SECOND ANNUAL REPORT—STRATIGRAPHIC GEOLOGY. 
157 
central part of the peninsula it is known to have a thickness of 20 to 
30 feet at several localities. 
Physiographic Expression of the Pleistocene:—In the coastal belt 
the Quaternary is characterized by low relief, being a region of low 
sandy plains crossed by shallow valleys and often covered by broad 
marshes and ponds which are seldom more than 2 or 3 feet in depth. 
The Quaternary of the interior is usually characterized by the same 
topography as the underlying rocks. It commonly forms a thin coat¬ 
ing on the hilltops and a broad terrace deposit in the valleys. Locally 
erosion has removed the Quaternary from the hilltops or slopes, 
thereby exposing the underlying beds. In some localities, especially 
along the east coast, wind action has built the sand into dunes and 
ridges which locally rise to a height of 30 to 50 feet and form con¬ 
spicuous topographic features. 
Paleontologic Characters of the Pleistocene:—The Pleistocene 
fauna bears a close resemblance to that now living along the coast. 
This fact is illustrated by the collection from North Creek which, 
according to Dali , 1 comprised seventy-one species, of which five are 
believed to be extinct. •» 
Structure of the PleistoceneThe beds of Pleistocene age show 
no indications of having been subjected to marked deforrpation; and 
their general attitude has probably not been materially changed since 
their deposition. They appear to have a gentle dip toward the sea 
and they were apparently raised to their present altitude by a broad 
movement which was not of such a character as to produce notable 
flexures in the beds. 
RECENT. 
The Recent formations of Florida include the alluvial and 
lacustrine deposits, the recent beach sand and sand rock, coquina 
rock, and the aeolian sand. The alluvial deposits occur along all the 
large streams where they form belts from a few yards to a mile or 
more in width. The alluvium is divisible into the Recent flood plain 
and terrace deposits of Pleistocene age. During high water, the flood 
plain is partially overflowed; and, in some localities, the inundated 
tracts take the form of nearly impenetrable cypress swamps which are 
flooded during a large part of the year. 
Alluvial Deposits:—The Recent silts and sands seldom rise more 
than a few feet above the high water levels of the streams, and the 
transition to the terraces above is often poorly defined. The ter¬ 
races are thought to belong to the Pleistocene and to be associated 
with a submergence and subsequent emergence during that epoch. 
1 Dali, Wm, H., Wag. Free Inst. Sci., Trans., vol. iii, pt. 6, 1903, p. 1616. 
