i n a passage where i t runs from the mainland to the Island Fringe. Finlayson -43-Ghannel and Fisher Channel both occupy such positions, and i t i s s i g n i f i c a n t that both are i n a r e l a t i v e l y low and deeply indented part of the inner coast, facing the wide 1 breach between the Vancouver and Queen Charlotte Ranges." I t would appear that downfolding had been r e l a t i v e l y great i n this area. Thus the deeper channels are accounted for without drawing on the powers of g l a c i a l erosion to any untoward extent. To date, the d i r e c t evidence on the nature of submerged thresholds i s p r a c t i c a l l y n i l . I n d i r e c t l y i t seems that many cases of apparent discordance i n f i o r d f l o o r s are due to morainic interruptions of the otherwise gradual slope. Marked examples of these are to be seen at the deltas now forming at the heads of these f i o r d channels. GARDNER CHANNEL head of APPARENT DISCORDANCECc/e/fa.). ) 1. Peacock, M. A. Fiord-Land of B. C. B u l l , of Geol. Soc. of America, Vol. 46, 1935, p 669. — 4 5 a . -Cascade point,Knight inlet. Shows hanging valley and the face of a truncated spur. A through valley looking west head of Boughy Bay. from the -44-Below i s a t y p i c a l drowned hanging v a l l e y at Ocean P a l l s , B.C. The above type i s an important feature of the coast scenery of British. Columbia, both, above sea-level and i n the sub-merged condition. These discordances are, therefore, t r u l y d e f i n i t e rock features. Link Lake discharges into Cousins Inlet over a massive rock lip ( g r a n o d i o r i t e ) with a ninety-foot discordance between the f l o o r of the lake and that of the i n l e t . The conclusion arrived at i s that.discordances are independent of sea-level and that many are true rock features, because both hanging valleys and rock bars or l i p s are to be found both above and below sea-level. Thresholds or rock l i p s at the entrance to channels have created much i n t e r e s t . F i r s t , the writer wishes to point out a few d i f f i c u l t i e s . Hydrographic charts give so l i t t l e d e t a i l at sa l i e n t points that t h e i r evidence i s misleading. The actual center of the channel being sounded shows considerable meandering, whereas the actual measure -ments made are too widespread. A single glance at the ordinary chart emphasizes th i s point. -45-DEPTHS IN FATHOMS The following diagram of Belize I n l e t shows marked uniformity of depth. The deepest soundings down Cousins I n l e t , Fisher Channel and Fitzhugh Sound.are shown below. 20, 26, 35, 42, 40, 30, 94, 262, 256, 287, 326, 249, 38, 24, 68, 57, 64, 92, 140, 101, 88, 77, 82, 64, 8B~T89, 93, 183, 26, 76, 139. 99, 95, 86, 55, 93, 66, 64, 12, 67, 63, 90. Note the sudden change at the mouth of Cousins Inlet (30, 94, 262) with the accompanying threshold. Then mark the t r e -mendous depths i n Fisher Channel near i t s confluence with Dean Channel (326 fathoms, or almost 2,000 f e e t ) . G l a c i a l depression, according to other data presented, could have accounted for approximately 1,000 feet of t h i s . I t i s to be -46-noted that depression of such, a great area by the weight of ice imposed upon i t must have been d i f f e r e n t i a l . That is,' sections under greater ice masses must have been bowed down r e l a t i v e l y deeper as, for instance, the d i s t r i c t l y i n g be-tween Queen Charlotte Islands and Vancouver Island which probably had greater ice f i e l d s because of i t s greater pre-Pleistocene waterways. This, might help to account for the generally lower elevations across t h i s whole transverse section. The i n i t i a l cause would nat u r a l l y be r e l a t i v e l y deeper down-foldin g during orogeny; but one would lead to the other. Large streams now aggrading t h e i r overloaded beds are building up deltas of the coarser g l a c i a l debris. However, a much greater proportion of the load, consisting of f i n e mud and sand, i s gradually working along the channel bottoms by undertow of tide and current which are exceptionally strong i n places. A further e f f e c t i s created by the junction of two channels. Here, as i n the confluence of two streams, the smaller one usually builds up a l i p or threshold at i t s mouth. I f the i n i t i a l i r r e g u l a r i t i e s of a f l u v i a l v a l l e y are increased by g l a c i a l erosion and deposition, plus i n i t i a l folding-d i f f e r e n t i a l downasmstag both from orogeny and ice-load, the res u l t would be much the same as the f i o r d - l a n d to-day. Thus i t i s unnecessary to c a l l upon g l a c i a l erosion to account for overdeepening of more than a few hundred f e e t . Undoubted-l y some gouging did occur, and i t must have been quite intense where the ice encountered softer schistose pendant areas and i n c l u s i o n s . I t could be expected to show best r e s u l t s , -47-then, i n a NW-SE d i r e c t i o n . According to Burwash, the expansion of the v a l l e y g l a c i e r as i t leaves the confining W H I I S would resu l t i n thinner ice at t h i s point, and, there-fore, less severe erosion than farther up the v a l l e y . G-eomorphic Development A survey of other writers leads us to believe that Dawson"considered the trough-like shape of f i o r d channels to be due to d e t r i t a l blockades near th e i r mouths. He believed also that the summit accordance of the Coast Range was not the r e s u l t of d i s s e c t i o n of an u p l i f t e d peneplain, but was due to more rapid d i s i n t e g r a t i o n of rock above the snow l i n e . 4 Clapp has concluded, from work on Vancouver Island, that traces of a Cenozoic peneplain (Miocene) are s t i l l recognizable as high as 1,600 feet above the present ocean l e v e l . There must have been at least a 1,600-foot u p l i f t i n the Pliocene. Since the ice depression there has been as much as a 700-foot u p l i f t . This i s proven d i r e c t l y by beach terraces at t h i s 5 a l t i t u d e containing Recent f o s s i l s . Bancroft considered that the ice deepened the troughs by as much as 1,000 feet. 1. Burwash, E. M. J. Geol. of Van. & V i c i n i t y , 1918, p 8. 2. Dawson, G. M. On the Super. Geol. of B. C. Geo... soc'. of London, Quart. Jour., Vol. 34, 1878, p 91. 3. Dawson, G. M. Rep. on the Area of the Kamloops Map-Sheet. G. S. C. Annual Report, Vol. 7B, 1896, p 12. 4. Clapp, C. H. South Van. I s . G. S. C. Mem. 13, 1912, p 12. 5. Bancroft, J. A. Geol. of Coast and Is. bet. St. of Georgia and Queen Charlotte Sound, B. C. G. S. C. Mem. 23, p 51. -48-1 Burwash proposes physiographic c o r r e l a t i o n of the mainland Coast Range with the. well recognized stages of Washington. Uglow brings out a f i n e point i n the description of Eocene sediment remnants overlain by Miocene lavas l y i n g i n the wide v a l l e y f l o o r of the North Thompson River i n the I n t e r i o r Plateau country. Such, an observation designates a Cretaceous peneplain which i s thought by Schofield to be part of that Mainland Range peneplain. Spencer offers a general explan-ation, from studies i n Alaska and a survey of B r i t i s h Colum-bia data, which begins with entire peneplanation of the Mainland Range and the Central Belt i n Cretaceous times. D i f f e r e n t i a l u p l i f t gave the Mainland Range i t s dissected plateau character, whereas the I n t e r i o r Plateau remained a lower peneplain. Transverse erosion was able to keep pace with orogenesis. The Mainland Range suffered upwarping and flexure with some d i s l o c a t i o n along the contact of the two belts which i s probably due to d i f f e r e n t i a l horizontal thrust. Now the resultant form of any land mass i s de-pendent on sub-surface structure plus the sum of a l l i t s physical moderations. Therefore, each period of geologic time must be delved into that i t s s t r u c t u r a l effects on the problem may be brought f o r t h . The p r i n c i p a l unknown factors are the regional v e r t i c a l movements which have provided the motive power of erosion. These must be i n f e r r e d from physio-graphic evidence since no sedimentary record was l e f t during 1. Burwash, E.M. Geol. of Van. and V i c i n i t y , Chicago, 1918. -49-the period of geomorphic development. To begin with, one of the major influences on present land forms of the coast was the Jura-Cretaceous Revolution. Its forces were most l i k e l y acting upon an area that had long been reduced to a trough by erosion. Great thicknesses of marine sedimentation and bedded volcanics attest to t h i s . The Jura-Cretaceous orogeny was accompanied by momentous deformation and intrusions, probably not con-tinuous, over a long period of geologic time. This extensive l i f t i n g and f o l d i n g served to heighten considerably the speed of erosion, so that the late Cretaceous most l i k e l y saw the entire Western Belt peneplaned. Immense thicknesses of Cretaceous sediments (10,000 feet) on the northeast side of Vancouver Island are mute evidence, and the enormous depth of sedimentation i n the Rocky Mountain geosyncline i s further proof of b a s e - l e v e l l i n g . I t i s s t r i k i n g testimony that the Skagit formation of B r i t i s h Columbia, near the base of the Cretaceous, contains gra n o d i o r i t i c pebbles i n a conglomerate that rests upon the f u l l y denuded Jura-Cretaceous grano-d i o r i t i c core as i n the following diagram. -50-The Eocene saw renewed u p l i f t both i n the Mainland Range and the I n t e r i o r Plateau country but d i f f e r e n t i a l l y , so that erosion was dissecting at the same time a plateau and a peneplain respectively. L i t h o l o g i c a l data shows l i t t l e compression deformation with mainly upward displacement accompanied by smaller magmatic upwellings. The l a t e r sedi-mentary record i s very fragmentary, only small basin deposits surviving - mainly a period of erosion. Most of these remnants are undeformed, as i n the v i c i n i t y of Vancouver where 4,000 'feet of Eocene and Oligocene estuarine sediments show only s l i g h t f a u l t i n g . The Miocene period saw marine