34 GEOLOGY OF THE BLACK HILLS 



'i'he greater portion of" tliis would seem to belong to the Niobrara 

 group, but the lower 200 feet are perhaps referable to the Fort Benton or 

 No. 2. 



Beaver Creek at its forks is a stream of small dimensions, but draining 

 a large area of these alkaline strata of the Cretaceous it is highly impreg- 

 nated with salts, which are exceedingly unpalatable and are medicinal in 

 their effects. It may be remarked here that the streams which rise in or 

 flow for a long distance through the Cretaceous strata are almost invariably 

 undrinkable by reason of the large amounts of salts dissolved from these 

 beds; but the streams that flow Jirough long stretches of the Tertiary or 

 bad land country, generally contain a large amount of suspended clayey 

 matter with less of soluble salts, and are more endurable. 



A section of the rampart foothills, as exposed on the east fork of the 

 Beaver, is given in annexed figure. 



10 97S 7 R54 3 I 1 



Fig. 3. — Section tbrougli outer Foothills at Camp Jenney, East Fork of Beaver. 



1. Red clays of the lied Beds 



2. Jurassic sandstones, clays, &c .' 



3. Massive sandstones, lower part very ■white ^ 



4. Thin-bedded sandstone 1 



5. Grayish shale or marl, ^vith relenitc [^ °- ^ Cretaceous, Dakota group. 



(). Massive soft white sandstone, with carbonaceous matter j 



7. Black or drab, alkaline shales or marls ") 



8. Shalv calcareous sandstone I ^ ^^ 



9. Slialy calcareous sandstones, ■witli impure limestones contain- ( " 



ing fossils J 



10. Gray shales and marls No. 3 (?) Cretaceous. 



From Camp Jenney, after a delay of two or three days, the entire 

 expedition moved into the Hills proper, establishing the first base of opera- 

 tions at the stockade on French Creek. Here in order to expedite the 

 work the corps was divided into two parties: (1) Mr. Jenney, Avith the 

 miners, assumed the work of examining the mineral deposits and prospect- 

 ing the various districts for gold, and (2) Mr. Newton, Dr. McGillycuddy, 

 and Captain Tuttle were directed to undertake the more detailed and 



