538 GEOLOGICAL SURVEY OF THE TERRITORIES. 



three or four ledges of white fossiliferous limestone. The slope between 

 each of the limestone-beds was thickly strewn with chips derived from 

 the ledges, and the true character of the intermediate beds was largely 

 concealed from this cause. They appeared, however, to be mainly 

 whitish clays, with, in places, a slightly bluish tinge. The fossils were 

 mostly fish-remains, impressions of scales, spines, and bones, but in the 

 upl^er ledge we found casts of a small Planorhis, and in the lowermost 

 one a Helix, closely resembling 11. Leidyl, from the Tertiary of the 

 Upper Missouri. The upper beds here apparently dipped a little to the 

 north of east, but scarcely more than two or three degrees altogether. 

 The uuconformability between them and the underlying rocks was not, 

 as far as we could see, very noticeable at this point, though I thought 

 that I saw in the lower beds a slightly increased dip to the eastward. 

 These lower reddish beds are seen along the railroad to the west of this 

 station in various places, and apparently lie unconformably upon the 

 whitish Cretaceous strata which come into view in that direction. 



Aspen. — The Cretaceous strata which appear near Aspen Station ap- 

 parently belong to a lower member of the formation than any of the 

 beds examined by us either to the east or west of this point. Immedi- 

 ately at the station they form rounded hills, or ridges, rising to the 

 height of 200 feet or more, and composed of hard, splintering, whitish 

 and bluish slates, the former color predominating toward the summit, 

 and the latter appearing near the base. These slates are full of fish- 

 scales, with occasional impressions of bones and teeth, and near the top 

 of the hills we found a fragment of an Ammonite. The lower bluish 

 beds are also well exposed in several cuts along the railroad for a short 

 distance west of the station, and here also contain numerous fish re- 

 mains; their color in places is nearly black. In one of these cuts, un- 

 der the snow-shed just west of the station, we saw one or two thin 

 layers of grayish limestone, full of unrecognizable fragments of fossils. 

 The total thickness of these slates, from their lowest to their highest 

 exposures, cannot be less than 300 or 400 feet ; they pass beneath the 

 level of the valley to the westward with an estimated dip of ten or 

 fifteen degrees in a general west-southwest direction. To the westward, 

 within a distance of about two miles, there appear one or two parallel 

 ridges, which, with the valleys between, must represent some 1,500 feet 

 or more of overlying strata, consisting, as far as could be seen in the 

 exposures of light gray and whitish sandstones, and light-colored clays, 

 or shales. The railroad cuts through the westernmost one of these 

 ridges at a point some three miles from Aspen, where we made the fol- 

 lowing rough section: 



Sectio7i at Bock Cut. 



1. Light-colored shales and shaly sandstone 50 feet or more. 



2. Whitish sandstone containing Ostrea o feet. 



3. Light-colored shaly bed 10 feet. 



4. Heavy-bedded whitish sandstone 40 to 50 feet. 



5. Alternating shales and thin sandstone-beds 40 feet or more. 



The heavy sandstone-bed No. 4 forms the crest of the ridge, the 

 upper beds appearing on the slope in the artificial cut. The oyster in 

 bed No. 2 was identified by Mr. Meek as Ostrea soIeniscu.Sj Meek, a species 

 which we found farther w^est in Cretaceous beds at Coalville and else- 

 where. The dip of the main sandstone was about 30^ in a direction 

 nearly southwest. 



A little west of this point is the interesting locality at old Bear River 