sedimentation with some vulcanism, and preserved remnants of i t s b ase-levelling are to be seen at about 2,000 feet elevation. There has been an u p l i f t during the Pliocene of almost 2,000 feet. The deposits and sculpture of the P l e i s -tocene indicate the action of an ice-sheet moving south-westward from the Central Belt and across the Mainland Range by way of the transverse pre-G-lacial v a l l e y s . The ice re-united i n the Intermont Valley Belt and escaped to the sea through the breaches between the Island Ranges. Some of the higher peaks were probably exposed, but the upper l i m i t of . g l a c i a t i o n i s higher than ice sculpturing tends to show, because, above snow l i n e , d i s i n t e g r a t i o n i s so rapid that g l a c i a l modifications have been wiped out. The. Ice made more than one advance as i s shown by i n t e r g l a c i a l sediments i n various locations. Sporadic vulcanism and s l i g h t u p l i f t (700 feet as shown by beach terraces) have occured since -51-the Pleistocene. Peacock believes that d i f f e r e n t i a l horizontal pressure from the north-east seems the most l o g i c a l agent to explain the curved arc and cusp form of B r i t i s h Columbia's -coastal margin. Since l i t t l e deformation followed the Jura-Cretaceous Revolution, i t would appear that the pressure originated during that period of orogeny and b a t h o l i t h i c i n t r u s i o n . In cl o s e l y associated genesis can be placed the grain of the coastland, the gently curved trend of the fold i n g and the geological contacts. I t appears that the Intermont Valley Belt waa an inherent part of t h i s same mountain bui l d i n g , appearing as a s y n c l i n a l f o l d (synclin-orium) between the two areas of extensive u p l i f t . This seems an e n t i r e l y l o g i c a l r e s u l t of the horizontal thrust. The thick narrow belts of Cretaceous sediments to the south-west were deposited i n this long trough. Its eastern margin, the Island Fringe, was a product of post-compressive forces -a tensional release causing longitudinal step down-faulting along the s y n c l i n a l trough. The bed of the depression i s larg e l y sediment f i l l e d , being a dumping ground f o r streams and g l a c i e r s . P r e - g l a c i a l l y i t was a trunk r i v e r v a l l e y , probably well cut down and denuded of most of i t s Cretaceous sedimentation. The Intermont Valley Belt, or trough, includes the waterways of the S t r a i t of Georgia, Johnstone S t r a i t , Queen Charlotte S t r a i t , Queen Charlotte Sound, Hecate S t r a i t , the -52-eastern l i m i t of Dixon Entrance, the complex channels of the Alexander Archipelago and Lynn Canal. Chilco River Valley marks the northerly extension, being one of the sections of the trough, that has had r e l a t i v e l y l i t t l e depression. The deepest section i s that between Hecate and Queen Charlotte S t r a i t s and i s at a maximum opposite the breach i n the Insular Range. S i m i l a r l y , the average or general elevation of the Coast Range i n this transverse section i s only 7,000-7,500 feet, whereas the average i s much higher further north-west or south-east. Naturally this area has a much more i n t r i c a t e network of submerged fiords penetrating deeply into the Coast Range, as, f o r example, Dean and Gardner.Channels• The cross-section appears to be, then, r e l a t i v e l y depressed i n a d i r e c t i o n transverse to the grain. Even the f i o r d f l o o r s show greater depth (as i n Fitzhugh Sound). Thus i t i s not necessary to conclude that g l a c i a l overdeepenlng caused greater submergence. However, It i s only natural that the ice action would be at a maximum i n th i s region of great trough v a l l e y s . I t , i s to be noted that a rapid decrease i n the submergence of the trough occurs north, of the Queen Charlotte islands. There i s a r e l a t i v e u p l i f t at Seymour Narrows and again south of puget Sound. The accompanying map (after Peacock) #6* shows the probable ancient r i v e r s occupying the trough before pleistocene time. The comparative upwarping i n the v i c i n i t y of Seymour Narrows i s suggested by the general trend of the i n l e t s , the more important of which, are Knight and Butte. As Lord states i t , these i n l e t s "on a map ft Mop* -53-present the appearance of a drowned former r i v e r v a l l e y which drained towards the region of Puget Sound.""*" The close r e l a t i o n between mineralized shear zones and "concordant" fracture system, as displayed i n the f i o r d -land, d e f i n i t e l y places the time of o r i g i n of the system as Jurassic, after the plutonic rocks had become r i g i d . A consideration of the through, valleys shows that they were born with the r i s e of the Jurassic Ranges and, keeping pace with th e i r r i s e , were soon controlled by the sub-surface structure, a product of orogenesis. I t can be c l e a r l y re-cognized, from a study of the fracture system, that drainage was securely established with sub-surface control by pre-G l a c i a l times. General physiographic evidence points to the Mainland Range as having been i n a state of mature f l u v i a l erosion i n the early pliocene and rejuvenated by a powerful regional u p l i f t i n the late Pliocene. Neglecting p o s t - g l a c i a l forms, i t may be seen that the lower r i v e r valleys were simple steep-sided incisions i n a dissected plateau surface i n Upper Pliocene times, peacock considers this Pliocene terrace effect i s at least 4,000 feet high i n the Mainland Range -p r a c t i c a l l y certain proof of a 5,000-6,000-foot upwarped base-level. Thus he i s led to the conclusion that there was at 1. Lord, C. S. The Physiography of the Coast Range of B.C. and S.E. Alaska, Bachelor's Thesis, U. B. C , 1929. -54-least a 5,000-foot Mainland Range u p l i f t i n the pliocene, but the u p l i f t may have been greater i f there has been any subsidence since the late Pliocene. I t i s f u l l y believed that such a subsidence did occur, and well defined submarine valleys such as the S t r a i t of Juan de Fuca offer d i r e c t evidence. Such a p e r f e c t l y p a r a l l e l - s i d e d r i v e r v alley, con-tinuing out over the Continental Shelf for 60 miles, making o a 90 turn around Cape F l a t t e r y and picking up a major t r i b u -tary 30 miles off shore from Vancouver Island, can only be explained by the reasoning that the r i v e r was Incised above sea-level. This would place the coast^llne 60 miles out from Vancouver i s l a n d and would explain the disappearance of g l a c i a l debris. Since these submarine valleys are almost 1#000 feet below a possible r i v e r v a l l e y l e v e l and since they have already r i s e n 700 feet after the ice retreat, they must have been depressed about 1,700 feet by the g l a c i a l mass, or at least by some pleistocene force. Above i t was concluded, following Peacock, that the base-levelled, early pliocene peneplain i s now 5,000 feet higher than i t was then. I t has just been shown that the from the late PJio. until the /ate Pleistocene and uplifted fOO' area has been depressed 1,700 f e e t ^ i n the Recent, or a sum t o t a l of 1,000 feet depression since the late Pliocene. Therefore, as estimated by him, the grand t o t a l of Pliocene u p l i f t must have been at least 5,000 feet plus 1,000 feet, or 6,000 fe e t . sediments containing Pliocene f o s s i l s are to be seen i n the v i c i n i t y of Bellingham, Washington. These rocks are p r a c t i c a l l y at sea-level and, due to warping and s l i g h t block-faulting, are now several hundred feet below the posi-tion they v/ould be occupying i f undeformed. At Vancouver older sediments (Oligocene and Eocene) belonging to the same deposition basin are s i m i l a r l y only 100 feet above sea-level, although they have been s l i g h t l y down-faulted. Assuming, not i l l o g i c a l l y , from the above that the pliocene formations would now be approximately 1,000 feet above sea-l e v e l i f not faulted or warped, the conclusion is'reached that Seacock's estimation of at least a 3,000-foot u p l i f t on the coast during the Pliocene i s possibly erroneous. The B e l l i n g -ham sediments have been depressed close to 1,000 feet since the early Pleistocene and must, therefore, have been 1,000 feet plus 1,000 feet,or 2,000 feet above sea-level at the end of'the Pliocene. Knowing that they are coastal or brackish i n o r i g i n , i t seems that the pliocene u p l i f t must have been less-than 2,000 feet. I t i s to be noted that the two measure-ments of v e r t i c a l displacement used above are f a i r l y accurate. Considering the 1,000 feet of g l a c i a l depression, i t w i l l be seen that the submerged r i v e r v a l l e y s , sounded close to t h e i r late Pliocene mouths and, therefore, only a short distance above sea-level, are now 600 feet below the ocean surface. They could not have been more than 200 feet to 400 feet above the sea then, which points to a t o t a l depression during the Pleistocene and Recent of less than 1,000 feet, and most l i k e l y 800 or 900 feet, because of i n i t i a l slope. The other 1,000-foot measurement i s less accurate -56-but appears l o g i c a l l y to be the upper l i m i t . The only f a u l t s noted i n the v i c i n i t y of Vancouver are of l i t t l e v e r t i c a l displacement, according to Johnson"'" who surveyed the area i n 1923. Actual measurements of the movement are not known, but they v/ere c e r t a i n l y less than 500 feet. Downwarping, when i n i t i a l dip of the basin sedi-ments i s taken into consideration, could not have accounted for more than 500 feet. This allows an upper l i m i t of 1,000 feet and most l i k e l y about 500 feet of change i n elevation. Regarding the Intermont Valley Belt i n the l i g h t of these conclusions, i t i s seen that the deepest parts of the area are now 600 feet below sea-level, that they were 1,300 feet below at the end of the pleistocene, that they were almost 400 feet above at the beginning of the pleistocene, and that they were u p l i f t e d only 2,000 feet, or s l i g h t l y l e s s , during the pliocene. This would result i n the Inter-'mont Valley Belt being submerged i n i t s deepest areas less than 1,600 feet at the start of the Pliocene. Does this not appear more l o g i c a l than peacock's figure of at least 2,600 feet and probably 3,600 feet? I f Peacock i s correct i n his estimation, the area was almost 2,000 feet further below the sea during the early pliocene than It was at the end of the pleistocene - an Incomprehensible r e s u l t . 