HINTZE, GEOLOGY OF WASATCH MOUNTAINS, UTAH 103 



formations. Subaerial deposition in an arid region would also account 

 for the highly oxidized character of most of the beds. While a final con- 

 clusion must be reserved for future more extended studies, the presump- 

 tion from the facts at hand is in favor of a continental origin for all of 

 the Wasatch Algonkian and a large part of the Arizona, Idaho and Mon- 

 tana occurrences. 



We may now inquire into the probable situation of the Archean old- 

 land from which these sediments were derived. It is clear from the gen- 

 eral distribution of the Algonkian rocks above referred to in a north-south 

 belt from Arizona, through Utah, Idaho and Montana into British Colum- 

 bia, that the source must have been to the east or west. If we examine the 

 sections to the eastward, we find that as we approach the north-south line 

 of the Front Eange, these pre- Cambrian quartzites thin away and disap- 

 pear, and we have late Cambrian strata resting with unconformity upon 

 Archean rocks. It appears then that here we have an area which was 

 actively eroded during Proterozoic and most of Cambrian time and that 

 did not become an area of deposition until late Cambrian time. From the 

 general absence of Lower Cambrian formations in this region and their 

 presence in the Wasatch Mountains and westward in Nevada, it is clear 

 that the Cambrian sea came in from the west. This seems to indicate the 

 absence of any considerable land mass to the west and reduces our source 

 of supply to the eastern oldland. We may then consider the continental 

 divide to be the Archean axis of the Front Range in Colorado and its 

 northward extension into Canada, from which the rivers fiowed to the east 

 and to the west. Those draining the western slopes of this Archean eleva- 

 tion opened out upon lowlands in central and eastern Utah and to the 

 north and south. Here subaerial deposition began in the formation of 

 great fans spreading westward and becoming more or less confluent toward 

 the north and the south. 



CAMBRIAN STRATA 



The base of the Cambrian strata is now drawn at the unconformity 

 above described. The separation of the rocks from the much older Algon- 

 kian formations has reduced their thickness from 12,000 feet, as formerly 

 estimated, to less than 1000 feet. 



The lowest Cambrian formation is a conglomeratic quartzite 700 feet 

 thick. No fossils have been found in it, and its age is fixed by its position 

 above the well marked unconformity and below the succeeding shale bed 

 carrying the Olenellus fauna. At the base lies a heavy conglomerate com- 

 posed of rounded pebbles and bowlders of quartzite and gneiss and the 



