PALEOZOIC CORDILLERAN GEOSYNCLINE 



65 



The oldest Cambrian rocks over much of eastern and southern Nevada 

 and southwestern Utah is the Prospect Mountain quartzite, which may 

 be over 5000 feet thick in places. The Osgood Mountain quartzite in 

 north-central Nevada, the equivalent of the Prospect Mountain, may be 

 as much as 10,000 feet thick. Overlying the quartzite are shale, dolomite, 

 and limestone formations of uniform and wide occurrence. Stratigraphic 

 sections from the eugeosyncline to the miogeosyncline of north-central 

 Nevada are shown in Fig. 6.9, and of the miogeosyncline of western and 

 northern Utah in Figs. 6.9 and 6.10. 



In southeastern British Columbia is another succession of Cambrian 

 strata which totals about 10,000 feet in maximum thickness. From the 

 Burgess shale of this succession Wolcott took an amazing assortment of 

 fossils and greatly enriched our knowledge of life at the beginning of 

 Paleozoic time. Lower Cambrian beds are absent at the international 

 boundary, but further north in the Mount Robson vicinity they are 

 present and consist of 3900 feet of quartzitic sandstone, siliceous shale, 

 and limestone. Upper Cambrian strata are restricted and consist mostly 

 of limestone ( Lord et al., 1947 ) . 



Another thick Cambrian sequence is known in northeastern Washington 

 where at least 12,000 feet of beds dated by fossils occur. The Gypsy 

 quartzite lies at the base; over this is the Maitlen phyllite, and over this 

 the Metaline limestone (Park and Cannon, 1938; Campbell, 1947). The 

 assemblage is miogeosynclinal in aspect and contains elements of the 

 same fauna as the miogeosyncline of western Utah and eastern Nevada 

 ( Wm. Lee Stokes, personal communication). 



Representative of the eugeosynclinal assemblage in Cambrian time is 

 the Scott Canyon formation in Battle Mountain. It is composed of green- 

 stone, chert, and some shale, and is about 5000 feet thick ( Roberts et al., 

 1958). 



Lower and Middle Cambrian sediments are just about entirely re- 

 stricted to the geosyncline, but Upper Cambrian strata are spread widely 

 over the Central Stable Region of the United States as far as Wisconsin 

 and Ohio. Here they are overlapped by Ordovician sediments which 

 extend to the north and northeast over the Precambrian rocks of the 

 Canadian Shield. 



CAMBRIAN 



Fig. 6.2. Thickness and paleographic map of the Cambrian. 



