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Geology of the STANFORDRANGE of the Rocky Mountains

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Geology of the STANFORDRANGE of the Rocky Mountains BRITISHCOLUMBIA DEPARTMENT OF MINES HON.R. E. SOMMERS, Minister JOHNF. WALKER, Deputy Minister BULLETINNo. 35 Geology of the STANFORDRANGE of the Rocky Mountains Kootenay District, British Columbia By G. G. L. Henderson VICTORIA, B.C. Printed by DONMcDua~lo, Printer to fhe Queen's Most Excellent Majesty 1954 " . .. ILLUSTRATIONS FlOURE .. 1. Key map of southeastern Brltlsh Columbia ..............~ ..... ~.~~~~ ...... ~..~..~~........ ~~ ...... ~.~~~.9 2. Geological map of the StanfordRange.- ....~~~~ ...... ~~~ ....... ~~~~ ......... inpocket 3. Structural cross-sections of the Stanford Range.............. ~~ .....~~~..~~ .......~ ....... in pocket 4. Regional geology of part of the Rocky mountains^"....... ~~ ~ ........~~ .......... ~..~...45 5. Structural sections W-X and Y-Z across the Rocky Mounfains~~.-~....... ~~~ ......... ~..~~..47 6. Diagrammatic cross-sections showing theoretical development of wedge and of White River break................. ~~~ ......~ ..................................... ~~..~.........~~~ ......~...~ 50 7. Preliminary graph of the transition temperature of gypsum to anhydrite...~.~..~....... 59 8. Geological map of Columbia Gypsum workings on Windermere Creek....".-. In pocket 4 PHOTOGRAPHS PLATE Pme I. Aerial view of large nappe-like dragfolds near Gibraltar Rock ......................... 30 I1. Looking northeast across Stanford Range." .................................. following 84 I11 . Looking south across Madias Basin to Indianhead Mountain............ Following 84 IV . Typical laminated character of Lower Jubilee do1omite~- .................. Following 84 V . Calcareous chloritic phyllite in the canyon of the White River..... following 84 VI . Recumbent fold on major overturned limb in the eastern fault block ............ ................................................................... following following following 84 VI1. Dragfolded anticline of McKay strata on the eastern flank of Indianhead Mountain ................................................................................. fo following 84 VI11 . Block of contorted Harrogate formation down-dropped between Lower Jubi- lee dolomite and Beaverfoot-Brisco formation ....................... fo following 84 IX . Faulted anticline on Mount DeSmet ................................................. Following 84 X . " Hoodoos " of Redwall fault breccia on the divide between Mary-Anne and Tatley Creeks.~-~................................................................... fo f following 84 XI. Junction of Kootenay and White Rivers ........................................... Following 84 XI1. Overturned, compressed anticline on Hawk Ridge, east of Vermilion River .... ...................................................................... following 84 XI11. Contorted Goodsir (?) formation above a southwest-dipping thrust fault near the head of Palliser River." ....................................................... following 84 XIV . Flat-lying gypsum forming a cliff more than 200 feet high on Kootenay River ................................................................................................. following 84 XV . Well-laminated gypsum at quarry on Windermere Creek 84 XVI . Closely spaced joints in well-laminated gypsum on Windermere Creek .......... .................................................................................................... Following 84 XVII . Columbia Gypsum Products quarry on Windermere Creek . winder mere following 84 5 Geology of the Stanford Range of the Rocky Mountains, Kootenay District, British Columbia SUMMARY 1. The Stanford Range is one of the western ranges of the Rocky Mountains lying between the Rocky Mountain trench and the Kootenay River, about midway between Cranbrook and Golden. 2. The range has a maximum relief of over 6,000 feet and an average local relief of ahout 3,000 feet. Although it contains no glacial erosion features, the presence of erratics at high elevations indicates that at one time at least it was covered with ice. 3. All the rocks in the Stanford Range are sedimentary. They range in age from Late Precambrian to Middle Devonian and consist mostly of limestones, dolomites, argillaceous limestones, and limy shales. The remainder of the section, about 30 per cent, is made up of black shales, quartzites, argillites, slates, conglomerates, and rock gypsum. 4. The gypsum occurs in a thick section interbedded with occasional calcareous members, andthe whole comprises a new formationfor which the name Burnais is proposed. The age of the Burnais formation isbetween Middle Silurian and Middle Devonian. 