PALEOENVIRONMENTAL EVENTS DURING THE LAST 13,000 YEARS IN THE CENTRAL RED SEA AS RECORDED BY PTEROPODA

A high-resolution record was obtained by investigating a sedimentary sequence from two cores taken in the central Red Sea (R/V Meteor cruise 5, leg 2). The numerical variations between nonmigratory and migratory pteropods and their stable isotopic record were studied together with variations in the carbonate and total organic carbon content in order to estimate changes in the structure of the water column during the last 13 kyr. The results indicate the existence of a highly stratified water column during deglaciation and early Holocene (13-8.5 ka). During this period the depth of the mixed layer varied between less than 50-100 m at most, and productivity was markedly reduced in comparison to the recent situation. The intermediate and deep water were constantly highly depleted in oxygen. A pronounced Younger Dryas event was recognized at 10.4 ka which coincides with an arid phase on the border land. The oxygenation of the intermediate water improved remarkably after 7.5 ka and peaked during the period between 4.6 and 2.0 Ka. During this period the mixed layer reached its present depth and the productivity which was maximal during middle Holocene attained present level during the last 4.6 kyr.