LAEAMIE PLAINS. 87 



Rock Creek Station of the old Overland Stage Road. Owing to some 

 misunderstanding in regard to the directions for finding the deposit, it was 

 not visited by our parties, but through the kindness of ranchmen living on 

 Rock Creek, we were able to procure specimens of the coal, together 

 with the overlying sandstone. It would appear from descriptions, and 

 general structure of the country, that the coal beds occur in the Fox Hill 

 foiTnation in a somewhat similar manner to those on Cooper Creek, and in 

 nearly the same geological horizon. The coal is said to occur in a rich 

 carbonaceous clay, with a dip slightly to the eastward, and has been 

 known for many years, having been used by the Overland Stage Company 

 for blacksmithing purposes. Neither of these coal banks have been thor- 

 oughly opened, nor their true value and extent for commercial purposes 

 made known, although they are situated within 15 miles of the railroad, 

 with a gentle down grade for the entire distance. 



Rock Creek, which has a broad open valley, is the most important 

 stream north of the Little Laramie River, and drains, as has already been 

 mentioned, into the Medicine Bow River north of the limits of the map. 

 The upper valley runs through Cretaceous sandstones, stretching from the 

 Medicine Bow Range, far out to the eastward. A short distance above 

 Rock Creek Station, on the railroad, the soft clays and marls of the Fort 

 Benton group reach the surface, the character of the country changing very 

 greatly, while the broad valley narrows and cuts a deep channel through 

 the easily-eroded clays. West of Miser Station, the sandstones give place 

 to the argillaceous beds, and from there westward, nearly to Como Station, 

 the Fort Benton and Niobrara Cretaceous occur as the surface formations. 

 At Rock Creek Station, the Fort Benton beds are well shown on the high 

 banks, and in the numerous narrow ravines and gullies, cutting through 

 the clays at right angles to the main stream, which expose between 350 

 and 400 feet of dark plastic clays, with interstratified beds of sandstone and 

 arenaceous clays. The Fort Benton formation is in many localities char- 

 acterized by beds of ferruginous clays, which, when the iron is present in 

 only small quantities, gives them either a black earthy appearance, or 

 is indicated by a nodular and concretionary structure, with a considerable 

 variety in color of the different layers, especially on exposed surfaces. 



