34 



LOWER EOCENE FLORAS OF SOUTHEASTERN NORTH AMERICA. 



uucortainly correlated lignites at the base of the 

 Wilcox nortluvard through the greater part of 

 the outcrop in Mississi])pi. 



The Nanafalia fonnatiou maintains a rather 

 uniform thickness across Alal)ama of aliout 

 200 feet. The lignite bed at its])aseis a most im- 

 portant factor in the interpretation of the 

 geologic history of Wilcox time, for it unques- 

 tionably indicates a relatively extensive emer- 

 gence at the close of the Midway, an emergence 

 marked by the withdrawal of marine waters and 

 faunas from the neighborliootl of the mouth of the 

 Ohio southward beyond the present outcrop of 

 the fonnation in southern Alabama, a distance 

 of over 400 miles, and by the occupation of the 

 surface by extensive swamp vegetation, as the 

 lignite was clearly formed at the place of growth 

 of terrestrial vegetation. 



The Tuscahoma formation, formerly termed 

 the "Bells or Greggs Landing series," consists 

 of about 140 feet of gray or yellowish cross- 

 bedded sands and sandy clays massive below 

 and laminated above, generally poor in fossils 

 except at two horizons where glauconitic shell 

 marls carry an abundant and distinctive fauna. 

 The lower horizon is exposed at Greggs Land- 

 ing on Alabama River and the upper at Bells 

 Landhig on Alabama River and Tuscahoma 

 on Tombigbee River. 



The Bashi formation, fonnerly termed the 

 "Bashi or Woods Bluff series," from Bashi 

 Creek in Clarke County and Woods Bluff on 

 Tombigbee River, where the glauconitic and 

 higlily fossihferous horizons in the formation 

 are exposed, consists of about SO feet of calca- 

 reous glauconitic sands and sand}- clays. The 

 shalloAving of the Wilcox sea in this area, first 

 apparent in the upper part of the Tuscahoma 

 formation, culminated in an emergence which 

 is marked by the 2-foot bed of lignite that 

 marks the base of the Bashi formation. 



The Hatchetigljee formation, named from 

 the bluff of that name on Tombigbee River, 

 consists in the region of maximum thickness 

 near the river of about 17.5 feet of brown, pur- 

 plish, and gray laminated sandy days, and 

 cross-bedded, more or less glauconitic and cal- 

 careous fossihferous sands. It thins both east- 

 ward and westward from the type locality and 

 is overlain uncoiiformahly by the characteristic 

 sediments of the Tallahatta bulu-stone, the low- 

 ermost formation of the Claiborne^ group, a 

 horizon which is well marked lithologicidly 



across Alabama and mirtliwcstward thi"ough 

 Mississippi. 



A large numi)cr of detailed local sections and 

 lists of animal species of the Wilcox formations 

 are given in the various reports by Dr. E. A. 

 Smith,' of the Alabama Geological Survey, and 

 his associates T. H. ^Vldrich, L. C. Johnson, and 

 D. W. Langdon, jr., the major outlines of 

 which, first puhhshed in 1SS7, seem destined 

 to stand. 



Along Chattahoochee River the Wilcox is 

 represented l)y less than 200 feet of glauco- 

 nitic fossihferous sands and dark, laminated, 

 commonly lignitic clay. The clay is at some 

 places rather hard. Several possible expla- 

 nations of the thinness of the Wilcox along 

 the Chattahoochee and eastward in Georgia 

 su<rgest themselves. The beds mav never have 



Co 



attained the thickness that they did in cen- 

 tral and western xVlabama; they may have 

 been deposited and subsequently removed 

 by erosion, or they may be almost entirely 

 covered by the extensive Claiborne transgres- 

 sion that characterized the Georgia area. That 

 an interval of erosion was followed by one of 

 transgression is indicated by the almost exact 

 lithologic similarity of the de]>osits to those 

 found in Alabama and Tombigbee River sec- 

 tions, which would not be the case if there had 

 been a marked difference of physical condi- 

 tions in the west Georgia area. In addition the 

 extensive interval of emergence at the close of 

 the Wilcox and a transgression of the basal 

 Claiborne wliich I have claimed on general 

 grounds finds local confu-mation in the Geor- 

 gia region in the admittedly great overlap of 

 the lower Claiborne deposits and in the phys- 

 ical evidences of unconformity between the 

 Wilcox and Claiborne observed by Veatch and 

 Stephenson.^ 



From Chattahoochee River northeastward 

 poorly fossUiferous exposures of the Wilcox are 

 identified at intervals over a belt 5 or 6 miles 

 in width as far as Flint and Ocmulgee rivers. 

 If the Wilcox was ever present in eastern Geor- 

 gia it is now deeply buried beneath the Clai- 

 borne overlap. Deposits carrying a small 

 fauna suggesting the Nanafalia formation, and 



1 Smith, E. A., and Johnson, L. C, Tertiary and Crotaceous strata or 

 the Tuscaloosa, Tombigbee, and Alabama rivers: T. S. Cool. Survey 

 Bull. 43, 1887. Smith, E. A., Johnson, L. C. uml Langdnti. !>. W.. jr., 

 Report on the geology of the Coastal Plain of Alabama, -Mabama Geol. 

 Survey, 1894. 



s Georgia Geol. Survey Bull. 26, p. 228, 1911. 



