ABSTRACTS OF PAPERS PRESENTED 73 



ORIGIN OF THE SANDSTONE AT THE STATE PRISON NEAR CARSON CITY. 



NEVADA 



BY W. S. TANGIER SMITH 



(Abstract) 



From the size of this area, the character of the rock, its similarity to other 

 sandstones in the adjoining region, the present and past existence of hot 

 springs in the immediate vicinitj'. as well as other evidence, it is believed that 

 this sandstone is the result of cementation of alluvial and reolian sands by hot 

 springs deposits during late Pliocene or early Pleistocene time. 



Discussion b)'^ Louderback, Merriam, and Anderson. 

 The meeting then adjourned for lunch, reassembled, and was called to 

 order at 2 p. m. 



The following papers were presented : 



NOTES ON THE CENOZOIC HISTORY OF CENTRAL WYOMING 

 BY CHARLES LAURENCE BAKER 



(Abstract) 



The Cenozoic histoiy of this portion of the central Rocky Mountain region 

 can be best considered as beginning with the withdrawal of the last interior 

 epicontinental sea at the close of the epoch of the Fox Hills sandstone in the 

 northeast and east and of the Lewis shale in the southwest and south, pro- 

 vided that the view is taken that the major divisions of geologic time are sepa- 

 rated by intervals of great diastrophism. In central Wyoming the Laramide 

 period of deformation was accompanied by thrust faulting and volcanism. 

 Intermontane structural basins formed by these complex orogenic movements 

 were the sites of deposition of sediments eroded from the surrounding moun- 

 tains during the Laramie epoch and earlier Tertiary times ; later, when these 

 basins had become filled, the places of maximum terrestrial deix)sition were 

 shifted to the borders of the Cordiileran area. During the Green River epoch 

 and probably during the Bridger also a lake, or lakes, existed in the Green 

 River basins of southwestern Wyoming and northeastern Utah. A peneplain, 

 which, according to all evidence at present available, probably existed over the 

 entire region, was developed near the middle of the Miocene period. This first 

 Cenozoic cycle of erosion was closed by an uplift, accompanied by volcanism, 

 probably of later Miocene date, which appears to have been both regional and 

 orogenic along the old liites of Cretaceous-Eocene movements. The Wyoming 

 conglomerate and similar gravels covering flat-topped buttes and high inter- 

 stream areas are believed to be the products of streams rejuvenated by the 

 mid-Cenozoic uplift before the warped pei oplain had been greatly eroded. 

 The history of the yet existent second Cenozoic cycle of erosion has lieen great 

 subaerial denudation of the loosely consolidated deposits of the basins and 

 deep canyon-cutting in the more resistant rocks of the mountains. The drain- 



