CRETACIC PERIOD 595 



The floral evidence has recently been summed up by Knowlton, who refers 

 the Ceratops beds to the Lower Fort Union of Tertiary age. He states : 



"It is shown that the lower member rests, in some cases unconformably, in 

 others in apparent conformity, on the Fox hills or Pierre, and the conclusion is 

 reached that an erosional interval is indicated during which the Laramie — if 

 ever present — and other Cretaceous and early Tertiary sediments were removed. 



"It is shown that the beds under consideration, being above an unconformity, 

 can no longer be considered as a part of the 'conformable Cretaceous series/ 

 and hence are not Laramie. 



"The final conclusion is reached that the beds here considered ('Hell Creek 

 beds,' 'somber beds,' 'Ceratops beds,' 'Laramie' of many writers) are strati- 

 graphically, structurally, and paleontologically inseparable from the Fort 

 Union, and are Eocene in age" (237, 238). 



Stanton has reviewed the stratigraphy and paleontology of these beds 

 from another standpoint, with the result that "the Ceratops beds are of 

 Cretaceous age." His evidence sums up as follows : 



"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 beem 

 found, and in the Fish Creek, Montana, region this overlying series also con- 

 tains primitive mammals related to those of the Puerco and Torrejon faunas. 



"Throughout a large part of the area no evidence of an unconformity be- 

 neath the 'Ceratops beds' has been found, while higher in the section uncon- 

 formities have been demonstrated or suggested at a number of places. Uncon- 

 formities have been reported below the 'Ceratops 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 [279]. . . . 



"Soon after the Benton, however, large areas west of the Front Range in- 

 Colorado and Wyoming and west of the 108th meridian in Montana previously 

 covered by the sea began to emerge, either by uplift or by filling of the basins 

 with sediment, and as they came up to sealevel or a few feet above it land 

 and marsh flats became established and all the conditions became favorable for 

 the formation of coal beds. Land animals also came in and the streams and 

 fresh-water lagoons received their appropriate population from adjacent areas, 

 while the bays and estuaries were inhabited by brackish-water forms. . . . 

 The neighboring land-masses must have formed large areas and have had con- 

 siderable elevation in order to furnish the immense thickness of Upper Cre- 

 taceous sediments known in this region (280). 



"There were oscillations, so that occasional brackish-water or marine deposits 

 were brought above those of land and fresh-water origin, and it is probable that 

 these oscillations were not always synchronous throughout the region. . . . 

 Locally, as in part of Bighorn Basin, this non-marine sedimentation may have 

 been almost continuous until the end of the Cretaceous, but over most of the 

 area there was a more important subsidence which brought the marine sedi- 



