COOKE : JACKSON AND VICKSBURG DEPOSITS 191 



As the upper Eocene limestone of southeastern Alabama is 

 continuous with the Ocala limestone of Florida and southwestern 

 Georgia and does not differ materially from it in lithology or in 

 fossils, the name Ocala limestone is extended to all of the deposits 

 of Jackson age in that part of the state, but future more detailed 

 field work may show the propriety of restricting the name 

 Ocala to the upper part of the formation. Just where the 

 boundary between the Ocala limestone and the Jackson forma- 

 tion should be drawn is a matter of expediency, for the transi- 

 tion area, although narrow, is without definite natural limits. 

 Either the Tombigbee River or the 88th meridian might con- 

 veniently be selected. 



» 



VICKSBURG GROUP 



In Mississippi the Vicksburg group falls naturally into three 

 divisions, the upper, middle, and lower Vicksburg, which differ 

 from one another in both lithology and fossils. The first of 

 these, which corresponds to the ''Higher Vicksburgian" of 

 Meyer'- and to the ''Upper Vicksburgian" of Casey, '^ is herein 

 named Byram calcareous marl; for the second, which is approxi- 

 mately equivalent to the "Middle and Lower Vicksburgian" of 

 jMeyer and to the "Lower Vicksburgian" of Casey, the name 

 Marianna limestone, already in use in Florida, is available; the 

 third includes two facies, a shallow-water or nonmarine facies in 

 western Mississippi, which will be called the Forest Hill sand, 

 and a marine facies in eastern Mississippi and western Alabama 

 known as the Red Bluff clay. In the middle division, or Mari- 

 anna, two subdivisions are recognized, herein named Mint 

 Spring calcareous marl member and Glendon'^ limestone mem- 

 ber. East of Clarke County, Alabama, the middle and lower 

 Vicksburg are similar lithologically and are both included in 

 the Marianna limestone. 



12 ]\Ieyer, Otto, Amer. Journ. Sci., 2cl. ser., 30: 71. 1885. 



" Casey, T. L., Philadelphia Acad. Nat. Sci. Proc. 53: 515. 1901. 



" The name Glendon limestone has been adopted, with mj- consent, by O. B. 

 Hopkins (U. S. Geol. Survey Bull. 661-H. 1917) who had access to my notes and 

 manuscripts. 



