Geochemistry of the Pleistocene/Holocene Carbonate-Evaporite Sediments of the Khiran Area, Southern Coast of Kuwait

Qabazard, Suad AbdulKareem, Fawzia Hussein Abdullah, Kuwait University, Kuwait

The complex of the Pleistocene/Holocene sediments of the Khiran area along the south­ern coast of Kuwait represents a petroleum setting, where organic-rich source sediments of lagoons are closely associated with porous potential reservoir rocks of the oolitic ridges.

The coastal areas, near their connection to the open gulf, and the mouth of the tidal creeks are dominated by coarse-grained, moderately-sorted beach carbonate sands, with low amounts of organic matter (TOC = 0.3%wt). Landward, at the ends of the creeks, the concentration of ooids decreases, where silt-clayey sediments composed mainly of pellets and calcareous mud interbedded with algal mats are found. This low energy setting revealed relatively higher organic matter content ( TOC = 0.9%wt.), compared to the sediments deposited at the mouth of the tidal creek.

The Pleistocene oolitic limestones are elongate, cross-bedded, thinly-laminated ridges of carbonate sands, directed parallel to the strong tidal currents. The rocks exhibit excellent reservoir potential system as a result of prolong exposure to the freshwater leaching.

The overall low amounts of trace metal, low organic matter contents and the relatively high O/C atomic ratios of the organic matter in the beach sediments and ridges indicate that they were laid down under highly oxygenated and bioturbated, open marine conditions, where current and wave actions lead to destruction of the organic matter. However, sedi­ments deposited at the end of the creeks show relatively higher trace metals and higher TOC contents. These physical and chemical conditions allowed for the preservation of amor­phous algal marine type organic matter.