AGE OF THE UNDERLYING ROCKS OF FLORIDA 
95 
WELL OF FLORIDA EAST COAST RAILWAY AT MARA¬ 
THON, ON KEY VACA, MONROE COUNTY, 
FLORIDA. 
Depth of well represented by samples 2,300 feet. The amount 
of casing used was 10-inch, 589 feet; 8-inch, 605 feet; 6-inch, 
1,128 feet. 
No foraminifera. 
Few foraminifera. Pleistocene. 
No foraminifera. 
Scattered foraminifera. Miocene. 
Mostly quartz sands. No foraminifera. 
Orbitolites and Gypsina. Probably Tampa formation. 
Fragments of foraminifera—perhaps same. 
Hard limestone. No identifiable foraminifera. 
Amphistegina. 
852 and 900 feet. Heterosteginoides. Unlike northern or central Florida. Cf. 
0-35 
feet. 
35-78 
feet. 
78-174 
feet. 
180-412 
feet. 
412-585 
feet. 
589-628 
feet. 
660 
feet. 
682-755 
feet. 
786 
feet. 
984 feet. 
1025-1115 feet. 
1210-1230 feet. 
1248 feet. 
1248-1318 feet. 
1318-1328 feet. 
1790 feet. 
Panama. 
Lepidocyclina. Unlike northern or central Florida. Cf. Cuba. 
Hard limestones. 
Hard limestones. 
Conical Orbitolina common. 
Orbitolina common, and at intervals to bottom of well. 
Flatter and larger specimens and at intervals to bottom of well. 
Low, concave forms of Orbitolina and at intervals to bottom. 
PROBABLE STRATIGRAPHY. 
Pleistocene formations are indicated at least to 78 feet. The 
Pliocene is not definitely indicated although there is a barren 
stretch between the Pleistocene and the beginning of the Miocene 
which includes the series between 180 and 412 feet and probably 
at least part if not all of the quartz sands below 585 feet. 
Oligocene begins as far as can be determined with the 589-foot 
sample to 628 and perhaps 660 feet. This seems to be of Tampa 
age. 
At 852 and 900 fe.et the fossils no longer resemble those of 
northern and central Florida and there appears a genus I have de¬ 
scribed from the rocks of the Panama Canal Zone and found 
again in the Leeward Islands. This represents Middle Oligocene 
probably or the base of the Upper Oligocene: Below it at 984 feet 
