HINTZE, GEOLOGY OF WASATCH MOUNTAINS, UTAH \\:] 



The stratigraphic relations of these beds to the -underlying non-fos- 

 siliferous limestones provisionally assigned to the Ordovician is one of 

 disconformity. The beginning of Devonian sedimentation is very clearly 

 marked by a limestone conglomerate which rests upon a thin bed of 

 yellowish-green shale, which in turn rests on a thick limestone member. 

 This condition is best shown on the Reade and Benson ridge, just above 

 the old mine workings of the same name. It is also exposed on the ridge 

 between Day's Fork and Little Cottonwood Canyon, just west of Flag- 

 staff Mountain, i^o angular discord between the beds above and below 

 the break could be detected, though the presence of the hiatus is phys- 

 ically indicated by the unmistakable conglomerate. 



Upward, the Devonian strata seem to be continuous with the succeeding 

 Waverlyan limestones. In this respect again, the central Wasatch is like 

 the Colorado and Xew Mexico areas where deposition is thought to have 

 proceeded continuously from the Upper Devonian into the Mississippian. 

 From the occurrence of these limestone beds on the Eeade and Benson 

 ridge, the name Benson limestone is proposed to designate the part be- 

 longing to the Devonian. They range as above stated from Middle to 

 Upper Devonian and are succeeded by Lower Mississippian limestones 

 without any observed disconformity. 



MISSISSIPPIAN STRATA 



Rocks of Carboniferous age have been known from the Wasatch Moun- 

 tains and the Great Basin region since the first explorations of Captain 

 Stansbury in the early fifties. It was left, however, to the Fortieth 

 Parallel geologists to give them a name and describe their stratigraphic 

 relations, thickness and distribution. King applied the name Wasatch 

 limestone to a succession of strata 7000 feet thick and composed mostly 

 of limestones supposed to be of "sub-Carboniferous" age. Aside from 

 the fact that this name was preoccupied for a Tertiary formation, it is 

 now known that the original Wasatch consists of several stratigraphic 

 members, ranging in age from Ordovician to Mississippian. In the 

 northern Wasatch, the Paradise limestone of Silurian age and nearly a 

 thousand feet of limestone identified by Kindle as the equivalent of the 

 Jefferson have been separated from the lower part of the Wasatch. The 

 rest has been regarded by Girty as Lower and Middle Mississippian, the 

 lower division probably correlating with the Madison limestone. It 

 seems advisable, therefore, to discontinue the use of the name Wasatch 

 limestone as employed by King. 



In the central Wasatch region, the Mississippian strata admit of a 

 three-fold subdivision into a lower limestone series with a Productus 



