THE FLORA. 



101 



this may be the correct interpretation finds 

 physiographic support in a paper read by W. T. 

 Lee 11 before the Geological Society of Wash- 

 ington,^ entitled "Relation of the Cretaceous 

 formations to the Rocky Mountains. " In this 

 paper data were presented to show that the 

 entire marine Upper Cretaceous section was laid 

 down uninterruptedly over the area now occu- 

 pied by the Rocky Mountains. Lee held 

 that the Cretaceous sediments of the Rocky Mountain 

 region came mainly fromHhe continental land mass that 

 lay west of the interior sea during Cretaceous time. * * * 

 Comparisons of published sections viewed in the light of 

 personal observation in the field indicate that the Cre- 

 taceous formations on opposite sides of the mountains and 

 in the intermontane basins are comparable in thickness, 

 character, and stratigraphic succession. * * * It seems 

 probable that the interior Cretaceous basin, which includes 

 the present Rocky Mountain areas, was a great geosyncline 

 in which, until near the close of the Cretaceous, the main 

 movement was downward, with minor warpings. It also 

 seems probable that there was no effective barrier in the 

 relatively small area now occupied by the mountains to 

 prevent the uniform spread of sediments derived from the 

 continental mass west of the Cretaceous sea. 



If, as Lee contended, the entire marine 

 Upper Cretaceous section was laid down over 

 the Rocky Mountain area, there is every reason 

 to suppose that the Laramie was also, for it is 

 everywhere conformable with the marine beds 

 on which it rests; indeed, the definition of the 

 Laramie — as the uppermost member of the 

 conformable Cretaceous section above the Fox 

 Hills — demands that it be considered with the 

 marine portion of the section. With the up- 

 lifting of the Rocky Mountains came erosion 

 and unconformity. In the Denver Basin the 

 Laramie has a maximum thickness of approxi- 

 mately 1,200 feet, -but 90 miles to the south, 

 in the Colorado Springs area, it is reduced to 

 less than 400 feet, and in the Raton Mesa 

 region the Laramie has entirely disappeared 

 and the Eocene (Raton formation) there rests 

 on the Montana (Vermejo formation). In 

 North Park, Colo., the Laramie is not known 

 to be present, but in Carbon County, Wyo., 

 the "Lower Laramie" occupies the same 

 stratigraphic position as the Laramie of the 

 Denver Basin and has a thickness of several 

 thousand feet. The strong similarity of the 

 floras of the Medicine Bow and the Laramie of 

 the Denver Basin is interpreted as evidence of 

 identity in age. 



ii Washington Acad. Sci. Jour., vol. 5, pp. 29-3"i, 1915; U. S. Geol. Sur- 

 vey Prof. Paper 95, pp. 27-58, 1915. 



For an account of the latest interpretation 

 of the stratigraphic relation in Carbon County 

 as worked out by Bowen, the reader is referred 

 to page 60. 



It remains to be, pointed out that the fossil 

 plants support the contention of Veatch, 

 perhaps as modified by Bowen, namely, that 

 there are some 5,000 or 6,000 feet of beds in 

 the "Lower Laramie," and that this portion, 

 at least, is of the same .age as the true Laramie 

 of the Denver Basin. In my opinion the 

 "Lower Laramie" is not Lance. On the other 

 hand I believe that the Lance is to be corre- 

 lated with a part of the "Upper Laramie" of 

 this region, a view supported by the plants 

 and in the main by the vertebrates also. 



RELATIONS TO THE DENVER FORMATION. 



The following species are common to the 

 Laramie and Denver formations: 



Sequoia acuminata Lesquereux. 



Quercus viburnifolia Lesquereux. 



Ficus coloradensis Cockerell. 



Ficus denveriana? Cockerell. 



Nelumbo tenuifolia (Lesquereux^ Knowlton . 



Dombeyopsis obtusa Lesquereux. 



Laurus wardiana? Knowlton. 



Paliurus zizyphoides? Lesquereux. 



Rhamnus salicifolius Lesquereux. 



The flora of the Denver formation numbers 

 about 98 named and described species, but in 

 addition to these there are a number of others 

 in manuscript or otherwise recognized, which 

 will bring the total number up to ,about 225. 

 Nine species in common is really a very small 

 number. 



The status of the several species in this list 

 may be briefly considered. Sequoia acuminata 

 was described originally from specimens ob- 

 tained at Black Buttes, Wyo. Its presence in 

 the Laramie of the Denver Basin rests on a 

 single, rather doubtful fragment found at 

 Cowan station, near Denver, and its presence 

 in the "Dawson arkose rests on a specimen 

 found near Templeton Gap, 4 miles northeast 

 of Colorado Springs. Ficus coloradensis is one 

 of the most satisfactorily identified of the spe- 

 cies occurring in both Laramie and Denver in 

 the Denver Basin. The types are preserved 

 in the characteristic andesitic material from 

 Golden, Colo., and it has been found in subse- 

 quent collections from the same horizons. It 

 occurs in the Laramie at Marshall and 1£ miles 



