192 COOKE : JACKSON AND VICKSBURG DEPOSITS 



FOREST HILL SAND 



The name Forest Hill sand (from Forest Hill, 5| miles south- 

 west of Jackson, Mississippi) replaces the ''Madison sands" of 

 Lowe,^^ which name is preoccupied. The Forest Hill sand appears 

 to rest conformably upon the Yazoo clay member of the Jackson 

 formation. Although the character of the sediments indicates 

 a change from marine to very shallow water or palustrine con- 

 ditions at the close of Jackson time, it is probable that the 

 change was gradual and that deposition was nearly continuous. 

 The Forest Hill is overlain conformably by the Mint Spring 

 marl member of the Marianna limestone. The relations of the 

 Forest Hill to the Red Bluff clay are not definitely known, but 

 it is believed that the two were formed contemporaneously, the 

 latter having been deposited under more strictly marine con- 

 ditions than the Forest Hill sand. 



In the type area, the Forest Hill sand consists chiefly of cross- 

 bedded or laminated, more or less ferruginous, silicious sand 

 and some clay.^" West of this area, the formation becomes 

 more argillaceous and contains lenses of lignite and lignitic clay. 



In Warren and southern Yazoo counties, the Forest Hill sand 

 is estimated to be about 60 or 70 feet thick, and at Forest Hill it 

 is between 50 and 60 feet thick. 



Petrified wood, leaves, and other plant remains are common 

 in the Forest Hill sand, but recognizable forms are not abun- 

 dant. No animal remains have been found in the formation. 



The Forest Hill sand crops out along the bluff from Vicks- 

 burg northward to within a few miles of Satartia. Exposures 

 are numerous in eastern Hinds County and in Rankin County 

 as far east as Rankin. Outliers of the Vicksburg group in 

 Madison County afford good exposures of the Forest Hill sand. 

 Southeast of Rankin the country has not been explored in suffi- 

 cient detail to determine the extent of the formation in that 



15 Lowe, E. N., Op. cit., 82. 



1^ A section at Forest Hill School has been published by O. B. Hopkins (U. S. 

 Geol. Survey Bull. 641-D: 100. 1916). I consider the lower 7 beds of his 

 section as typical Forest Hill sand and refer the upper 6 beds to the Marianna 

 limestone. 



