FLORIDA DEPARTMENT OF NATURAL RESOURCES
published by BUREAU OF GEOLOGY


MAP SERIES NO. 57


D E














































































E 0 N

FE so




















.t u-mar








.. ............


- ---- -- - - ^ ~ H 2

848


BOUGUER ANOMALY MAP OF THE FLORIDA PENINSULA
AND ADJOINING CONTINENTAL SHELVES

--

SBy Ma.
W.R.Oglesby,' M. M. Ball2 and Susan Chak 13

This map was prepared from data supplied by the deposition of alternating carbonate-evaporite cyclothems EXPLANATION
Department of Defense Gravity Library and incorporates the occurred in the region of the positive anomaly in the Lower +62
previous data published as Map Series No. 41, 1971, by the Keys leading into the basin, where barrier reefs were lacking. POSITIVE --- 2 Contour Interval 4 milligals
Bureau of Geology, Florida Department of Natural The northeast flank of the minimum anomaly west of Fort ANOMALY
r- Resources. The density value employed to correct the Free Myers is underlain by anhydrite. The Lee County minimum INCREASE Base of the Continental Slope
0 Air values to the Bouguer Anomaly values is 2.0, except in was tested to the basement at Lehigh Acres where diabase +30
G) the extreme Southwest corner of the map (uncolored) where was recovered in cores. It is assumed the diabase was a dike
0- a density of 2.67 was used. This increase in density value was or sill, probably cutting a rhyolitic mass. The density of
r, selected for the small area beyond the continental slope, rhyolite, approximately 2.65, is considerably less than the
C where the shelf sediments are missing. average density of the sediments at depth in the Lower 2
It is interesting to compare the present map with one Cretaceous (limestones of densities of 2.73 and anhydrite, I
contained in Map Series No. 19 (1965, Florida Division of density 2.94). This is sufficient contrast to account for the
-< Geology), an isopachous map of the Sunniland Limestone of minimum gravity anomalies. The age of the rhyolite has been
the South Florida Basin. The similarity between the two determined by Potassium-Argon ratio as Late Triassic or 2NEGATIVE
D maps suggests that the large minimum area located in the Early Jurassic. The diabase is dated early Jurassic. The NEGATIVE FLORIDA DEPARTMENT OF NATURAL RESOURCES
t Gulf of Mexico west of Fort Myers may be favorably located rhyolite may have been expressed as topographically high ANOMALY BUREAU OF GEOLOGY ,/" -
ar. for Lower Cretaceous reef build-up. The minimum area cast areas during the Lower Cretaceous period, which offered INCREASE
. I of Miami in the Straits of Florida may also contain Lower favorable environment on which the reefs developed. -30 This public document was promulgated at a total cost of
Cretaceous reefing. Northward beyond the confines of the $485.00 or a per copy cost of $0.485 for the purpose of
(Ii South Florida Basin, the minimum anomalies are not Bureau of Geology disMemiating oologic data. o re p o
iU) associated with Lower Cretaceous reef build-up, as the Rosentiel School of Marine and Atmospheric Sciencen a- .
Sunniland Limestone is in fact absent. It appears that marine University of Miami
influx into the South Florida Basin during Cretaceous Bureau of Geology


4p


';i


I