296 T. O. MABRY 



to have been confined to the vicinity of the river courses at that 

 time. 



I may call attention, however, to the fact that in section c of 

 the bluff at Memphis, as previously described, a humus stained 

 horizon, indicating an old soil, was found at the upper surface of 

 number 2, but this seemed to me to be the upper surface of 

 the Lafayette, and not a part of the Loess-Loam at that place. 



Because of the evident twofold division of the Loess in the 

 north we should naturally expect the same for the Loess in the 

 south, and perhaps for its interfluvial equivalent, the yellow or 

 brownish surface loams. But this does not necessarily follow, 

 for reasons stated above, and the results of my observations, 

 considered without regard to exposures which I have never seen 

 in other localities, will not justify me in an attempt to subdivide 

 the Loess-Loam formation of this region. The formation is, there- 

 fore, considered in its entirety and the question of its delimita- 

 tion discussed more fully in the following paragraphs . 



A. Lower limit of the Loess-Loam. — This subject has already 

 been discussed more or less fully in the description of the 

 stratigraphic relations of the Brown Loam. The first Glacial 

 epoch is divided by Chamberlin and Salisbury [Am. Jour. Sci., 

 Vol. XLI, pp. 362—363) into two episodes, and the inferior 

 member of the Loess is referred to the close of the second Glacial 

 episode of the first Glacial epoch. From the foregoing evidence 

 it will be seen that the Brown Loam cannot be earlier, and that 

 it is the interfluvial equivalent of at least one, perhaps of both, 

 divisions of the Loess. And neither seems to be the full repre- 

 sentative, in the South, of the northern Drift. The Natchez 

 formation was probably deposited during the first Glacial episode 

 of the first Glacial epoch, and towards its close, and I have 

 given reasons above for believing that the same episode is 

 represented in north Mississippi by scattered patches of sub- 

 aerial deposits. These deposits, as already noted, are composed 

 of local material, and while they may be contemporaneous with 

 the earlier Drift, they are not genetically related to it, as the 

 Natchez formation along the river is said to be. 



