Depositional and diagenetic history of Pleistocene and Holocene oolitic sediments and sabkhas in Kuwait, Persian Gulf



The Pleistocene and Holocene oolitic sediments of southern Kuwait appear as parallel ridges—ancient and recent barrier beaches and coastal dunes. They are underlain by Tertiary clastic deposits and interfingered with sabkhas. Considering the superposition, primary composition and diagenetic alterations five lithostratigraphic units were distinguished within the oolitic complex. Their formation and preservation were related principally to eustatic oscillations of sea level during Quaternary times, although post-Pliocene tectonics also played an important role both in physiographic and sedimentary developments of the region.

The large accumulation of oolites in southern Kuwait might be related, at least partly, to the existence of two tidal channels, khors, discharging waters over-saturated with respect to calcium carbonate over broad tidal flats. The formation of oolites culminated in late Pleistocene probably due to an extreme aridity of the climate.

The subaerial diagenesis of the oolitic ridges led to gradual cementation and recrystallization of oolites. The four stages of progressive diagenesis distinguished in the area are compared with schemes suggested by Land, Mackenzie & Gould (1967) for Quaternary sediments in Bermuda and by Gavish & Friedman (1969) for aeolianite ridges in Israel.

On the sea floor the cementation has produced widespread beach rocks and hard layers. Aragonite encrustations and dripstones occur within the intertidal zone of channels and lagoons. The shallow, occasionally flooded depresssions in sabkhas are occupied by algal mats.

The amount of dolomite in sabkha sediments is rather low in comparison with similar environments of the southern Persian Gulf. This might be at least partly explained by the absence of dolomitic rocks in the Tertiary substratum in Kuwait.

The complex of Quaternary sediments in southern Kuwait represents a petroleum setting in which the organic rich source sediments of lagoons and sabkhas are closely associated with highly porous reservoir rocks of the oolitic coastal ridges.