Reconstruction of the sedimentary environment of Nayband Bay during the last 1600 years; implications for relative sea level and climate change in Northern Persian Gulf

This paper reconstructs the relative sea level (RSL) and palaeoclimate of the northern coasts of the Persian Gulf (PG) during the last 16 centuries using physiochemical and ecological proxies from a radiocarbon-dated sediment core from the Nayband Bay (NB) estuary. The results show that between 1600 and 1150 cal yr BP, the NB was a marine lagoon with high river discharge, indicated by low organic matter content sandy silt sediments, high foraminiferal abundance (7900 tests per 10 cm³), and balanced agglutinated and hyaline taxa. During the Medieval Warm Period, the NB became a shallow lagoon, and consequently, a playa with high eolian input and low river discharge formed in the studied site that extended until 500 cal. yr BP. This condition is indicated by sediment finning trend, elevated magnetic susceptibility in sandy mud sediments, and low foraminiferal frequency dominated by hyaline taxa (mainly opportunist Ammonia beccarii). During the stillstand condition corresponding to 500–250 cal yr BP, the evolution of tidal channels in the area provided a platform for developing the upcoming mangrove habitat. In the last 250 years, RSL in the north of NB dropped enough to create a low-energy intertidal flat sheltered by a sandbar, which allowed mangrove growth. We conclude that the ecological and sedimentological evolution of the shallow marginal NB is mainly driven by eustatic RSL decline superimposed by local uplift. We suggest that the current orbitally-induced increasing insolation trend, enhanced by human-induced global warming, could increase aridity in the PG and the southern Zagros.