COASTAL FORAMINIFERA FROM THE IRANIAN COAST OF MAKRAN, OMAN SEA (CHABAHAR BAY TO GAWATER BAY) AS AN INDICATOR OF TSUNAMIS

Notable coastal inundation associated with the 2004 Indian Ocean and 1945 Makran tsunamigenic-earthquakes highlights the risk of tsunamis to the Makran coast and other adjacent coastlines. Paleotsunamis deposits preserved in the geologic record provide a means of extending the record of tsunamis from several hundreds of years to several thousands of years, capturing both the frequent and infrequent, but higher magnitude events. Foraminifera have been used as indicators of paleotsunamis because their allochthonous tests, found in low-energy environments such as in coastal lagoons, ponds, and marshes, indicate marine overwash. Most of these studies have been conducted in temperate regions, with only a few in tropical regions, and even fewer in arid environments. In this study, we constrain the modern distributions of foraminifera from coastal Iran so that they may be used to identify and interpret paleotsunami deposits in the geologic record. Chabahar Bay to the middle part of the Gawater Bay lies on the Iranian coast of Makran, on the northern coast of the Gulf of Oman. The Iranian coast of the Oman Sea consists of three major sub-environments: coastal platforms (terraces), sandy beaches, and mud flats (deltas and estuaries). We collected surface sediment samples from sixteen sites along the Iranian coast of the Oman Sea from Chabahar Bay to the border of Iran and Pakistan. We selected locations that were impacted by the 1945 Makran tsunami. These include the intertidal, subtidal, and supratidal environments of the coastal platforms, sandy beaches, and mud flats. Foraminifera obtained from these locations are dominated by intertidal (Ammonia spp., Elphidium spp.) and subtidal (Amphistegina spp.) species with minor abundances of planktics. Cluster analysis was used to determine two foraminiferal assemblages within the Makran coastal zone: subtidal and intertidal. Samples collected from subtidal locations are characterized by high abundances of individuals that are iron stained, while samples collected from intertidal locations are dominated by corroded (e.g., edge rounded and pitted) individuals. Characterizing modern distributions of foraminifera along the Makran coast of Iran will aid in ascribing sediment provenance to older overwash deposits previously identified at this location.