1. johnson, W. A. Geology of eraser River Delta Map-Area, Mem. 135, 1923. This gives a remarkably clear cut picture of the sharp contacts between inclusions(dark) and acid apophyses (light) near the ancint roof horizon of the batholith. The location is Howe Sound,B. C. near Horseshoe Bay. Notice especially the inclusion marked X which can be seen in 3 dimensions because of a fortunate break in the rock. The acid dyke is seen penetrating in behind the fragment and also forming a network through the front of i t . Note also the clear cut contact at Y. The dyke was probably too small in extent and at too low a temperature to assimilate the fragments. -57-Summary The history, then, i s one of peneplanation i n early rliocene with u p l i f t of almost 2,000 feet i n the intermont Valley Belt by late Fliocene. This was followed by a de-pression of at least 1,700 feet i n the Pleistocene, and an u p l i f t of 700 feet i n Recent times. The area must r i s e at least 1,000 feet more to be approximately near i t s late Pliocene elevation. As noted e a r l i e r i n t h i s chapter, a r i s e of 600 feet would suf f i c e to connect the Islands with the Mainland. This means that the Intermont Valley Belt was a system of r i v e r valleys well incised (at least 400 feet above sea-level) at the beginning of g l a c i a t i o n . Peacock says of the transmontane v a l l e y s : "These have the appearance of Post-G l a c i a l valleys where they enter the Mainland Range from the north-east. I t i s , therefore, quite possible, as Dolmage has suggested i n conversation, that the transverse drainage connection between the Central Belt and the Western Belt v/as created by ice tongues, from the Central Belt, wearing down divides that bad migrated close to the inland margin of the Mainland Range."''' Schofield sees no possible reason for such a conclusion, but considers a l l evidence as pointing to antecedent action. 1. Peacock, M. A. Fiord-Land of B. C. B u l l , of the Geol. Soc. of Am., 1935, Vol. 46, p 688. - 5 7 a. Glacial groove in Loughborough inlet. The writer saw a similiar groove of two foot width on Kitsaway island in Douglas channel. It looked as though i t had been put there by a giant hand wielding a chisel. r ^ Cascade point,Knight inlet. Shows profile of the truncated spur. This is typical of the entire fiordland. It is due to side-swiping of cl i f f s previously steepened by Pliocene uplift. \ -58-Actual widening and straightening of the f i o r d valleys by ice action i s of no great magnitude because t y p i c a l f i o r d s of B r i t i s h Columbia are narrow and tortuous. Truncated spurs are numerous enough to show some carving, but the ice appears to have flowed more or less p l a s t i c a l l y along the o r i g i n a l corridors. Less evident i s the amount the ice removed by gouging from the f i o r d channel bottoms. Rock l i p s , or bars, 1,000 feet higher than the lowest soundings i n many of the channels are mute testimony of i r r e g u l a r 1 overdeepening of the bottoms. Buddington notes that there i s a difference of 600 feet i n the deepest part of Clarence S t r a i t (Ernest Sound) and i t s threshold (Dixon Entrance). This, he considers, may give an idea of the minimum g l a c i a l gouging, but the shallowness at the mouth may be due to a deposition of g l a c i a l debris. Certainly the ice-sheet cut deeper i n softer rocks, as i s d e f i n i t e l y proven by the shape of roches moutonnes. Also, the o r i g i n a l f l u v i a l erosion may have had a f a l l s v/ith accompanying rock l i p at the f i o r d mouth. Hanging valleys may be produced by p o s t - g l a c i a l eros-ion where the master stream i s downcutting too rapi d l y for i t s t r i b u t a r i e s which are forced to cascade seaward. Sub-marine hanging valleys can not be explained i n this manner, and so must be a product of ice-gouging at the v a l l e y sides, unless these too were products of the p r e - g l a c i a l d i f f e r e n t i a l i n c i s i o n . The fact that the continental shelf v/ith i t s 1. Buddington, ,A. F. Geol. & Min. Deps. of S. E. Alaska U. S. G. S., B u l l . 800, 1929. -59-contained submerged r i v e r valleys i s shallower than the fiords by several hundred feet i s ample proof that the glac i e r s did not gouge out channels away from the Island Fringe, or that they deposited t h e i r debris i n the Intermont Valley Belt and thus raised i t s l e v e l . At any rate, they did not produce these valleys outside of Vancouver Island by gouging, because these also follow the fracture system of B. C. and were, therefore, produced by f l u v i a l erosion. Submerged Valleys on Continental Slopes and Changes of Sea-Level 1) 1893-1902 several writers brought f o r t h the idea that cer t a i n submerged topographic features were drowned r i v e r v a l l e y s . This idea met unfounded c r i t i c i s m for 30 years. 2) Then F. P. Shepard did much work to attract attention. 3) The development of accurate sonic sounding by U. S. Coast and Geological Survey allowed the location of b a t h i m e t r i c contours which show undoubtedly the presence  of these r i v e r v a l l e y s . 4) Daly believes that the valleys might be a product of submarine erosion by muddy g l a c i a l waters when the water locked up i n the form of ice reduced sea-level by approximately 250 fe e t . This hypothesis appears weak from several factors. -60-5) Hess and MacGlintock a. favor subaerial o r i g i n . b. point out at least 40 val l e y s . c. t r y to show those i n the southern latitude are deep-est - not enough, information yet. d. would presume a very youthful state for these v a l l e y s . This i s very doubtful. They mention that Veatch, Stetson and Shepard have evidence of the Congo sub. v a l l e y being Pleistocene, but this i s no reason for accepting a l l valleys as such - no more than a l l the r i v e r valleys above sea-level are youthful. Naturally these submerged valleys would appear youth-f u l , because, although they may have had an ancient beginning (Cretaceous), they have only been exposed above sea-level for part of the t o t a l time that has elapsed since then. That i s , i f the base-levelling of Cretaceous, Late Eocene, Oligocene and Late Miocene times be accepted as f a c t s , these presently submerged r i v e r valleys were most l i k e l y submerged then also, and could,therefore, receive l i t t l e erosion i n com-parison with the continual erosion proceeding i n the higher r i v e r v a l l e y s . I t would c e r t a i n l y appear that the drowned rivers of B. C. are i n a state of maturity, having been born of the Jura-Cretaceous u p l i f t , as were t h e i r shoreward extensions, the present Praser, Skeena, etc. - 60a.— r i if/9. A remarkably clear example of truncated spurs and hanging valleys showing clearly that side-gouging by ice was extensive. A well defined U-shaped valley commonly to be seen at the headwaters of most of the tributary streams of B.,C. This one is at the headwaters of a tributary of the Stikine river. -61-I f the ancient land mass of Cascadia, lying at least p a r t l y off the present shoreline i s to be accepted as a fact (as proven by the presence of large boulder conglomerates^composed of ancient rocks not to be found exposed at any other l o c a l i t y i n B. C ) , then some erosion of this now sunken land must have taken place through a long period of Palaeozoic time. e. Consider that the world-wide d i s t r i b u t i o n of the sub-merged valleys points to a change i n r e l a t i v e sea-l e v e l and not to independent v e r t i c a l movements of the various continents. They suppose that the change must have been sudden, and after a short erosion  i n t e r v a l was followed by a return to the former  l e v e l . f. propose that the r e l a t i v e change i n sea-level must have resulted from a sudden change i n rate of  revolution of the earth. A•sudden decrease would resul t i n the hydrosphere being drawn into polar l a t i t u d e s . The s o l i d earth would respond less rapidly and i n the meantime erosion of the formerly sea-covered areas would take place. F i n a l l y the earth and water would come to rest with their former attitude, and the r i v e r valleys would be submerged. 1. Buddington, A. F. Geol. and Min. Dep. of S.E. Alaska, Mem. 800,(Silurian Rocks). -62-g. can think of no suitable cause for a change i n rate of revolution. h. point out that i f the above change i n sea-level did take place i t would r suit i n deeper valleys  towards the equator and higher marine terraces towards the poles. I t appears that they assume that the facts bear this out, but i t i s the writer's b e l i e f that too l i t t l e work has been done on the problem. Further-more, how can terraces (Recent) at 700-foot elevations and submerged r i v e r valleys (which they consider Recent also) 1,600 feet below sea-level be explained where they both occur In the same la t i t u d e , as i s common i n B. C ? The existence of the present Island Fringe helps to support the contention that there was a t o t a l subsidence of 1,700 feet since the early Pleistocene. Furthermore, the shoreline presents many of the features of a "Shoreline of Emergence" superimposed on those of a "Shoreline of Submer-gence". F i n a l l y , p o s t - g l a c i a l erosion i s r a p i d l y tearing down the U-shaped p r o f i l e s of the f i o r d s and i s reducing them to the V-shaped p r o f i l e of repose. The conclusion drawn i s that there must have been submergence and that purely g l a c i a l erosion cannot account for a l l the flooding of the f i o r d - l a n d . Undoubtedly ice action resulted i n a few hundred feet of gouging. The accompanying map of the E s t a l l River drainage offers proof of •^Dca/ei:-/"*sm/. - M o p to ^> ho'w /oca t ton — Page G2.CX.