ABSTRACT
This paper presents a depositional model for the distribution of sedimentary facies in elongated,
narrow tidal creeks debouching into a shallow landlocked sea in an arid region with relatively
low eolian sediment accumulation.
The tidal creeks were part of an active drainage system established during the last glacial
low-stand of sea-level.
Sediments of the creeks are marine, mainly autochtonous carbonates with minor eolian
siliciclastics. The carbonates are predominantly preserved as faecal pellets produced by mudeating
invertebrates. The creek deposits also include abundant skeletal debris. Oolites are
formed in areas agitated by waves. Carbonate muds are partially introduced to the tidal
creeks from the open sea by tidal currents. ,
Tidal currents and, to a lesser extent, wind generated currents, are the major agents
transporting sediment in the creeks. Coarser sediments are found in the channels and finer
sediments accumulate in distal parts of the tidal flats and at the landward end of the major
channels. The amount of eolian sediments also increases landward. Grain size of sediments
and their flooding frequency determine the type of the infaunal and epifaunal community
of organisms living in them.
Tidal flat sediments are actively burrowed by crabs and other invertebrates, while the channels
contain abundant gastropods and bivalves. The molluscan communities of the channels are
more diverse towards the mouth of the creeks, near their connection to the open sea.
Diurnal fluctuations in salinity are only apparent in the tidal flat and at the heads of the tidal
channels. Sites of extreme fluctuations at distal parts of the tidal flats and the creeks are
characterised by massive development of algal mats.
Similar carbonate sediments formed in creeks could be recognised in the fossil record by the
predominance of pelletal carbonate facies (pelmicrite) becoming finer landward and
surrounded by supratidal, anhydrite-bearing sabkhas. Also the distribution pattern of the
biofacies, recognizable through various organic structures (burrows, invertebrate fossil
assemblages, stromatolites), can be useful indicators for such geographical settings.