14 Geological Survey of Alabama. 



where it forms vertical bluffs, it is firm and compact and resembles black 

 clay. Thickness about 7 or 8 ft. 



6. The Black Bluff Section. Here, again, we have difficulty in deter- 

 mining the exact thickness, since, on the Tombigbee, the strata of this 

 section are spread over an extent of surface which would, with uniform 

 dip, correspond to a thickness of over 200 feet, while, on the Alabama, 

 and more particularly inland, in the eastern part of Wilcox County, the 

 thickness is not greater than 35 to 40 feet. Since 80 feet of these beds 

 are seen in superposition at one locality (Black Bluff), we think that the 

 maximum can not be less than 100 feet. 



The characteristic strata which compose nearly the whole of this section 

 are black or very dark-brown clays, which are in part fossiliferous. A 

 detailed section would present nothing of importance for our present 

 purpose. 



7. The Midway or Pine Barren Section. Thickness 25 feet. The 

 strata are a white, argillaceous limestone, holding a large nautilus, which 

 is characteristic of the horizon, 10 feet thick; followed by calcareous 

 sands and a yellowish, crystalline limestone, with turritellas, carditas and 

 corals the sands six feet, the limestone eight or nine feet. This section 

 is best seen in eastern Wilcox County, on Pine Barren Creek ; but the 

 upper or nautilus-bearing rocks occur at Midway, on the Alabama River, 

 and westward across Marengo County. No exposure of these rocks has 

 been observed on the Tombigbee River, but they will probably be found a 

 short distance below Moscow. 



