COOKE: JACKSON AND VICKSBURG DEPOSITS 193 



direction, but lignitic clays that are tentatively referred to the 

 Forest Hill have been observed at a number of places in Smith 

 County. 



RED BLUFF CLAY 



Fossiliferous deposits on Chickasawhay River at Red Bluff, 

 1^ miles below Shubuta, were first noted by Harper ^^ in 1857. 

 Three years later they were called the Red Bluff group by Hil- 

 gard, who correctly announced that their stratigraphic position 

 lies between the Jackson and typical Vicksburg strata and that 

 their fossils are more closely related to those of the Vicksburg 

 than to those of the Jackson. ^^ 



Wherever the contact of the Red Bluff clay with the under- 

 lying Jackson has been observed, the two appear to be conforma- 

 ble. The upper limits of the formation are less well known, 

 but there seems to be no break between it and the Marianna 

 limestone. As the formation has not been traced west of Wayne 

 County, its relations to the Forest Hill sand are conjectural, but 

 it is believed that the two were approximately contemporaneous 

 in origin and that the Red Bluff clay represents the marine 

 equivalent of the exceedingly shallow water deposits of the 

 Forest Hill sand in the Mississippi Embayment. The formation 

 extends eastward into Alabama but rapidly thins, becomes cal- 

 careous, and merges laterally into the Marianna limestone. 



The Red Bluff consists chiefly of stiff blue or greenish gypseous 

 clay, but contains also discontinuous ledges of indurated marl or 

 sandstone and a thin bed of shell marl. On Buccatunna Creek 

 Jhe formation is 70 feet thick. 



The Red Bluff fauna includes more than 128 mollusks, 6 

 corals, and a considerable number of Bryozoa. Of the 134 

 species listed from Mississippi, about 60 appear to be restricted 

 to the Red Bluff beds; about 55 are present in the Mint Spring 

 marl or have varieties there; and about 49 species or varieties 

 are known in the Byram marl, of these species 10 have not yet 



^^ Harper, L., Preliminary Report on the Geology and Agriculture of the 

 State of Mississippi, p. 142. 1857. 



" HiLGARD, E. W., Report on the Geology and Agriculture of the State of 

 Mississippi, p. 136. 1860. 



