36 The Badland Formations of the Black Hills Region 



Gray sands with pipy concre- 

 tions 



Loose gray sands with gray 

 and pebbly streaks 



Stratified and cross -bedded 

 sands 



Unconformity 



Volcanic ash 



-4190 



Pink clays ... 

 Volcanic ash 



4100 



Light buff-gray shales 

 Sandstones 



Greenish sands and sandy clays 



Greenish sands. 



Pierre shale? 



Figure 6 — Section from Round Top to Adelia, Sioux county, Nebraska. 

 Above Pierre shale to 3725 is Chadron, 3725 to 4275 is Brule, 4275 to 

 4390 is Gering, 4390 to 4525 is Arikaree. After Darton. 



THE CHADRON FORMATION 

 The Chadron formation, better known by the much older 

 term, the Titanotherium beds, from the name of the large ex- 

 tinct animals, whose bones occur in it so abundantly, receives 

 its name from the town of Chadron in northwestern Nebraska. 

 The formation is best developed and has been most studied in 

 and near the Big Badlands of South Dakota, but is of import- 

 ance along the northerly facing escarpment of Pine Ridge in 

 South Dakota, Nebraska and Wyoming. Owing to the slight 

 dip of the strata away from the Black Hills, the Pine Ridge 



