200 



SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, lf>21. 



Kansas, Colorado, the western Black Hills, 

 and presuraably elsewhere in this region has 

 been pretty well known f(ir a number of years. 

 Their exact age has been a matter of consider- 

 able difi'erences of opinion. 



The history of paleobotanic discovery of the 

 so-called Dakota flora has been given in Les- 

 cpiereux'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 1S90 he de- 

 scribed a cross-bedded sandstone (the Chey- 

 enne sandstone) which underlay marine beds 

 in southern Kansas and whicla he considered 

 to be related to the Potomac, Tuscaloosa, Trin- 

 ity, and " Atlinilomurii.'^ beds," and the next 

 year he publisiied 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- 

 comian. 



The first definite announcement of the flora 

 contained in the Cheyenne sandstone was made 

 by Hill,'^ who recorded the following species 

 from collections made l)y Hill, Gould, and 

 Shattuck in 1S94; 



Rhus iiddcni I/esquereu.\. 

 Sterculia smiwii Lesquercux. 

 Sassafras mudgii Lesqueroux. 



< I-e Conte, J. L.. Notes on the geology of tht^ survey for the extension 

 of the Uiiiou Pacific KaU\vay, Philadelphia, 1S6S. 



^ lliU, K. T., Discovery of a dicotyledonous flora in the Cheyenne sand- 

 stone: Am. Jour. Sei., 3d ser., vol. 49, p. 47:t. 1S05; On outlying areas of 

 theCoraaucheseriesin Kansas, Oiclahonia, and New Mexico: Idem, vol. 

 50, l)p. 205-234, 1S95. 



Sassafras cretaceum obtusiim Lesquereux. 

 Sassafras n. sp. 



Glyptostrobiis gracillimiis Lescniereux. 

 Sequoia sp. (cones). 



Cragin's conclusions were given in a paper 

 published in 1S9.5," in which the section is given 

 its follows: 



Kiowa shales. 



Champion shell lied. ic..l i i ^ 



' !„.,,,,, Stokes sandstone 



Elk Creek bedsw i- u i 

 ( 'heyenne sandstone iLanphier shale. 



ICorral sandstone. 



From the "Elk Creek beds" he recorded 

 Sterculia snowii, Sassafras mudgei, Sassafras 

 crefaccvm, Sassafras sp., Rhus nddeni, Sequoia 

 sp., and Glijptostrobus gracUUmus.'' Only the 

 first two of these are contained in the collections 

 studied by me. 



Other contributors to the stibject prior to 

 1900 were Mudge, Prosser, Jones, Stanton, and 

 Gould. Their i-esults are not pertinent to my 

 present purpose beyond the fact that the}' show 

 conclusive!}' 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 faima that 

 is correlated with that of the Washita group 

 at tiie top of the supposed Lower Cretaceous 

 section of Te.xas 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 identictd 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 Kanstis 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 

 1016 it has been shown " that the formation 

 from which Lieut. Beckwith collected the 

 ''Dakota ' phints from Morrison, Colo., that 



' Cragin, F. W.. .\ study of the Belvidere beds: Am. Geologist, vol. 18, 

 pp. 3.-)7-;iS5, ISIK. 

 7 Idem, p. 367, quoted from Hill. 



» Twcnliotel, W. n., Kansas Acad. Sci. Trans., vol. 28. pp. 213-223, 1917. 

 s Cragin, F. W., Am. Geologist, vol. 16, pp. 162-165, l.S'JS. 

 1" Twenhotel, W. U., Am. Jour. .Sci., 4th ser., vol. 49, pp. 281-297, 1920. 

 11 Lcc, W. T., Am. Jour. Sci., 4th ser., vol. 49, np. 183-188, 1920 



