200 



SHORTER CONTRIBUTIONS TO GENERAL GEOLOCiY, r.>21. 



Kansas, Colorado, the western Black Hills, 

 and presumably elsewhere in this region has 

 been pretty well knowTi for a number of years. 

 Their exact age has been a matter of consider- 

 able differences of opinion. 



The history of paleobotanic discovery of the 

 so-called Dakota flora has been given in Les- 

 quereux's three memoirs and need not be re- 

 counted here except to point out that the col- 

 lections, a study of which resulted in the identi- 

 fication of over 400 species of plants, were made 

 at different times and places by a number of 

 different collectors, who, as in so much of the 

 early exploratory work in the West, paid little 

 attention to stratigraphic position or locality. 

 Any yellowish or reddish sandstone with im- 

 pressions of dicotyledonous leaves was Dakota 

 in age, and for a large number of species "Da- 

 kota group of Kansas," or at most the county 

 from which the specimens were collected, is all 

 we know of the whereabouts of the outcrop. 



Apparently the first to notice marine fossils 

 at the base of the red Cretaceous (Dakota) 

 sandstones was Le Conte.' Cragin, while at 

 Washburn College, Topeka, Kans., did much 

 work upon the Cretaceous and published many 

 short paleontologic papers. In 1890 he de- 

 scribed a cross-bedded sandstone (the Chey- 

 enne sandstone) which underlay marine beds 

 in southern Kansas and which he considered 

 to be related to the Potomac, Tuscaloosa, Trin- 

 ity, and " Atlantomurus beds," and the next 

 year he published the statement that the Chey- 

 enne sandstone was probably of the same age 

 as the Trinity of Texas, the Potomac of the 

 Atlantic Coastal Plain, and the Wealden or 

 Purbeck of Europe. Invariably in his discus- 

 sions he used the term Comanche as the inter- 

 changeable equivalent of the European Neo- 

 eomian. 



The first definite announcement of the flora 

 contained in the Cheyenne sandstone was made 

 by Hill,'^ who recorded the following species 

 from collections made by Hill, Gould, and 

 Shattuckin 1894: 



Rhus uddeni Lesquereux. 



Sterculia snowii Lesquereux. 



Sassafras mudgii Lesquereux. 



* Le Conte, J. L., Notes on the geology of the survey for the extension 

 of the Union Pacific Railway, I'hiladelpliia, 1S68. 



& H il l , R. T., Discovery of a dicotyledonous flora in the Cheyenne sand- 

 stone: Am. Jour. Sci., 3d ser., vol. 49, p. 47.3, 1895; On outlying areas of 

 the Comanche series in Kansas, Oklahoma, and New Mexico: Idem, vol. 

 SO, pp. 205-234, 1S95. 



Sassafras cretacciim obtiisum Lesquereux. 

 Sassafras n. sp. 



Glyptostrobus ^racillimus Lescjuereux. 

 Sequoia .sp. (cones). 



Cragin 's conclusions were given in a paper 

 published in 1895," in which the section is given 

 as follows : 



Kiowa shales. 



Champion shell bed. roi i > ^ 



rr,,, ,, , , , Stokes sandstone. 

 Elk Creek bedsw u- u i 

 Cheyenne sandstone ILanphier shale. 



[Corral sandstone. 



From the "Elk Creek beds" he recorded 

 Sterculia snowii, Sassafras mmlgei, Sassafras 

 cretaceum, Sassafras sp., Rhus uddeni, Sequoia 

 sp., and Ghjptosfrohns gracillimus.'' Only the 

 first two of these are contained in the collections 

 studied by me. 



Other contributors to the subject prior to 

 1900 were Mudge, Prosser, Jones, Stanton, and 

 Gould. Their results are not pertinent to my 

 present purpose beyond the fact that they show 

 conclusively the presence of a sandstone, the 

 Cheyenne, containing the remains of a land 

 flora in southern Kansas beneath a marine 

 series, the Kiowa shale, carrying a fauna that 

 is correlated with that of the Washita group 

 at the top of the supposed Lower Cretaceous 

 section of Texas as elaborated by Hill. 



During his residence in Kansas Twenhofel 

 studied the Cretaceous of the central part of the 

 State, and in a brief paper ^ published in 1917 

 he confirmed Cragin's earlier results " that a 

 situation identical with that of southern Kan- 

 sas prevails in central Kansas. In a more 

 recent article '" he contends that the Dakota of 

 Kansas and the Washita group of Texas are of 

 the same age, and that both the Cheyenne- 

 Kiowa-" Medicine beds" sequence of southern 

 Kansas and the Mentor-Dakota sequence of 

 central Kansas should be referred to the 

 Comanche series. 



The " Dakota flora" of the Denver Basin has 

 recently been revised by Knowlton. As a 

 result of field work by Lee and Cannon during 

 1910 it has been showTi '' that the formation 

 from which Lieut. Beckwith collected the 

 "Dakota" plants from Morrison, Colo., that 



' Cragin, F. W., K study of the Belvidere beds: Am, Geologist, vol. 19, 

 pp. 357-385, 1S95. 

 ' Idem, p. 367, quoted from Hill. 



e Twenhofel, W. H., Kansas Acad. Sci. Trans., vol. 2s, pp. 213-223, 1917. 

 » Cragin, F. W., Am. Geologist, vol. 16, pp. 162-165, lS9o. 

 " Twenhofel, W. H., Am. Jour. Sci., 4th ser., vol. 49, pp. 281-297, 1920. 

 n Lee, W. T,, Am. Jour. Sci., 4th ser., vol. 49, pp. 183-188, 1920 



