122 



GEOLOGY OF THE BLACK HILLS. 



is Hocessaril}' inconiplete and wanting- in absolute accuracy, but it is believed 

 to present the character and thickness of the Carboniferous strata with a 



fair amount of exactness. The exposures of 

 the Potsdam were not sufficiently perfect for 

 measurement. 



9 



2 



a 

 o 



I 



Carboniferous. 



Feet. 



2 



t» 







E 1^ ,^ o 



C F-J '^ ^^ 



«5 t«' 00 ci 



1. Liinestoiio, pink, imi)iire aud silicious, cou- 

 taiuiiig fragments of criuoid stems (No. 

 1) exposed . . 20 



2. Limestone, white or gray (No. 2) 180 



3. Limestone, silicions, containing much flint 

 and <;olored silicions matter; has a brec- 



I (aated appearance (No. 3) 250 



>. 4. Alternating limestones and calcareous sand- 

 stones; yellow, reddish, white, and pink ; 

 near the base a marked stratum of deep 

 red, calcareous sandstone 10 feet thick; 

 the top beds a dee]) red sandstone, with 

 ranch lime in nodules or concretions 



(lower part of No. 4) estimated . . 200 



5. Variegated sandstone, distinc^tly banded in 

 strata of different colors, red, yellow, and 

 white (upper part of No. 4) 100 



® S 



n 



^ a 



IB ^o 

 S 05 t! 



o a b 



« ' o 

 P o 1^ 



"2 a 



Red Beds. 



6. Eed clay, with some soft, red sandstone 100 



7. Puri)le limestone 25 



8. Eed clay and gyiisum forming the Eed Val- 



ley 



■^;z ■" o 



mi 



In obtaining the above section, series of 

 partial measurements were made as follows: 

 Jlici Having- measnred the first section the canon 

 was followed down imtil the capping bed of 

 the section was seen to reach the creek, when 

 another section was made, and so on through the canon. 



The limestones were not found at any place to be fossiliferous, but the 

 different beds correspond closely in their lithological characters with tlie 

 Carboniferous as described in other parts of the Hills. No. 5 of the local 



