326 DESCKIPTIVE GEOLOGY. 



SECTION II. 

 FEOM ASPEN TO ECHO CITY. 



BY S. F. EMMONS. 



Upper Bear River Valley. — Along the line of the railroad, from 

 Aspen Station to a few miles west of Bear Eiver City, there is exposed a 

 great thickness of beds of the Cretaceous formations, having a general strike 

 of north 30° east, and dipping at various angles from 30° to the perpen- 

 dicular. These beds form a continuation of the uplift noticed on the valley 

 of the Little Muddy, on Map II; but from the soft character of the rocks 

 which compose them, and the fact that their outcrops can be traced only 

 short distances, being covered by the horizontal beds of the Vermillion 

 Creek Tertiaries, which overlie them, the exact details of their structure 

 can hardly be arrived at. At Aspen Station is exposed a thickness of 300 to 

 400 feet of whitish and bluish shales, abounding in fish-scales, with occa- 

 sional impressions of bones and teeth, and fragments of Ammonites. Within 

 them are a few thin beds of grayish limestones. They dip to the westward 

 about 10° to 15°, and are overlaid by a series of gray and whitish sand- 

 stones. These beds were considered to represent the Colorado Cretaceous. 



On the west side of the divide, near the bend of Sulphur Creek, the same 

 overlying sandstones form a narrow ridge, having a trend north 30° east, 

 whose beds dip 30° to the westward. They consist of 50 feet or more of 

 light-colored shales and shaly sandstone, underlaid by a whitish sandstone 

 full of remains of Ostrea soleniscus, beneath which is a light-colored shaly 

 bed, and at the base 50 to 100 feet of heavy white sandstones. From the 

 lithological character of these beds and their fossil remains, they have been 

 considered to represent the Fox Hill group. Between this ridge and Bear 

 River City, in the hills northeast of the railroad, is found a great thickness 

 of beds of blue and gray shales, and some sandstones, which lithologically 

 seem to represent the Colorado series. In general, these beds stand about 

 perpendicular, and it may be supposed that a sharp fold has brought up the 



