440 GEOLOGICAL SUKVEY OF THE TEEEITOEIES. 



and Cyrena, and millions of Cypris. The larvae are dipterous, some 

 nearly an inch long, and others minute, and in prodigious numbers. With, 

 them are found stems of plants, but no leaves. These beds rise with a 

 very gently dip, and twenty miles from the mouth of the creek terminate 

 against steeply-inclined strata of earlier age. At this point the lower beds 

 exhibit the bright-red colors that are so often seen in the lower parts of 

 the formation at other points. The uplifted beds form a ridge of high 

 hills having a north by east and south by west trend, through which the 

 Fontanelle cuts its way in a deep caiion. This range is monoclinal,the 

 strata dipping 45° east, and their outcrop on the summit and eastern 

 face. The first bed which forms the surface of the incline is rather thin, 

 and is composed of a reddish quartzite without fossils, no doubt of Cre- 

 taceous age. Below it is a stratum of highly fossiliferous bluish lime- 

 stone of Jurassic age, containing Pentaerinus asteriscus, M. and H. ; Tri- 

 gonia, &c. Below this a reddish sandstone presented a similar thickness, 

 which may represent the Trias, which rests on a bluish-shale formation. 

 We have now reached the base of the western side of the hills ; from 

 their summit we have had a beautiful and interesting view of geological 

 structure. The valley, of three or four miles in width, is bounded on the 

 west side by a range of low mountains, whose summits are well-tim- 

 bered. The valley is excavated at an acute angle to the strike of the 

 strata, so that as far as the eye can reach to north and south successive 

 hog-backs issue en echelon from the western side, and run diagonally, 

 striking the eastern side many miles to the southward. At the caiion 

 of the Fontanelle, six of the&Q hog-backs occupy the valley, and the num- 

 ber varies as we proceed down the valley. The structure changes from 

 the same cause as we explore in either direction. The dip of all these 

 hog-back strata is to the west and slightly north, less steep at the eastern 

 side, but reaching 45° and a still higher angle at the middle and west 

 side of the valley. There appears to be an anticlinal near the base of 

 the eastern range, which has been deeply excavated ; from its western 

 slope (in the valley) the upper beds, even in the eastern range, have 

 been carried away, leaving only probable Triassic and Carboniferous 

 strata exposed. In one of these latter I found a well-marked horizon of 

 carbonaceous shales extending as far as I explored them. Toward the 

 western side of the valley, the descending strata are sandstones, but 

 whether identical with that of the eastern hills of Cretaceous age I could 

 not ascertain. Lower down the valley (to the south) similar beds form 

 a high vertical wall of very light color, the scenery resembling that of 

 the Garden of the Gods in Colorado. I suspect that the existence of 

 more than one fold can be demonstrated in these hog-backs and mount- 

 ains. 



The result which bears on the history of the Bear Eiver group is, that 

 on this side of the Green River basin the Bitter Creek epoch is either 

 wanting or represented by a thin layer of red quartzite, (or perhaps 

 Cretaceous No. 1,) and that no coal of Cretaceous age exists along its 

 western rim. After following the valley to Ham's Fork Eiver, and pro- 

 ceeding a short distance along it toward the southeast, I crossed a thin 

 bed of coal in the upturned edges of the same beds crossed in the valley 

 above. The discovery of the extension of the fish and in«ect beds sixty 

 miles north of the principal localities is a point of interest in Tertiary 

 geology. 



The Ham's Fork Mountains form the divide between the waters of 

 Green and Bear Rivers respectively, and are passed by the Union Pacific 

 Eailroad at and west of Aspen station, as is described by Dr. Hayden, 

 (Annual Eeport for 1870, p. 149.) He here points out that the distinctness 



