SECOND ANNUAL REPORT—STRATIGRAPHIC GEOLOGY. 
135 
this formation is represented by low ridges which rise above the gen¬ 
eral level. 
Paleontologic Character:—The Alachua clay contains a few 
obscure remains of what appear to be fresh water shells, but the state 
of preservation does not admit of their identification. Locally, verte¬ 
brate remains are abundant, and it was this fauna which first called 
attention to the formation. On a subsequent page a list of the verte¬ 
brate fossils is given. 
Structure:—The Alachua clay appears to have undergone no dis¬ 
turbance since its deposition, and hence it presents no structural feat¬ 
ures of interest. . Its accumulation in local depressions prevents its 
having any general attitude, and the dips observed, while slight, are 
variable. 
Local Details:—Sections of the Alachua clay are to be seen in the 
vicinity of Gainesville and Archer, Alachua County. Near the wagon 
road, one mile northwest of Gainesville, there is an exposure in an 
old mill race. At this locality the outcrop probably does not exceed 
four feet, but farther up the hill to the east similar material is ex¬ 
posed in a ditch where it has a thickness of about fifteen feet, and is 
overlain unconformably by about four feet of white Pleistocene sand. 
The basal portion of this section, which evidently represents one of 
the localities mentioned by Dali 1 is a greenish gray clay containing a 
large admixture of coarse sand. It changes to a very light yellow 
when exposed to the weather; and, in this respect, agrees with the 
material on the hillside above. The complete section at this locality is: 
Light gray sand, Pleistocene ...... 4 feet. 
Erosion unconformity. 
Blue sandy clay, weathering light yellow.... 15 feet. 
Covered ... 15 feet. 
Blue sandy clay .......... 4 feet. 
Total .. 38 feet. 
About two and a half miles west of Gainesville, there is another 
exposure of Alachua clay, consisting of a light-yellow clayey sand 
which is very plastic when wet, but hardens into a moderately firm 
rock on drying. The thickness” of the exposure is not less than fifteen 
feet, and it is covered by a deposit of sandy loam of Pleistocene age, 
which rests unconformably upon the clays at this locality. Thin part¬ 
ings of sand are common; the upper four feet of the section contains 
many small calcareous nodules; and near the middle some casts of 
what appeared to be fresh water bivalves were noted. 
1 Dali, Wm. H., Neocene of North America, U. S. Geol. Survey, Bull. 84, 
1892, p. 128. 
