CORRELATION of the area INCLUDING KIMBERLEY, METALIHE AND COEUR D'ALENE by Camon Glenn Cheriton A THESIS SUBMITTED IN PARTIAL FULFILMENT OP THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE IN THE DEPARTMENT OF. GEOLOGY AND GEOGR/PHY THE UNIVERSITY OF BRITISH COLUMBIA APRIL 1949 SUMMARY Within the area under consideration there are two great series of strata. The lower one is known as the Purcell-Belt Series and is divided into two main groups. A widespread unconformity separates the Purcell Series from the younger and overlying Windermere Series. The Lower Purcell-Belt group consists of the Aldridge-Prichard, Creston-Ravalli, Kitchener-Wallace, and Siyeh-Striped Peak. They were deposited under marine conditions from the erosion of a western Precambrian Cascadia. The Upper Purcell-Belt group consists of the Dutch Creek, Mount Nelson and their equivalents in Canada and the Missoula Group of Montana and possibly the Priest River group of Washington. This group is separated from the Lower Purcell by a period of diastrophism marked by the intrusion of Purcell sills and the extrusion of Purcell lavas. The Upper Purcell-Belt sediments were derived from the positive areas as a result of the preceding crustad disturbance. The Purcell-Belt times were closed by large scale orogeny called the "Purcell Uplift". The north-south trending belt of Purcell mountains formed a landmass which greatly affected lower Palaeozoic stratigraphy. This positive area is commonly referrdd to as the "Montana Island". The Precambrian portion of the Windermere Series includes the Toby-Shedroof conglomerate, Irene- I3.eola volcanics and the Horsethief Creek-Monk formations. The clastic formations were derived from the Purcell Mountains and deposited on their western flank. Marine conditions arose during Horsethief Creek times. The Cambrian portion of the Windermere Series was deposited in a north-south trending geosynclinal trough which extended from the Metaline quadrangle to the Field- Golden area of the Rocky Mountains and probably beyond. It includes the lower quartzltic Hamill Group and the overlying limy and argillaceous Lardeau group. They were deposited as the shoreline transgressed south and east over the "Montana Island" and reduced It from one of high relief to one of low relief. Stages of emergence and resumed sedimentation are indicated, by upper formations of the Lardeau group. CONTENTS Page Introduction 1 Acknowledgment 3 Problems and Approach to the Correlation of the Purcell-Belt Series 4 Aldridge-Prichard 6 Oreston-Ravalli 12 Kitchener-Wallace 20 Siyeh-Striped Peak 25 General Summary and Theoretical Considerations of the Lower Purcell Belt Group 30 Upper Purcell-Missoula Group 39 General Summary and Theoretical Considerations of the Upper Purcell Group 44 Problems of Correlation of the Windermere Series 49 Toby-Shedroof Conglomerate 51 Irene-Leola Volcanics 53 Horsethief-Monk 54 Hamill Group 56 Badshot Limestone 60 Lardeau Group 61 General Summary and Theoretical Considerations of Winder^mere Series 65 Bibliography 81 Illustrations: Plate 1 37 A Plate 2 m Plate 3 74 Plate 4 80 Appendix Compiled map of the Kimberley-Metaline- / Coeur d' Alene Area Correlation chart of the Windermere and Purcell-Belt Series INTRODUCTION Cambrian and Precambrian strata, upwards of 80,000 feet in thickness, are exposed in the Kootenay district of south-eastern British Columbia. They trend south to underly large areas of Washington, Idaho, and Montana. Considerable work has been done in these areas by officers of the Canadian and the United States geological surveys, by the Idaho Bure.au of Mines, and a number of independent investigators. As a result of this work a considerable body of information has been accumulated. The following brief study is an attempt to link the Canadian and American data and interpret it without regard to geographical boundaries. In connection with the work a map on a scale of 1 inch to 4 miles has been compiled (see pocket). In a regional study of this nature many problems of sedimentation, stratigraphy,and correlation become apparent. The writer has drawn attention to several of these problems in the general summary. For example, the rusty-red weathering nature of the Aldridge- Prichard formation requires a careful analysis of the facts for a satisfactory explanation. However, time was not available for a complete analysis of most of the problems, and as a result they are presented and dismissed with but hasty generalizations and a possible answer. It is hoped that this may form a basis for future investigations. 