Geochemical and mineralogical study of calcareous marine terraces of the Quaternary in Qeshm Island

Qeshm is the largest island in the Persian Gulf. It is expanded along the coast and located at the furthest southeast of Zagros sedimentary-structural unit under the Bandar Abbas flat and it is a part of it. The stratigraphic units in this island are Hormoz Series, Mishan Formation, Aghajari Formation and Quaternary deposits. The calcareous marine terraces of this island are the important part of deposits assign to the Quaternary period. These deposits indicate the relative variance of sea level in Pleistocene and Holocene. Petrogarphical studies on the 40 samples collected from the terraces led to identification of 10 microfacies including mudstone, benthic foraminifera wackestone, oyster packstone, bioclastic mudstone, bioclastic wackestone, bioclastic packstone, bioclastic packstone- grainstone, oolitic packstone, intraclastic packstone and sandy bioclastic packstone. The facies show characteristics of 5 various depositional conditions including: supratidal, intertidal, lagoon, barriers and abundant tidal channel. Based on sediment analysis the environmental condition of inner ramp is indicated by the quantity of tidal channels of these sediments. Sediments are consist of these minerals: carbonates, quartz, clay, plagioclase, halite and clay minerals (chlorite and illite). These minerals show the entrance of the deposits from land by fluvial flows and distribution by marine flows. Geochemical studies of calcareous marine terraces indicate low salinity levels, the semi- reducing to reducing conditions the growth of the forming the terrace and primary composition of the deposits of bio calcite of magnesium.