Holocene sea levels at the Gulf of Aqaba, northern Red Sea

Abstract

A new relative sea level (RSL) curve is presented for the Holocene Gulf of Aqaba, northern Red Sea. The curve is based on U–Th ages of corals retrieved from leveled fossil reefs comprising the Tur Yam Terrace at the shore of the city of Elat, Israel and the Aqaba reef terraces, Jordan, located respectively east and west of the northern tip of the gulf. Both terrace tops are submerged under high tide and subaerial at low tide. The fossil corals are in growth position between two beachrock units. The corals comprise 100% aragonite, show pristine textures with no secondary aragonite cements and yield initial 234U/238U activity ratios of 1.146 ± 0.004, similar to the values of live corals and modern Gulf of Aqaba (GoA) waters. Sixteen U–Th ages of corals from the Tur Yam Terrace span the time interval of 6.8 to 5.5 ka, and are ordered along the growth direction of the terrace. Detailed mapping of the terrace, the distribution of corals’ genera and the order of their ages on the terrace, suggest that the exposed terrace was the back reef/lagoon zone, a very close to shore environment of a fringing reef. Identification of this reef zone was based on a detailed ecological study that we conducted on the Nature Reserve Reef (NRR), a modern fringing reef located several hundred meters to the south. A morpho-tectonic analysis of the Elat shore indicates that the Tur Yam Terrace lies on top of the footwall of the active Elat Fault and has remained at its original level, with negligible vertical shift. Thus, it appears that during the time interval of formation of the Tur Yam corals, sea level at GoA reached a maximum stand that was 1–2 m above the modern elevation. A similar figure is shown by Mid-Holocene corals from the Aqaba fossil reefs and shore indicators from the Red Sea. The relative sea level (RSL) curve deduced from the Gulf of Aqaba corals and from the Red Sea indicators resembles those of precisely-dated stable reefs off west and east Australia and a few other well dated reefs in the Indo-Pacific. This similarity calls for coeval response of the Indo-Pacific oceans to ice melting during the early to mid- Holocene, and a similar pattern of decline to the present level during the late Holocene. Such a coeval rise of distant parts of the Indo-Pacific oceans is consistent with dominance of melt waters releases over the oceans with minor effects of all other “sea level drivers".