68 SEDIMENTARY GROUPS OF THE PLATEAU PROVINCE. 



the Cretaceous sea of the Basin Province was continuous with that of Texas. 

 The geological evidence seems to indicate this ; the evidence derived from 

 the fossils I leave for others to discuss. 



FLAMING GORGE GROUP. 



The epoch separating the Flaming Gorge Group from the Henry's Fork 

 Group above was one which produced a change from bad-land sandstones 

 to a conglomerate. The beds which overlie the conglomerate contain marine 

 fossils, but all the fossils which we have obtained from the upper portion of 

 the Flaming Gorge Group are of lacustrine habitat. The Mid-Group Lime- 

 stone contains marine species, and this is true of the limestone at the base, 

 i. e., the White Cliff Limestone. The White Cliff period ended with the 

 deposition of a massive cross-bedded sandstone; the Flaming Gorge period 

 commenced with a deposition of limestone; thus we have an important 

 epoch of change separating the two groups and this is widely spread, for 

 it has been seen wherever the junction of the two groups has been studied. 



WHITE CLIFF, VERMILION CLIFF, AND SHINARUMP GROUPS. 



These groups can be separated, only in a very general way. The 

 upper group is characterized near the summit by a very persistent, massive, 

 cross-bedded sandstone. The Vermilion Cliff Group is also a massive sand- 

 stone, and the base of the White Cliff Group is sometimes composed of 

 massive sandstones, sometimes of thinly bedded sandstones, and often these 

 beds are highly gypsiferous, in which case they disintegrate so rapidly that 

 the bedding cannot be studied. The group has yielded no fossils. 



The Vermilion Cliff Group as a great mass is easily recognized every- 

 where, but just where we should draw the line above is rarely plain. Often 

 the massive sandstones of this bed are separated by very irregular and 

 inconstant layers or aggregations of hard calciferous sandstones. These 

 layers have yielded a few imperfectly preserved fossils. 



The summit of the Shinarump Group is a series of gypsiferous sand- 

 stones exceedingly friable. They have often been called marls, and the 

 separation between them and the massive vermilion sandstone is never very 

 distinct. The difficulty is much greater where the gypsum disappears from 



