36 



LARAMIE FLORA OF THE DENVER BASIN. 



was held to be of the same age as the Lance 

 formation of Converse County, Wyo., and 

 thence throughout Montana and the Dakotas. 

 "The Lance flora embraces about 100 named 

 and described species. Of these 100 species, 

 over 75 are typical Fort Union species that have 

 never been found in older beds and most of 

 them only in the Fort Union." The Fort 

 Union was said to be of acknowledged Eocene 

 age. 



In discussing the European time scale it was 

 shown that 



(1) The Cretacgous and Tertiary systems were originally 

 established on a physical basis, and the exact line of 

 separation between them was determined by the struc- 

 ture; (2) after more than a century, during which the 

 several lines of evidence have been tested, the last authori- 

 tative word on the European standard is to the effect 

 that the structure is the determining factor in separating 

 them, and that even dinosaurs that have been appealed 

 to so often as proof of Cretaceous age did not end with the 

 Cretaceous. 



The vertebrate and invertebrate evidence 

 was briefly considered. In conclusion, the 

 thesis given at the beginning of the paper was 

 repeated and considered as follows: 



Evidence, believed to be competent, has been pre- 

 sented in support of this view from the side of stratigraphy, 

 diastrophism, and paleobotany, ' and what is thought to 

 be the weakness and insufficiency of the vertebrate and 

 invertebrate evidence has been pointed out. The verte- 

 brate paleontologist would place the Cretaceous-Tertiary 

 line at the highest horizon at which dinosaurs have been 

 found, notwithstanding the fact that this is 'a variable 

 boundary, unattended by structural or diastrophic action. 

 The invertebrate paleontologist would place this line at 

 the highest point where marine invertebrates of Cannon- 

 ball type occur. The paleobotanist would place the line 

 at the lowest horizon at which Tertiary plants have been 

 found, which corresponds with the structure. The 

 paleontologists are not in accord. What, then, is to be 

 the court of final appeal? There is but one answer: 

 Structure resulting from diastrophism. The evidence 

 from these sources supports the thesis. 



The second paper of the symposium, by 

 T. W. Stanton, 27 began with a discussion of 

 the typical Cretaceous and Eocene of western 

 Europe, in which it was held that the Anglo- 

 Parisian basin "can perhaps with' justice be 

 considered the typical area of both Cretaceous 

 and Eocene." It was shown that here there 

 is a well-marked structural break, as well as a 

 strong faunal break, and it is of course easy 

 to distinguish between them, but that in other 



27 Boundary between Cretaceous and Tertiary in North America, as 

 indicated by stratigraphy and invertebrate faunas: Geol. Soc. America 

 £ull., vol. 25, pp. 341-354, 1914. 



areas (Denmark, Belgium, center of Paris 

 Basin, etc.) there are deposits, 



in part marine and in part continental, which seem to 

 belong between the highest Cretaceous and the lowest t 

 Eocene represented in England. These intermediate 

 deposits have been called Danian, Montian, and other 

 more local names and have been assigned by some geolo- 

 gists to the Cretaceous, by others to the Tertiary, and by 

 still others part to the Cretaceous and part to the Terti- 

 ary. * * * 



All will agree, I think, that when two contiguous 

 systems as originally defined are separated by an un- 

 conformity, if there is other evidence of a break in sedi- 

 mentation, it is probable that intermediate deposits will 

 be found in some part of the world, and that when found, 

 if they are subordinate in character, they should be as- 

 signed in each case to the system to which they are most 

 closely related. 



In discussing the contact between marine 

 Cretaceous and marine Eocene in North 

 America, Stanton pointed out tbat 



In America, as in England, wherever marine Cretaceous 

 is directly overlain by marine Eocene, there is no diffi- 

 culty in recognizing the boundary between them,;^d 

 there is no controversy concerning the boundary. * jjjj& .* 

 In the Interior Province, including the Great Plains and 

 Rocky Mountain region, conditions were different. The 

 Upper Cretaceous sea during the Colorado epoch covered a 

 large part, if not the whole, of the province, and by the end 

 of the Cretaceous it had entirely retreated from the area; 

 but the Ebcene sea did not return into this province at 

 all. Instead of marine deposits great continental deposits 

 were formed, beginning in the Cretaceous and continuing 

 with many interruptions and with increasing restriction 

 of areas throughout Tertiary time. 



As regards the evidence of land areas in the 

 Rocky Mountain region during the Cretaceous, 

 Stanton wrote as follows : 



/The idea has sometimes been expressed that this was a 

 period of quiet and universal submergence for the province, 

 with no land masses within it until the end of the period, 

 when the whole area was lifted above sea level by a single 

 movement. There are many facts opposed to this view — 

 so many that they form convincing evidence that at several 

 times during the period there were differential movements 

 which brought previously submerged local areas above 

 sea level. The greatest submergence of the sea, and pre- 

 sumably the deepest submergence, seems to have been 

 near or after the middle of the Colorado epoch; but even 

 at that time it is probable that there were large islands. 

 Local variations in thickness and character of sediments 

 bespeak the nearness of land at some localities. 



As examples in support of this contention 

 were given the Datil Mountain area in western 

 New Mexico, where a land flora was developed 

 in the Colorado; the Mesaverde formation of 

 Colorado, Wyoming, Utah, etc., which shows 

 extensive coal deposits; various coal fields of 



