68 FLORIDA GEOLOGICAL SURVEY—15TH ANNUAL REPORT 
another. Likewise distinct changes in the character of the clay may occur 
from place to place in the same bed. 
There are several forms of sedimentary clay deposits based upon 
the conditions of sedimentation. The following with the exception of 
the last two, glacial and aeolian clays, are all found in Florida. 
Marine Clays —Fresh water in rivers, etc., may contain much clay 
substance, consisting of the very finest and lightest particles, which it 
carries in suspension. This acts as a solution of clay in water. When this 
fresh water becomes mixed with sea water the clay flocculates and is de¬ 
posited on the sea floor, or, as is frequently the case, in estuaries or 
lagoons along the coast. Extensive clay deposits are frequently thus 
found. 
Flood-Plain Clays —Streams carrying clay material in suspension 
or rolling it along on the stream floor often deposit much of it in the 
adjacent lowlands during periods of flood. Subsequent overflows de¬ 
posit additional layers. Extensive flood-plain deposits are often formed 
in this manner along the larger streams and in their deltas. Flood-plain 
clays are extremely variable in their nature and are often calcareous or 
sandy. 
Lacustrine Clays —Clay material carried by streams into lakes or 
ponds gradually settles to the bottom of the quiet water to form a de¬ 
posit of clay on the lake floor. Such clays may be of great purity or they 
may be mixed with a great amount of sand or other impurities. 
Glacial Clays —These are sometimes termed till or bowlder clay. 
These are deposits, which are of heterogeneous character and usually 
impure, formed by the grinding of rocks or rock fragments by glacial 
action and deposited by the ice as it melted or by the resulting water in 
the redeposition of the material. Deposits of this type are only found 
in glaciated regions. None exist in Florida. 
Aeolian Clays —Deposits of clay formed by the ac'ion of the wind 
are termed aeolian clays. In arid regions clay in the form of dust is 
blown about and sometimes accumulates in extensive beds. Some loess 
clays are believed to have been deposited in this manner. No such clays 
are known in Florida. 
