388 GEOLOGICAL EXCURSION TO THE BOCKY .MOUNTAINS. 



beyond the conglomerate, primordial trilobites have been found in the 

 shales at the base of the limestones. 



To the north of ( lamp Douglas, the United States military post three 

 miles (4.8 km.) east of the city, are upper Carboniferous and Permian 

 beds, mostly limestones, carrying characteristic fossils. Bed Butte 

 canyon, northeast of ('amp Douglas, marks the dividing line between the 

 shaly limestones of the Permian and the pink red sandstones of the 

 Trias. The latter furnish much of the building stone for Salt Lake 

 city. Above these, dipping 40° to the southeast, are the drab lime- 

 Stones and argillaceous shales of the Jurassic. These beds strike 

 about N. 40° B., and thus cross the ravines whose direction is more 

 nearly east and west. Emigration canyon, directly back of Camp Doug 

 las, lies nearly in the axis of the synclinal fold included between the 

 two great Archean masses to the north and south (3 and 4 on the map). 



doing south from Emigration canyon, along the foothills, one crosses 

 the ends of a series of beds dipping north and northwest, ranging in 

 geological horizon from the Jurassic down to the base of the Cam- 

 brian, a thickness in round numbers of 35,000 feet (10,750 in.). 



Between Emigration and Parleys canyon a .secondary anticline brings 

 up the Permian beds from under the Trias. At Parleys canyon, up 

 which runs the narrow gauge railway to Park city, the Permian beds 

 are again exposed with the regular nort herly dip. They carry abundant 

 Permian forms, ArUulopcvivn. Jut microtis, Myalina, etc. 



Mill Creek canyon, the next to the south, is in the Weber quartzites 

 of the Middle Carboniferous. South of this is a re-entering angle of 

 the foothills in which the outcrops are more covered by debris and 

 the succession less easy to trace. The high projecting spur beyond is 

 formed of the great mass of Cambrian : ' :i quartzites and slates strik- 

 ing northwest and dipping 45° to the northeast. 



An excellent section across these beds and up into the Carbonifer- 

 ous is obtained by following up the next canyon gorge, called Big Cot- 

 tonwood, as the beds curve in Strike more to the southward at the 

 upper part of the canyon, wrapping around the granite body of Little 

 Cottonwood canyon. 



The section (Fig. 10), on a nearly east and west line through Twin 

 Peak, a little south of Pig Cottonwood canyon, shows the position these 

 beds occupy relatively to the granite. The lowest ( 'ambrian beds, near 

 the contact with the granite, contain fragments of the latter, showing 

 its eruption to have been at least Pre-Cambrian, and that all these 

 beds were deposited around it, and have been subsequently uplifted 

 into their present position. 



The next canyon south, known as Little Cotton wood, is a deep glacier- 

 carved gorge cut almost its entire length in granite, but showing east- 

 erly dipping Paleozoic beds at its very head. The steep face of Twin 



