Continuous pollen diagrams for the last 3.5 m.y. from Israel: Vegetation, climate and correlation with the oxygen isotope record

Several continuous pollen diagrams have been obtained from boreholes penetrating the entire Quaternary sequences of the Hula and Dead Sea lakes in the Jordan Rift Valley, Israel. The Dead Sea served as a terminal base level through this period, thus ensuring a complete, continuous deposition. Volcanic intercalations within the Hula lake sediments permit some control of the absolute datings. A paleoclimatic model for the last 150 k.y., based on better dated sequences, serves as a basis for correlating the Israeli sections with the oxygen isotope records known from the oceans and the Mediterranean. The glacial phases are manifested in Israel by periods of somewhat lower temperatures and higher rainfall, some in summertime; the interglacials are hot and dry, with Saharan conditions prevailing; the interstadials are of the present-day character of a short, rainy winter and a dry, hot, long summer. The first major cooling of the Quaternary in Israel took place some 2.4-2.6 m.y. ago, followed by a series of alternating wetter and drier phases corresponding quite well to changes in the global ice volume expressed by the oxygen isotope curves. It seems however that some successions of the glacial phases are grouped in Israel into longer wetter periods, with the interglacials manifested as interstadials. A similar case is seen for some of the interglacials successions, with glacial phases as interstadials. A possible explanation for the difference between the continental and the ocean records may lie in the distribution of the global ice volume. Differences in the accumulations of ice at the Arctic and Antarctic regions during some of the glacial phases could explain the extent of a glacial period on land while not being apparent from the oxygen isotope records, and vice versa for the interglacials. Thus a well-developed ice cap on Antarctica may cause only a minor glaciation in the northern hemisphere, but be recorded as a full glacial in the oceans.