140 



LOWER EOCENE FLORAS OF SOUTHEASTERX NORTH AMERICA. 



All the storms moved from tlio Equator 

 northward, the main oceiiii currents liad thn 

 siime generid direction, and the prevaUirifz; 

 winds were easterly, so that all these inij)or- 

 tant factors combined to cause a rehitively 

 rapid introduction and sprea(Un<; of forms 

 along the Wilcox coasts. Given favorable 



dei-stantling but because of the early descrip- 

 tion of the Tertiary stages in France and, 

 fnrth(>rmore, because of tiic remarttaljh' aller- 

 nafion of fossiliferous fluviatile, lacustrine, ter- 

 restrial, and marine dejtosilion in that country. 

 Western North Amei-ica affords an almost 

 complete succession of continental deposits 



climatic conditions many of the forms need not from the Cretaceous to tlie top of the Oligo- 



cene, and the Mississippi emba\nnent affords 

 an almost unparalleled succession of marine 

 and estuary deposits from the Cretaceous well 

 into the Oligocene. In the western interior 

 section, however, practically all the described 

 fossil plants are from the lower (Fort Union) 

 and the middle (Green River) Eocene, but in 

 the embayment area there are considerable 

 floras at numerous other Tertiary horizons. 

 As the French nomenclature is used in the 

 the successive stages of the Franco-Belgian comparative discussions throughout the pres- 

 basin should be adopted as the time scale, ent work, it is desirable to indicate at this 

 These stages shoidd be universally adopted for point the sense in which its units are employed. 

 Tertiary discussions not only because of the The stages employed for the basal and lower 

 desirabihtv of writing in terms of general un- Eocene are the following: 



have taken the time to spread from Central or 

 South America along continuous coasts. 



Many examples of the means of dispersal of 

 the modern relatives of the Wilco.x species are 

 given in the systematic part of this paper. 



CORRELATION. 



NOMENCLATURE. 



In the consideration of the correlations indi- 

 cated by the Wilco.x flora it is desirable that 



Lower Eocene. 





Ypresian (Dumont, 18-19) 



Basal Eocene. 



/Marine facies=Cuisian. 

 "I Lagoon facies= Laonnian . 

 [.Sparnacian (Dollfus, 1880)=Upper Landenian (Mayer Eymar, 1857). 



/Thanetian ( Rene\'ier, lS73) = Heersian (Dumont, 1849), Lower Landenian (Mayer Eymar, 1857). 

 iMontian (Dewalque, 1869)=Paleocene of Von Koenen and others (not of Schimper, 1874). 



Together these stages correspond to the The Wilcox flora, from the intrmsic evidence 



Eonummuhtic of Haug (1911), to the Suesso- which it furnishes, as well as from the evidence 



nian of D'Orbigny, and to the Paleocene of of stratigraphy in the eastern Gulf area, where 



Schimper (1874), but not to the Paleocene of a nearly complete section is available for study, 



Von Koenen, DoUo, and others, which is limited may be divided into a lower, middle, and upper 



to the Montian stage. 



CORRELATION OF LOCAL SECTIONS WITHIN 

 THE WILCOX GROUP. 



Before taking up the question of the relative 

 age of the Wilco.x as compared with the early 

 Eocene of other areas, it is desirable to indi- 

 cate the relation of the different fossiliferous 

 Wilcox sections to each other. Tliis has been 

 done to a certain e.xtcnt in the discussion of 

 local sections on pages 38-60, so that a sum- 

 mary in this place will suffice. The fossil 

 plants are much more valuable for precise cor- 

 relations than the invertebrate faunas not 

 only because they are so much more abun- 

 dant over so large a portion of the Wilcox out- 

 crop but also because the life periods of the 

 plants appear to have been shorter and there- 

 fore can l)e applied to more mmute stratigraphic 

 diffcrrentiation thaii the faunas. 



Wilco.x, corresponding with the lithologic divi- 

 sions proposed by Lowe for Mississippi, namely, 

 the Ackerman formation (lower Wilco.x), the 

 HoUy Springs sand (midcUe Wilcox), and the 

 Grenada formation (upper Wilcox). 



The flora of the Ackerman formation is the 

 most incomplete because of its discovery at 

 fewer outcrops. It includes these forms: 



Ly<;odiuni binervatum. 

 Asplenium eolignitica. 

 Asplenium hurleyensLs. 

 Chamsedorea danai. 

 Myrira elfeanoides. 

 Dryophyllum nioorii. 

 Mens piiryoaronsis. 

 Ficus .schimperi. 

 Ficus monodon. 

 Ficus oceiilentalis. 

 Pisonia chlorophylloides. 

 Magnolia leei. 

 Aeimina leiocarpa. 

 Cinnamomum mi.s.sissippicn.sis. 



