OIL IN THE REELFOOT AREA. 27 



The formation consists largely of loose sand, but it is inter- 

 bedded with lenses of clay. It was put down in shallow water 

 that contained rather strong shifting currents, that here 

 and there along the course of their greatest strength, scoured 

 out the bottom. The troughs thus formed were soon filled up 

 by other sand and clay, the result being irregular deposition 

 a prominent character of the formation. 



While lenses of clay enter rather largely into the composi- 

 tion of this formation, its character as a whole, where it is ex- 

 posed, would not interfere with the free circulation of water 

 or of oil, should it contain that product. It contains more or 

 less brown-coal or lignitic material, and petrified wood. The 

 thickness of the Eutaw formation in Tennessee is thought by 

 Dr. L. C. Glenn to be from 250 to 275 feet.* 



This formation shows at the surface in Tennessee only in 

 parts of Benton, Decatur, Henderson, Hardin and McNairy 

 counties. That it is continuous entirely across the Embayment 

 area is indicated by its probable occurrence in southeastern 

 Arkansas where it is known at the Bingen sand.f Its north- 

 ward extent is more doubtful, as it is overlapped in that direc- 

 tion by younger deposits. It may reach nearly to the northern 

 border of the Embayment area, and again it may fall far short 

 of that. 



The next formation above the Eutaw sand is the Selma clay. 

 In Alabama and Mississippi this formation is known as the 

 Selma chalk, but before reaching Tennessee it loses its chalky 

 nature, and becomes a clay that in places contains large num- 

 bers of fossil shells. The clay is leaden gray, green, or blue, 

 depending partly upon whether it is wet or dry or unaffected 

 by the weather, and partly upon its somewhat different com- 

 position in different parts. Its thickness in Tennessee, as given 

 by Dr. Glenn, is from 100 to 275 feet.J 



This formation can be seen at the surface in Tennessee only 

 in a belt from 6 to 8 miles wide, just west of the one where the 

 Eutaw is exposed. Like that formation, it is covered to the 



*U. S. Geological Surv. Water Supply and Irrigation Paper, No. 164, p. 25. 

 tUnpublished tentative correlation table by L. W. Stephenson, U. S. Geol. 

 Surv. 

 %Loc. cit., p. 26. 



