K ajvsas Academy of Science. 17 



PLIOCENE TERTIARY OF WESTERN KANSAS. 



BY B. P. MUDGE. 



The Tertiary deposits of Western Kansas have been but little examined, and conse- 

 quently our knowledge of the peculiar character of its geology is quite limited. The 

 exceedingly rich and varied fossils of the Cretaceous (Niobrara group), immediately under 

 it, have probably led to its neglect. Even its extent has hardly been noticed. Professors 

 Cope and Marsh have both in their visits to the Cretaceous made some casual notices of 

 it, without spending much time in searching for its fossils. The writer, in the summer 

 of 1872, spent a fortnight in its examination in the vicinity of Prairie Dog creek, but as 

 the deposit was there very barren of organic remains, little satisfaction was obtained 

 During the past summer and fall we have been engaged in careful exploration of the Cre- 

 taceous, lying immediately under it, and consequently have seen it over a wide extent 

 and found its fossils more numerous and more varied in character than we had at first 

 supposed. 



In tracing its limits, we tind it most easterly in the northern part of Smith county, 

 ■where it is seen only on the tops of the highest hills. Its position there as elsewhere is 

 very nearly horizontal, but usually dipping slightly (not more than live or eight feet to 

 the mile) northwesterly. As the country rises about eight feet to the mile toward the 

 headwaters of the Republican and Solomon, the deposits in question gradually descend 

 lower down, and in Norton county entirely compose the hills, and fill the valleys and 

 ravines. It then continues to the extreme western boundary of Kansas. Tlius it extends 

 on the Nebraska line, on the hilltops of Smith and Phillips counties, about fifty miles, 

 and then, becoming the only deposit seen in Norton and other westerly counties, for one 

 hundred and twenty miles farther, or a total of one hundred aud seventy miles within 

 the bounds of our State. Tracing its boundaries southerly and westerly, we find its limits 

 bending rather rapidly toward Colorado. 



It is not found in the southern part of Smith or Phillips counties; and in Rooks county 

 still farther south and west, it is seen only in the western portion, crossing the Solomon on 

 the hills in the yicinity of Logan. From thence it tends more directly south, and is found 

 on all the hills in the northeastern part of Ellis county, on both sides of the Saline river. 

 It does not, however, cross to the Smoky Hill river, twenty miles distant, for the next 

 seventy-five miles. It turns towards Colorado, and is not seen again in the lower valleys, 

 but only as a landmark forming the tops of the hills. In the vicinity of Fort Wallace it 

 appears south of the Smoky, and is seen occa.sionally for forty miles south and southeast 

 of that place. 



On examination of the country westerly of the boundary given, we shall find that the 

 Pliocene occupies, in common with the Cretaceous (Niobrara group), about one-half of 

 the area of the country for three thousand square miles, while it entirely covers the north- 

 western part of Kansas to the extent of about twice that number, or six thousand square 

 miles. It will thus be seen that if a geological map were to be made of the Pliocene, its 

 outlines on the east and south would be very irregular; the higher portions of the 

 country presenting the sandstones of the Pliocene, while the ravines and valleys would 

 show the chalky limestones and shales of the Cretaceous. 



The fossils which we at first supposed rare in the Pliocene, were found in our later visit 

 more abundant and very interesting. As our labors the past six months were devoted to 

 the collection of vertebrate fossils from the Niobrara, our examination of the former was 

 casual, and only along the line of their union. The fossils of the two were found in situ- 

 and within ten vertical feet of each other, and frequently in the shales, mingled together. 

 The contrast is very great. While the Cretaceous are nearly all marine, with no mam- 

 mals, those of the other are nearly all mammalia of modern types. 



