Carbonate Coastal Accretion in an Area of Longshore Transport, NE Qatar, Persian Gulf
In early Holocene times coastal embayments near Khor and Dakhirah on the E coast of Qatar Peninsula contained little sediment, and cliffs of Tertiary dolomite constituted the irregular coast line. After stabilization of the present sea level, fine grained, carbonate sediment and dolomite out-wash from the land began to fill and regularize the embayments. Concurrent longshore transport of Recent coarse grained carbonates from the north created “chenier” beaches with hook-shaped spits at their southern ends, which gave added protection to these pre-Recent embayments, creating an environment in which fine-grained carbonates could accumulate. Sedimentation continued within the coastal embayments until wide supratidal flats eventually formed. Contemporaneously, additional cheniers and spits were forming seawards of the older one creating quiet water embayments seawards of the older, high energy cheniers and spits. Fine grained carbonates accumulated between successive cheniers. During this five to six thousand year period, a complicated tidal channel system developed on the flats behind and between successive cheniers and spits. Progradation of this tidal-flat-channel belt and the construction of new cheniers has preserved the numerous channel deposits.
Chenier beach and spit development has straightened the coast. When the remaining embayments are eventually filled the character of deposition will probably change to that of simple beach accretion. Thus, the tidal-flat complex described in this text may, in time, be preserved as a distinct body of sediment differing notably from the sands and coral reefs at present accumulating a short distance off-shore.
The area of sedimentation described is 18 km long and up to 7 km wide. Its thickness exceeds 8 m in places. The system of coastal accretion by carbonate sediment influenced by longshore transport differs markedly from the pattern and textures of Bahamian tidal flats.
KeywordsSulphide Sedimentation Beach Lime Dolomite
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