2 The writer haa had the advantage of personal acquaintance with some of the problems involved during 2 seasons of field work in the East and West Kootenay districts of B.C. Recent palaeontological discoveries have shown that younger strata of the supposedly Precambrian rocks of the Kootenay district are of Cambrian age. Further• more, these rocks can be correlated across the great physiographic feature, "the Rocky Mountain Trench," to link with the Cambrian strata of the Rocky Mountains. This leads to the postulation of new concepts regarding the location and movement of the geosynclinal basins of deposition preceding and during early Cambrian times• On the Canadian side, the tremendous thickness of strata is divided into two series by a great angular unconformity, at the base of the Toby-Shedroof conglomerate. Formations below or older than the unconformity are included in the Purcell-Belt Series and those above, in the Windermere Series. The first part of thfia thesis deals with the Purcell-Belt Series and the second part considers the Windermere Series and its equivalent American formations. 3 ACKNOWLEDGMENTS The writer wishes to acknowledge the constructive criticism and biostratigraphical assistance received from Dr. V.J. Okulitch of the Department of Geology and Geography of the University of British Columbia. Dr. H.C. Gunning has also made many helpful suggestions drawn from his own field experiences in this area. 4 PROBLEMS OF CORRELATION OF THE PURCELL-BELT SERIES The greatest single handicap in attempting the correlation of the Proterozoic strata is the lack of fossils. Other than a few algal structures the Purcell-Belt Series is unfossiliferous. The formations of Lower Purcell show no sign of disconformity and tend to grade into one another so that precise boundaries do not exist. Even over short distances some formations change laterally both in thickness and lithological character; therefore, one becomes rather dubious of a regional correlation. Some districts have been mapped accurately on a scale of one mile to the inch; other areas have been done only in a sketchy reconnaissance fashion on a scale of 8 miles to the inch. Furthermore, the lithologic units - in some areas have not been satisfactorily differentiated. To simplify the treatment of formational names, each formation has been given a composite name in which the most common Canadian and American names are linked with a hyphen. APPROACH TO PROBLEMS OF CORRELATION OF PURCELL-BELT SERIES Since fossils and unconformities are not present in the Lower Purcell Group it is necessary to rely upon lithology and stratigraphy for correlation. Actual continuity of a formation as traced by the geologist in the field is the ideal basis for a lithological correl• ation. This is impossible for a large area with inform• ation from isolated districts by different observers. So that it is necessary to consider the stratigraphic succession and the lithologic description of each formation of each map area, compare them, and correlate similar strata. For a graphic presentation several sections have been plotted on vertical scale of 1 inch equal to 5000 feet to form a correlation chart which is included with this discussion (see pocket). Attention is now turned to the plotted sections of the Purcell-Belt Series. A horizontal line has been drawn through the Purcell lavas in the Canadian section on top of the Siyeh-Striped Peak formation in the western Belt Series, and on top of the calcareous Wallace or equivalent formations in the eastern Belt section. It is realized that this probably does not represent strata deposited at the same time but a better datum is lacking. Those formations below this horizontal line are referred to as the Lower Purcell Group and those above as the Upper Purcell Group. The Lower Purcell Group includes, from the bottom up, the Aldridge-Prichard, Creston-Ravalli, Kitchener-Wallace and Siyeh-Striped Peak formations. The first part of the section on the Purcell- Belt Series consists of a brief description of the most 6 likely correlative formations based largely upon lithology. The description is largely verbatim from the areal geological report by the geologist to whom reference is made. The sequence of map-areas under discussion is based upon the correlation chart which consists of type sections selected from areas first in a north-south direction and then in a West-east direction, respectively along and across the trend of the Purcell-Belt Series. From north to south these sections are:.. Cranbrook Area, Nelson Area East, Boundary County, Clark Fork District, Trout Creek Quadrangle, and the Coeur D'Alene district. From west to east the sections include Kootenai County, Coeur D'Alene district, Mission Range, Missoula District, Phil)fipsburg Quadrangle, and the Belt Mountains. Aldridge-Prichard Cranbrook Area Except in one small part of the region the Aldridge formation is the lowest stratigraphic subdivision of the Purcell Series; however, in the Cranbrook Area north of Fort Steele in the Rocky Mountains, 7000 feet of rock are exposed and have been placed by Rice (1937,page 4) below the Aldridge and named the Fort Steele Formation. The lowest member of the Fort Steele consists of hard massive quartzite and argillaceous quartzite having well developed crossbedding and ripple marks and a thickness in excess of 1000 feet. These rocks grade upward into 2000 7 to 3000 feet of banded dark grey argillite and white to grey quartzite.