THE TERTIARY FORMATIONS. 



15'J. By far the greater portion of the State of Mississippi is 

 occupied by deposits of the tertiary age, if we leave out of con- 

 sideration the strata of the Orange Sand, which undeniably forms 

 the greater portion of the actual surface. 



The position of the Tertiary strata appears to be more or less in 

 conformity with that of the cretaceous beds. It certainly is so in 

 the southern portion of the State, where their dip is distinctly 

 southward. Whether or not the same is true in reference to the 

 strata occupying the northern portion of the State. I have thus far 

 been unable to determine, in consequence both of the rare accessi- 

 bility of the strata, and of their character. If, however, any 

 westerly dip exists in the tertiary strata of N, Mississippi (as is 

 the case in the cretaceous strata) it is certainly much less than that 

 of the latter. 



The tertiary of Mississippi exhibits, essentially, three different 

 facies, viz : That of lignitiferous clays and sands, varying in color 

 from black to brown, blue, green, yellow, gray and almost white, 

 with remains of vegetables ; that of siliceous sandstones and 

 claystones with marine fossils ; and that of limestones and 

 calcareous marls, with marine fossils. 



160. The several marine stages are in most cases separated by 

 intervening strata of dark colored, often lignitic clays, as above 

 mentioned ; moreover, both the base and the top of the older 

 tertiary are formed by strata of this character, of considerable 

 thickness. Small estuary deposits of marine fossils arc occasionally 

 found in the Lignitic strata ; and vice versa, small masses of 

 lignitic deposits sometimes occur in the calcareous tertiary, as they 

 do in the upper cretaceous formation. Chemically, the Lignitic 

 strata arc characterized (with very rare exceptions) by the absence 

 of the carbonate of lime, and the presence, per contra, of sulphate 

 of lime or gypsum in its various forms, usually accompanied by 

 sulphate of magnesia or Epsom salt, and common salt ; while these 

 ingredients are almost entirely absent from the marine Tertiary.-' 



161. The following general section of the Tertiary of Mississippi will serve 

 to show its prominent traits, as far as ascertained up to the present time. The 

 approximate thickness given may be taken as minima, which are often greatly 

 exceeded. 



*I shall not include, for the present, in the general remarks on the tertiary of 

 Mississippi, the imperfectly known strata of the Sea-Coast, which may be 

 Pliocene or Post-pliocene, and will be treated of at the conclusion of the 

 description of the more ancient Tertiary. 



