SECOND ANNUAL REPORT—SOUTHERN EEORIDA. 
2’27 
EITHOEOGY OF PLEISTOCENE BEDS. 
The summation of the evidence indicates, except along the keys, a 
larger proportion of siliceous material in the early Pleistocene beds than 
in the surficial limestones, and less consolidation of sediments. Con¬ 
sidering the total bulk of the Pleistocene deposits, and the relative pro¬ 
portion of limy and sandy materials, the facts indicate that on the main¬ 
land the Pleistocene beds as a whole are not to be grouped as limestones. 
There are limy beds and limestones which can be mapped as lithologic 
units, but the proportion of siliceous and unconsolidated material is 
much greater than has been supposed. 
THICKNESS. 
The maximum thickness of the Pleistocene formations of southern 
Florida can not be determined from the available evidence. There was 
no distinguishable break in deposition nor sharp change in marine life 
to mark the beginning of Pleistocene time. The sequence of events 
shown by the sands, marls and limestones and the organic remains 
they contain is practically continuous. Pliocene time passed and Pleis¬ 
tocene time began with no distinct record of the change. 
For this reason the total thickness of the Pleistocene formations 
can not be determined from the available evidence. It could be ap¬ 
proximated with considerable exactness from a study of the fossils 
and a determination of the relative percentages of living and Pliocene 
species found in a given bed, but the drillers of the more important 
wells on the east coast saved few fossils. The evidence such as it is, 
shows that the Pleistocene beds are over seventy-five feet thick at West 
Palm Beach, over 118 feet thick at Delray, over fifty feet at Dania, fully 
145 feet at Key Vaca and over fifty feet at Buck Key. Of the above 
measurements the only one that is at all definite is the Key Vaca. Frag¬ 
ments of reef building coral were found there at 100 feet. Below was 
marl and soft limestone with shell casts that graded downward into a 
sandy limestone (quartz sands) at 152 feet, this limestone continued 
to 176 feet and then the drill struck a clean white quartz sand, the 
first upper fifty feet of which contained many irregular nodules of 
quartz sand held by a limy cement. The changes from quartz sand to 
limestone at 176 feet, and from limestone to undoubted reef rock at 
about 100 feet, are suggestive but insufficient for drawing a sharp line 
between Pleistocene and Pliocene material. It is probably safe to say 
that below 176 feet are Pliocene sands, and above 105 feet is Pleis¬ 
tocene reef rock. Though the thickness of the reef rock at Key Vaca 
does not necessarily indicate the thickness of the Pleistocene beds at 
Palm Beach or the mouth of the Caloosahatchee River, yet taking all 
the data into consideration, the maximum thickness of the Pleistocene 
of southern Florida is probably about 125 feet. 
