28 RESOURCES OF TENNESSEE. 



west and north by younger formations, and like the Eutaw it 

 probably covers the Embayment westward to southwestern- 

 Arkansas, where it is known as the Annona chalk.f It prob- 

 ably extends northward well toward the head of the Embay- 

 ment. 



Unless this formation becomes more sandy in the middle of 

 the Embayment than in the area where it outcrops in Tennes- 

 see, it could not be expected to contain oil or gas ; but it would 

 form a good cover to seal in such of these products as might 

 occur in the Eutaw sand beneath. 



The formation above the Selma clay is the RipleyJ This 

 is described by Dr. Glenn as bearing a close resemblance to 

 the Eutaw sand, inasmuch as it is composed of sand containing 

 beds of clay. The clay beds are reported by him as being 10 

 to 20 feet or more thick. Many of them contain lignite in small 

 pieces or thin beds, and leaf remains are common. 



This formation extends across Tennessee, entering the state 

 from Mississippi on the south, and passing into Kentucky on 

 the north. Dr. Glenn thinks it is probably 500 feet thick in 

 the southern part of Tennessee and says it is reported to be 

 400 feet thick at Wickliffe, Ky. As it is composed largely of 

 loose sand, it should form a good reservoir for oil or gas, at 

 such points as the other conditions for those products obtain, 

 if they obtain anywhere. 



Tertiary formations. As above stated, the sea withdrew 

 from at least a large part of the Embayment area, after the 

 Ripley formation, the last of the Cretaceous ones in Tennessee, 

 was put down. The land thus formed remained such for a 

 long period of time, during which it was partly removed by 

 running water. After this land period, the sea again advanced, 

 and put down upon the old surface, a deposit known as the 

 Porters Creek formation. Dr. Glenn* says that "the forma- 

 tion is composed mainly of fine-grained clay that is very dark 



[Correlation by L. W. Stephenson, U. S. Geol. Surv. 



JThis recently has been redefined by Stephenson, U. S. Geological Survey, 

 Professional Paper 81. Stephenson puts the lower part of the Ripley, as 

 defined by Glenn (Water Supply and Irrigation Paper Xo. 164, p. 27), in the 

 Eutaw and the upper part he calls the McNairy sand; but for convenience, 

 Dr. Glenn's definition is here used. 



*Loc. cit. 



