THE CRETACEOUS RIM OF THE BLACK HILLS. 257 



over the hard sandstones on the right bank of the stream above 

 the electric light plant (5, Fig. 2). 



This bed was easily followed to the quarry, where it consti- 

 tutes the overlying mass which it is necessary to remove in order 

 to uncover the workable sandstone below. At this point the bed 

 also contains layers of soft white sandstone more or less massive. 

 Large blocks of this had been thrown down and lay strewn at 

 the foot of the quarry. On the surfaces of these and more or 

 less scattered through their mass were impressions of dicotyle- 

 donous leaves of Dakota types. The shales were also found in 

 places above the quarry, and some of these yielded very good 

 specimens (4, Fig. 2). 



The massive sandstone of the quarry is entirely barren so 

 far as could be ascertained, and no fossils were found at any 

 point lower than the bed that overlies it. For a long distance 

 on both sides of the canon it forms the crest of the ridge, pre- 

 senting a more or less abrupt escarpment of from 25 to 75 feet. 

 Below it, higher up the stream, beds of softer sandstone, argil- 

 laceous shales, and carbonaceous layers with impure coal seams, 

 all highly charged with gypsum, come down to the bed of the 

 stream, and are finally seen resting upon the Jurassic clays, which 

 in turn overlie the Red Beds. Some distance below Hot Springs 

 the Cretaceous can be seen at the summit of the cliffs, with the 

 whole thickness of the Jurassic below them and the Red Beds at 

 the base. At and about Hot Springs there are some heavy beds 

 of conglomerate about which little seems to be known. 



The following is the Cretaceous section as measured : 



SECTION NO. II. 



Fort Benton. 



II. Grayish black clays with layers of ferruginous concretions, extending to 

 the south Fork of the Cheyenne River — contact conformable. 



Dakota of Newton, jjg Feet. 

 10. Pink sandstone, mostly thin-bedded, with ripple-marks and fucoid-like 



impressions 30 feet 



9. Soft black shales with traces of carbonized plant remains and some frag- 

 ments of fossil wood 15 feet 



8. Pink and gray sandstone 30 feet 



