596 D. W. LANGDON, JR. — CRETACEOUS AND TERTIARY STRATA. 



feet thick and abundaut in variety of marine forms. Tiie top of the series 

 is marked by the most persistent and thickest stratum of lignite noticed in 

 Alabama, an outcrop of 7 feet showing on Landrum's creek, Marengo county. 



On the Tombigbee river this group is nearly 200 feet thick, and contains 

 a limited, though characteristic, fauna ; on the Alabama it is about 3 50 feet 

 thick, and contains a most abundant variety of marine species ; while at Oak 

 hill, Wilcox county, it is only 125 feet thick. In the western part of Bar- 

 bour county the thickness is barely 50 feet, the strata consisting mainly 

 of slightly fossiliferous sands ; and, like the foregoing member, it is lacking 

 on the Chattahoochee. 



The Nanafalla. — The Nanafalia series, marked by thick beds of Gryphcea 

 thirsce, Gabb, is the most abundant in organic remains of the lower Tertiary 

 groups. So far as is known, it has not been noted in Mississippi. On the 

 Tombigbee river the series is about 200 feet thick, the same on the Alabama, 

 and 175 feet on the Chattahoochee. In the Tombigbee drainage the fossil- 

 iferous strata are composed of incoherent beds of Gryphcea thirsce, Venere- 

 cardia planicosia, Turritella mortoni, Osteodes cauUfera, and a few remains 

 of Ostran compressirostra, the interstices between the shells being filled 

 by sand and grains of glauconite. On the Alabama river and eastward the 

 upper part of the group is marked by a gray aluminous rock containing 

 numerous casts, and called, from its resemblance to a younger member of 

 the Tertiary, " pseudo-Buhrstone." 



On the Chattahoochee this series presents no particular features, except at 

 Fort Gaines, Georgia, where it rests unconformably on the strongly eroded 

 surface of the Midway or Clayton limestone. This was considered Claiborne 

 by Loughridge.* 



The Tuscahoma. — This series, consisting in the main of gray and yellow 

 laminated and cross-bedded unfossiliferous sands and sandy clays, with one 

 or two beds characterized by Voluta newcomhiana, Whitf , and unusually 

 large specimens of Turritella mortoni, Venereeardia planicosta, Hostellaria 

 trinodiferct, Con., and Osircea compressirostra, extends across the state practi- 

 cally unchanged, except that east of the typical locality on the Alabama 

 river there is a paucity of fossils. 



The Bashi. — One of the marked features of this series in western Alabama 

 is a bed of lignite about 25 feet below the characteristic stratum of marl. 

 The eastern limit of lignitiferous strata appears to be the head-waters of 

 Sepulgah river, where the carbonaceous material is intermixed with the 

 marl. Aldrich has pointed out the existence of fresh- water shells at the 

 typical locality. 



The thickness of this group on the Tombigbee is about 80 feet; on Pea 

 river it increases to about 150 feet, and is highly fossiliferous ; while on the 



=5^ Rep. on Cotton Production of Ga., lOth Census U. S., vol. VI, 1884, p. 280. 



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