36 



LOWER EOCEXK FLORAS OF SOUTITEASTERX XORTil AJIERICA. 



Tlu> strike of the beds of Wilcox a<j;e swings 

 ti) the northwest a short (Hstance within tiie 

 State of Kentucky and becomes west in 

 McCracken and Ballard counties. Tiie land- 

 ward niargin of the beds crosses the southern 

 end of Illinois, where, however, they are as a 

 rule either entirely removed by the erosioTi of 

 Oliio and Mississippi rivers or are (h'eply buried 

 by alluvial deposits. Deposits correlated with 

 the Wilcox are 82.") feet tliick in the well at 

 Cairo, 111. Litiiologically the deposits of Wil- 

 cox age in Kentucky are like those of Tennes- 

 see, but several beds of lignite oc(-ur toward the 

 top aud numerous local unconformities mark 

 oscillations in level. (Sec pp. 50-51 for discus- 

 sion of sections.) The clays contain well- 

 preserved plant remains at several localities, 

 notably the classic ones at Wickliffe and Boaz. 

 At Wickliflfe well records give a thiclaiess of 

 430 feet for the deposits of Wilcox age. 



Little is known regardmg the presence of 

 strata of Wilcox age in southeastern Missouri 

 because of erosion and subseciuent alluvial 

 cover. Deposits of that age are, however, 

 reported in wells. The strike of the beds of 

 that age is southwest across iVi-kansas and the 

 deposits underlie the surface of the whole State 

 south and east of the Cretaceous and Midway 

 outcrops. The surface of the State of Louisi- 

 ana is also underlain by these beds, except in 

 small areas where doming or fault blocks have 

 brought up Cretaceous or Midway deposits. 

 The Wilcox deposits in Arkansas and Louisiana 

 have an estimated thickiiess of 400 to 800 feet 

 and are predominantly dark carbonaceous 

 sands and brown laminated, commonly selenitic 

 cla3'-s. In places the beds are indurated and 

 contain transported balls of lignite and claj', 

 especially toward the Texas border, wliere cal- 

 careous concretions are also common. (See PI. 

 V, p. 39.) In many places also they contain leaf 

 remains, as in the vicinity of Slu-eveport. Leaf 

 remains in the clays are commonly fragmentary 

 and indeterminable. More or less sandy ferru- 

 ginous segregations contain identifial)le remains 

 of plants, as at Coushatta, Frierson Mill, Na- 

 borton, and Mansfield, La., and Little Cypress 

 Bayou across the Texas border. Brine in some 

 places occurs in the pervious sands of the Wil- 

 cox, and they are reported to contain small 

 quantities of oil. 



A few invertebrate fossils occur from Shreve- 

 port southwcstward to Sabine River, along 



which fossiliferous calcareous glauconitic marls 

 are i'(>ported frt)m several outcrops. Deposits 

 of Wilcox age extend aci'oss Texas from the 

 Saliine .southwcstward to the international 

 boundary and on across the Eio Grande an 

 indeterminable distance into Mexico. West- 

 ward fi'om Sabine Kiver, that is. landward from 

 the Eocene sea, the complex of sands, clays, 

 lignites, and marine fossiliferous calcareous 

 glauconitic marls of tlic Sai)ine section merge 

 in a short distance into pi-actically unfossilifer- 

 ous littoral deposits nnide up of intertunguing 

 lenses of sands, lignitic selenitic clays with 

 traces of leaves, and lignit(>s. Large concre- 

 tionary masses of hard sandstone are character- 

 istically developed in some areas. These lig- 

 nitic and littoral sands and days have an esti- 

 mated thickness of 500 to 600 feet. The upper- 

 most Wilcox in northeast Texas consists of 

 stratified white and red sands and sandy clays, 

 entirely unf ossilif erous and free from any consid- 

 erable cjuantity of lignite. These sands con- 

 stitute the Queen City beds of Kennedy.' 

 West of Colorado River no detailed studies have 

 been made, but deposits of Wilcox age are 

 extensively developed along the Rio Grande as 

 coarse sands overlain l\v fine micaceous sand- 

 stones, which are succeeded l)y alternating beds 

 of shales, sandstones, aud workable lignites. 

 The whole thickness is estunated to be at least 

 850 feet. 



These data complete a brief sketch of the 

 lithologic character, succession, and areal dis- 

 tribution of the deposits of Wilcox age, from 

 their easternmost occurrence in Georgia to the 

 place where they cross the Rio Grande into 

 Mexico, a distance of nearly 2,000 miles along 

 the strike. 



STRATIGRAPHIC RELATIONS. 



The stratigraphi<' relations of I lie Wilcox 

 group ai-e relatively simple. Tlu'ougliout its 

 known extent it overlies the (l("|iosits of the Mid- 

 way formation and is in tui'u overlain by those 

 of the Clail)orne gi-oup. Tlicse relations have 

 always been considered to t)e those of conform- 

 ity, l)ut there are many indications of a long 

 interval of erosion between the Midway and the 

 Wilcox, and a less conclusive amount of data 

 indicates a similar interval lietween the Wilcox 

 and the Claiborne. Considering first the un- 



1 Kennedy, William, .\ctid. Nat. Sci. riiiladelpliia I'roc, \(p. 135-136, 

 1,S95. 



