Evolution of the Holocene Carbonate Ramp Complexes of Southern Kuwait

Lomando, A. J.¹, E. Gischler², A. Al-Dharmi³, T. Al-Adwani³ (1) ChevronTexaco, Kuwait, San Ramon, CA (2) Univ. of Frankfurt, (3) Kuwait Oil Company, Kuwait

Offshore to onshore southern Kuwait contains a complete carbonate ramp suite from outer-ramp muds and mid-ramp reef buildups to inner-ramp ooid shoal-beach-dune sys­tems and backshore tidal flats and sabkhas. The modern coastal system is the site of shoal and tidal channel–delta ooid factories that feed the beach systems. These factories, in turn, have fed an extensive coastal beach dune-ridge complex for the past 6000 years. From southern Kuwait into northern Saudi Arabia, shallow folds and faults perpendicular to the regional coastline strike create a series of headlands and intervening cuspate reentrants with periods of 20 to 50 kms. Depositional packages include long, narrow oolite dune-ridge complexes in reentrants and wide oolite ridge strand plains down current of each headland. Inter-ridge fills are a combination of wind-blown reworked ooids, very fine quartz sand, gypsum crystals, and clay dust derived from the upwind deserts of Iraq and Syria. Biogenic structures in the dunes are most commonly rhizoliths and rare insect and mammal bur­rows. Complex progradational units formed during high-frequency, low-amplitude Holocene sea-level cycles. Rare complete exposures have been vertically measured and age dated from their skeletal-ooid beach and shoreface deposits up through the aggrading, overlying oolite dunes. This has permitted construction of a calibration curve using eleva­tion and the time difference between the establishment of the shoreline and the formation of oolite dunes above them. Thus, respective shoreline ages can be established from dune ages of known elevation when exposures are incomplete. Mapping dated groupings of oolite ridge complexes combined with satellite imagery have permitted the Holocene progradational history to be subdivided into Bronze, Iron, and Arab age high-frequency Holocene progradational pulses.