Biogenic Assemblage and Hydrodynamic Settings of the Tidally Dominated Reef Platform Sediments of the Zanzibar Channel
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Date
2002
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Abstract
The biogenic assemblage and hydrodynamic settings of the tidally dominated reef
platform sediments (TDRPS) east of the Zanzibar channel were investigated in order to
characterise the carbonate sediments. Benthic foraminifera were found to be the most important
group, both in terms of average abundance (> 60 % by weight) and also in terms of spatial
distribution, with common occurrence in all sediments samples. Pelecypods, with an average
abundance of 8 % were slightly less widely distributed. The remaining groups occurred at
lower average abundance and less frequently in the sediments. Current measurements indicated
that the maximum current speed is higher during spring than during neap tides. The direction is
phase-dependent with flood tidal current flowing from the northern and southern tips of the
island towards Zanzibar town. The ebb current flows in the opposite direction. The
geomorphological setting of the carbonate platforms together with the present investigation of
the currents and biogenic assemblage of the clastic sediments permits us to subdivide the reef
platform area in the Zanzibar Channel into two sub-provinces: the northern and the southern. The
northern sub-province contains significantly higher proportion of lithogenic particles, pelecypods,
gastropod and ostracods than the southern sub-province. Some samples from the southern subprovince
had significantly higher proportion of corals, than those from northern sub-province.
Description
http://www.oceandocs.org/handle/1834/32
Keywords
Biogenic assemblage, Hydrodynamics, carbonate sediments,, Reef platforms, Zanzibar channel
Citation
Wannas, K.O., Mahongo, S.B. and Shaghude, Y.W., 2002. Biogenic assemblage and hydrodynamic settings of the tidally dominated reef platform sediments of the Zanzibar Channel.