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



varying from a few feet near the inland margin of the coastal 

 plain to more than 100 in the counties bordering the Gulf. 



Thousands of observations in tins and other States, show- 

 that the beds of Lafayette materials occur at elevations differ- 

 ing by two or three hundred feet in localities closely contigu- 

 ous, precisely as if the deposits had been laid down mantle- 

 wise upon a previously eroded surface, the main topographic 

 features of which were at the time of deposition essentially 

 what they now are. It seems almost necessary to consider the 

 third terraces, either as marking the very latest episode in the 

 deposition of the Lafayette, or as a result of its rearrangement 

 and redistribution in times very much more recent than that 

 of the first deposition on the heights, nor do I see how its 

 present position on such different elevations, along slopes, and 

 in general so closely conforming with the existing land relief 

 can be explained except as due in some measure to rearrange- 

 ment, and yet after many years of close examination of these 

 deposits, I have been unable to discover any material difference 

 between the Lafayette on the hill tops, the Lafayette on the 

 slopes, and in the valleys, and the Lafayette upon the river 

 terraces, whether in the material themselves, or in their rela- 

 tive positions, and for this reason all its phases are considered 

 under one head. 



In Mississippi at the typical locality, there are great accumu- 

 lations of cross-bedded sands of this formation, that have few 

 if any representatives in this State, where the great bulk of 

 the Lafayette consists of rounded water-worn pebbles of quartz, 

 chert, and quartzite, and rounded grains of iron-stained sand 

 mixed with some red clay, and with a few small rounded peb- 

 bles of limonite. In the Chattahoochee drainage scales of 

 mica are also abundant. Where all three of the principal con- 

 stituents above named, pebbles, sands, and loam, occur to- 

 gether, as a rule the upper part of the formation is a very 

 sandy red loam, while the pebbles are mostly to be found in 

 the lower part. Where the pebbles are absent the surface is 

 usually red loam, with the sands below, and in some places the 

 whole formation is sand. 



The pebbles sometimes contain markings or fossils which 

 show that they are fragments of the siliceous rocks of the Sub- 

 Carboniferous, Silurian and Cambrian and Crystalline forma- 

 tions, and in their distribution they are more localized than 

 the other main constituents. They are most abundant and of 

 larger size in two locations : 1, along the line of contact of 

 the formations of the coastal plain with the Paleozoic terranes, 

 i. e. along a belt 10 or 15 miles wide stretching from the 

 northwestern corner of the state around in a curve to Colum- 

 bus in Georgia. If, at the beginning of the Lafayette period, 



