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Geochemistry of
the Pleistocene/Holocene Carbonate-Evaporite
Sediments of the Khiran Area, Southern Coast of
Qabazard, Suad AbdulKareem, Fawzia Hussein
Abdullah,
The complex of the Pleistocene/Holocene sediments of the Khiran area along the southern coast of
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.