TO JOTOTION OP 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, and it is therefore im- 

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

 section given 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 lithologica] characters quite unlike the strata which are gen- 

 erally found immediately beneath the Lower Cretaceous Bandstones of New Mexico. 

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

 ered by Dr. Bayden 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 wail the 

 detection of fossils in the -roup 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. dray, yellow, or brown coarse sand-rock, the equivalent of that of the Smoky 



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



feet. 



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



3. Hard light-blue or dove-color.ed limestone in thin layers, Jurassic? 50 feet. 



4. Slope covered, about 30 feci. 



5. Yellow or reddish quartzose sandstone, 2 feet, 

 G. Red shale, 5 feet. 



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



20 feet 



8. Brecciated conglomerate, 5 feet. 



9. Blood-red shale, 25 feet. 



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



1 1. 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 base, 8 feet. 

 Much of the coarse sand rock, Xo. 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 bard. Other portions of the mass 

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

 Mexico. The limestone, Xo. 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 ( Jretaceous sandstones; but the limestone is entirely for- 

 eign to the geol >gy of those portions of New Mexico which I have examined. 1 am 

 Strongly inclined to beli >ve that ii is a member of the series not represented further to 

 the south and west, and 1 shall be surprised if it does not yield to future explorers well- 

 marked Jurassic fossils. 



