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system migrated southward approximately 200 km
to near the southernmost margin of the Florida
Platform.
This scenario poses several related critical
questions. (1) What was the source of quartz
sand and gravel that fi lled the Tampa Bay and
Charlotte Harbor sub-basins and enabled proga-
dation of a deltaic depositional system 200 km
south, approaching the margin of the south Florida
Platform? (2) What caused the late Miocene-to-
Pliocene fl uvial-deltaic activity to be signifi cantly
enhanced as compared to the present, since today
there are no bay-head deltas? (3) What was the
nature of the palaeofl uvial network - several
large long rivers or a complex network of high-
discharge local, short-length streams? (4) What
shut down this siliciclastic remobilization event
and allowed the return to primarily carbonate
deposition in the Pleistocene forming the Florida
Keys consisting of the Miami Oolite and the Key
Largo Limestone (Enos & Perkins, 1977)? Finally
(5) what is the geological signifi cance of these
karst sub-basins?
Eustatic Curve
150
100
50
0 m
0
3.10
3.9
3.8
3.7
3.6
3.5
3.4
3.3
3.2
2
Ma
4
6
8
3.1
10
Ma
Ma
2.6
2.5
2.4
12
14
2.3
16
2.2
18
2.1
20
1.5
22
1.4
24
1.3
1.2
1.1
26
The >1000-km long siliciclastic transport
pathway
28
Fig. 13.
Relationship between lithostratigraphic units,
chronostratigraphy and sea level showing the timing of
sub-basin formation, deformation and infi lling (modifi ed
from Fig. 2, Cunningham
et al
., 2003; eustatic curve from
Haq
et al
., 1988).
The primarily chemical weathering of exposed
silicate-rich bedrock of the southern Appalachian
Mountains and Piedmont provided the ultimate
source of quartz sands and gravels to the Florida
Platform that eventually reached the Pourtales
Terrace lying in 200 m water in the southern
Straits of Florida. The following scenario (Figs 1
and 14) is suggested in order to partially explain
this >1000-km long source-to-sink pathway -
a pathway that consisted of multiple sedimentary
compartments (coastal plain, river deltas, coast-
lines, karst entrapment basins and ultimately the
open marine shelf and slope) and involved mul-
tiple sedimentary transport processes. Thus, the
transport and deposition of siliciclastics prob-
ably proceeded as a series of steps modulated
by Cenozoic sea-level fl uctuations, topographic
variations and climate changes.
Streams from the Appalachian Mountains
and Piedmont brought sediment to the coastal
plain where it was deposited along adjacent
fl oodplains or reached deltas discharging into the
marine environment. Through time, river deltas
prograded across and fi lled the Georgia Channel
System during sea-level lowstands in the late
Eocene and early Oligocene (McKinney, 1984).
Probably, during the middle Oligocene major
perhaps even stimulated deep-seated dissolution.
Whereas, the Bahama Banks, being physically
isolated, cannot receive groundwater infl ux
from some lateral source, but only receive their
fresh water from local rainfall perhaps limiting
subsurface dissolution.
Based upon the lithostratigraphy and chrono-
stratigraphy provided by boreholes adjacent
to Tampa Bay, Charlotte Harbor and the
Caloosahatchee River, the infi lling of the semi-
enclosed sub-basins beneath these Florida west-
coast estuaries occurred during the very late
Miocene and Pliocene sea-level highstand (TB3.4
and TB3.5; Fig. 13). This was part of the major
remobilization and southward transport of sili-
ciclastics in south Florida as pointed out by the
various authors associated with the South Florida
Drilling Project (Guertin
et al
., 2000), and sum-
marized by Cunningham
et al
. (2003) and McNeill
et al
. (2004). During the late Miocene and
Pliocene, a major fl uvial-deltaic depositional
