E. A . Smith — Pod-Eocene Formations of Alabama. 293 



the whole coastal plain were submerged, and the waters of the 

 Mississippi Gulf lapped up on the Paleozoic terrane, the peb- 

 bles, sands, etc., washed down into this Gulf would come to 

 rest along this old coast line. 2. The other main pebble 

 streams appear to follow the principal lines of drainage, not 

 being confined, however, to the present narrow channels of 

 the rivers, but occurring beyond the third terraces, on the 

 slopes leading down toward these channels, often at a distance 

 of 25 or 30 miles on each side, and sometimes over the divides. 

 As if, upon the comparatively rapid emergence of the coastal 

 plain from below sea level, the continuing currents from the 

 land either carried new contributions of pebbles and other 

 materials, or took up and redistributed those previously de- 

 posited along the coast line mentioned, down the wide shallow 

 drainage valleys, and over the low divides. The third terraces 

 may perhaps mark a pause in this upward movement occurring 

 towards the close. 



The two authors who have given this formation most study 

 are Dr. Eugene W. Hilgard and Mr. W. J. McGee. The 

 former refers the origin of his " Orange Sand " of the great 

 Mississippi embayment, to a period of continental elevation, 

 and the deposition of its materials essentially to fresh water in 

 the form of broad shallow floods coming in from the north- 

 ward and practically devoid of organic life of which the re- 

 mains would be likely to be preserved.* On the other hand 

 Mr. McGee accounts for the structure and disposition of the 

 Lafayette materials upon the assumption of a submergence of 

 the coastal plain below the waters of the Gulf and the invasion 

 of the sea to the landward limit of this plain, accompanied by 

 a warping of the land and a seaward tilting which stimulated 

 the streams to greater activity both of erosion and transporta- 

 tion. The total absence from the formation of any traces of 

 marine life finds its explanation by Mr. McGee in the compara- 

 tive rapidity of the submergence and subsequent emergence of 

 the coastal plain. Both authors assume continental elevation, or 

 at least increased seaward slope of the areas beyond the 

 coastal plain, while they differ in their ideas as to the position 

 of the coastal plain during the time of accumulation of the 

 deposits, the one requiring shallow submergence below sea 

 level, the other assuming the flooding of this plain (above sea 

 level) by fresh waters from the land. The wide distribution 

 of these deposits over the whole coastal plain of the United 

 States from the Potomac to the Rio Grande, with essentially 

 the same characters of material and structure, favors the one 

 view ; while the peculiar structure of the deposits, the total 

 absence of all sign of marine life, and of beach or coast mark- 



* This Journal, vol. xliii, p. 394. 



