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



the lower courses of the rivers. In all cases they are only a few 

 feet above the level of the first bottom, or present alluvial 

 plain. The surface material of universal occurrence along 

 these flats is a fine yellow loam several feet in thickness, which 

 is everywhere an excellent " brick clay," and everywhere forms 

 the basis of soils of more than ordinary fertility. For this 

 reason we find most of the great plantations of former days 

 located upon this terrace. The yellow surface loam is under- 

 laid by ten feet or more of grayish sands, into which it gradually 

 shades: near the base of the sands it is common to find peb- 

 bles. It is not very often that a fresh clean section can be 

 observed down to the level of low water, because of talus, 

 and deposits of recent river muds, but when such sections are 

 exposed, they show below the gray sands a varying thickness 

 of dark gray or blue clay filled with fragments of vegetable 

 remains in the shape of drift wood, roots and stumps, in a 

 state of preservation ranging from what can hardly be dis- 

 tinguished from fresh drift wood, to highly bituminized mate- 

 rial. It is probable that this blue clay underlies all the second 

 bottoms of our larger streams, though it is generally hidden by 

 recent deposits. The subjoined sections from localities em- 

 bracing the entire coastal plain, appear to justify this conclu- 

 sion : 



(a) At the site of old Fort Jackson, a few miles below 

 Wetumpka, the Coosa and Tallapoosa Eivers approach within 

 a quarter of a mile of each other, and a " cut-off " has been 

 formed connecting the two channels. Here is shown a perfect 

 section of the entire second bottom formation. Near the low 

 water mark is the blue clay stratum filled with stumps, twigs, 

 and roots, all in a remarkable state of preservation. The blue 

 clay is covered by at least 25 feet of gray sands capped with 

 the usual surface loam of the Second Bottom plain. If we 

 should be disposed to consider the blue clay stratum as a recent 

 river swamp deposit, and only in a2>pearance below the sands 

 and loam by reason of re surfacing or overplacement, this sec- 

 tion extending entirely across the Second Bottom terrane 

 which makes the plain between the two rivers, would leave no 

 room for doubt as to the relative position of the constituent 

 members above named. 



(b) At Mcintosh Bluff, on the Alabama Kiver, about fifty 

 miles north of Mobile, a similar dark gray or bluish clay filled 

 with vegetable remains, may be seen below the yellow loam 

 and sands ; and wells sunk in any part of the second bottom 

 plain there, pass through this blue clay stratum before reach- 

 ing water in the sands which underlie it, usually less than 

 thirty feet from the surface. From this it would seem that in 

 some places at least, the blue clay forms a layer between sands. 



