Geology Reference
In-Depth Information
Fig. 14.
Map (adapted from Fernald,
1981, p. 16) illustrating the transport
pathway and suggested modes of trans-
port of Cenozoic siliciclastic sediment:
(1) across the Georgia Channel System
from the southeast coastal plain via
deltaic progradation infi lling this
seaway; (2) sediment onlap onto the
Florida Platform and transport down
north and central peninsular Florida to
the southern terminus of the Lake Wales
Ridge, primarily by longshore trans-
port during high stands of sea-level;
(3) palaeofl uvial infi lling of mid-
platform sub-basins such as Tampa
Bay and Charlotte Harbor during lower
stands of and/or falling sea level;
(4) continued southward palaeofl uvial
progradation covering an exposed car-
bonate ramp in south-central peninsu-
lar Florida; (5) introduced to the marine
environment beneath and seaward
of the present Florida Keys forming a
shelf-slope system infl uenced by cross-
shelf and downslope currents; and
(6) eventually downlapping of sediment
onto the 200 m deep Pourtales Terrace.
Metres
sea-level lowstand (Haq
et al
., 1988; Popenoe,
1990; Brewster-Wingard
et al
., 1997), the Georgia
Channel System was fi lled completely and
siliciclastic sediments started to cover north-
central peninsular Florida. Peninsular Florida,
being elevated (Fig. 1; St. Johns Platform, Sanford
High, Brevard Platform and Ocala Platform;
Popenoe, 1990; Scott, 1997), could not support
a long-distance, north-to-south fl uvial system.
Consequently, primary sediment movement
probably occurred in coastal longshore transport
systems during higher sea level.
Secondary sediment movement to the east and
west occurred by local rivers during lower sea
level. The late Miocene to early Pliocene Bone
Valley Member of the Peace River Formation
represents a palaeofl uvial reworking of older
Hawthorn Group siliciclastic and phosphatic-rich
units (Riggs, 1979). The surfi cial geomorphology
of peninsular Florida, dominated by numerous
palaeoshoreline features, is best illustrated by
the Lake Wales Ridge complex. These extensive
north-south-trending coastal features have been
subsequently incised and eroded by numerous
local streams - some of which provided the remo-
bilized siliciclastic sediments that fi lled in the
semi-enclosed, restricted karst sub-basins beneath
Tampa Bay and Charlotte Harbor.
The Lake Wales Ridge ends in south-central
peninsular Florida (Figs 1 and 14), indicating
that extensive north-to-south, coastal long-
shore transport probably ended there as well. To
complete the sediment transport pathway to the
southern Straits of Florida, data from Cunningham
et al
. (2003) and other papers associated with the
South Florida Drilling Project (McNeill
et al
.,
2004) indicate that a late Miocene-to-Pliocene
prograding deltaic depositional system carried
quartz sands and gravels on top of a carbonate
ramp that had been exposed for 8 million years
thus burying the underlying Arcadia Formation.
As this delta complex approached the carbonate
