390 N. H. DARTON — JURASSIC FORMATIONS OF THE BLACK HILLS 



Buff slabby sandstones, ripple-tnarked 40 feet thick. 



Pale red, massive, soft, cross-bedded sandstones 7 " " 



Purple and buff" sandy clays on hard, gray sandstone. . 4 " " 

 Red beds. 



Fason Creek locality. — In the vicinity of Fuson creek the exposures are 

 not sufficiently complete to afford a complete cross-section. The beds 

 outcropping are 8 feet of buff sandstone lying on the Red beds and over- 

 lain by 15 feet of dark gra}^ shales with thin, interbedded sandstones, 

 which are succeeded by 20 feet of buff, slabby, ripple-marked sandstone. 

 Some distance higher on the slope there are exposed dark green shales 

 with abundant belemnites and other fossils in calcareous layers. The 

 entire thickness to the base of the Unkpapa sandstone appears to be 

 about 350 feet. 



Lame Johnny Creek locality. — In the vicinity of Lame Johnny creek 

 the following section is exposed : 



Unkpapa sandstone. 



Buff" sandstone, thin bedded below 15 feet thick. 



Dark shales with belemnites and other fossils 90 " " 



Buff" sandstones '. . 35 " " 



Red sandstones and sandy shales 80 " " 



Buff slabby sandstones, ripple-marked 26+ " " 



Black shales 8 " " 



Buff" sandstones 15 " " 



Dark shales 5 " " 



Red and buff" massive sandstone 10 " " 



Red beds. 



Region south of French creek. — In the first can3'on south of French creek, 

 nearly due west of Fairburn, the formation is seen to be much thinner 

 than it is elsewhere in the region, and to consist of very arenaceous ma- 

 terials. In the fine section on French creek, a mile north, the formation 

 presents more of its usual composition, as shown in the following sec- 

 tion : 



Unkpapa sandstone. 



Red and buff" soft sandstone 20 feet thick. 



Shales with few thin fossiliferous sandstone layers SO " " 



Buff", soft sandstones and shales 20 " " 



Massive, buff to red sandstone 30 " " 



Red beds. 



Dry Creek canyon. — In the canyon near the head of Dr}' creek, north- 

 west of Fairburn, the Sundance formation is represented by onl}^ 60 or 



