74 GEOLOGICAL SURVEY OF THE TERRITORIES. 



First series. — The coal strata, lower eocene, characterized by numerous 

 impressions of deciduous leaves, marine and fresh-water mollusca. 



Second series. — Arenaceous, upper eocene, characterized by a profusion 

 of fresh-water shells, as Unios, Goniobasis, Vivvparas, Lymneas, &c. ; a 

 portion of these being casts. 



Third series. — Calcareous, lower miocene, containing the greatest 

 abundance of fresh- water shells, plants, fishes, &c. 



Fourth series. — Arenaceous clays — upper miocene — turtle shells ; no 

 other fossils observed. The third series of beds contains the plants and 

 shells that were found in such profusion near Barrel Springs on the 

 Muddy. 



Continuing our way eastward, we descend across valleys and over 

 ridges, with the outcropping edges of bed after bed of sandstone and 

 clay rising to view, until we come to the coal strata near Washakie 

 Station, on a branch of the Muddy flowing down from Bridger's Pass. 

 The dip is hardly perceptible at first, but gradually it reaches 5°. 



Through the eocene and cretaceous beds, even to the granites, 

 the inclination may increase, or in some cases diminish. In some 

 instances the eocene beds are vertical, while the carboniferous strata 

 beneath, incline at a small angle. There is no apparent discordancy 

 between the four series of tertiary beds noted above. Along Green 

 Biver, at Bock Springs, Black Buttes, and west of Bridger's Pass, 

 no want of conformability could be ascertained. Yet there must be 

 some discordance between the upper tertiaries and the older beds, 

 from the fact that the Bridger group aud the Monument Creek group, 

 as well as the upper portions of the White Biver group, jut up against 

 the older beds in many places in a horizontal position or incline at an 

 angle of 3° to 5°. This is the case along the eastern flanks of the Laramie 

 range, and ou the sides of other mountains in numerous localities. Near 

 Fort Laramie the White Biver beds, which may possibly be of pliocene 

 age, have been deposited high up, in the ravines, on granites, or on the 

 upturned edges of carboniferous limestones, and yet in the plains these 

 same beds seem to conform perfectly to the old tertiaries, and the latter 

 conform perfectly to the cretaceous, Jurassic, triassic, carboniferous, and 

 Silurian beds. 



After passing Duck Lake Station we ascend barometrically, although 

 we descend geologically, lower and lower beds rising to view continu- 

 ally, and just before reaching Washakie Station the lower tertiaries or 

 lignite beds make their appearance, with a dip of about 10°. I think 

 the fresh-water shells that occur here in sandstones so abundantly be- 

 long to the third series of upper eocene beds that gradually pass down into 

 the coal strata. About a mile west of Washakie the beds of coal are ex- 

 posed, and the examples of the baking, and even the melting, of the 

 adjacent rocks by the spontaneous ignition of the coal-beds, are very 

 common. The ridges are covered with these red or burnt places, which 

 look like piles of cinders. In some beds of gray calcareous sandstone 

 over the coal I collected great quantities of large deciduous leaves of 

 trees belonging to the genera Platanus, Fopulus, Tilia, &c, evidently the 

 same species as those found in other localities connected with the coal 

 formations. The coal strata reach a great thickness around Bridger's 

 Pass, and are composed of alternate beds of sandstone with layers and 

 concretions of calcareous sandstone. In the upper portions the clays 

 predominate aud contain the coal seams, which vary in thickness from 

 a few inches to ten or twelve feet. As we descend toward the creta- 

 ceous beds, the sandstones begin to predominate, until they rise on our 

 left hand, as we ascend the " pass," in lofty, nearly vertical walls. The 



