Paleoecological Relations of Foraminifera in a Desert‐Enclosed Sea ‐The Gulf of Aqaba (Elat), Red Sea

摘要

Abstract.Planktonic and benthonic foraminifera live in the desert‐enclosed, hypersaline and oligotrophic Gulf of Aqaba and northernmost Red Sea near the edge of their ecological tolerance. Marked changes in foraminiferal abundance patterns in the past, resulting from hydrological shifts related to global climatic fluctuations, facilitate a high‐resolution ecostratigraphic subdivision of deep‐sea records covering the last 150,000 years. Of particular significance are the foraminiferal plankton/benthos ratios, the presence/absence pattern of such species asGlobigerinoides sacculifer, as well as the frequency variation ofGlobigerina bulloules‐falconensis, Buliminacea, Miiiolaceaand various “rotaliform” species. Paleoceanographic interpretation of the shifts in assemblage composition and of stable oxygen isotope data obtained on planktonic foraminifera and pteropods indicates that during glacial intervals ‐ because of global cooling, lowered sea‐level and reduced water exchange at the straits of Bab‐el‐Mandeb ‐ the temperature of the upper waters fell by about 4–6oC (to 15–17oC), salinity rose by about 10o to more than 500while residence time of the water became longer and the input/output ratio of nutrients became higher. As a consequence, fertility of the photic zone was higher, the organic content of the sediments increased and oxygen levels in the deep basin became reduced. Thus, sea level‐oscillations and strait‐dynamics played a major role in the foraminifera