1902.] Loomts, American Jurassic Stratigraphy. 4^5 



posures where more or less of the face has not faulted and 

 slipped to some extent. The majority of all the Dinosaur 

 prospects were in clays which were faulted out of place. 



Of all the sections the Inyan Kara Peak one is the thickest. 

 This is due in great part to the frequency and extra thickness 

 of the sandstones. The Beaver and Salt Creek sections in the 

 same general neighborhood also have larger quantities of 

 sandstone, which fact I take to mean that in the neighbor- 

 hood there was some land mass during a part at least of the 

 Jurassic period. 



EXPLANATION OF THE PLATES. 



Fig. I, Map of the country on the west side of the Black Hills, cov- 

 ered by the prospecting party of the American Musetim of Natural 

 History in June, 1901. 

 Line A-B, Belle Fourche Section. 



C-D, Inyan Kara Creek Section. 

 E-F, Sheldon P. O. Section. 

 G— H, Inyan Kara Peak Section. 

 I-J, Salt Creek Section. 

 K— L, Beaver Creek Section. 

 The map is modified from Scott's Mineral and Geological Map of the 

 Black Hills. 



Fig. II, Belle Fotu-che Section. 



The vertical and longitudinal enlargements are the same in all the 

 sections. 



Fig. Ill, Inyan Kara Creek Section. 

 Fig. IV, Sheldon P. O. Section. 

 Fig. V, Inyan Kara Peak Section. 

 Fig. VI, Salt Creek Section. 

 Fig. VII, Beaver Creek Section. 