5. A unique metamorphic rock, resembling a pbyllite, is developed within a mile- wide zone of shearing that follows the Kootenay and White Rivers on the northeastern side of the map-area. This shearing is associated with a regional longitudinal fault named the White River break, and remains within the limits of McKay group strata throughout its exposed length. 6. The Stanford Range is divided into three fault blocks by two longitudinal faults, the Redwall and Stanford, that extend throughout the length of the range. The fault blocks are named the Eastern, Central, and Western, and each contains distinct types of structures. 7. The Eastern fault block, between the Kootenay River (White River break) and the Stanford fault, contains the lower limb of a southwesterly overturned, almost recum- bent fold which is locally contorted into large nappe-like dragfolds. 8. The Central fault block, between the Stanford and Redwall faults, is character- ized by upright, inclined, and overturned anticlines which are separated from each other by faulted synclines. 9. The Western fault block, between the Redwall fault and the Rocky Mountain trench, contains complex, longitudinal trending folds which are intricately dissected by a network of faults. In addition, a large area is underlain by obliquely trending, imbri- catethrust structures. These are indicative of shortening of the range alongan axis almost parallel with its trend. 10. The Redwall and Stanford faults, as well as many of the other faults in the range, are characterized by wide red- or brown-coloured breccia zones. The movement on the Redwall fault is large and is mostly strike-slip. Strike-slip movement may also have occurred on the Stanford fault, hut,unlike the Redwall fault, this cannot be proved. 11. Metamorphism in the Stanford Range is generally restricted to areas of tight folding and the border zones of major faults. With the exception of the intense aha- 7 tion of McKay group rocks along the White River break, the effects of metamorphism are limited to those usually attributed to low-grade dynamic metamorphism. 12. The Rocky Mountains at this latitude are composed of four separate structural sub-provinces for which the following names areproposed: Foothills sub-province, Front Ranges sub-province, MainRanges sub-province, and Western Ranges sub- province. Each of these contains distinct structure, stratigraphy, and topography. 13. The Stanford Range forms part of the Western Ranges sub-province, which is distinct from the other sub-prolinces inasmuch as the folds are overturned toward the southwest instead of the northeast, the structures are a great deal more complex, and the structural trend is about 10 to 15 degrees oblique to the trend of the Rocky Moun- tains and the Rocky Mountain trench. 14. The Western Ranges sub-province is separated from the Main Ranges sub- province by a major longitudinal fault zone that extends from Blaeberry southeastward along the Beaverfoot, Kootenay, and White Rivers for at least 120 miles. The name White River break is proposed for this fault.The sub-province is bounded on the southwest by the Rocky Mountain trench. 15. The White River break separates the southwesterly overturned structures of the Western Ranges sub-province from flat to gently folded strata of the Main Ranges sub-province. It also marks a distinct break in the stratigraphic continuityof the western Rocky Mountains. 16. The White River break appears to dip southwest. It is interpreted as a thrust fault of younger age than the southwesterly overturned structures of the Western Ranges sub-province, which are believed to have been formed by a major wedge uplift of the Main Ranges sub-province. 17. Gypsum of commercial grade occurs in enormous quantities within the map- area, particularly along Windermere Creek and the Kootenay River. It is in the form of sedimentary rock gypsum, and the evidence of primary origin is conclusive. 18. A preliminary graph is presented showing the stability relationships of gypsum and anhydrite as functions of temperature and pressure. Under average thermal condi- tions, gypsum appears to he metastable at depths helow 3,500 feet, and in the presence of a water solution should be converted to anhydrite. In the presence of a salt solution, transformation should occur at shallower depths. 19. The thickness of the known strata overlying the primary gypsum suggests that there was no post-Middle Devonian deposition in this part of the Western Rocky Mountains. x CHAPTER 1.-INTRODUCTION LOCATION The Stanford Range is one of the western ranges of the Canadian Rocky Mountains in southeastern British Columbia (see Fig. 1). It is bounded on the west by the Rocky Mountain trench and on the east and south by the Kootenay River. On the north it is separated from the Brisco Range by the low Sinclair-Swede Creek divide. The map-area flanks Columbia and Windermere Lakes and extends from Canal Flats on the south toabout
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