— = = ' V A of high through" \/o/7ey. "P1 roof .'that ya//eys formed by ^ frearr? eras/on under controt of fractures - on/y modified by ice action. — Verf- /"=5ooo'. t/or/z.r/"='¥-M>/es. Pitt Is Crosasecfi on A toJQ -*s/?ows abrupt end of*U"\/a//e.y  ne ar J3 atCer In/e t sea / ev<&, datum .//'ne. Grenvilie Ch. J3aker Intef. Mop.* 7 -63-lack of great overdeepening by g l a c i e r s . Here there are a number of p a r a l l e l v alleys that show g l a c i a l modification, but are not cut down at t h e i r divides, which were i n the path, of ice moving south-west towards Grenville Channel. These divides are only a few hundred feet higher than the v a l l e y f l o o r s , are r e l a t i v e l y t hin, are d e f i n i t e l y aligned 'and show smoothing action. Yet they were not removed e n t i r e -l y . Ill/by should the ice stop i t s gouging action within a few hundred feet of Grenville Channel i n each case, and climb' up and over, i f i t did gouge the valleys to t h e i r depth of almost 1,000 feet? Furthermore, the ice-sheet, moving through old r i v e r valleys towards the P a c i f i c , could not have cut down divides at the summit of the Range and thus allowed the water to flow across the entire mountainous region instead of both ways, because the t r i b u t a r y streams entering antecedent valleys to the east of the summit show normal downstream d i r e c t i o n . A good example i s the Dean River as shown i n the drainage map with t h i s t h e s i s . Now i f the ice d i d not cut down these numerous divides for more than a few hundred feet, i t does not seem l o g i c a l that i t could cut down the f i o r d channels more than the same distance. Why, for instance, did not the ice remove the B e l l a Coola Riv.er divide at the height of land? — Page 63a.— Piatcau R^cj/on. = J~5ummit of Coa^t Fiancee M ounta/n^. N O T E (1 JDe.an 7^.. A3 ante, c e t - /'t cro^^e^s th& ^ summit. It^ tri-butaries ffow in the. "norma/ direction. -D&pe./^ theory of cjf/ac/o/ remoya/ of ct/V/c/e^s. — 63 h. -Added Hdte on Hanging Valleys It i s well known1 that many geologists consider that the known height of hanging- valleys above sea'level i n B.C. may be used as indirect evidence of the amount of g l a -c i a l overdeepening of the f i o r d s . This height has been stated by Burwash among others as at least 2000*. Now i t i s a generally accepted fact that i n B.C. continued erosion during Eocene and Oligocene and Miocene times had reduced the area to a state of peneplanation. So that at the inception of the Pliocene the Coast Range had an extremely low r e l i e f * and was i n a condition of physio-graphical maturity. S i m i l a r l y , i t i s recognized that a decided u p l i f t of approximately 2000* took place i n the Pliocene. Therefore, the greatly increased power of erosion of the maj or streams would allow for a much more rapid i n -c i s i o n in bed rock than i n the case of the minor t r i b u t a r y streams which were "at grade" at the points of confluence with the master streams before the u p l i f t occurred. This i s only a natural result since both types of streams were u p l i f t e d the same amount and the larger ones contain more water, therefore having a much higher r a t i o of erosive power. It may be seen then that the side t r i b u t a r i e s would remain suspended or precipitous u n t i l enough time has lapsed to allow them to cut down to "grade" once more. This — 63 c. — time i s determined by the- time required for the master stream to approach a base l e v e l whence i t s rate of i n c i s i o n i s m a t e r i a l l y decreased'. Naturally, i f before t h i s new equilibrium could be reached, a period of g l a c i a t i o n was superimposed on the already unbalanced drainage, a further offset would r e s u l t . That i s , a very i n s i g n i f i c a n t amount of "side gouging" by the flowing ice mass would produce a grandly elevated t y p i c a l hanging v a l l e y from one of these suspended" or precipitous t r i b u t a r y stream v a l l e y s . The above s i t u a t i o n i s p r e c i s e l y what took place in B r i t i s h Columbia's Coast Range in Pliocene to recent times. Such an explanation does not c a l l f o r an undue amount of trough deepening by the action of i c e . -64-Chapter III FRACTURE SYSTEM AND RELATIVE MINERALIZATION F i r s t Observations The data used i n th i s discussion i s mainly the work of Schofield^who was the f i r s t to open th i s i n t e r e s t i n g 2 topic. There are also references to Peacock's study of fior d s combined with personal observations made by the author. Schofield's Work At f i r s t glance a tabulation of vein and shear zone strikes i n B r i t i s h Columbia shows no c h a r a c t e r i s t i c d i r e c t i o n a l control. However, a su r p r i s i n g l y constant system of directions i s noted when bedded deposits are disregarded. The f i r s t set, more t y p i c a l of the coastal area, i s the NW-SE st r i k e of shear zones such as the one forming the Rivers Bright zone on Princess Royal Island. The second, more prominent on the eastern contact margin, i s the NE-SW stri k e of vein types. Bedded deposits are disposed of on the l o g i c a l s t r u c t u r a l grounds that they follow l i n e s of weakness not under the same control as the fracture system, 1. Schofield, S.J Fissure Systems of B.C., C.I.M.M. B u l l . 159, 1925, p 759. 2. Peacock, M.A. Fiord-Land of B.C., G.S.A., Vol. 46. 193b. y -6b-since beds may strik e i n any d i r e c t i o n dependent upon attitude. The fracture directions are found to vary quite re a d i l y up o to 15 , but when the great variations i n rock texture and strength are taken into consideration the constancy of the result i s remarkable. Schofield found d i f f i c u l t y i n sum-marizing the directions due to lack of s p e c i f i c statements as r.gards the use of magnetic or astronomic bearings. I t i s a point of inter e s t that Dr. Mandy^is the only Resident Engineer to state s p e c i f i c a l l y his choice. Comparisons The following i s a l i s t of various mining camps 2 with recorded vein and shear zone s t r i k e s , and a diagrammatic method of i l l u s t r a t i n g the small v a r i a t i o n . ACCORDING TO SCHOFIELD (astronomic bearings) By veins and shear zones A. Coast Range  West Surf I n l e t N25°W(mag.) Lasqueti Is. N35 E Anyox indefinite^ Porcher Is. N60 W Sunlock N27° to 60°W Britannia N45 W East Wheaton D i s t r i c t N45°W - N70°W Salmon River N70°E A t l i n N35°E Upper Hi t z a u l t Beaver R., Y.T, Keno H i l l , Y.T, N45 W N30°- 50°E N30°E N30 - 60°E 1. Mandy, J. T. An. Rep.'B.C. Min. Mines, 1934, p BI, N.Y/. Mineral survey D i s t r i c t . 2. Minister of Mines An. Rep. on B. C. by Res. Engineers, 1923-34. A large sea cave t y p i c a l of marine erosion at an unsettled stage as along B.,C.*s yout h f u l shoreline. The coast i s now at one of i t s periodic temporary s t a n d s t i l l s . A shoreline of emergence has been superimposed on one of submergence due to the conditions that were bringing about o s c i l l a t i o n of the land. The coa s t l i n e has not therefore been long enough s e t t l e d at any one l e v e l to allow any great impression to be made. The r e s u l t i s a heterogeneity of features made more complex by g l a c i a l a c t i o n . The caves are forming along weaknesses determined by the s e h i s t o s i t y of a roof remnant character-i s t i c of the area. The hole extends about f i f t y f e e t i n t o the b l u f f and i s marked on the photograph by an X£ -66-B. I n t e r i o r Plateau C . Kootenays N. Thompson N25°- 45°E N. Thompson N22 - 75°W rhoenix N30°E Cariboo N45°W Cariboo N45°E Bridge R. N45°E Bridge R. N45 W Coquihalla N20°-70°W Coquihalla N50°E Hazelton N55°- 80°E Rossland N60 UE Rossland N60° 5 80°W Ainsworth N45 - 70 W Franklin Camp. N35°-80°E Slocan N45°W Slocan N45 E Yrnir Camp N35 - 65°E St. Eugene N55°W Note: This table shows a s t r i k i n g relationship between the three areas, i t suggests a common genesis of horizontal thrust and, therefore, of b a t h o l i t h i c intrusions whatever th e i r size may be. Thus i t v/ould seem that those long, narrow in t r u s i v e zones, such as the Cassiar, lying p a r a l l e l to the Coast Range are probably cl o s e l y connected i n the zone of flowage being p a r a l l e l l i nes of weakness and subjected to similar stress, ±n one sense, then, they are a part of the Coast Range composite b a t h o l i t h of Jura-Cretaceous age. Cairnes Work I t i s i n t e r e s t i n g to note that i n 1912 Cairnes applied the same method of study to the fracture system of B r i t i s h Columbia as Schofield did i n 1925. However, the work done by the former was too l o c a l i z e d and, therefore, not general In i t s application. Fortunately Cairnes^gave some r e a l value to his work by stating that a l l the bearings used 1. Cairnes, D.D. Portions of A t l i n Dis., B.C., Mem. 37, 1913, G. S. C., P 80. i n his report (1913) were magnetic with an observed v a r i a t i o n of 33°E. In lQlS^he discussed the vein systems of the Wheaton D i s t r i c t , Yukon T e r r i t o r y , under: A. Gold-silver quartz veins B. Antimony-silver veins C. S i l v e r - l e a d veins The l a s t w i l l be omitted from t h i s summary as they are t y p i c a l l y bedded. vN21°E - Astr.) A. Gold-silver According to Cairnes "The veins are generally steep-l y i n c l i n e d and dip, p r e v a i l i n g l y , to the east." 1. Cairnes, D. D. Wheaton D i s t r i c t , Y. T., Mem. 31, 1912, G. S. C., p o7• -68-He also states that the majority str i k e i n a di r e c t i o n p a r a l l e l to the general trend of the Coast Range (NNW - a s t r . ) . In trying to apply Becker's^fracture system and o r i g i n (which requires 2 sets at 90°) he discovered, as above, that there were no evidences of cross-fracturing as far as the g o l d - s i l v e r veins were concerned i n the small area examined. Here i t may be seen that the f a u l t was i n being too l o c a l . The d i s t r i c t must be considered as an entity and not by me'ns of i t s separate vein types. Furthermore, Cairnes allows no idea of ro t a t i o n a l force as a possible o r i g i n . 