136 GEOLOGICAL SURVEY OF THE TERRITORIES. 



side the rusty-gray sands and sandstones dip away from the road at an 

 angle of 10° to 15°. This anticlinal valley is most marked near Fort 

 Steele at the crossing of the North Platte. 



About five miles east of Fort Steele I made a careful examination of 

 a railroad cut through a ridge of upheaval, which inclined about south 

 or a little east of south. We have exposed here, commencing at the 

 bottom — 



1. Gray, fine-grained sandstone, rather massive and good for building 

 purposes, and easily worked, eighty feet thick — dip 25°. 



2. A seam, two feet thick, of irregular, black, indurated slaty clay, 

 with layers of gypsum all through it, then two feet of arenaceous clay. 



3. Ten feet of rusty-gray, compact sandstone. 



4. Eight feet of clay and hard, arenaceous layers, very dark in color, 

 passing up into harder layers, which split into thin laminse, the surfaces 

 of which are covered with bits of vegetable matter. 



5. About fifty feet of rusty, yellowish-gray sandstone. All these sand- 

 stones contain bits of vegetable matter scattered through them. 



6. One hundred to one hundred and fifty feet of steel-brown indurated 

 clay with some iron concretions. The clay is mostly nodular in form. 



7. A dark-brown arenaceous mud rock, quite hard, thirty feet. 

 From bed five, I obtained numerous species of marine shells, among 



them a species of Ostrea and Inoceramus in great numbers. The upper 

 surfaces of the hard clay layers appeared as though crowded with im- 

 pressions of sea- weeds or mud markings. In another railroad cutting 

 about four miles east of Eawlings' Springs I obtained the same Inocera- 

 mus and a large species of Ammonite. These fossils are important in es- 

 tablishing the age of these rocks. Fort Steele is located on the north side 

 ot the railroad, and presents a pleasant and quite pretty appearance to 

 the traveler. I intended to make a more careful examination of the geo- 

 logical features of this interesting region, but failed for want of time. 

 The officers at this post have always manifested great interest in hav- 

 ing the scientific as well as the practical resources of the surrounding 

 country examined, and their favors to my party have been very gener- 

 ous. I take great pleasure in thanking the commandant, Colonel L. A. 

 Bradley, of the Ninth Infantry, also Captain James Jackson, quarter- 

 master, for favors extended to me in time of need. 



In the channel of the North Platte, near Fort Steele, the black clays 

 of the upper cretaceous are most distinctly shown, then gradually pass 

 up into the series of sandstones and clays that form the lofty walls or 

 ridges on the north side of the railroad. We can count from six to ten 

 beds of yellowish-brown sandstone, with inclining beds of arenaceous 

 clay. In the lower portions the Inoceramus or Baculite is rarely found, 

 the arenaceous character of the sediments seeming to have been unfavor- 

 able to abundant animal life. Higher up a seam of oyster-shells of an 

 unknown species occurs. They are probably what I have regarded as 

 the transition or beds of passage from the cretaceous to the tertiary. 

 They are even better displayed from the west side of Bridger's Pass to 

 Elk Mountain, along the old overland stage road. Beds of coal are 

 known to crop out among the distant hills on either side. There is 

 undoubtedly a mingling of the two formations to such an extent that a 

 careful detailed survey of this district is necessary to clear up all the 

 obscure points. It is probable, however, that the North Platte cuts 

 down into the cretaceous beds most of the way, and possibly entirely, 

 from the mountains to the south, far north of the railroad. 



Fig. 11 may be introduced in this connection to illustrate the style of 

 the erosion of the lower tertiary coal formations in the Laramie plain. 



