THE SOILS OF FLORIDA. 
Pleistocene age. Mr. George O. Matson, at the time of the publica¬ 
tion of his paper on the stratigraphy of Florida, regarded these gray 
sands throughout the State as representing a distinct formation of 
Pleistocene age.* The yellow sands he rightly surmised were 
residual in origin. In a subsequent page I shall endeavor to show 
that the difference in color between the gray and the yellow sand is 
due in most cases purely to the different drainage and other condi¬ 
tions under which they have accumulated. The loamy character of 
the yellow sands is due to the presence of a larger percentage of 
clay than is found in the gray sands. 
One of the arguments advanced for regarding the gray sand as 
a formation distinct from the underlying clayey sands is the seem¬ 
ing unconformity which separates them. This distinct and clearly 
marked line is observed in practically all exposures. Ordinarily it 
approximately follows the contour of the hill or approaches the sur¬ 
face at the sides of the hill. Usually it is a fairly even line of 
division between the loose top sands and the more or less cemented 
clayey sands. Very frequently, however, the line is wavy or shows 
relatively abrupt trenches or small gullies. Unquestionably all 
these features closely simulate a true unconformity. But the fact 
must not be overlooked that in the processes of decay of superficial 
deposits, the line showing varying depth of decay is not infrequently 
an abrupt line and may show many of the irregularities of an un¬ 
conformity. The true explanation of the well defined line marking 
the boundary between the loose sand and the clayey sand is as fol¬ 
lows: The rainfall in passing through the top sands carries the 
finely divided clay which it holds to a lower level. This process 
results in an increased amount or concentration of clay in the lower 
strata. The percolating waters upon reaching this stratum are 
checked and move laterally to a point of exit. In its lateral move¬ 
ment water naturally tends to fall into water courses as it would 
do if flowing on the surface. In the process of time the water 
courses thus followed are widened and lowered, forming the irregu¬ 
larities observed in the exposure. The character of the clayey sands 
in question is such as to make the development of such lines of pseu¬ 
do-unconformity particularly well marked. 
Another argument advanced is the considerable depth to which 
the sands sometimes extend. The depth, however, is determined by 
the conditions of drainage, and by the soil water table which itself 
is determined by the drainage conditions. The deepest sand is found 
where the drainage is good, either by lateral seepage or by sub- 
*Fla. Geol. Survey, Second Annual Report, pp. 152-153, 1909. 
