890 HISTORICAL GEOLOGY. 



In Nortli Carolina tliese deposits are much thinner than in Maryland and 

 Virginia, and in South Carolina they xisually occur in isolated basins or sinks 

 in the subjacent Eocene or Cretaceous strata ; they often show a reworking 

 or rearrangement of material, so that Miocene, Pliocene, and even Cretaceous 

 fossils occur in one and the same bed. The component materials are sand, 

 clay, and comminuted shells. 



There are deposits in Georgia of limestone, buhrstone, and conglomerates 

 that belong to the older Miocene series, but their geographical extent is not 

 well determined. 



Florida presents the most complete section of American marine Miocene 

 and Pliocene formations. Immediately above the Eocene along the Chatta- 

 hoochee Eiver occur beds of limestone, clay, and marl, — the Chattahoochee 

 group of Langdon, — having a thickness of about 200 feet. Higher still are 

 the fossiliferous Chipola sands, su.cceeded in turn by the Alum Bluff sands, 

 40 feet thick, containing few organic remains save lignite and plants. Above 

 these occurs a gray marl having a Yorktown fauna 35 feet thick. These 

 Miocene deposits occupy much of the northern portion of the state. To the 

 south the Peace Creek lacustrine deposits and Caloosahatchie beds of Plio- 

 cene or Pleistocene age are probably well developed, though their exact limits 

 are not definitely determined. 



The Neocene beds of Mississippi as well as Alabama and Louisiana — 

 Grand Gulf group oi Hilgard — contain but few animal remains, and their 

 horizon has been, and still is to some extent a matter of dispute ; but the 

 labors of L. C. Johnson and Langdon in southeastern Mississippi, southern 

 Alabama, and northwestern Florida tend to show that they should be corre- 

 lated with the lower Miocene of the Floridian section. They are well devel- 

 oped in Mississippi, and although concealed to the south, doubtless underlie 

 the greater part of the state south of a line roughly drawn through Vicks- 

 burg, Raymond, Byram, Brandon, Raleigh, and Waynesboro, or, in other 

 words, south of the Vicksburg formation. Below and to the east these beds 

 are clayey, lignitic, and gypsiferous ; above and to the west the aranaceous 

 material predominates, and when indurated gives a rugged topography to 

 the region in which it occurs. No traces of similar deposits have been found 

 in Tennessee or Arkansas ; but in Louisiana they occur resting upon the 

 Vicksburg limestone and extending in a southwestern direction toward the 

 Sabine River. 



Certain deposits of clay, lignite, and sandstone in Texas — the Lafayette 

 beds of Penrose — have been correlated with the Grand Gulf vocks of Missis- 

 sippi ; but the presence of Lower Claiborne species — although rare — 

 throughout much of their vertical range, renders it quite probable that all 

 should be referred to the Eocene period. To the seaward marine Neocene 

 beds are unknown at the surface ; yet borings from the Deep Well at Galves- 

 ton show that at no great depth such deposits do occur with a thickness of 

 1500 feet or more. Many lacustrine deposits are found at the surface bearing 

 Vertebrate remains of a late Tertiary age. 



