TP^KTlAliY FORMATIONS. 205 



That they had a connection to tlie south through the same gap with the 

 Green River beds at the eastern end of the range is, however, probable 



The later history of the Green River basin is still involved in some ob- 

 scurity ; no representative of the Miocene beds of the eastern slopes of the 

 Rocky Mountains have been discovered within its limits, and no connection 

 ■probably existed with the eastern Tertiary seas. When drained, it was 

 probably to the southward, at the eastern end of the Uinta range. A local 

 deposit of Pliocene strata is said to exist within the limits of the basin on 

 the southern flanks of the Wind River Mountains. There is a possibility, 

 also, that the upper beds of Brown's Park, which have been colored as Green 

 River Eocene, may prove, on further investigation, to be of Pliocene age, 

 which would heighten the probability that the North Park Tertiaries belong 

 also to that period. If the basin was drained previous to Pliocene times, 

 the erosion that took place afterward was of broad, general character, and 

 had no relation to the present topography. 



The last deposit that was made in this basin in pre-Glacial times is of 

 a peculiar character, and has been so largely removed by recent erosion 

 that the scattered remnants that now remain afford but meagre data for 

 tracing the character and extent of its original deposition. This deposit 

 is a structureless conglomerate, called by us the Wyoming Conglomerate, 

 entirely barren of fossil remains, and made up of comparatively coarse, 

 generally rounded, fragments of the harder rocks wdiich form the present 

 crest of the Uinta Mountains, cemented together by calcareous material. 

 It is found in greatest thickness along the immediate flanks of the Uinta 

 Range, and is in all cases horizontal, having evidently filled in and lev- 

 elled off the valleys and ridges of the pre-existing topography. It was 

 therefore, in some measure, a littoral deposit, and probably in a shallow 

 sea, subject to great changes of level, at a time when great storms and 

 floods prevailed. As indicated by the exisiting remnants, it extended as much 

 as 20 or 25 miles from the shore-line, and covered the lower eastern portion 

 of the Uinta Range, bordering the present course of Green River. 



It was on the level surface left by this deposit, then, that the present 

 sinuous course of Green River through the Uinta Range was determined, 

 though the general direction of this course was probably governed by the 



