TO JUNCTION OF GRAND AND GREEN RIVERS. 29 



of alternations of strata which are quite different in color., texture, and composition. 

 They are, as far as my observation extended, destitute of fossils, nnd it is therefore im- 

 possible to fix accurately their place in the geological Scale. It will be seen from the 

 section i>'iven below that they underlie the coarse red and yellow sandstones of Lower 

 Cretaceous age, which have been so frequently referred to in the preceding pages. 

 They are, however, in Hthological characters quite unlike the strata which ;ir<> gen- 

 erally found immediately beneath ihe Lower Cretaceous sandstones of New Mexico. 

 The position they hold is apparently the same with that of the Jurassic rocks discov- 

 ered by Dr. Hayden in the Black Hills. It is possible, therefore, and perhaps prob- 

 able, that they are of the same age. It will, however, be necessary to wait the 

 detection of fossils in the group before its place in the series can be more than conjec- 

 tured. The section taken from the summits of the hills at Enchanted Spring, down 

 the side of the valley toward the Cimarron, as far as the rocks were exposed, is as 

 follows : 



1. Gray, yellow, or brown coarse sand-rock, the equivalent of that of the Smoky 

 Hills, here containing obscure impressions of large dicotyledonous leaves, 70 

 feet. 



'2. Thin layers of laminated brown sandstones, with very smooth surfaces, 20 feet. 



,">. I hn'il lif/lit-h/itr tii' ilorc-colnrcil /'nitcx/iiiti' in tltiu layers, Jurassic? 50 feet. 



4. Slope covered, about 30 feel. 



5. Yellow or reddish quartzose sandstone, 2 feet. 

 (I. lied shale, 5 feet. 



7. Yellow calcareous sandstone or silicious limestone, with ferruginous concretions, 



20 feet. 



S. Brecciated conglomerate, 5 feet. 



!). Blood-red shale, 25 feet. 



10. Yellow calcareous sandstone, similar to No. 7, 8 feet, 



11. Blood-red shale, with one or two narrow bands of green, 10 feet. 



12. Red and yellow argillaceous limestone, somewhat concretionary, often laminated, 



sun-cracked and ripple-marked, pierced by vertical cavities from one to two 

 inches in diameter, to bast*, 8 feet. 



Much of the coarse sand-rock, No. 1 of the section, is precisely like that contain- 

 ing the fossil plants of Blackbird Hill, Nebraska; being partly dark-brown and ferru- 

 ginous, and partly gray, quartz-like, and intensely hard. Other portions of the mass 

 are yellow and softer, in this respect resembling the general aspect of this rock in New 

 Mexico. The limestone, No. 3 of the section, is the most interesting feature of the group, 

 and the one to which we must look for fossils that shall determine its age. It is a fine- 

 grained, homogeneous rock, such as I have nowhere seen near the same geological 

 horizon in the Southwest. With the exception of the limestone, I should have no great 

 difficulty in supposing that this group represented the strata which in New Mexico im- 

 mediately underlie; the Lower Cretaceous sandstones; 4mt the limestone is entirely for- 

 eign to the geology of those; portions of New Mexico which I have examined. I am 

 strongly inclined to believe that it is a member of the series not represented further to 

 the south and west, and I shall be surprised if it does not yield to future explorers well- 

 marked Jurassic fossils. 



