Mid-Holocene stable isotope record of corals from the northern Red Sea

We present a study based on X-ray chronologies and the stable isotopic comp osition of fossil Porites spp. corals from the northern Gulf of Aqaba (Red Sea) covering the mid-Holocene period from 5750 to 4450 C-14 years BP (befo re present). The stable oxygen and carbon isotopic compositions of five spe cimens reveal regular annual periodicities. Compared with modern Porites sp p. from the same environmental the average seasonal delta(18)O amplitude of the fossil corals is higher (by ca. 0.35-0.60 parts per thousand), whereas annual growth rates are lower (by ca. 3.5 to 2 mm/year). This suggests str onger seasonality of sea surface temperatures and increased variability of the oxygen isotopic composition of the sea water due to changes in the prec ipitation and evaporation regime during the mid-Holocene. Most likely, summ er monsoon rains reached the northern end of the Red Sea at that time. Aver age annual coral growth rates are diminished probably due to an increased i nput and resuspension of terrestrial debris to the shallow marine environme nt during more humid conditions. Our results corroborate published reports of paleodata and model simulations suggesting a northward migration of the African monsoon giving rise to increased seasonalities during the mid-Holoc ene over northeastern Africa and Arabia.