3. Ant imony-Si1ve r These are confined to a small area and strike i n a general westerly d i r e c t i o n . The writer considers that t h i s set represents cross-fractures and may, therefore, form another system as f a r as the Wheaton D i s t r i c t i s concerned, i t i s to be noted that both the A and B types occur i n Coast Range intrusives as well as i n the host rocks. 1. Becker, C F . G. S. A . , B u l l . Vol. 4, pp 13-90. JUG ISLAND. in Indian Arm at the head of Burrard inlet. Note the perfect handle of rock that the forces of erosion have carved out of solid rock. The island is a small pendant area of volcanics closely underlain by the southerly plunging roof hor-izon of the 6oast Range batholith. The highly altered volcanics are intensely sheared and show a high degree of metasomatism the resultant oxidation of these sheared areas has resulted in very easy erosion along lenticular lines giving such forms as this handle. -69-Cairnes states that most of the B type dip ver-t i c a l l y . The writer believes that the set shown above belongs to the NW-SE, NE— S W system, and that the A set belongs to the minor system (N-S, E-W) or vice versa, i f Cairnes has given astronomic bearings. Cairnes was unable to e s t a b l i s h anything d e f i n i t e about the o r i g i n of the f i s s u r e s i n the Wheaton section because of three f a c t o r s . 1) He assumes non-rotational applied stress. 2) Does not combine the sets into systems - too l o c a l i z e d and, therefore, cannot apply compression. 3) Not enough f i e l d data as .to other s t r i k e s . The writer believes that c a r e f u l work i n the area under surveillance would emphasize four main d i r e c t i o n s , although two of them would be very minor and, therefore, might e a s i l y be l o s t i n averaging. However, Cairnes does attribute the fractui-es of the d i s t r i c t to the same causal stress. He believes that the A type was most l i k e l y tensional (a r e s u l t of post-orogenic movements such as r e l a t i v e c r u s t a l displacements v e r t i c a l l y ) . I t should be r e a l i z e d that he i s thus dating the time of formation of the fractures as s l i g h t l y post-mountain building and not i n the time of compression. The B type i s considered compressional because of a p o s s i b i l i t y of two sets, and i s , therefore, not of the same age of formation as the A type, according to the reasoning applied by Cairnes. Thus his results are inconclusive due to lack of data. -70-The 1913 memoir by Cairnes deals with the fracture system of a portion of the A t l i n D i s t r i c t . Here he again confines his considerations of o r i g i n to a r e l a t i v e l y small area, whereas he admits that the majority of the fissures must be gen e t i c a l l y related. There i s l i t t l e doubt that the causal stresses produced by intrusion and folding are effe c -tive over r e l a t i v e l y large d i s t r i c t s i n approximately the same way and to the same degree with such a large zone of deformation. The following diagram i s a compilation of a l l the bearings given by Cairnes i n the A t l i n D i s t r i c t . Note:-•Solid lines-one set Of vein ^triKes-SroKen lines a 2nd. sst at approx-TO Red - one "system Green - a 2nd. system at -4-50. Arrows marK averages X>ips for This S e r i e s a r s almost vcr-t. 6?0*). — I \ l u 3 . # / 3 . — -71-The diagram results i n four directions being emphasized. Such a conclusion i s e n t i r e l y compatible with that arrived at i n using the strikes of the f i o r d s , where there i s no chance for the minor sets of fractures to be lo s t i n the process of averaging. The A t l i n D i s t r i c t has as an en t i t y , then, two systems of fis s u r e s i n t e r s e c t i n g at 45°, and each system i s composed of two sets approximately at 90° to each other, AS i n the case of the f i o r d s , the NW-bE, NE-SW system i s concordant and usually the stronger (shown i n red). In thi s s pecial area, due to such conditions as hetero-geneity of rock texture, the E-W fractures are the least well represented. i t i s to be noted that the N-S bearing i s a common one for veins, as i t Is also for f i o r d s and ri v e r s 1 P (Stikine e t c . ) , contrary to the opinion of peacock and LordT Lees -•Yukon In exploring the Laberge Area, Yukon, L e e s 3 d i s -covered a d i s t i n c t l y regular system of drainage i n four d i r e c t i o n s . 1) NW-SE 2) A l i t t l e W of N 3) E-W 4) SW-NE 1. reacock, M.A. Fiord-Land of B.C., B u l l . G.S. of Am., Vol. 46, 1935. 2. Lord, C.S. fhys. of C. R. Bath, of'B.C. and s.E. Ala. Thesis, U.B.C., 1929. 3. Lees, E.J. Geol. of Laberge A r e a , M.T., Trans, of Royal Canadian I n s t i t u t e , Vol. XX, Part 1, 1934. -72-The f i r s t two are the most common, and i t i s no coincidence that the two major strikes of formations are i n similar d i r e c t i o n s . Here, then, i s d i r e c t confirmation of str u c t u r a l control giving subsequent drainage. Cairnes would explain the Engineer fi s s u r e s as the res u l t of a highly concentrated v e r t i c a l thrust l o c a l i z e d at this point. The force might be that of growing cr y s t a l s i n the central area or "hub", and would resulo m a radiating set of fractures formed over a long period of mineralization. This theory appears weakly hypothetical. Why should the "hubs" be so l o c a l i z e d i n the f i r s t place? Peacock's Systems Schofield emphasizes the abundance of copper de-posits i n NW shear zones on the western flank,or Intermont Valley Belt, as compared v/ith the single fracture, s i l v e r , lead and gold type s t r i k i n g NE on the eastern flank of the main Coast Range bath o l i t h . This i s not apparent i n the Inte r i o r or Kootenays. Whereas Schofield points out the presence of the concordant system of fractures by using mineral deposits as examples, Peacock, by tracing the strikes of straight-edged islands and f i o r d s , has shown a second sys-tem to be imposed on the f i r s t . This second system he c a l l s discordant. The accompanying map # by the v/riter emphasizes thi s e f f e c t by the use of red ink for the second system. Here i t might be pointed out that Peacock's discordant fractures (far less common) may e a s i l y be lo s t i n averaging the strikes Concordant set of fractures-Black. Discordant set-Red. Note ••- Notice gradual curving of the whole plan with i t s arcuate arrangement. The l i n e s are drawn along a l l straight margins of channels,islands,rivers,lakes etc. -73-of ore deposits. Accordingly they may be mineral bearing, although Peacock assumes on very weak grounds that they are not and, therefore, terms them post-Jura-Cretaceous. A short perusal of the geology of the coast and islands of B r i t i s h Columbia soon brings to l i g h t a f a i r proportion of mineral-f i l l e d fractures s t r i k i n g at 45°to the concordant deposits (Surf Inlet shear zone - N3°E). Peacock assumes that, i f the discordant system i s younger (Eocene), the horizontal thrust that developed i t would have to come from some d i r e c t i o n c l o s e l y p a r a l l e l to the d i r e c t i o n of application of the f i r s t thrust; otherwise the strained area would give along the old l i n e s of weakness. I t i s well recognized that there was tensional down-faulting, as along the Intermont Valley Belt; but thi s was reactionary to the compressive forces, mostly post-mineralization, and took place i n those z'ones of weakness already created by the e a r l i e r compressive stresses. Lord - Schofield Lord, under the able guidance of Schofield, made the f i r s t attempt to plot.the f i o r d s as a method of determining t h e i r main s t r i k e s . He states, "The present writer w i l l attempt to show, In the following pages, that the f i o r d s , i n part at le a s t , are determined i n d i r e c t i o n by a f i s s u r e system developed as a resu l t of pressure and subsequent tension from the west and south." 1 He used c i r c u l a r diagrams 1. Lord, C.S. The Phys. of the C. R. of B.C. & S. E. Alaska, Thesis, U.B.C., 1929, p 70. -74-and allowed f o r v a r i a t i o n l o c a l l y by a d i v i s i o n of the coast into three sections - southern, central and northern. One of the main d i f f i c u l t i e s encountered by Lord v/as the personal f a c t o r . Due to Inaccuracy of d e t a i l s on the maps, the judg-ment of angular changes i s exceedingly rough. The accom-panying large-scale maps by the writer are an attempt to reduce this error and, therefore, they only deal with limited sections. {#3,S/dj. Any channel with varying, i n d e f i n i t e bearing v/as disregarded. These are often due to curving contacts between quartz-diorite and schist and, therefore, need not be considered. Lord's results are as follows: 1) Southern Area - 3 bearings stressed. N10°E, N27°W and N83°W 2) Intermediate Area - 3 bearings stressed. N53°E, N, N45°W. The N-S set was unusually well defined. 3) Northern Area - 3 sets stressed. N37°E, N6°W and N40°W Note that angular relations of the three sets are approximately the same i n each case. Each diagram had two o sets at 90 and one oblique set. Lord assumed non-rotational horizontal force and, therefore, placed his major applied stress at 45° to the rectangular system, or at 90° to the oblique set. Here he further assumed the greatest elongation of the applied s t r a i n e l l i p s o i d as horizontal ( d i r e c t i o n of easiest r e l i e f ) . I t can r e a d i l y be seen that no attention has been paid to dips, and therefore the planes of maximum shearing are not accurately known. The two most northerly ^ c o / e . - / V j , 7 m i . By V. * &£~>* i 936. Hofe:- green - one *y«7<?