E. A. Smith — Post- Eocene Formations of Alabama. 291 



directly, have the yellow loam similar to that of the Alabama 

 rivers. Perhaps the more rapid slope of these minor streams 

 may have prevented the deposition of anything so light and 

 fine grained as the yellow loam. 



Mr. Johnson believes that he has traced the Port Hudson 

 clays with their included roots and stumps, continuously along 

 the Mississippi shores eastward to the Alabama line, where 

 they form the basis of the Pine Meadows of Mississippi and 

 of similar flats along the waters of the Escatawpa in Alabama. 

 But between the waters of the Escatawpa and the Bay of 

 Mobile, intervenes a great deposit of Lafayette extending as a 

 high ridge down to within a few miles of the Gulf. The sub- 

 marine prolongation of this probably interposes a barrier to 

 the extension of the true Port Hudson beds quite up to the 

 entrance of Mobile Bay. We should be inclined to retain the 

 name Port Hudson for these Pleistocene formations in Ala- 

 bama, but for the manifest differences in the origin of the 

 materials in the two States, and for the break in their conti- 

 nuity along the Gulf coast ; but that the Alabama Second 

 Bottom deposits, from stump layer to yellow loam capping, 

 are the equivalents in time of the Port Hudson, Loess, Yellow 

 loam series of the Mississippi River, can, I think, hardly admit 

 of doubt ; nor is there much room for doubt that they are in 

 the main, equivalent to the Columbia formation of Mr. W. J. 

 McGee. 



Third Terraces and the Lafayette. — Our larger rivers have 

 a third terrace still more extensive and important than the 

 second. It is upon this terrace, often three or four miles wide, 

 that so many of our river towns are situated, e. g. Tuscaloosa, 

 Coffeeville, Jackson, Claiborne, Selma, Montgomery, Girard 

 (opposite Columbus, Ga.), and Columbia. The third terrace is 

 from 75 to 100 feet above the second, and exhibits in its struc- 

 ture two sets of materials ; a substratum of Cretaceous or Ter- 

 tiary, and a mantle of pebbles, sand, and loam of much later 

 date, which lies upon a deeply eroded surface of the older 

 formations and varies correspondingly in thickness. The 

 average on the terraces may be placed at about 15 feet, but 

 where old hollows have been filled up, the thickness may be 

 as much as sixty feet, as may be seen for instance, within the 

 limits of the city of Tuscaloosa. 



The capping mantle of the third terrace is in the quality 

 and arrangement of the material, so far as I have been able to 

 make it out, identical with the beds which under the name of 

 Orange Sand or Lafayette are spread more or less continuously 

 over the entire coastal plain of Alabama, Mississippi, and 

 Georgia and probably of other States beyond, in thickness 



