22 EXPLORING EXPEDITION FROM SANTA PE 



timi with the Qearly horizontal position of the strata, that the interval which here sep- 

 arates the Carboniferous and Cretaceous series is far less than at any point where it 

 has been examined farther to the south and west. Thisisalso proved from the sec- 

 tions given by Messrs. Meek and I Iayden in the report of their explorations in Kansas, 

 where it is shown that the roeks filling this pip have not more than one-third or one- 

 fourth the thickness of those which occnpv the same relative position in New Mexico. 



The interesting discovery by Dr. Hayden of a group of strata in the Black 

 Hills, which represent a portion of the Grypsum formation and yet contain numerous 

 well-marked Jurassic fossils, shows that this series exhibits in different localities consid- 

 erable diversity of character and development, and encourages us to hope that here- 

 after similar industry and energy, by bringing to lighl Other localities where these 

 strata are fossiliferoiis, will permit an accurate classification to be made of them on 

 paleontological grounds. It may then he possible to establish a parallelism between 

 subdivisions of this group and the Jura and Trias of Europe, but it is evident that 

 until unmistakable Triassic fossils are discovered in the Southwest, even this general 

 parallelism can hardly be said to be established. Thai it will ever be possible to iden- 

 tify in the members of the Gypsum formation the Oolite, Lias, the Mwnes-Irisees, the 



Muschelkalkj and Gres-bigwrr^ is more than doubtful, 



( )n the banks of the Little Arkansas there is an exposure of laminated, yellowish- 

 white, fine-grained, rippled-marked sandstone, and a singular cellular amygdaloid-like 

 magnesian (?) limestone, which apparently belong to the ( • ypsum formation, yet which 

 exhibit litholosrical characters such as 1 have not elsewhere seen in any member of 

 that group. As far as observed they contain no fossils whatever, and without further 

 "evidence it is impossible to say what are their precise equivalents in other localities. 



1 shall soon have occasion, in speaking of the geology of the region borderingthe 



Upper Cimarron, to refer to another group of strata which underlie the Lower ('reta- 

 ceous rocks and hold a place usually occupied by a portion of the Gypsum series. 

 These strata present characters somewhat at variance with those usually exhibited by 

 the Qypsiferous group, and such as have led me to suspect that they form part of a 

 somewhat local deposit, which may be the representative of the Jurassic strata, dis- 

 covered by Dr. Hayden in Nebraska I have been able to discover no evidence 



of the existence of similar rocks, beneath the Cretaceous and above the Permian, east 

 of Walnut ( Jreek. 



WALNUT GREEK TO PAWNEE FORK. 



LOWEE CEETACEOUS BOCKS. 



1 before reaching Walnut Creek, the Santa Fe road enters the valley of the Arkansas, 

 which is several miles in width, and is bounded on the north and west by the abrupt 



edges of the "high prairie," a nearly level plateau, which occupies an immense area west 

 of this point. In this plateau the tributaries of the Arkansas have excavated valleys 

 of greater or less breadth, bul they are generally narrow and are separated by "divides" 

 of the 1 1 i u'l » prairie, which to the eye are as level as the surface of still water, and are 

 everywhere covered with a velvety carpet of buffalo-grass. Smoky Hill Fork of the 

 Kansas, Cottonwood Creek, the Little Arkansas, Cow Creek, Walnut ('reek, &c, all 



