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terminating by downlap onto the approximately
200 m deep Pourtales Terrace (Missimer, 1992;
Warseski
et al
., 1996; Guertin
et al
., 1999, 2000;
Cunningham
et al
., 1998, 2001a,b, 2003; McNeill
et al
., 2004). The partial burial of this deep-
marine, erosional Miocene terrace marked the
southern end of a >1000-km-long siliciclastic
transport system that originated with the weath-
ering of crystalline bedrock of the southern
Appalachian Mountains and Piedmont
(
Fig. 1).
In general, this siliciclastic transport from the
north produced a relatively thin (1-150 m) late
Neogene to modern quartz-rich veneer covering
a thick (2-6 km) Jurassic-to-Neogene carbon-
ate succession over peninsular Florida (Klitgord
et al
., 1984).
Results from the South Florida Drilling Project
also indicated that there was a late Miocene-to-
Pliocene remobilization of siliciclastics in south
Florida. Earlier studies had shown that silici-
clastics entered the northern Florida peninsula
by post mid-Oligocene after the Georgia Channel
System (Huddleston, 1993; T. Scott, personal
communication) seaway complex had been fi lled
by prograding deltas probably during a major
sea-level lowstand that occurred during the early
Oligocene (Hull, 1962; Chen, 1965; McKinney,
1984; Popenoe
et al
., 1987; Popenoe, 1990;
Brewster-Wingard
et al
., 1997). These sediments
made their way to central Florida and formed an
important part of the Hawthorn Group, possibly
transported by extensive longshore sediment
transport during sea-level highstands. However,
to the south, carbonate sedimentation persisted
ultimately depositing the late Oligocene-to-middle
Miocene Acadia Formation and lower Peace River
Formation. These lithostratigraphic units are
unconformably overlain by the siliciclastic sedi-
ments of the upper Peace River Formation, which
represents renewed siliciclastic transport in the
late Miocene to early Pliocene of the Hawthorn
Group quartz-rich sediments lying in central
peninsular Florida (Cunningham
et al
., 2003;
McNeill
et al
., 2004).
benefi t of digitally acquired and processed and
GPS located, high-resolution seismic-refl ection
profi le data gathered in closely spaced line. Such
data enable loop-tying and thus three-dimensional
mapping of seismic sequences and bounding sur-
faces (Stahl, 1970; Willis, 1984; Hebert, 1985;
Green
et al
., 1995; Ferguson & Davis, 2003).
Duncan
et al
. (2003) and Suthard (2005) have
provided such a data set and correlated their
seismic data (~1000 line km) to six neighbouring
boreholes on land and numerous short cores
within the estuary itself (Fig. 2).
The seismic data of Duncan
et al
. (2003) and
Suthard (2005) clearly demonstrate that Tampa
Bay is underlain by a sediment-fi lled sub-basin
having multiple smaller-scale sub-basins each
separated by bedrock highs (Figs 3 and 4). Recent
data have revealed that 'seismic basement'
crops out in middle-central Tampa Bay forming
hardbottoms supporting appropriate benthic bio-
logical communities. The seismic basement con-
sists of the Arcadia Formation - an open-marine
limestone-dolostone, with occasional thin beds of
phosphatic quartz sands (<1.5 m thick) and clays
(<1.5 m thick and of limited areal extent) scattered
throughout (Scott, 1988; Suthard, 2005). Suthard
(2005) jump-correlated his seismic lines to adja-
cent onshore boreholes (Green
et al
., 1995) for
chronostratigraphic control. Since these basins
have 40-60 m of subsurface relief and the average
water depth of Tampa Bay is only 4 m, approxi-
mately 5-10% of the remaining accommodation
space is unfi lled.
The seismic data indicate deformation of the
Arcadia Formation and some of the immediately
overlying seismic sequences forming the sub-basin
fi ll. Folds and sags dominate the lower Tampa Bay
part of the sub-basin (Fig. 5). These deformational
features are not anticlines and synclines in the
classic structural geology sense in that they have
very limited lateral continuity (no axial planes) -
rather they are small, broad domes (>1 km across)
and narrow (<1 km), circular depressions - some
even representing individual sinkholes. This
style of deformation is more consistent with
deep-seated collapse from below rather than from
lateral compression due to tectonic activity.
Finally, seismic refl ection and borehole data
reveal that the sub-basin underlying Tampa Bay
is laterally restricted and does not extend sea-
ward beneath the modern continental shelf more
than ~30 km (Fig. 4; Hebert, 1985; Duncan, 1993;
Duncan
et al
., 2003). Rather, the seismic basement
underlying Tampa Bay rises seaward where it
TAMPA BAY SUB-BASIN
Tampa Bay is a large (~1000 km
2
), shallow
(average depth ~4 m) estuary located along the
west-central Florida Gulf of Mexico coastline.
Although there has been considerable geological
framework research performed within Tampa Bay
in the past, much of this work did not have the
