Page 118 - Carbonate Sedimentology and Sequence Stratigraphy

CHAPTER 7: SEQUENCE STRATIGRAPHY OF THE T FACTORY 109

Fig. 7.6.— Satellite image of Andros Island and surroundings on Great Bahama Bank. Despite uniform recent sea-level history,
conditions for all three systems tracts are realized simultaneously in the vicinity of Andros. This is due to the interplay of inherited
topography, variations of sediment production and lateral sediment transport. Lowstand conditions (L) exist on the narrow shelf between
Andros and the deep-water trough of Tongue of the Ocean. Transgressive conditions (T) are well documented on the NW side of
the island where the narrow belt of tidal flats is being eroded on the seaward side and transgresses the island on the landward side.
Highstand conditions (H) prevail on the SW-facing tidal flats and on the Joulters Cay oolite shoal N of Andros. The platform E of Tongue
of the Ocean is mostly in transgressive conditions. After Harris and Kowalik (1994), modified. (Reprinted by permission of the AAPG
whose permission is required for further use).

7.5). See also Purdy et al. (2003, p. 562) for a seismic example A connection between geometry of sediment bodies and
from the Pleistocene. their facies is indeed very likely because the geometry re-
flects conditions that must also affect the depositional envi-
SHOAL-WATER FACIES OF T-FACTORY SYSTEMS ronment. With respect to carbonate platforms, the geometry
TRACTS
of the three systems tracts immediately leads to several con-
The geometric definition notwithstanding, many authors clusions about the depositional environments and thus the
have suggested that systems tracts also display characteris- facies of the systems tracts. For instance, lowstand tracts can
tic facies patterns (see Posamentier et al., 1988 for siliciclas- be expected to be rather narrow, normal marine and devoid
tics; Handford and Loucks, 1993, for carbonates).