428 A. F. FOEHSTE — LIMESTONES OF TENNESSEE AND KENTUCKY 



The phosphate rock varies considerably in thickness, even in localities 

 in the same neighborhood. In a general way it increases toward the 

 southwest, and was, until very recently, quarried at many points in 

 Hickman and Perry counties. It appears to take the ])lace, at some 

 points, not only of the earthy brown beds at the base of the fissile black 

 shales, but even of the fissile shales themselves. This, according to 

 Professor Safford, is especially true of some of the exposures in Hardin 

 and Wayne counties. It should be remembered, however, that the 

 fissile black shales diminish considerably in thickness in southern Ten- 

 nessee, irrespective of any change in thickness in the phosphate rock. 



North of Mount Pleasant the nodules at the top of the Black Shale sec- 

 tion are found 12 inches above the coarse sandstone which forms the base. 

 This leaves only a thickness of one foot for the fissile black shales. Half 

 a mile northeast of Lynnville the fissile black shales do not exceed 1 

 foot in thickness. At Dodsons station, north of Ljmnville, the fissile 

 shales are 12 to 15 inches thick, and at one locality west of the station 

 are underlaid by a little sandy phosphatic rock. 



Erosion of Black shale during early deposition of the Waverly. — South of 

 Rockdale the upper part of the fissile black shale loses its fissile char- 

 acter. For instance, half a mile above the Oliver Williams house, in 

 the Cook hollow, the base of the Black shale consists of coarsely sandy 

 rock overlaid by 28 inches of phosphate rock, 2 feet of fissile black 

 shale, and 3 to 4 feet of much less fissile shale, black below, becoming 

 greenish toward the top. Half a mile up the old Saw Mill hollow, also 

 called the Rattlesnake hollow, the conglomeritic sandstone, 6 inches 

 thick at the base of the section, is overlaid by 16 inches of dark phos- 

 phate rock; the fissile shales are absent; immediately above the phos- 

 phate rock occur 3 feet of a very fine-grained rock, not fissile, containing 

 traces of Chonetes and of other fossils. In the gully southeast of the 

 Oliver Williams house the base of the section consists of a dark, sandy, 

 partly conglomeratic rock 18 inches thick. Both the Black shale and 

 phosphate rock are absent. Immediately above the conglomeratic rock 

 occur 11 inches of light green clayey rock containing purple brown 

 phosphatic material, both in the form of small, irregular particles and 

 of nodules. Above this are found 8 inches of crinoidal, greenish rock, 

 with fish teeth. At the " Big hill," immediately westward, on the road 

 to Waynesboro, the entire Black Shale section is absent. 



The purple brown phosphatic material found immediately above the 

 conglomeratic, sandy rock at the Oliver Williams locality resembles 

 the material forming the phosphatic nodules at the top of the Black 

 Shale section in most parts of Tennessee and Kentucky. The fish teeth 

 appear to belong to the same horizon as the bed from which the phos- 



