FLORIDA GEOLOGICAL SURVEY


County to Dade and Monroe Counties. It forms the Atlantic Coastal Ridge and extends beneath
the Everglades where it is commonly covered by thin organic and freshwater sediments. The
Miami Limestone occurs on the mainland and in the southern Florida Keys from Big Pine Key to
the Marquesas Keys. From Big Pine Key to the mainland, the Miami Limestone is replaced by
the Key Largo Limestone. To the north, in Palm Beach County, the Miami Limestone grades
laterally northward into the Anastasia Formation.
 The Miami Limestone consists of two facies, an oolitic facies and a bryozoan facies
(Hoffmeister et al. [1967]). The oolitic facies consists of white to orangish gray, poorly to
moderately indurated, sandy, oolitic limestone (grainstone) with scattered concentrations of
fossils. The bryozoan facies consists of white to orangish gray, poorly to well indurated, sandy,
fossiliferous limestone (grainstone and packstone). Beds of quartz sand are also present as
unindurated sediments and indurated limey sandstones. Fossils present include mollusks,
bryozoans, and corals. Molds and casts of fossils are common. The highly porous and
permeable Miami Limestone forms much of the Biscayne Aquifer of the surficical aquifer
system.

 Oal Obd Otr Qu Undifferentiated Quaternary Sediments Much of Florida's surface
is covered by a varying thickness of undifferentiated sediments consisting of siliciclastics,
organic and freshwater carbonates. Where these sediments exceed 20 feet (6.1 meters) thick,
they were mapped as discrete units. In an effort to subdivide the undifferentiated sediments,
those sediments occurring in flood plains were mapped as alluvial and flood plain deposits (Qal).
Sediments showing surficial expression of beach ridges and dunes were mapped separately
(Qbd) as were the sediments composing Trail Ridge (Qtr). Terrace sands were not mapped
(refer to Healy [1975] for a discussion of the terraces in Florida). The subdivisions of the
Undifferentiated Quaternary Sediments (Qu) are not lithostratigraphic units but are utilized in
order to facilitate a better understanding of the State's geology.
 The siliciclastics are light gray, tan, brown to black, unconsolidated to poorly
consolidated, clean to clayey, silty, unfossiliferous, variably organic-bearing sands to blue green
to olive green, poorly to moderately consolidated, sandy, silty clays. Gravel is occasionally
present in the panhandle. Organics occur as plant debris, roots, disseminated organic matrix and
beds of peat. Freshwater carbonates, often referred to as marls in the literature, are scattered
over much of the State. In southern Florida, freshwater carbonates are nearly ubiquitous in the
Everglades. These sediments are buff colored to tan, unconsolidated to poorly consolidated,
fossiliferous carbonate muds. Sand, silt and clay may be present in limited quantities. These
carbonates often contain organic. The dominant fossils in the freshwater carbonates are
mollusks.



 Holocene Series

 Oh Holocene Sediments The Holocene sediments in Florida occur near the present
coastline at elevations generally less than 5 feet (1.5 meters). The sediments include quartz
sands, carbonate sands and muds, and organic.