/7?. -75-areas proved to have almost i d e n t i c a l bearings, and the southern one shows an angular s h i f t comparable with that of the grain of the coast-line i n this section. (Cape Scott) I f the various assumptions are correct, Lord has proven the pressure to have acted from the east or west, but most l i k e l y the west. South of Cape Scott the d i r e c t i o n of application was south-west. His interpretation states, "Not only do the t i d a l waterways tend to follow t h i s f i s s u r e system, but the same may be said of many of the r i v e r s and lakes The arrangement of the f i o r d - l i k e lakes along these l i n e s i s quite s t r i k i n g and applies not only to those within or along the border of the range but also to the many lakes of t h i s type scattered throughout the i n t e r i o r of the province." 1 The l a s t point i s to be expected only upon con-sideration of the close orogenic relationship of the Selkirk, Cassiar, Insular and Coast Range Mountains. The much less common fourth set of Peacock's (E-W) has seemingly been l o s t i n the p l o t t i n g method used, but It i s only by e s p e c i a l l y c a r e f u l work that such a minor set of fractures could be retained i n averaging. Lord maintains that he knows of no mineralized N-S fractures, but one notable instance i s that of the Surf Inlet Gold Mine. Furthermore, the three valleys of the S t i k i n e , Klena Klene and Homathko Rivers occupy north and south v a l l e y s , which v/ould be impossible i f the s t r u c t u r a l 1. Lord, C. S.. Phys. and Geol. of the C. R. of B.C. & S.E. Alaska, Thesis, U. B. C , 1929, p 76. -76-control was not pre-Cretaceous. L e i t h Before discussing the o r i g i n of the fracture system (a highly conjectiiral problem v/ith the existing data), i t 1 might be well to consider some of Leith's ideas on stress and s t r a i n r e l a t i o n s . He emphasizes the fact that many f i e l d geologists assume compressional forces to be non-rotational when they might equally well be r o t a t i o n a l . Furthermore, i t i s only i n rare cases where f i e l d .relations show, not only the p o s i t i o n of a l l three axes of the s t r a i n e l l i p s o i d , but, in'addition, whether the stress was r o t a t i o n a l or non-rotation-a l that the angular relations of the fracture to the applied compressive stress can be stated with some pre c i s i o n . The d i r e c t i o n of the applied deforming pressure i n fold i n g may be s i m i l a r l y misconstrued (may or may not be at 90° to axis of f o l d i n g ) . I f the forces are known to be non-rotation-a l , then the d i r e c t i o n of application bisects the angle be-tween the fracttires. I f the forces are r o t a t i o n a l , the d i r e c t i o n may vary considerably. I t i s possible that the Coast Range fracture systems originated by either compressive r o t a t i o n a l or non-rotational forces, or by both. L e i t h i n s i s t s , and r i g h t l y so, that i n order to gain a proper picture of conditions involved i n a r i g i d , e l a s t i c body under stress, three dimensions should be 1. L e i t h , O.K. Structural Geology, 1923. #23. Lit par l i t injection of aplo-granite on the north-easterly shore of Howe Sound one mile north of Horseshoe Bay. The area marks a small roof pendant in the batholithic granodiorite which is underlying at a relatively short distance the schists shown here. The intrusive rock is light coloured(acidic) and is part of the residium left over in the magma chamber and literally squeezed out as a last minute healing solution into the fractures and openings. They are not pre-granodiorite because they are usually discordant and apparently were not subjected to the intense folding that the schists suffered. -77-considered. He brings into f u l l use a conventional unit of reference - the s t r a i n e l l i p s o i d - which describes c l e a r l y stress and s t r a i n r e l ations i n any imaginable sphere of a body when deformed. This, he claims, can be applied to a l l s o l i d bodies, including rocks. I t must be remembered that this e l l i p s o i d can only describe c l e a r l y the known facts i n a three-dimensional manner. I t cannot give the d i r e c t i o n of the compressive forces or the i r r o t a t i o n a l or non-rotational character. Thus, i f the e l l i p s o i d be applied to any imagin-able sphere of the batholith under compressive s t r a i n (ro-t a t i o n a l or non-rotational), i t w i l l show re a d i l y the approx-imate location of the olanes of maximum shear or no d i s t o r t i o n - or vice versa. This i s because there are only two c i r c u l a r cross-sections i n such an e l l i p s o i d , and these planes can be the only ones that have suffered no d i s t o r t i o n and, therefore, a maximum of shearing. I t might be noted that a l l other planes i n the e l l i p s o i d are under shearing strains of varying i n t e n s i t y , but they have had f a i l u r e by d i s t o r t i o n also, unlike the two c i r c u l a r cross-sections. The two .planes of no d i s t o r t i o n , or maximum shear, occupy similar positions i n the e l l i p s o i d for either r o t a t i o n a l or non-rotational s t r a i n s . -78-I t may be seen i n both, c i s . s that the applied stress u i s always at 90 to the intersection l i n e of the two maximum she'-r planes (or the mean stress a x i s ) , although i t bisects the angle between the planes i n the non-rotational exampley£$. and i s at any i n c l i n a t i o n to the planes i n the rot a t i o n a l example. I t may be observed from L e i t h 1 s conclusions that non-rotational s t r a i n i s just one special case of ro t a t i o n a l i n which the angular i n c l i n a t i o n of the stress axes to the st r a i n axes has become zero. That i s , r o t a t i o n a l stress shows an i n c l i n a t i o n between the applied deforming stress and the p r i n c i p a l axes of stress (because they are i t s normal com-ponents), as well <is an i n c l i n a t i o n between the greatest axis of stress and the least axis of st r a i n or minimum elongation. This angular r e l a t i o n of both the stress and s t r a i n axes to the d i r e c t i o n of applied stress i s continuously changing, due to the inherent rotating nature of the l a t t e r . At any given instant the greatest elongation, or the greatest axis of -79-strain,tends to be normal to the greatest axis of stress, but rotation prevents the continuation of t h i s r e l a t i o n , with the result that the axis of greatest t o t a l elongation may be in c l i n e d at considerably less than 90° to the greatest axis of stress. ±t can be understood, then, that there are many d i f f i c u l t i e s i n the way of pict u r i n g the axes of stress. What i s seen i s t o t a l s t r a i n or elongation - this must be inferred stress. The d i r e c t i o n of the applied stress cannot be t o l d , because i t may be either r o t a t i o n a l or non-rotational i n i t s nature. I t must be recognized that the shape of the Coast Range ba t h o l i t h has very l i t t l e to do with the attitude of the applied s t r a i n e l l i p s o i d . I t i s not i t s greatest length of mass, but i t s greatest elongation due to deforming pressure, that must be considered. That i s , i t s greatest length i s KW-SE, but i t s greatest elongation could be v e r t i c a l under certai n conditions explained i n the following. I f i n the case of the Coast Range ba t h o l i t h the axes of stress (normal components of the applied stress) can be shown to be p a r a l l e l to the axes of s t r a i n , then It i s non-rotational and the applied stress i s p a r a l l e l to the greatest axis of stress, or bisects the angle between the planes of maximum shearing. Conversely, knowing the position of the planes of maximum shearing, i f i t could be proven that the deforming stress bisects t h e i r angle of in t e r s e c t i o n , the case i s non-rotational and the axes of stress are p a r a l l e l to the axes of s t r a i n . With the known data this cannot be done. -80-L e i t h says i t has been a common practice to assume that where two sets of joints intersect at 90° , or nearly so, the system represents a non-rotational s t r a i n . This i s no c r i t e r i o n , as may be seen by applying the e l l i p s o i d , f t has been e s p e c i a l l y common to assign intersecting sets of v e r t i c a l joints to horizontal non-rotational compression, but this assumption implies that the mean axis of the e l l i p s o i d i s v e r t i c a l , the other two horizontal and that they cannot be placed i n any other p o s i t i o n . I t w i l l be noted that schofield' suggests horizontal non-rotational compression from the west as the o r i g i n of the intersecting sets of v e r t i c a l joints i n the Coast Range ba t h o l i t h . He i s , therefore, assuming the attitude, as above, of the e l l i p s o i d . Then he states, from general observation, that the maximum elongation, or the maximum s t r a i n axis of the e l l i p s o i d , i s v e r t i c a l . This statement i s inconsistent with the above fracture system. That i s , assuming the force non-rotational and accepting the two directions of fracture as co r r e c t l y determined, the applied s t r a i n e l l i p s o i d can only be placed with i t s mean axis v e r t i c a l , or easiest elongation N-S. Given, then, the attitude of the e l l i p s o i d , i t i s possible to locate the planes of maximum shear (planes along which the stress i s at a maximum) without regard to whether 1. L e i t h , C.K. Structural Geology, 1923, p 42. 