296 E. A. Smith — Post-Eocene Formations of Alabama. 



being lower Miocene (Chattahoochee and Chipola divisions), 

 while the uppermost of the fossil beds at the bluff are con- 

 sidered as upper Miocene (Chesapeake). These discoveries 

 soon attracted the attention of geologists and collectors, and 

 other localities were speedily found where the lower shell bed 

 of Alum Bluff was more easy of access and more prolific of 

 well preserved specimens than at the Bluff itself. Such locali- 

 ties on Chipola River have furnished the name which is now 

 commonly applied to these beds. Between these fossiliferous 

 sands, which according to Mr. Dall, contain a certain number 

 of Eocene shells, and the undoubted Vicksburg orbitoidal 

 limestone, lie as above intimated, some two to three hundred 

 feet of calcareous rocks, constituting the series to which Mr. 

 Langdon has given the name Chattahoochee. Thus the exist- 

 ence of marine basal Miocene beds was established along or 

 very near to the eastern border of Alabama. 



Then in 1892, Mr. L. C. Johnson, working for our Alabama 

 survey, discovered at Healing Springs in Washington County, 

 immediately contiguous to the Yicksburg limestone, the char- 

 acteristic gray siliceous mudstones splotched with purplish fer- 

 ruginous stains, of the Grand Gulf formation. 



These and other equally characteristic Grand Gulf rocks, 

 dark gray clays, he followed eastward through the lower part 

 of Monroe County and through Escambia to the Conecuh 

 River, on the borders of which they are well exposed in the 

 vicinity of Mason, always immediately adjacent on the south 

 to the Yicksburg limestone. At Roberts on Silas Creek, a 

 tributary of the Conecuh River, Mr. Johnson observed these 

 characteristic and unmistakable Grand Gulf beds, underlying 

 and in direct contact with sands containing shells which Mr. 

 Dall has identified as belonging to the Chipola division of the 

 Chattahoochee River series. And a few miles further south 

 in Florida at Oak Grove, Mr. Johnson found a shell bed with 

 excellently preserved forms which Mr. Dall identifies as of 

 Chesapeake or upper Miocene age. The Pascagoula shells 

 above alluded to, have also been classed with the Chesapeake, 

 and borings from an artesian well at Mobile, have furnished a 

 number of shells characteristic of the same period. We have 

 thus certain evidence from our Alabama work, that the Grand 

 Gulf occupies a place between the Yicksburg limestone and 

 the Chipola division of the lower Miocene, being thus identi- 

 cal in position with the calcareous beds of Langdon's Chatta- 

 hoochee section. Although the Grand Gulf rocks have not" 

 been followed farther eastward than the vicinity of the Cone- 

 cuh River, being deeply covered by sands, it seems to us 

 reasonably certain that the siliceous and argillaceous rocks that 

 characterize this formation in the west, become calcareous 

 eastward, and find their marine equivalents in the Chatta- 

 hoochee, of Landgon. : .: .-:/., 



