CERATOPS BEDS OF WYOMING AND MONTANA 279 



So far as it goes the evidence in the Carbon County field tends to 

 show tliat the "Lower Laramie" is conformable and continuous with 

 the marine Cretaceous and that it includes the equivalents of the Black 

 Buttes coal group and of the "Ceratops beds" of Converse County. 

 It is also probable that the "Upper Laramie" is Fort Union. In 

 thickness of strata and in the number and character of its coals this 

 formation seems to be strictly comparable with the Fort Union of the 

 Sheridan and Red Lodge fields. 



General Stratigraphic and Structural Relations 



It has been shown that, within the large area considered, the 

 "Ceratops beds" with the Triceratops fauna are always pretty 

 closely associated with the uppermost marine Cretaceous strata or are 

 separated from them by transitional brackish-water beds. They are 

 always overlain by a thick series of rocks containing a Fort Union 

 flora in which no dinosaurs have been found, and in the Fish Creek, 

 Montana, region this overlying series also contains primitive mammals 

 related to those of the Puerco and Torrejon faunas. 



Throughout a large part of the area no evidence of an unconformity 

 beneath the "Ceratops beds" has been found, while higher in the sec- 

 tion unconformities have been demonstrated or suggested at a num- 

 ber of places. Unconformities have been reported below tbe " Cera- 

 tops beds" on Hell Creek, Montana, on the Little Missouri in North 

 Dakota, and in Weston County, Wyoming, but in none of these cases 

 has any proof been furnished that the erosion interval is important. 

 The fact seems to be overlooked that in irregular non-marine deposits 

 like these, which were in part at least fluviatile, an eroded surface 

 should normally be expected at the base of a sandstone, but such an 

 eroded surface may mean a time interval too brief to be worthy of con- 

 sideration in geologic history. Because Ceratopsia were found in the 

 Denver Basin above an unconformity that has been interpreted as 

 representing an enormous time interval, is not a valid reason for 



hundred feet above the unconformity separating that formation from the 

 Laramie. If that is true it is somewhat remarkable that all the fossils found 

 here are reptilian and show considerable variety, while other Puerco localities 

 not many miles away yield chiefly mammals and no dinosaurs. Mr. Gardner 

 proposes to restudy this section. 



