Morphology and sediment distribution of the Zanzibar Channel

A morphological study conducted on the Zanzibar Channel shows that the chan nel consist of a "central deep" of about 30 to 40 m in depth, which is flan ked to the east by irregular and steep coral platforms. On the other hand, the western flank is rather smooth and gentle. The morphological exceptions are the patch reefs that disturb the otherwise smooth morphology. The morp hological differences between the eastern and western flanks are interprete d to be partly caused by differences in the tectonic development of the two areas. To a large extent, terrigenous input of sediments from the mainland through River Ruvu and Wami controls the sediment distribution patterns on the sea bottom in the western part of the channel. This is demonstrated by the distribution of carbonates as well as the grain-size parameters. The a bsence of any major rivers on Zanzibar means that no major transport mechan ism is available for terrigenous material in the east. The high carbonate c ontent on the eastern side of the Channel (> 70%), consists of biogenic as well as erosional material from coral systems and Pleistocene reefs.