Abstract:

A detailed study on the microfacies analysis and depositional environments of Tertiary sedimentary rocks exposed in Socotra Island were conducted. The investigation was based on fifty four samples collected from five stratigraphic sections and included four formations from base to top are Umm er Radhuma (Paleocene - Eocene), Dammam (Eocene), Aydim (Upper Eocene) and Mughsayl (Oligocene-Miocene). These rock units are mainly composed of carbonates. The petrographic study of unstained and stained thin sections have been carried out to investigate its sediment logy, microfacies associations and depositional environments. According to Dunham classification of limestone (1962), eight carbonate facies were distinguished. They are Mudstone, Dolomitic mudstone/wackestone, Fossiliferous wackestone, Packstone, Marly limestone, Sandy limestone, Reefal limestone, Brecciated wackestone/packstone and Chalky limestone. The recognized microfacies associations were correlated with the standard microfacies associations (SMA) which were supposed by Wilson (1975) and Flügel (1982 and 2005). The detailed microfacies analysis show that the studied rock units were deposited within the shallow marine environment except the upper parts of Mughsayl Formation, which were deposited in a slightly deep marine environme nt.

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