TO JUNCTION OF GRAND AND GREEN RIVERS. 27 



following the windings of the Arkansas; the other, called ^the 'dry road,' rising on to 

 and crossing the table-land which separates the valleys of Pawnee Fork and the 

 Upper Arkansas^ This table-land is underlain by a white tufaceous limestone, exposed 

 in the bed of the Coon Creeks, and still better at the point where the dry road comes 

 down again to the Arkansas. It is also thrown out in many different places from the 

 burrows of the prairie-dogs. In lithological characters, this rock is precisely like a 

 portion of the strata of the 'bad-lands' of Nebraska; contains no fossils, but a few 

 pebbles of crystalline rock. At .the ( 'aches, sixteen miles below the crossing of the 

 Arkansas, the same stratum is seen overlaid by some thirty feet of coarse, soft, light- 

 bro\vn conglomerate-, much cross-stratified. The cement is coarse silicious sand; the 

 pebbles, from the size of an egg downward, of granite, trap, quartz, porphyry, trachyte, 

 jasper, quartzite, chert, etc., with a few of Carboniferous limestone." 



"At the crossing of the Arkansas, the following section is exposed: 



" 1. Spongy tufaceous limestone like that on Dry road. 



"2. Coarse, soft conglomerate, same as at Caches, 35 feet. 



" o. Tufaceous limestone, like No. 1, to base." 



"The sand-hills, which border the Arkansas on the south side, seem to have been 

 derived from the decomposition of the Tertiary conglomerate." 



"The same stratum forms the banks of the Cimarron, and has apparently given 

 character to its- sandy and sterile valley. The 'Jornada,' the divide between the 

 Arkansas and Cimarron, is another portion of the high prairie, precisely like, in physi- 

 cal and geological structure, that crossed by the 'dry road.'" 



"At Eighteen-mile ridge, on the Cimarron, the coarse conglomerate and chalky tufa 

 are exposed, as at many points below. The conglomerate is composed of a coarse 

 sandy cement, with pebbles from the size of shot to eight inches in diameter. The 

 larger ones are compact, fine-grained, reddish-yellow sandstone, doubtless of Lower 

 Cretaceous age, and such as comes to the surface farther westward. Others are com- 

 posed of granite, amygdaloid, clay-slate, quartz, jasper, &c. The greater size of the 

 pebbles in this conglomerate perhaps indicates that, in going westward, we are 

 approaching the source from which they were derived. The conglomerate would 

 seem to be a drift from the Rocky Mountains, where, and where only, as far as I am 

 aware, such materials occur in place. If this is true, when on the Cimarron, we were 

 doubtless standing in the channel of a great line of drainage of the Tertiary epoch." 



At the middle spring of the Cimarron a very instructive and interesting section is 

 exposed, in which we again see the base of the Tertiary series. On Pawnee Fork, the 

 tufaceons limestones and conglomerate which I have described rest upon the coarse 

 ferruginous Lower Cretaceous sandstone. Here we find them underlain by soft yellow 

 or red sandstone, of which the place is considerably lower than that last mentioned. 

 In other localities further west we shall see that these Tertiary beds rest first on Lower 

 Cretaceous sandstone, then on trap, again upon the Middle Cretaceous limestones and 

 shales, and, finally, upon the red calcareous sandstones of the Trias. The elements 

 composing the section of the middle spring of the Cimarron are indicated in the fol- 

 lowing table: 



