Vegetation and climate changes in the South Eastern Mediterranean during the Last Glacial-Interglacial cycle (86 ka): new marine pollen record

Abstract

The Eastern Mediterranean, located at the meeting between the Mediterranean vegetation of the Eurasian continent and the desert vegetation of the Saharan-Arabian desert belt, is ideal for tracking changes in regional vegetation as function of climate changes. Reconstruction of these changes in the South Eastern Mediterranean during the last 86 ka is based on a palynological record, from deep-sea core 9509, taken by R/V Marion Dufresne, off the southern Israeli coast. The chronological framework is based on the correlation of δ 18O records of planktonic foraminifera with the high resolution, well-dated U-Th speleothem record from the Soreq Cave, Israel and the occurrence of sapropel layers. Several cycles of humid/dry periods were documented during the last 86 ka. The record starts with the moderate humid and warm sapropel S3 marking the end of Marine Isotope Stage (MIS) 5. The climate during the Last Glacial period (75.5–16.2 ka) was cold and dry, with low Arboreal Pollen (AP) levels, and high values of semi-desert and desert vegetation (e.g. Artemisia - sagebrush). The driest and coldest period during the last 86 ka corresponds to MIS 2 (27.1–16.2 ka), characterized by the lowest tree cover along the sequence and the dominance of steppe vegetation. Some slightly more humid fluctuations were identified during the period of 56.3 and 43.5 ka with its peak between 56.0 and 54.4 ka. The most pronounced climate change started at the beginning of the Deglaciation (16.2–10 ka) and continued throughout the Holocene (last 10 ka), notwithstanding some short fluctuations. High AP levels were dominated by Quercus callipprinos (evergreen oak), suggesting that the Mediterranean forest was more extensive in the area and the climate was wet. