Geology Reference
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stratigraphic record of Florida Bay and the
southwest coast of Florida includes a transgres-
sive sediment package overlain by a regressive
package (Scholl, 1964; Enos & Perkins, 1979;
Parkinson, 1987). This transgressive package has
been interpreted to have been deposited dur-
ing a period of rapid relative sea level (RSL) rise
(~23 cm 100 yr −1 ) in the mid-Holocene (5500-
3200 yr BP ) (Parkinson, 1987). The regressive
package formed during a period with a slower
average rate of RSL rise, ~4 cm 100 yr −1 over the
past 3200 years (Scholl et al ., 1969; Robbin,
1984; Parkinson, 1987; Wanless et al ., 1994). This
decelerated rate of RSL rise, in combination with
abundant sediment supply, resulted in lateral
accretion of islands in Florida Bay (Gorsline, 1963;
Enos & Perkins, 1979; Cottrell, 1989; Wanless &
Tagett, 1989) and progradation of coastal facies
along the southwest coast of Florida (Evans et al .,
1985; Hine et al ., 1988; Parkinson, 1989; Stapor
et al ., 1991). Over the past 75 years, south Florida
has faced an accelerated rate of RSL rise of
> 23 cm 100 yr −1 (Wanless, 1982; Wanless et al .,
1988; Douglas, 1991). Hence, interpretation of
earlier Holocene deposits might suggest that the
existing coastal system should switch from aggra-
dational/progradational to retrogradational.
In order to understand how rapid RSL rise
and sediment availability might infl uence the
evolution of a low-energy coastal system, an integ-
rated study of a carbonate/organic system within
Cape Sable, southwest Florida, is presented. The
purposes of this paper are to (1) document the
patterns and rates of sedimentation in the shal-
lowing-upwards facies succession; (2) identify
the different sediment sources and sinks, and
(3) determine the process dynamics which gov-
ern the sediment redistribution and accumulation
style. An integrated approach is adopted that uses
sedimentological, hydrodynamic and geochemical
data, to link process dynamics to the associated
sedimentary products. The aim of the investiga-
tion is to fi ll a gap in the knowledge of quantitative
relations between processes and products, a fi eld
not well explored in mixed organic-carbonate
sedimentary systems.
The results of this research illustrate the
complicated nature of processes and related prod-
ucts in a low-energy setting. Recycling of organ-
ic-carbonate muds during rapid RSL rise can
result in a shallowing-upwards succession of tidal
deposits and a complete spatial reorganization
of facies. Thus, ancient metre-scale, shallowing-
upwards lithologic units need not necessarily be
the result of a stable or slow sea-level rise, such as
suggested by several models of tidal fl at prograda-
tion (Ginsburg, 1971; Goodwin & Anderson, 1985;
Pratt & James, 1986; Burgess, 2001), but instead
can be the depositional expression of a single
rapid rise of sea level during a high-stand.
AREA OF STUDY
Cape Sable (900 km 2 ) forms the southwestern tip
of the Florida Peninsula, an emergent low-relief
carbonate platform (Fig. 1). The area is situated at
the southwest end of the gentle Everglades depres-
sion between a Pleistocene limestone ridge to
the northeast and emergent Pliocene limestone
to the northwest. The karstifi ed surface of the
Pleistocene Miami Limestone lies at a depth of
3.5-4 m in the Cape Sable area (Fig. 2; Roberts
et al ., 1977).
Cape Sable is located at the intersection of
Florida Bay and the Gulf of Mexico. Characteristics
of both the southwest Florida coast (tide-
dominated, sand-starved, continuous mangrove
belt) and Florida Bay (shallow coastal lagoon,
carbonate mudbanks, mangrove-capped islands)
are present in Cape Sable. Cape Sable has shell
beach or mangrove shorelines along its western
(Gulf of Mexico) coast, a storm-built marl ridge
on its southern (Florida Bay) coast and man-
groves bordering the interior coast on Whitewater
Bay (Fig. 2). The southern interior of Cape Sable
includes a series of at least three linear, emer-
gent ridges (Fig. 1) composed of calcium carbon-
ate mud (marl), interpreted as ancient shorelines
(Roberts et al ., 1977). Landward of the youngest
(most seaward) marl ridge is a vast wetland
historically dominated by freshwater marsh
species such as sawgrass and cordgrass. Today,
salt-tolerant species including mangroves occur
throughout this region. Seaward of the marl ridge
lies Lake Ingraham (Fig. 1), formerly a shallow
freshwater lake; more seaward of the lake lies a
shelly beach ridge complex. This shell beach is
just a thin veneer over a 4-m-thick marl sequence
(Fig. 2), except at the three capes, where more than
2 m of sand has accumulated. Southeast of the
coastal lagoon Lake Ingraham is an intricate com-
plex of ponds, mudfl ats and tidal creeks, hereafter
called the Southern Lakes (Fig. 1).
In the past century, this region has been modi-
fi ed by humans. Through the early to mid-1920s,
several narrow canals (less than 4 m in width)
were constructed connecting the different
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