202 
FLORIDA state; geological survey. 
place. Still the present growth of the swamps favors a recent depres¬ 
sion. 
The testimony of the shore lines is contradictory. Possibly the best 
evidence is that of the series of low beach ridges extending from East 
Cape to North Cape on Cape Sable. This strip of foreland having a 
steep beach of coarse shell sand facing the Gulf and falling off inland 
to a mangrove swamp flooded at spring tides, seems to show that there 
has been a slight sinking of the coast since waves started to heap up 
the sand. 
The human records to which appeal can be made are the numerous 
indian mounds, or kitchen middens, composed chiefly of oyster shells, 
found at many places along the coast. Some of the mounds are of 
great size, notably the accumulation of shells on Chokoluskee Island 
which covers over fifty acres to an average depth of seven feet. Since 
the mounds stand in swamps the relation of the bottom layers of shells 
to present sea level and to the deposition of marl and vegetable matter 
in the surrounding swamps should be an index of any coastal rise or 
fall. An examination of mounds at Jupiter Inlet, in and near Choko¬ 
luskee Bay and at Marco, however, gave less data than was anticipated. 
In places creek channels have cut into the mounds, in places wells have 
been sunk through them, consequently sections showing relations of 
the lowest layers of shells to sea level and to the underlying materials 
are not hard to find. Around the edge of the mounds there has been 
some burying of shells by wash, but the bottom layers rest on swamps 
and if the first Indian dwellings stood on posts in ground flooded at 
high tide, there is no sign of a measureable sinking of the coast since 
the time when the building of the mounds began. 
Thus the evidence at hand shows that the coast of this part of Flor¬ 
ida is not now rising, but is stationary or sinking. - If it is sinking, then 
the rate of depression is so slow that it can not be determined from 
human records which must long antedate the discovery of America. 
GEOLOGY. 
GENERAL STATEMENT. 
The general geologic structure of the Florida peninsula, the char¬ 
acter of the materials which underlie the surface, their areal distribu¬ 
tion, relative position and age have already been discussed , 1 and will 
not be reviewed here, but as the topography of southern Florida, as a 
whole, is different from that of the central and northern parts of the 
State, so the geology has features which differentiate the region from 
the greater portion of the peninsula. 
Pp. 46 to 164 of this report. 
