Douglass: A Geological Reconnaissance. 241 



the town. This bluff is several hundred feet in height, and it furnishes 

 a very good exposure of a large portion of the strata nearly down to 

 the river which washes its southern base. The grade for the road is 

 between loo and 200 feet above the stream. Below the road are 

 dark shales with layers of sandstone. In the shales are fragments of 

 bones of dinosaurs. Higher are alternating shales and sandstones, in 

 the latter of which were found a few impressions of plants and of non- 

 marine mollusca. The bluff is capped by gray sandstone. In the 

 shale just beneath the sandstone are non-marine mollusca. Northeast 

 of Columbus, the beds, though capped by gray sandstone, are some- 

 what different. As will be seen later, these strata extend northward 

 to the Lake Basin, a distance of fifteen miles or more. There the 

 beds lie above the Bearpaw shales, which contain typical Pierre fos- 

 sils, though beds of the age of the Fox Hills may intervene. 



North of Columbus and a little eastward, at the foot of the bluffs, 

 are dark marine shales with bands of sandstone and some brown con- 

 cretions containing marine fossils. These are "undoubtedly Upper 

 Pierre or Fox Hills. Some fossils were also found in the darker 

 shales higher than the layers containing the concretions. These 

 shales, as they continue upward, appear to become on the whole 

 more arenaceous until they suddenly end, and are overlaid by heavy 

 beds of gray sandstone, which cap the bluffs. These sandstones are 

 in part massive and in part they have more the appearance of lamina- 

 tion. These and the underlying shales and sandstones, probably belong 

 to the Fox Hills formation, though the upper sandstones may be 

 Laramie. 



In the bluffs nearly north of Columbus is a short ravine opening 

 upon the sage-brush flat. To the right of the ravine the marine 

 strata dip, at least at the foot of the bluffs, at a considerable angle. 

 West of this little ravine or amphitheatre, the strata are nearly hori- 

 zontal, but they consist, as on the east side of the ravine, of dark 

 shales and thin bands of sandstone. If we follow them to the west- 

 ward they appear to suddenly cease, giving place to a heavy band of 

 sandstone, which continues to the western end of the hogback where 

 the rock is being quarried for building stones. I did not have time 

 to carefully investigate the matter, but it looks as if there were a fault 

 here, and the Fox Hills or Laramie sandstone lies on a level with the 

 marine Cretaceous. Some fossil plants were seen in the sandstone at 

 the quarry. 



