654 INDEX TO THE STKATIGRAPHY OF NOETH AMERICA. 



I 16-17, J 16. EASTERN GULF REGION, GEORGIA, AND SOUTH CAROLINA. 



As a result of the recent studies of the Coastal Plain of the United States, con- 

 ducted in cooperation between the Federal and the State geological surveys, data 

 have been procured on the stratigraphic and age relations of the several Cretaceous 

 formations. L. W. Stephenson contributes the following review of the Hterature 

 and discussion of the subject: 



C. A. White ^" in 1891 published a r&ume of the hterature on the Cretaceous of these 

 areas to that date. The more important previous investigators were Tuomey,*^^ Winchell,'*' 

 and Smith and Johnson '^° in Alabama, Hilgard "«• *^^ in Mississippi, Safford ''^*' "»' in Tennessee, 

 and Euffin "^^ and Tuomey ^" in South Carohna. 



The principal contributions to the geology of these regions, since the pubhcation of those 

 enumerated by White,^" have been by Langdon,^^" Smith, Johnson, and Langdon,'^i* Crider,"^^ 

 Qlenn^369a sioan,'*^' '"<= and Veatch.'" 



A table which sets forth in condensed form the present writer's views regarding the age rela- 

 tions of the hthologic divisions heretofore recognized in the region is inserted opposite to enable 

 the reader to understand more clearly the following discussion of past and present interpretations. 



In 1860 Eugene W. HUgard,^^^^ State geologist of Mississippi, differentiated four major divi- 

 sions in the Cretaceous deposits of that State. These were, in ascending order, the Eutaw 

 group, Tombigbee sand group. Rotten hmestone group, and Ripley group. 



His Eutaw group rests upon Carboniferous rocks and includes all the Cretaceous deposits 

 below the Tombigbee sand. These deposits consist of "bluish-black or reddish laminated clays, 

 often hgnitic, alternating with and usually overlain by noneffervescent sands, mostly (though 

 not always) poor in mica, and of a gray or yellow tint. Contains beds of hgnite, very rarely 

 other fossils." "«" 



HUgard's reason for adopting the name "Eutaw group" is given in the following quotation: 

 "I adopt this name in view of these beds having been first examined in detail and recognized 

 as being of Cretaceous age, by Tuomey," near Eutaw, Ala., where they are characteristically 

 developed." ^='«'= 



The type region of the Tombigbee sand is in the vicinity of Columbus, in Lowndes County, 

 Miss., where the beds are mapped as a belt 15 or 18 miles wide. The type exposures occur in 

 bluffs of Tombigbee River. To the north of Lowndes County the Tombigbee belt is repre- 

 sented as narrowing down to a strip 2 to 4 imles wide, with a corresponding widening of the 

 Eutaw area. By thus narrowing the Tombigbee belt, what Hilgard actually did was to run his 

 Eutaw-Tombigbee boundary hne obUquely across the strike of the beds so that to the north of 

 the line he represented as belonging to the Eutaw a thickness of strata which correspond in age 

 and stratigraphic position to the lower two-thirds or three-fourths of the Tombigbee as mapped 

 south of the hne; indeed the sections given as typical of the Eutaw are within these northward 

 Tombigbee representatives. 



In 1887 Eugene A. Smith, State geologist of Alabama, and Lawrence C. Johnson ''^"^ pub- 

 hshed a classification of the Cretaceous deposits of Alabama, the divisions recognized being, in 

 ascending order, the Tuscaloosa formation, Eutaw formation, Rotten Limestone, and Ripley 

 formation. They described the Tuscaloosa formation as consisting of at least 1,000 feet of 

 "purple and mottled clays interstratified with white, yellowish- white, pink, and light-purple 

 micaceous sands, and near the base of the formation dark-gray, nearly black, thinly laminated 

 clays, with sand partings." The Eutaw formation is described as " a series of laminated sands 

 and sandy clays at least 300 feet in thickness." 



If only those parts of the area in Mississippi immediately west of the Alabama line, mapped 

 by Hilgard respectively as Eutaw and Tombigbee, are considered, his Eutaw division corre- 

 sponds almost exactly to the Tuscaloosa formation of Smith and Johnson, and the Eutaw divi- 



o Tuomey 's account of the beds near Eutaw to which reference is made is given in First Bienn. Rept. Geol. Survey 

 Alabama, 1850, pp. 118-120.— L. W. S. 



