Geology Reference
In-Depth Information
Karst sub-basins and their relationship to the transport of Tertiary
siliciclastic sediments on the Florida Platform
ALBERT C. HINE
*
, BEAU C. SUTHARD
*1
, STANLEY D. LOCKER
*
, KEVIN J.
CUNNINGHAM
†
, DAVID S. DUNCAN
‡
, MARK EVANS
§
and ROBERT A. MORTON
¶
*
College of Marine Science, University of South Florida, St Petersburg, FL 33701, USA
(E-mail: hine@marine.usf.edu)
†
U.S. Geological Survey, 3110 SW 9th Avenue, Fort Lauderdale, FL 33315, USA
‡
Department of Marine Science, Eckerd College, 4200 54th Avenue South, St Petersburg, FL 33711, USA
§
Division of Health Assessment and Consultation, NCEH/ATSDR, Mail Stop E-32, 1600 Clifton Road,
Atlanta, GA 30333, USA
¶
U.S. Geological Survey, 600 4th Street South, St Petersburg, FL 33701, USA
ABSTRACT
Multiple, spatially restricted, partly enclosed karst sub-basins with as much as 100 m
of relief occur on a mid-carbonate platform setting beneath the modern estuaries of
Tampa Bay and Charlotte Harbor located along the west-central Florida coastline.
A relatively high-amplitude seismic basement consists of the mostly carbonate,
upper Oligocene to middle Miocene Arcadia Formation, which has been signifi cantly
deformed into folds, sags, warps and sinkholes. Presumably, this deformation was
caused during a mid-to-late Miocene sea-level lowstand by deep-seated dissolution
of carbonates, evaporites or both, resulting in collapse of the overlying stratigraphy,
thus creating palaeotopographic depressions.
Seismic sequences containing prograding clinoforms fi lled approximately 90%
of the accommodation space of these western Florida sub-basins. Borehole data
indicate that sediment fi ll is mostly siliciclastic deposited within deltaic depositional
systems. The sedimentary fi ll in the Tampa Bay and Charlotte Harbor sub-basins is
mostly assigned to the upper Peace River Formation of late Miocene to early Pliocene
age. This fi ll is part of a >1000 km long, Tertiary siliciclastic deposit that stretches
north-to-south down peninsular Florida. Sediment fi ll of these two sub-basins is linked
to erosion and remobilization of pre-existing, middle Miocene quartz-rich sediments
via enhanced sediment transport by local, short-length rivers and discharge into coastal-
marine depositional environments. Increased sediment discharge possibly resulted
from amplifi ed thunderstorm activity and enhanced runoff during a warm period of
the Pliocene.
Rather than incised valley fi lls or reef-margin, backfi lled basins, Tampa Bay and
Charlotte Harbor represent spatially restricted, sediment-fi lled karst palaeotopographic
lows. The 'dimpling' of a carbonate platform by karst sub-basins provides a previously
unrecognized mechanism for the creation of accommodation that can result in the
'drowning' of a carbonate platform by siliciclastics.
Keywords
Karst, carbonate platform, siliciclastics, sediment transport, deltas, sea
level, deformation, palaeofl uvial.
INTRODUCTION
Gulf of Mexico coastline, seem anomalous in that
they do not appear to have formed as drowned,
incised river valleys typical of other estuarine
systems in dominantly siliciclastic settings such
as those along coastal plains (Dalrymple
et al
.,
1994). Indeed, Tampa Bay and Charlotte Harbor
reside in the centre of the large, dominantly car-
bonate Florida Platform and are only fed by a few
very small, low-sediment and water discharge
Tampa Bay and Charlotte Harbor, two major
estuaries located along Florida's west-central
1
Present address: Coastal Planning and Engineering Inc,
Tampa Bay Regional Offi ce, 101, 16th Ave So., Suite 4,
St. Petersburg, FL 33701, USA (E-mail: bsuthard@coastal-
planning.net).
