ZRSITY 



or 



>A' troRii^^ 

 MURPHREE'S VALLEY; GEOLOGICAL Fok'SrAT16"Ss. 23 



integrated has formed immense beds of sand, and (on the 

 north-west side of the Main valley,) covered the little 

 valley at its base with sandy soil. No fossils were found in 

 this rock. It seems to have been so rapidly formed as to 

 preclude marine life ; and yet the types of life, so abundant 

 in the rocks beneath it, again present themselves in the lime- 

 stone above it, as though there had been no break in their 

 existence. This is the more remarkable, because this plate 

 of rock is of great extent, being apparent in all the valleys 

 of North and North-East Alabama. 



c. Fort Payne Chert (Siliceous group). Beneath the Ox- 

 moor or Lagrange sandstone, in Murphree's Valley, is a thick 

 bed of cherty rocks of Sub-Carboniferous age, to which we 

 have given the above name.* 



These are, by estimate, usually about 200 i'eet thick, and 

 terminate at the Black Shale. 



These siliceous rocks of the Subcarboniferous are well ex- 

 posed on the north-west side, and generally can be easily 

 traced on the south-east side. They are usually so full of 

 fossil forms and fragments as to be readily identified wherever 

 seen. At two places on the south-east side of the valley 

 were found large deposits of limestone lying at the base of 

 this formation. This limestone is not common in Alabama, 

 except in the Tennessee Valley, though it has been seen at 



*rhis group, which as a whole, seems to correspond with the St. Louis, 

 Keokuk and Burlington beds of the Western geologists, is made up in Ala- 

 bama of limestones of varying degrees of purity. When the limestone is 

 highly siliceous, as is usually the case in this state, the calcareous matter 

 has been thoroughly washed out, in exposed outcrops, and the siliceous 

 matter remains mostly in fragments full of cavities, caused by the dissolving 

 out of the stems of encrinites and of other fossils. In the valley of the Ten- 

 nessee it is usually not diffiult to distinguish between the 'St. Louis division 

 and those underlying it ; but in the anticlinal valleys further south, where 

 this part of the Subcarboniferous formation is represented, as a rule, by 

 loose cherty fragments, the distinction is not so clear, and we have, there- 

 fore, been accustomed to use one term to designate the whole siliceous series 

 below the Oxmoor sandstone, and we call it Fort Pavne Chert. 



E. A. S. 



