Page 137 - Geology of Carbonate Reservoirs

118 DEPOSITIONAL CARBONATE RESERVOIRS

Oolitic Sands Oolitic Beaches And Dunes
Pelletoidal Sands Sebkha Sediments
Muddy Bioclastic Sands Pre-Holocene Outcrops
Carbonate Mud
Barrier Island
Reefs
Tidal Deltas
Algal Mats

Lagoon

Sebkha
10 KM
Figure 5.3 The tidal - flat or sebkha environment of the Trucial Coast near Abu Dhabi,

United Arab Emirates. Note that small barrier islands partially enclose the lagoon and tidal
channel zone. This tidal - fl at environment would not exist on an open ramp without the pro-
tection of the barrier island. The hot, arid climate of the Trucial Coast is conducive to the
formation of evaporites in the upper intertidal and supratidal zones. (Adapted from an illus-
tration in Purser (1980) .)

8 km
Intertidal flat Supratidal marsh
Supratidal Pond
levee

Pond Marsh
- Channel belt sediments
Pond
Pleistocene
limestone
Beach ridge
Subtidal
Intertidal
Subtidal sediments

Figure 5.4 An idealized model of the channelized tidal flats on the west side of Andros

Island, Bahamas. The channels provide access to incoming tides that flood the channel belt

and sometimes flow over the channel margins to fill the ponds, or lakes, that lie between them.

The wet climate of the Bahamas favors algal mats, grasses, mangroves, and small palm trees.
Evaporites are absent and channels are deeper and more widespread than on the sebkhas of
the Persian Gulf. (Adapted from an illustration in Shinn et al. (1969) .)