A study of the sedimentary characteristics and geochemistry of Gorsuzan estuary deposits in the north of the Persian Gulf, Hormozgan Province, Iran

Abstract

The Gorsuzan estuary, located in central Bandar Abbas, southern Iran, was studied to understand its sedimentary characteristics. Eight surface sediment samples were collected and analysed for grain size, heavy minerals, XRD, XRF, petrography, and optical mineralogy. Results indicate that sediments are mainly sandy, with gravel found mostly in the northern part and minor silt and clay in the northern and middle parts. Particle size generally decreases from the estuary’s origin towards the coast, reflecting the influence of marine processes and wave action. Sediments range from sandy gravel to mud-gravel sand, with gravel particles showing variable sphericity (low to high) and roundness (sub-angular to semi-rounded). Petrographic studies revealed three microfacies: limestone mudstone, bioclastic wackestone, and calcareous sandstone, all attributed to the Aghajari Formation (Middle Miocene to Middle Pliocene) based on fossil content and grain size. Fine sediments contain quartz, dolomite, and minor amounts of albite, orthoclase, muscovite, chlorite, and calcite. Autogenic minerals like calcite and dolomite, as well as transition minerals such as muscovite, originate from calcareous marl deposits of the Aghajari Formation. Heavy minerals identified include oligisto, garnet, and zircon, which likely derive from igneous and metamorphic rocks of the Hormuz series. Geochemical analysis shows SiO₂ and CaO as the dominant oxides. Source rock investigation classifies the deposits as litharenite, indicating immature to medium maturity under semi-arid climatic conditions with low to medium chemical weathering.