TO JUNCTION OF GRAND AND GREEN RIVERS. 31 



■I. Bluish shale, containing impressions of leaves, and a thin bed of lignite 4 feet. 



5. \ cllow soft Bandstonej with impressions of dicotyledonous leaves, apparently 



identical with some of those from Smoky Hill, to base of section 50 feet 



From Cedar Spring to BfcNee's Creek the road passes over a high prairie under- 

 lain by Tertiary limestones. At McNee's Creek the Tertiary rocks are cut through and 



the Cretaceous series freely opened. Xo fossils were found here, hut the rock is gener- 

 ally similar to that atCedar Spring. ^tCottonwood Spring the surface rock is Tertiary 

 tufaceous limestone, which is cut through by the stream, and its line of junction with 

 the underlying ( Iretaceous rocks exposed. The sandstone is here considerably disturbed 



and metamorphosed apparently by the upheaval of the erupted mass of the "Rabbit- 

 ear Buttes," which are near by. Upon the uneven surface of the sandstone the 

 Tertiary strata arc laid down nearly or quite horizontally, and have evidently been but 

 little disturbed since their deposition. In the upper part of the Cretaceous sandstone 

 near the spring I found many vegetable impressions, generally trunks of trees and 

 fragments of wood, and also some leaves. One of \}u^v is apparently a Sctiix, and 



perhaps identical with S. Mrr/,ii. There are also others, which are similar to the leaves 

 found at Smoky I lili. The metamorphosis of the ( Iretaceous strata is shown not only in 

 the peroxidation of the iron which they contain, but an associated (day-shale is rendered 

 nearly as white and as hard as porcelain; the contained iron being segregated in thin 

 vein-like bands. 



COTTONWOOD SPRING TO RED FORK l,F CANADIAN. 

 TRAP, TERTIARY, .WD CRETACEOUS liOCKs. 



The interval indicated by the above heading includes a portion of the volcanic 

 district adjacent to the baton Mountains, to which I have before alluded. Rabbit-ear, 

 Round Mound, Wagon Mound, &c, form part of a group of trap buttes, which are 

 scattered over the prairie for a long distance east of the mountains. Tin v are in some 

 cases entirely isolated, and seem to mark minor vents, where a portion of the molten 

 matter contained in some vast subterranean reservoir found exit. Othess are connected 

 by sheets of trap, and in some instances are but portions of a volcanic Hood, separated 

 from their connections by subsequenl erosions. Toward the mountains the erupted 

 material more completely covers the country, and forms extensive mesas, or high table- 

 lands, which have been deeply (ait by the canons of the streams once flowing over 

 but now through them. They have also been left in strong 1 relief bv the cutting down 

 of the country bordering them on the east 



In many places the sheets of trap are covered by Tertiary tufa, which has been 

 deposited quietly and uniformly over their surfaces, and is evidently much more recent 



than they. This Tertiary bed is here not of great thickness, and perhaps represents 

 only the extreme upper portion of the series described in the preceding pages. 



Wherever the trap is cul through in the stream-beds it is found resting on the 

 Lower Cretaceous sandstones, which are in such cases somewhat metamorphosed ; being 

 vitrified, or at least hardened; the iron being neroxidixod, and more or less segregated 

 in bands or veins. In other localities the Lower Cretaceous sandstone is covered by 



