GEOLOGICAL SUEVEY OF THE TERRITORIES, 191 



age. The layers are nearly horizoutal, and, as shown in the valley of 

 Green River, present a peculiarly banded appearance. When carefully 

 studied these shales will form one of the most interesting gToups in the 

 West. Tiie flora is already very extensive, and the fauna consists of 

 Melanias, Gorhulas, and vast quanties of fresh-water fishes, preserved in 

 much the same way as those in the Solenhofen slates of Germany. 

 There are also numerous insects and other small undetermined fossils 

 in the asphaltic slates. One of the marked features of this group is 

 the great amount of combustible or petroleum shales, some portions of 

 which burn with great readiness, and have been used for fuel in stoves. 



The next group commences not far west of Bryan, and is doubtless a 

 prolongation upw^ard of the Green Eiver shales, and may be regarded 

 as of upper tertiary age. 



The sediments are composed of more or less fine sands and sandstones, 

 mostly indurated, sometimes forming compact beds, but usually weath- 

 ering into those castellated and dome-like forms which have given such 

 celebrity to the '' Bad Lauds" of White Eiver. Church Buttes, near 

 Fort Bridger, is an example of this grouj), and shows the style of 

 weathering to which I refer. I have called this series of beds the 

 Bridger group, from the fact that it is best developed in this region. It 

 has already yielded remarkably fine species of Uiiio, M^lania, PlanorMs, 

 Vivipara^ Selix, &c., with a great variety of turtles and mammalian re- 

 mains. There are indications that when this group is thoroughly ex- 

 plored it will i3rove to be second only to the " Bad Lauds" of Dakota in 

 the richness and extent of the vertebrate remains. 



Immediately west of Fort Bridger commences one. of the most re- 

 markable and extensive groups of tertiary beds seen in the West. They 

 are wonderfully variegated, some shade of red predominating. This 

 group, to which I have given the name of Wasatch group, is composed , 

 of variegated sands and clays. Very little calcareous matter is found " 

 in these beds. 



In Echo and Weber Caiions are wonderful displays of conglomerates, 

 fifteen hundred to two thousand feet in thickness. Although this group 

 occupies a vast area, and attains a thickness of three to five thousand 

 feet, yet I have never known any remains of animals to be found in it. 

 I regard it, however, as of middle tertiary age. 



After passing Rock Springs station, Union Pacific railroad, the next 

 exposures of coal are at Bear River City, and at Evanston, and also at 

 Coalville, near the entrance of Echo Creek into Weber Eiver. The coal 

 beds at Evanston are the finest known in the West, and reach a thick- 

 ness of twenty-six feet at one locality. These coal beds seem to be sep- 

 arated from those at Separation and Carbon, and to present some feat- 

 ures difierent from those in any other x>ortion of the West. I am in 

 doubt as to their precise position, but I am inclined to regard them as 

 of lower tertiary age, possibly on a parallel with the oldest beds of the 

 great lignite group in other localities. On Bear River we find several 

 species of Ostrea, both above and below the coal, and in a cut just west 

 of Bear River City is found the greatest profusion of molluscous life 

 that I have ever seen in any of the tertiary beds of the West. There 

 seems here to be a mingling of fresh and brackish water fossils. At 

 Evanston, impressions of deciduous leaves are abundant in beds above 

 the coal. No portion of the fauna seems to be identical with anything 

 found in other places. The flora seems also to be distinct, although 

 some of the forms may be identical with species elsewhere. I have 

 named the group of coal strata which is exposed from beneath the mid- 



