■\VILCOX GROUP. 



35 



coiiscquoiitly rcfcrrod to th(> Wilcox grou]), are 

 roprcsciitcd ill tlic Santoo drainage hasiii of 

 South Carolina t>y tlu' Wiiliainshur^ I'oniia- 

 tioM, Mliicli is tlu> easternmost known outcrop. 



The Acjuia formation of t!ie middle Atlantic 

 slope in Maryland and \'iri;inia is un'(uestion- 

 alilv in ])art contemporaneous witii the Wilcox 

 of tile Soutliern Stales. It represents, iiow- 

 ev<'r. either a (hfl'ereiif LCeoloLjic proxince or an 

 area of sedimentation separated hy a consiiler- 

 abl(> (>as1ward extetisioii of Koecne land in the 

 North Carolina iH'i,Mon. its fauna and lithol- 

 o<;y lieiiote typically marine (h'])()sition, and as 

 only two vague ft)rms ascrilied to Caroolilhus 

 represent the terrestrial llora. it lias little int(>r- 

 est in the present t'onneclion.' 



West of Tonil)igl)e(" Kiver in Alahama the 

 strike of the Wilcox formations swings around 

 to the northwest ami hecoiiies due north in Mis- 

 sissippi. The formational units of Alaliaina 

 lose their identity within a short distance from 

 the Mississippi line l)y a gradual transition into 

 sands and clays without marine faunas but 

 containing an abundant representation of the 

 terrestrial flora. The Wilcox deposits form a 

 belt in northern Mississi[)pi in places .5tJ miles 

 wide and underlie all tii(> State exc(>pt the 

 northeastern tier of counties. Lithologically 

 these beds are divisible info ihi'ee formations, 

 which Lowe ^ has named the Ackerman beds 

 (at the base), the Holly Springs sands (middle 

 formation), and the Cirenada beds (at the 

 top). 



The Ackerman formation,^ named from the 

 to^\^l of Ackerman in Choctaw County, is pre- 

 vailingly argillaceous and consists of about .300 

 feet of dark-gray lignitic and ferruginous sandy 

 clays, beds of lignite, consiilerable concr(>- 

 tionary and bedded carbonate of iron, and fer- 

 ruginous sandstones. A 6-foot \n'x\ of li<rnite 

 occurs in southeastern Lafayette and north- 

 western Callioini counties. 



The Holly Springs sand, named from the town 

 in Benton Comity, Miss., is prevailingly arena- 

 ceous and constitutes an important artesian 

 horizon. The formation consists of about 350 

 feet of cross-bedded, mostly coarse, micaceous 

 white to yellow, red, and purjjle sands, indu- 

 rated in places, which contain lenses of greater 

 or less extent of pink or white, rarely chocolate- 



' Maryland Geol. Survey, Eocene, I'MH. 



2 Lowe, E. N., Mississippi Gool. Survey liull. 10, p. Zi, 1913. 



2 See local section for Potts Camp on p. 42. 



coloretl, and generally siliceous clays. Most of 

 tlie Wilcox plants of the eastern Crulf area iiave 

 come from tliis foiMiiatioii and a numbei- of 

 local sections of plant-i)earing outcnips are 

 given in the chai>ter devoted to local sections. 



Tile Grenada formaliun, n.-imed from tlie 

 town and county in nortii-centi-al Mississippi, is 

 prevailingly ai'gill.iceous and consists of about 

 200 feet iif |)iiikish ol' yellow to cimcolate, 

 sandv micaceous laminated (days and i'ei-rugi- 

 nous sands, givatly resembling lithologically tiie 

 llatehetigbee formaliun (if .Mabama. It has 

 not l)een found to contain any i-emains of inxcr- 

 tebrates. This formation dues nut contain any 

 considerable amount of lignite, and deleiiuina- 

 ble fossil pliuits have been found only at tiie, 

 type locality. 



In passing northward into Tennessee the out- 

 cropping strata carrying a AVilcox llora strike 

 somewhat east of north, appearing as a broad 

 belt fi-om 30 to 60 miles in widtli. The lower 

 (Ackerman) formation of tiie Wilcox group of 

 Mississippi has not been recognized in Tennes- 

 see. Tiie strata of Wilcox age in Tennessee 

 form an indivisiiih^ unit- fliat corresponds in 

 great pai't, iiotli lithologically and paleobo- 

 tanically, to the middle formation (Holly 

 Springs sand) of the Wilcox group of Missis- 

 sippi. The beds consist of interbedded sands, 

 clays, and lignites, but the lignites are much 

 less developed than in tiie basal Wilcox of 

 Mississippi and Alabama. The bedding dif- 

 fers greatly from ])lace to place and numer- 

 ous local unconformities are emphasized i)y 

 redeposited pei)i)les and l)alls from contem- 

 poran(H)us clay lenses. Tiie sands are fine lo 

 coarse and range from white to orange or red. 

 The clays range from pure gray plastic clays to 

 sandy lignitic clays. Mfist of tluMn are higii in 

 silica and contain an ai)undant flora. (See 

 pp. 40-42 forsections.) Tlie thickness has not 

 been determined but is proi)ai)ly from .lOO to 

 600 feet. Li tiie deep well at Memphis, 2.5 

 miles W(!st of fiie western outcrop of strata of 

 Wilcox age, these beds were reported to be 

 between 7.50 and 800 feet in fiiickness. Tiie 

 heavy beds of lignite, so ])idminent in tiie upper 

 beds of Wilcox age near tiie iiead of tlie embay- 

 nient from Maylicdd, Ky., westward, are appar- 

 ently represented l)v tiie fiiick beds of lignite 

 in the upper part of i\w strata of Wilcox ago 

 reported from numerous wells in the western 

 parts of Haywood and Weakley counties, Ten n. 



