UPPER RED BEDS OF THE BLACK HILLS 375 



Feet. Inches 



Purple limestone (Permian). 



XIX. NORTHEAST OF SPEARFISH ; VALLEY NEXT EAST OF LOOKOUT PEAK. 



Green shale (Jurassic) --.-_-._ io-|- 



Massive white gypsum -------- 2 



Clayey sandstone - - - - - - - - - 12 



Massive white gypsum --------20 



Red sandy shale with few green streaks - - - - - 50 



Gypsum .-..--_..- 2 



Red sandy shale - - - - - - - - -.. y^ 



Green clay -------..-.. y^ 



Chocolate-brown sandy shale, few gypsum veins - - - 20 



Green clay -----.--.-.. i 



Red sandy shale - - - - - - - - - 2 



Gypsum ------...-_. 2 



Red sandy shale --------- g 



More massive sandy shale -------.. 3 



Chocolate-brown sandy shale with streaks of green - - - i 

 Thin-bedded red sandy shale with specks of green - - - 10 



Chocolate-brown sandy shale with network of gypsum veins 



paper-thick to 4 inches. 

 Covered. 



XX. ONE AND ONE-HALF MILE WEST OF WHITEWOOD. 



Section generally covered. Impure gypsum exposed toward the middle of 

 red clays. Uniform dips of 28° and upper and lower contacts give 

 thickness here of 450 feet for the Spearfish red beds.- 



These sections show that the upper red beds of the Black hills' 

 consist of about four hundred feet of red sandy shales with inter- 

 stratified beds of gypsum. The shales are generally homogeneous 

 in color, composition, and texture, but subordinate variations 

 are caused by small green streaks and spots. The gypsum beds 

 are irregularly distributed in lenses throughout the formation. 

 Adjacent to the beds of gypsum frequently the red shales are 

 traversed by interlacing gypsum veins. No fossils have been 

 found in the Spearfish formation. 



The red beds are characteristically red, the shade varying 

 from chocolate-brown and dark red to light red ; the usual tint 

 is a uniform dark brick-red. The unaided eye sees in a hand 



