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



Tertiary. 



Miocene. 



1. The Pascagoula, upper Miocene. 



2. The Grand Gulf, lower Miocene. 



Eocene. 



The Biloxi. — Concerning the soils, rain wash and recent 

 river alluvium, we need say nothing here, but the character of 

 the coast deposits now in course of formation, has not hereto- 

 fore been clearly defined. Mr. L. C. Johnson has recently 

 given this subject some study and according to him, these 

 deposits consist of alternations of sand and fine mud or clay 

 to the depth of many feet. The agencies which have con- 

 tributed to their accumulation are the waves from the Gulf, 

 the minor rivers of Alabama and Mississippi, and the Missis- 

 sippi River itself. 



The washings of sand upon the coast, and the delivering of 

 sediment by the minor streams are constant factors, but the 

 contributions from the Mississippi are occasional, occurring 

 only when in times of flood the river breaks through the 

 levees and spi*eads over the lowlands on each side of the main 

 channel. Mr. Johnson has shown how this river a few years 

 ago, pouring its waters through the Nita Crevasse into Lake 

 Ponchartrain and Mississippi Sound, covered the Coast sands 

 with a varying thickness of its sediments as far east as the 

 western border of Alabama and almost to the mouth of Mobile 

 Bay, driving out the salt water fish and completely destroying 

 the oysters and other molluscs which were unable to retreat. 

 At Biloxi, borings for artesian water have given a section show- 

 ing alternations of sand with mud or clay down to the depth 

 of SO feet or more, and from this locality Mr. Johnson has 

 proposed the name Biloxi for the formation, the lower part of 

 which is probably of Pleistocene age. The upper part of the 

 Biloxi may hence be considered as the marine equivalent of 

 our river alluvium, and the sediments now accumulating in 

 Mobile Bay will form the estuafine connecting link between 

 the two 



Second Terraces and Geneva Sands. — As the Biloxi borings 

 show the gradual passage of these modern coast accumulations 

 into what must be considered as the marine equivalent of the 

 Port Hudson of the Mississippi River, and just as these Port 

 Hudson equivalents are seen along the lowlands bordering the 

 coast, so in Mobile Bay, beneath the sediments now accumu- 

 lating, and along the western coast, notably on Mon Louis 



