FLORA OF THE CHEYENNE SANDSTONE OF KANSAS. 



203 



ranging and more or less well known Creta- 

 ceous types. The collections include a sup- 

 posed cycadophyte seed, but this is of doubtful 

 relationship. There is also a fragment of a 

 trunk of the genus Cycadeoidea , which is of 

 somewhat uncertain value, as its exact strati- 

 graphic position has been questioned. There 

 are four coniferophytes and eleven angio- 

 sperms. One of these is a supposed monoco- 

 tyledon, ten are dicotyledons, and there are 

 two forms of uncertain botanic relationships. 



The dicotyledons represent the orders Sapin- 

 dales, Malvales, Thymeleales, and Umbellales 

 and are remarkable for the total absence of a 

 large number of elements generally found in 

 floras of this age. This aljsence can not be 

 wholly explained by accidents of preservation 

 and discovery and is due, I believe, to the pecu- 

 liar ecologic grouping resulting from the en- 

 vironment. 



The arenaceous portions of the Cheyenne 

 sandstone are very conspicuously cross-bedded. 

 The material is very friable, and the vegetable 

 remains are embedded in all sorts of positions 

 and ciu'led as they are when covered in a dry 

 condition by wind-blown sands. All are coria- 

 ceous forms, and the abundant Sequoia 

 cones all have their scales shrunken and widely 

 distended as in thoroughly desiccatetl modern 

 cones. They appear to have blown about and 

 collected in hollows along with the coriaceous 

 leaves that arc found in association with them. 

 With a single exception the ferns are fovmd in 

 the clays and evidently were confined largely 

 to stream banks. 



The variety of plants in such situations may 

 have been larger than the discovered flora 

 indicates, but it would seem as if in collections 

 so extensive there should be some traces of the 

 other plants preserved if they were growing 

 near at hand. 



Although the flora is too small and too remote 

 in time from existing floras to afford satisfac- 

 tory ecologic data, it does furnish some sug- 

 gestions. It seems to me to indicate a warm 

 and more or less arid climate, with a sparse 

 vegetation. I picture this vegetation as of 

 meager variety and as having been confined 

 largely to the region of watercourses between 

 which were larger areas of sand-hill or beach- 

 dune country over which the dried leaves and 

 fruits were blown, collecting in the hollows and 

 becoming covered by wind-blown sands. The 



clay lenses — for example, Cragin's "Lanphier 

 beds" — are waterlaid and might represent 

 seasonal rainfall and flood-plain or playa de- 

 posits or normal stream sedimentation, and 

 it is possible that some of the sands had a like 

 origin. 



There is no evidence of aridity in any of the 

 Cretaceous floras with which the Cheyenne 

 sanflstone flora may be compared, whether such 

 comparisons are made with the Patapsco and 

 Fuson floras, on the one hand, or the Woodbine, 

 Dakota, and Tuscaloosa floras, on the other. 

 I believe, therefore, that the Cheyenne flora 

 does not represent general conditions but is 

 purely an expression of the local environment 

 and perhaps represents a wide sandy coastal 

 plain or fluctuating beaches backed by dunes, 

 and that fartlier inland a more varied and nor- 

 mal flora probably existed throughout the 

 period when the shallow sea was migrating 

 back and forth across southern Kansas. 



A sample of the Cheyenne sandstone was 

 submitted to Mr. Marcus I. Goldman, who has 

 kindly furnished the appended observations: 



Macroscopic examination. — A solid but friable fine- 

 grained sandstone of a pale la\'ender-bro\vn folor fharar- 

 teristic of modjerately carbonaceous sandstones. No 

 lamination. Contains curled and wrinkled leaf impre.s- 

 sions suggesti\-o of deposition in a dry condition, hence in 

 wind-blown sand. 



Mechanical analysis. — The rock could be easily rubt)ed 

 down into its constituent grains. On sieving these divided 

 as follows: Fine sand through 60 on 100 mesh, 12.9 per cent, 

 0.4.5-0.26 millimeter; very fine sand through 100 on 200 

 mesh, 82.2 per cent, 0.2f)-0.04 millimeter; extra fine saud 

 through 200 mesh, 4.9 per cent, less than 0.04 millimeter, 

 ilicroscopic examination showed that the two finer parts 

 contained thoroughly disintegrated gi-ains. The coarsest, 

 however, consisted largely of compound grains which 

 yielded slowly to disintegration, so the following rough 

 figures may be taken: Fine sand, b per cent; very fine 

 sand, 90 per cent; extra fine sand, 5 per cent. In either 

 case the great predominance of the very fine sand is obvious. 

 This predominance of a single size at once suggests wind 

 action, but comparison with dune sands (cf. my paper on 

 the Catahoula sandstone," where several analyses are 

 assembled) shows that the ma.ximum is in the size next 

 finest to that which forms the maximum in typical dune 

 material. I have looked up the large collection of analyses 

 given by Udden '* and find that in this character the 

 gample resembles the finer sand carried by the wind out 

 of other deposits. Thus it corresponds %CTth only two of his 

 dune sands — No. 219, which is the finest material gathered 

 at the crest of a dune, and No. 248, from a blown f.eld. 



» Goldman, M. I., I'etrographice\'idence on the origin of the Catahoula 

 sandstone of Texas: .^m. Jour. Sci., 4th ser., vol. 39, p. 269, 1915. 



IS UUden, J. A., Mechanical composition of clastic sediments: Geol. 

 Sec. .\merica Bull., vol. 25, pp. 655-744, 1915. 