2. Schofield, S.J. Fracture System of B.C. C.I.M.M., Bull.159, 1925, p 762. -81-the applied force i s tensional or compressional, r o t a t i o n a l or non-rotational. Conversely, i f the planes of maximum shear he known, the p o s i t i o n of the e l l i p s o i d may be deter-mined. In the case of the Coast Range ba t h o l i t h the pre-viously computed concordant fractures are the planes of maxi-mum shear. The e l l i p s o i d may thus be placed. Its maximum elongation i s , therefore, N-S (assuming the deforming force to be h o r i z o n t a l ) , and i t s greatest shortening i s E-W. This i s true for either r o t a t i o n a l or non-rotational applied stress (assuming that the directions of fracture above are c o r r e c t l y determined), and i t i s therefore impossible to locate the d i r e c t i o n of the deforming stress without further data. In the case of the Coast Range bath o l i t h s c h o f i e l d 1 believes the deforming force to have been compressive, because of the presence of sheared zones and two sets of fractures at about 90°to each other. He states 7with reasonable assurance that (a) the d i r e c t i o n of easiest r e l i e f was up-ward, not necessarily v e r t i c a l . This appears l o g i c a l when the immensity of the batholith i s considered i n conjunction with the large l a t e r a l and t h i n roof areas that would require moving In horizontal and near v e r t i c a l elongation respectively. L e i t h r e a d i l y admits that i n most cases r e l i e f has been upward. However, s t r u c t u r a l weakness might have been great enough i n a N-S d i r e c t i o n to have allowed easiest r e l i e f 1. Schofield, y.J. Fissure System of B.C., C.I.M.M., b u l l . 159, p 762. 2. L e i t h , C.ii. Structural Geology, 1925. -82-along this l i n e . Schofield also states that (b) there was a horizontal shortening of the mass, and he considers the deforming force to be nearly horizontal. This l a s t i s an assumption generally accepted by geologists, although the cause i s highly contested. Assuming that (a) and (b) are correct, the .approximate position of the s t r a i n e l l i p s o i d as regards the bath o l i t h i s known. The axis of maximum s t r a i n , or least stress, i s upward (not necessarily v e r t i c a l ) , and the axis of mean s t r a i n i s i n a horizontal plane. But, as shown before, the position of the planes, or maximum shear, do not f i t into this attitude of the e l l i p s o i d . Mead performed an experiment that i s s t r i k i n g l y s imilar i n i t s fracturing to that of the two Coast Range systems - concordant and discordant. Whether i t may be applied to as heterogeneous and i r r e g u l a r a mass as the Coast Mountains i s problematical, but i t at least gives a possible l i n e of reasoning. He stretched a rubber square on a rack (B) and coated i t with a thin skin of c h i l l e d p a r a f f i n . Defor-mation was brought about by means of a screw (A) as shown. i.. ..ead, W.J. Notes on Lech, of Geol. Structures, journ. Geol., Vol. 38, 1920, pp 512-513. -83-The sketch shows two systems of fractures, the two •fe±se sets corresponding to the concordant system, and the two red sets corresponding to the discordant system of the Coast Range f i s s u r i n g . The concordant system i s the stronger i n both cases and appears more intense p a r a l l e l to the ap-p l i e d force i n the experiment. This l a t t e r system i s v e r t i c a l with horizontal displacement, and represents two directions of non-distortion or maximum shearing, the easiest r e l i e f l y ing i n the plane of the rubber. The f i r s t fractures to appear were the tension cracks (red) i n c l i n e d about 45° to the di r e c t i o n of the shearing force and at 90° to the maximum elongation. These were followed by the two tefere sets, and then by another set (thrust f a u l t s ) s t r i k i n g across the ten-sion cracks at 90° and i n c l i n e d approximately 45° i n either d i r e c t i o n . The l a t t e r are due to compression as shown below. compression / stress. / ~ / / Although this experiment cannot be applied d i r e c t l y to the batholith, i t does show what might have happened l o c a l l y , and It brings out the point that the o r i g i n a l d i -rection of the deforming force i s r e a d i l y masked by a multi-tude of developed components producing d i f f e r e n t sets and systems of fractures. Quoting L e i t h , "The assumed stresses - <SC5 d — Tombolo or a land-tied island at Whytecliffe,B.C. on Howe Sound. Note the reef projecting from the mainland to the island. The rock is granodiorite of the Coast Range batholith close to its roof horizon as indicated by the roof remnant patches. This type of island is characteristic of B.C.'s fiordland a drowned and indented coastline. The reef and island were formerly part of a headland but were reduced to their present state by wave and current action in the bay on either side of the headland. Erosion followed a line of structural weakness created by a thin roof-pendant of schistose volcanics. The rounded character is a glacial modification. -84-may be only minor components of the major causal stress and give no clue to i t s d i r e c t i o n . " 1 I t also stresses the fact that at least two systems may be formed by a single major d i r e c t i o n of pressure. There i s one f a i r l y d e f i n i t e thought that has occurred to the writer. The f r a c t u r i n g developed i n the Coast Range bath o l i t h could not have been the r e s u l t of deformation from a single point of application as i n the above experiment, but could only have been the r e s u l t of a presumable horizontal plane of thrusting extending the length of the mountain range. I t may be assumed that the major causal stress i s non-rotational, i n which case i t s d i r e c t i o n of application i s not as d i f f i c u l t to determine as i n non-r o t a t i o n a l deformation; but of course t h i s i s purely an assumption. Similar results are possible i n either vase. Comparisons - Beams o Finlay^maintains that the b a t h o l i t h can hardly be compared to a beam under stress, but he shows what happens i n the case of a tabular body of current undergoing deformation. The greatest amount of shearing i s l i k e l y to occur at the ends of the beam, because the r e l a t i v e displacement between the layers i s greatest here, while the greatest f r a c t u r i n g occurs i n the central portion, with compression on the side 1. L e i t h , O.K. Structural Geol., 1923, p 9. 2. F i n l a y , A.H. Prof, i n Structural Engineering at U.B.C. Personal communication. - . -of a p p l i c a t i o n of the f o r c e and t e n s i o n (open c r a c k s ) on the o t h e r s i d e , as i n the f o l l o w i n g diagram. Support-Applied force Note ••-the ob/ique "cranked'frcrctures thof devc/op in the intermediate ai-eas. I f the b a t h o l i t h i s c o n s i d e r e d i n a s i m i l a r l i g h t , t h e r e s h o u l d be a g r e a t e r number of sheared zones w i t h a p p r o x i m a t e l y NW-SE s t r i k e s a t the ends of the a r c shown on I l l u s t r a t i o n , w i t h a g r e a t e r number of f r a c t u r e s NE-SW towards the c e n t r a l p o r t i o n . Peacock's Assumptions P e a c o c k ^ r e g a r d s the b a t h o l i t h and i t s a u r e o l e of f o l d e d r o c k s as a t a b u l a r body of r i g i d m a t e r i a l u n d e r g o i n g d e f o r m a t i o n by d o m i n a t i n g h o r i z o n t a l f o r c e s a c t i n g from the 2 NE. Dr. J . G. D a v i d s o n p o i n t s out t h a t such a c o n c e p t i o n i s f u t i l e , i n t h a t a beam i s a s e p a r a t e u n i t , whereas the Coast Range i s o n l y a s m a l l p a r t o f a l a r g e r mass of r o c k , and i t s r e l a t i o n s w i t h such must be c o n s i d e r e d . That i s , w h i l e a 1. Peacock, B.A. F i o r d - L a n d o f B.C., B u l l . G e o l . Soc. of Am., V o l . 46, A p r i l , 1935, p 684. 2. D a v i d s o n , J.G. P r o f , of P h y s i c s a t U.B.C. P e r s o n a l Comraun. -86-beam would fracture compressionally on the side of application of pressure, a mass of rock would fracture tensionally i n open cracks due to i t s b r i t t l e n e s s and the anchoring e f f e c t of the surrounding rocks on i t s extremities. Naturally, when bent outwards i t must take up a greater space, as i n the fo 01 Peacock offers the "arc and cusp" plan of the coastland mountains as shown on I l l u s t r a t i o n #/£as proof of a deforming stress from the NE, but i t should be noticed that this arctuate form may have been developed previous to the time of f r a c t u r i n g , such as during the time of formation of the huge geanticlines and geosynclines that were to produce the l a t e r Coast Range. Furthermore, Peacock immediately assumes that, because the arcs are bent out towards the SW, the stress must have come from the NE, with utter disregard for the fact that the major causal stress may have been r o t a t i o n a l even though sortie of i t s components are normal. He states that under such a force t e n s i l e 'stresses would develop i n the advanced part of the arc as i n a bent beam. These would be r e l i e v e d by tension fractures running at 90° to the t e n s i l e stresses, or r a d i a l l y to the arc. They might deviate — Page 3 6 a . -This diagram shows the curving acuate trends of the Eastern and Western Mt. Belts and the r e l a t i v e position of the fiordland. One major arc extends from s l i g h t l y north of Vancouver to Yakutat Bay. Note the abrupt inflexions or cusps where the arcs j o i n . Peacock considers this plan strongly suggestive of d i f f e r e n t i a l horizontal crustal displace-ment by forces from the NE and greatest at the middle of the arc. However, this curved plan may have been due to an inherent structure such as a curved basin of sedimentation. It i s at the best a highly theoretical consideration. -87-considerably, as would any type of fracture i n such a hetero-geneous mass. Shearing stresses would also be set up along v e r t i c a l planes p a r a l l e l to the grain, and these would be relieved by longitudinal shear fractures. The above sets of fractures form Peacock's con-cordant system (because they are p a r a l l e l and normal to the grain of the coastland(). His discordant system, s t r i k i n g at 45° to the other, which, on very weak evidence, he terms younger, he considers a product of comparable, opposed, horizontal forces acting transversely (thus from the NE and SW) to the trend of the region. He also states that any other d i r e c t i o n would only cause further movement along the already established system. Curious to r e l a t e , he f i r s t compares the rock mass to a r i g i d beam and then to a p l a s t i c material. Such forces would cause the greatest deformation at the margins of the compressed be l t , and the least defor-mation i n the middle. Strange as i t may seem, most of the writers who have thus f a r dealt with the Coast Range fracture system have f a i l e d to tabulate the dips of fractures and shears -only t h e i r s t r i k e s . I t can r e a d i l y be seen that i n order to determine the attitude of the planes of maximum shear both of these must be known. In this manner only can the position of the e l l i p s o i d be accurately worked out. Care must be taken not to read into a fracture or j o i n t system a r e g u l a r i t y which does not e x i s t . -88-Summary A summary of the f a c t s , p o s s i b i l i t i e s and assump-tions concerning the b a t h o l i t h i s tabulated below. 