Geology Reference
In-Depth Information
1 9
Holocene Carbonate Tidal Flats
Eugene C. Rankey and Andrew Berkeley
Abstract
Carbonate tidal fl ats of the Bahamian archipelago and the Arabian Gulf have
served as important analogs for interpreting and understanding ancient tidal fl at
systems. Geomorphic associations include well-zoned subtidal, intertidal, and
supratidal environments and their deposits, each with distinctive associations of
biota and biologic and physical sedimentary structures. Although they include
broadly similar facies associations in each environment within and between tidal
fl ats, the occurrence and distribution of specifi c facies across landscapes differs
markedly between tidal fl ats. Depending on the details of climate, tidal amplitude,
regional setting and energy level, Holocene carbonate tidal fl ats include systems
penetrated by numerous sinuous channels with adjacent levees and ponds, areas
with broad, fl at progradational intertidal and supratidal plains, and regions
with shorelines that appear to have abruptly stepped oceanward or eroded.
Stratigraphically, each different type of tidal fl at includes a shallowing-upward
facies succession, although in many areas, a basal transgressive unit is present.
19.1
Introduction
successions throughout the stratigraphic record
(Wilson
1975
; Hardie
1986
; Pratt and James
1986
;
Grotzinger
1986
; Lehrmann and Goldhammer
1999
) .
Some stacked peritidal deposits are hundreds of meters
thick and occur across areas of several 1,000 km
2
. In
seeking to understand these successions, the geologic
history that they record, and the hydrocarbon, min-
eral, and water resources that they contain, sedimen-
tologists have studied several modern carbonate
tidal fl ats.
The purpose of this chapter is to outline general
aspects of sedimentology, geomorphic character, and
the Holocene stratigraphic record of some of these
tidal fl ats. The focus is on the tidal fl ats of the Bahamian
Archipelago, but for completeness, the chapter
includes brief discussions of patterns and processes
on the more arid tidal fl ats of the Arabian Gulf.
Shallowing-upward peritidal facies successions, passing
from shallow subtidal up through intertidal and
supratidal deposits, are a hallmark of many carbonate
