Terrestrial stable isotope records of Late Quaternary paleoclimates in theeastern Mediterranean region

Terrestrial stable isotope records (C-13/C-12, O-18/O-16, and D/H ratios) o f late Quaternary paleoclimates in the eastern Mediterranean region are rev iewed. Significant paleoclimatic reconstructions come from a variety of iso topic studies. Paleogroundwaters, although they cannot be accurately dated, show oxygen and hydrogen isotopic compositions highly depleted in heavier isotopes compared to modern meteoric waters in arid regions of southern Isr ael, Sinai and northeastern Africa and attest to a major difference in clim atic regime some time in the Pleistocene. Th-U dating of land snails showin g a similar O-18 depletion indicates ages of 100,000 yr and greater than or equal to 300,000 yr for this climatic regime in the Negev Desert of southe rn Israel. Carbon isotope records of organic matter have not been studied e xtensively in the region, except for the record of Holocene land snails in the Negev. These document a southward shift in pure Ca plant communities in the middle and early Holocene relative to their present distribution and i ndicate wetter conditions at those times. An oxygen isotope curve for the H olocene, reflecting changes in the isotopic composition of precipitation, h as been established from analysis of carbonate materials-land snail shells and speleothems. The curve indicates a depletion of ca. 2 parts per thousan d, in O-18 centered around 7000 cal yr sp, with modern levels being reached by 5000 cal yr sp. Carbon isotope analysis of soil carbonates in paleosols developed in loess in the Negev show the existence of dramatic north-south climatic gradients at the times of formation of the soils (ca. 13,000, 28, 000, and greater than or equal to 37,000 C-14 yr BP), as occur also today d ue to the waning influence of Mediterranean to the south. Some isotopic met hods, widely used in other regions, have received little or no attention in the eastern Mediterranean region. These include oxygen and hydrogen isotop es in wood, phosphate oxygen and organic carbon in bones and teeth, and car bon in soil organic matter. (C) 1999 Elsevier Science Ltd. All rights reser ved.