1) A concordant system of fractures s t r i k i n g NW and NE. Most common ( i f the method of determining these be accepted as c o r r e c t ) . 2) A discordant system s t r i k i n g N and W. Less common.(If accepted as c o r r e c t ) . 3) Both systems appear to be mineralized to some extent. 4) Therefore probably of similar age - (post-commencement of orogeny and pre-mineralization - Jura-Cretaceous) 5) The s t r a i n e l l i p s o i d may be applied to both systems. 6) The p o s s i b i l i t y that there may be more than 2 systems. That i s , one s t r i k e may have 2 dips, or the s t r a i n e l l i p -soid i s v e r t i c a l i n elongation. 7) No tabulation has been made of the dips. 8) Not enough data to show whether the deforming stress was r o t a t i o n a l or non-rotational. 9) Therefore cannot determine the d i r e c t i o n of application of the deforming stress. 10) I f the force i s assumed to be non-rotational ( i . e . the axis of greatest stress i s p a r a l l e l to the axis of least s t r a i n or greatest shortening) the d i r e c t i o n of applica-t i o n bisects the known fracture system or planes of maximum shearing. However, i n such a case the d i r e c t i o n of maximum elongation or easiest r e l i e f must be h o r i -zontal, i n order that 2 strikes at 90° may be seen. -89-(If i t be accepted that the 2 strikes be c o r r e c t l y determined) The attitude of the e l l i p s o i d i s determined from the po s i t i o n of the fractures, ( i . e . the planes of maximum shear or vice versa) I t i s generally accepted that the deforming stress was hori z o n t a l . (Most of the theories concerning orogeny emphasize this.) The intrusion of the bat h o l i t h could not have been the entire cause of the fr a c t u r i n g , be-cause i t i s large l y fractured i t s e l f , and thi s must have occurred during, or shortly after, emplacement and hardening. Geologists have a great propensity f o r assuming the deforming stress as non-rotational, although the s t r a i n e l l i p s o i d and planes of maximum shear occupy similar positions i n both r o t a t i o n a l and non-rotational stress. The arctuate form might have been determined equally as well by the po s i t i o n of the basin of sedimentation and the eroding geanticlines, as by the bending outwards by pressure from the NE. When the heterogeneity of the rock mass i s considered along with the variations i n pressure and t h e i r d i f f e r -e n t i a l application, i t i s wonderful that any system i s preserved at a l l . The pulsating nature of the intrusion (Eocene or Oligocene times) must have disrupted the system l o c a l l y , but not very completely, due to the much smaller.size of these l a t e r invasions. -90-Underlying Causes The actual cause of the overpowering stresses that have resulted i n "rock f a i l u r e " i n the Coast Range Mountains i s more highly conjectural than the d i r e c t i o n of application. I t has been variously ascribed to i s o s t a t i c adjustment, to a shrinking cehtrosphere, to t i d a l s t r a i n s , to changing c e n t r i -fugal pressure and to igneous i n t r u s i o n . The f i r s t signs of f a i l u r e that developed i n the sinking geosyncline might be attitbuted to loading stresses, thus i n i t i a t i n g lines of weakness, upon which followed shear-ing and f o l d i n g , factors i n orogenesis. I t i s known that d i r e c t u p l i f t of more than 4,000 feet did occur, but did pressure from the sides cause the folding and upliftingythus making room for the pressure-relieved magma to well up into the roof rocks, or did the l a t t e r force i t s own way nearly v e r t i c a l l y and thereby raise the rocks? Probably i t was both, combined with, a narrow margin of stoping at the actual roof surface. Leitb^believes that many b a t h o l i t h i c masses show evidence of having folded and exerted pressure against host rocks. (Zonal arrangement of f o l d s , cleavage and metamorphism.) The Coast Range shows an ,amazing r e g u l a r i t y of s t r i k e i n Its roof-pendants, and an otherwise uncalled f o r alignment of s t r i k e around the ends of the batholith. At any rate, the cause of the stresses i s too t h e o r e t i c a l to be 1. L e i t h , C.K. Structural Geology, 1923, p 250. -91-given further consideration i n t h i s work. Since Peacock's method of finding the bearings of the fracture systems of the f i o r d - l a n d deals mainly with g r a n i t i c rocks, i t seems only l o g i c a l to assume that the b a t h o l i t h was p r a c t i c a l l y i n place, and at least p a r t l y cooled near i t s roof horizon, when the fractures originated. Other-wise there would be no system but only a chaotic jumble of fracture planes. Thus the deforming stress must have been continued past the period when the b a t h o l i t h was p r a c t i c a l l y empl- ced. Many of the coastal channels show a fractured depth of at least a mile, and i f these fractures (which s t r i k e p a r a l l e l to those i n the roof rocks) are to be attributed to the same deforming stresses as the higher ones, the batholith must have been at least p a r t i a l l y s o l i d i f i e d ( i n order to r e t a i n any imposed s t r u c t u r a l weakness) at that time of stress. There i s the alternative that the deeper fractures, i f lacking signs of shearing, may be the product of cooling of the igneous mass, but such joints are r a r e l y regular over much area. Although Schofield believes that the deforming stress was from the west (the s i t e of Cascadia), and Peacock thinks i t v/as from the north-east (assuming non-rotational) i t i s e n t i r e l y possible that pressure may have been exerted from both, sides, due to the presence of a geanticline supplying sediments from those positions. The pressure undoubtedly varied along either margin and may have shown a net force greater on one side than the other. I t i s c e r t a i n l y s t r i k i n g that the mountains should have the arctuate -92-form described by Peacock, but this may have been determined by the s t r i k e of the o r i g i n a l geosynclinal seaways and, therefore,of the eroding geanticlines - Cascadia and the present I n t e r i o r Plateau. BIBLIOGRAPHY Peacock, A. M., Fiord-Land of B. C , B u l l e t i n of the Geological Society of America, Vol. 46, 1935. Schofield, S. J . , Coast Range Composite Batholith., personal publication. I s b i s t e r , A. K., Q. J. G. S., London, 1851, p 497. Camsell, C., Geological Survey of Canada, Summary Report, 1920. Bancroft, J. A., Geology of the Coast and Islands between S t r a i t of Georgia and Queen Charlotte Sound, B. C., Geological Survey of Canada, Memoir 23. Brooks, A. H., The Geography and Geology of Alaska, U. S. G. S. Professional Paper 45, 1906. Buddington, A. F. & Chapin, T., Geology and Mineral Deposits of S-E Alaska, U. S. G. S., B u l l . 800, 1929. B irwash, E. M. G., Geology of Vancotiver and V i c i n i t y , Chicago, 1918. Clapp, C. H., Southern Vancouver Island, G. S. C , Mem. 13, 191 Dawson, G. M., On the S u p e r f i c i a l Geology of B. C , Geological Society of London, Quart. Journ., Vol. 34, 1878, pp 89-123. Dolmage, V., Coast and Islands of.B. C. between Burke and Douglas Channels, G. S. C , Summ. Report, 1921A pp 22-49. Coa.;t and Islands of B. C. between Douglas Channel and the Alaskan Bo ndary, G. S. C , Summ. Report, 1922A, pp 9-34. Geographic Board of Canada, Nomenclature of the Mountains of Western Canada, Ottawa, 1918. 4 pages and map 100 miles to the inch, G i l b e r t , G. K., Glaciers and Glaciation, Harriman Alaska Series, Vol. 3, Washington, 1910. Graham, R. P. D., On a Preliminary Survey of the Geology of B.C. Coast from Kingcome Inlet to Dean Chan. Including Adjacent Islands, G. S. C , Summary Report, 1908, pp38-40. Leroy, 0. E., Preliminary Report on a Portion of the Main Coast of B. C. and Adjacent Islands Included i n Mew Westminster and Nanaimo D i s t r i c t s , Geol. Survey of Canada, Publication 996, 1908. Mackenzie, J . D., Geology of Graham Island, B. C , G. S. C , Memoir 88, 1916. Martin, Lawrence & Williams, F. E., An Ice-eroded F i o r d - the Mode of Origin of Lynn Canal, Geol. Rev., Vol. 14, 1924, pp 579-596. McCann, W. S., Geology and Mineral Deposits of the Bridge River Map Area, B. C , G. S. C , Mem. 130, 1922. Schofield, S. J . , The Fissure Systems of B. C , C. I. M. M., B u l l . , Vol. 159, 1925, pp759-764. Schofield & Hanson, C., Geology and Ore Deposits of Salmon River D i s t r i c t , B. C , G. S. C , Mem. 132, 1922. Uglow, W. L., Cretaceous Age and Early Eocene U p l i f t of a Peneplain i n Southern B. C , Geol. Soc. of Am. B u l l , , Vol. 34, 1923, pp 561-572. Wright, F. E. & Wright, C. W., The Ketchikan & Wrangell Mining D i s t r i c t s , Alaska, U. S. G. S., B u l l . 347, 1908. Johnston, W. A., Geology of the Fraser River Delta Map A r e a , Memoir 135, 1923. Brooks, A. H., Prelim. Report on Ketchikan Mining D i s t r i c t , Alaska, U. S. G. S., Prof. Paper 1, 1902. Kerr, F. A., Structural Relationships of Mineral Deposits along C. N. R., "The Miner", Sept. 1935, Vol. 8. Prelim. Report on Iskut, Summ. Rep. 1929, Part A. Mandy, J . T., Lode Gold Deposits of B. C , Dept. of Mines, B u l l . l , 1932. Minister of Mines, Annual Reports 1923-34 for B. C. - Resident Engineers. Le i t h , C. K., Structural Geology, 1923. 

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