Microfacies and cyclicity of two Paleo Lagoons in Oman – potential insight into Last Interglacial coastal evolution?

The last interglacial (around 125 Ma, MIS 5e) is the youngest timeframe that produced higher global sea level than observed nowadays and thus offers critical insight into coastal dynamics under future climate-change- and sea-level scenarios. Despite a global effort to record last interglacial shorelines, the Indian Ocean remains understudied in this respect. The northeastern coastline of Oman, from Muscat to Ras Madraka, shows seven shallow marine sedimentary successions located up to 4 m above mean sea level in areas that are tectonically stable. The sediments that include coral reefs, beachrocks, lagoonal and sabkha deposits are studied regarding their initial relationship to mean sea level and age to establish sea-level index points. Since radiocarbon dating has been ineffective, as deposition ages exceed the range of ¹⁴C methods, optically stimulated luminescence dating presents a promising avenue for chronological data. Special emphasis is placed on two lagoonal successions near Al Haddah and Ras Ru’ays. While the outcrop at Al Haddah shows more evaporitic sabkha deposits overlain by alluvial successions, Ras Ru’ays coastal cliff presents a choked lagoonal system overridden by a coastal barrier, before alluvial sedimentation sets in. As both outcrops record cyclic deposition that are potentially controlled by transregional processes, they allow to understand Late Pleistocene coastal evolution in more detail. In a multiproxy approach, macro- and micro facies analysis, as well as geochemistry, are applied to link cyclicity within the two lagoonal systems and unravel likely controls.