CAMBRIAN GEOLOGY OF THE ROCKY MOUNTAINS 



Bv C. E. RESSER, 



Associate Curator. Division of Siratif/rafliic Paleontology, 



U. S. National Mitscnni 



Continuing my stratigraphic studies through which it is hoped ulti- 

 mately to gain a clearer conception of the Camhrian system as de- 

 veloped in the Rocky Mountains, the past field season was devoted 

 to a study of the Camhrian beds as exposed in some of Wyoming's 

 larger mountain ranges. Again travel was by auto truck, which was 

 frequently driven considerable distances beyond the end of the roads 

 to more convenient camp sites nearer the outcrops. My son, Harold I. 

 Resser, again acted as camp assistant. 



After securing the auto truck and camp equipment at Salt Lake 

 City earl}' in July, we traveled northward through the picturesque 

 Bear Lake and Star Valleys and entered Wyoming across Jackson 

 Pass. A well-exposed section above Blackrock Meadows east of 

 Moran gave us a good idea of the structure where the lava-covered 

 Absaroka Plateau joins the better defined ranges that extend south- 

 ward from this point. Following this, our attention was turned to the 

 Wind River Range where, as at many other places, it was found 

 difficult to reach the Cambrian rocks without the use of horses because 

 these beds outcrop high up next to the granitic rocks of the mountain 

 core, and further because some of the younger sedimentary rocks, 

 which also dip away from the central core, are composed of massive 

 limestones that confine the many vigorous streams coming down from 

 the moist heights to narrow canyons walled in l)y unscalable clififs. 

 However, the recent building of roads to furnish outlets for lumber 

 camps and " dude " ranches has made it possible at places to drive up 

 over this sedimentary rim into the regions of less rugged relief beyond. 

 Contrary to the usual rule that roads entering or crossing mountains 

 should follow up stream courses, many of Wyoming's mountain roads 

 take a totally different route, zigzagging up a spur between two 

 streams until above the sedimentary rim previously referred to, and 

 only then following a stream course. But even here the open, park- 

 like landscape, with its relatively gentle slopes, permits the construc- 

 tion of roads almost anywhere ; consequently scarcely any of the roads 

 follow streams for long distances. Thus at Warm Spring and Torrey 

 Creeks it was possible for us to get up to two fine sections, as we also 

 did along the Atlantic Citv-South Pass road far to the south. 



