EARLIER TERTIARY (EOCENE AND OLIGOCENE). 737 



there is evidence of a local unconformity with the underlying McBean formation, but farther 

 south the relations are conformable. The Barnwell sand is overlain by the Jackson formation, 

 but as the exact contact between the two has nowhere been observed the nature of the contact 

 is not known. In Burke and Screven counties the formation is overlain by the Vicksburg for- 

 mation and in places questionably by the Chattahoochee and Alum Bluff formations. In the 

 eastern part of the State the Altamaha (Lafayette?) formation probably originally covered a 

 large part of it. The Barnwell sand consists largely of unconsolidated red and varicolored sands 

 with some thin layers of sandstone, quartzite, sUicified limestone or flint, and siliceous limonite. 

 The sands, especially where wealjiered, are somewhat similar in appearance to the red residual 

 sands of the Vicksburg formation. The maximum measured thickness of the Barnwell sand is 

 105 feet. East of Ocmulgee River the Barnwell sand is practically coincident in distribution 

 with the Claiborne group as a whole. The formation overlies both the marls and the clays 

 of the McBean formation and extends to the "fall line. " It is probable that red sands between 

 Flint and Chattahoochee rivers belong to' this formation, btit as yet no positive statement can 

 be made. 



In South Carolina the Claiborne group attains an extensive development, and Sloan'**"* 

 has applied a number of names to its local phases, some of which are of considerable importance. 

 The names he proposed are Congaree, Warley Hill, Cawcaw, Santee, Barnwell, and Mount Hope. 

 Near Savannah River the succession of material is similar to that in Georgia. At the base are 

 sHicified clays, fuller's earth, the Congaree shales of Sloan; these are overlain by glauconitic 

 sandy marls, locally with sUicified shells and buhr rock, and calcareous beds, the Cawcaw shales 

 and marls of Sloan, which are equivalent to his Warley Hill marl, Santee marl, and Mount 

 Hope marl of the Santee area and which are succeeded by calcareous beds containing in their 

 lower portion large numbers of Ostrea georgiana, these beds in turn being overlain by red sands, 

 the typical Barnwell buhr sand of Sloan. 



In the region of Santee River the geologic section is decidedly different in some respects from 

 that of Savannah River. The Congaree shales of Sloan can be identified, overlain by glauconitic, 

 more or less calcareous sands (the Warley HUl of Sloan), wliich is overlain by a soft limestone 

 (the Santee marl of Sloan), and this is succeeded by Sloan's Mount Hope, a limestone largely 

 composed of Bryozoa, among which are mollusks of Claiborne age. 



In Mississippi the Claiborne is divisible on lithologic grounds into three distinct formations. 

 The lower of these is the Tallahatta buhrstone, which is overlain by the Lisbon formation, and 

 at the top is the Cockfield formation. 



According to Crider and Johnson,"^'' the Tallahatta buhrstone, "called 'siliceous Clai- 

 borne' by Hilgard, consists chiefly of glauconitic coarse-grained micaceous sandstome that is 

 almost quartzite. The estimated thickness is 350 feet. The formation outcrops in a belt of 

 territory between the Wilcox and Lisbon beds and varies in width from 10 miles in northeastern 

 Clarke County to 30 nailes in Leake and Winston counties. The eastern line of outcrop is trace- 

 able from the Alabama line 4 miles south of Hurricane Creek post office to Eastville; thente it 

 swings southwest nearly to Sterling, south of Meridian; thence it bends northwest past Battle- 

 field, Philadelphia, Plattsburg, Hinze, and French Camp, 6 nules east of Winona, and west of 

 Grenada. No trace of the Tallahatta has been found north of Yalobuslia River. 



********* 



"Above the Tallahatta is a series of beds which Hilgard called 'calcareous Claiborne' and 

 which will be termed the Lisbon formation. The series is about 150 feet thick and is composed 

 of calcareous sands and laminated and lignitic clays. The character of the surface is little 

 affected by the Lisbon, which is almost everjrwhere overlain by the Lafayette. In Alabama the 

 area underlain by this formation is limited in extent, but in Mississippi it widens out and occu- 

 pies the territory from southeastern Clarke to southern Carroll County, varying from 5 to 25 

 miles in width." 



Hilgard *'*'' has described ""beds intervening between the Claiborne and Jackson groups." 

 These beds are exposed where the Quitman and Winchester road crosses Coonupy Creek, on the 

 48011°— 12 47 



