Page:Walcott Cambrian Geology and Paleontology I.djvu/17



In connection with the preparation of the section on the stratigraphic distribution of the Cambrian Brachiopoda for Monograph LI, of the U. S. Geological Survey, I find that it is necessary to refer to many undefined Cambrian formations of the Cordilleran area. The present paper is published for the information of geologists and for the purpose of properly defining and characterizing the formations in question, as the first reference to these formations should be accompanied by more information than can well be included in the pages of the monograph.

Since reading, in 1886, Mr. R. G. McConnell's report of 1885 on his section across the Rocky Mountains in the vicinity of the 51st parallel, I have had a strong desire to study the stratigraphy of the Cambrian portion of the section. It was not until the summer of 1907 that the opportunity came. Accompanied by Mr. Lancaster D. Burling as field assistant, a study was made of the typical Castle Mountain section of Mr.McConnell, the lower portion of the Mt. Stephen and Mt. Whyte sections, and the full section of Mt. Bosworth, on the Continental Divide, which proved to be the most complete.

Except where otherwise stated, the sections were carefully measured with rod and clinometer. The strata were so well exposed that it was rarely necessary to go any distance to avoid talus slopes and covered portions of the section. Collections of fossils were made at many horizons, but, owing to the limited time available, this part of the work was neither systematic nor exhaustive.

.—The area examined is on the line of the Canadian Pacific Railway between the Sawback Range on the east and the Van Horn Range on the west. In this limited area there was only time for the examination and measurement of the strata of Castle Mountain and Mt. Bosworth, the lower 3,800 feet of the Mt. Stephen section, and the Lower Cambrian formations on the slopes of Mts. Whyte and St. Piran, in the vicinity of Lakes Louise and Agnes.