POSSIBLE SILURIAN TILLITE IN SOUTHEASTERN 

 BRITISH COLUMBIA 



FRANCIS P. SHEPARD 

 The University of Chicago 



From the eastern slopes of the Purcell Range, in the vicinity of 

 Lake Windermere, the view across the deep depression known as 

 the Rocky Mountain trench to the Rocky Mountains on the east, 

 shows a series of bands of rocks varying in color and running 

 roughly parallel to the trench. One of these is a red conglomerate, 

 which can be traced almost uninterruptedly for ten miles between 

 the Sinclair River and Shuswap Creek, both of which are tributary 

 to the Columbia River in the Rocky Mountain trench. The red 

 formation was examined in two localities, and in a third a yellow 

 conglomerate was found, which is undoubtedly a part of the same 

 formation. In the last instance evidence was found which points 

 toward a glacial origin of the conglomerate. 



The conglomerate was first studied at Sinclair Springs. Here 

 an outcrop of red rock, with a dip of about 90°, forms a high wall 

 running down one side of the canyon and up the other (Fig. i). 

 Closer examination shows that the rock is not made up entirely of 

 red material, but consists of bowlders, which are predominantly red, 

 imbedded in a yellow calcareous matrix. The bowlders are lime- 

 stone with the exception of a very few pieces of quartzite. The 

 limestone varies considerably, having such varieties as purple, 

 black, white crystalKne, blue with white veins, and gray. The bowl- 

 ders are mostly sub-angular and in some cases are as large as four 

 feet in diameter (Fig. 2). The material of the conglomerate is unas- 

 sorted, and shows no trace of stratification. Two bowlders were 

 seen which had poHshed surfaces. It was difficult to remove the 

 bowlders from the matrix, and the exposed surfaces of the bowlders 

 were so weathered that any striations they may have once pos- 

 sessed have been destroyed. 



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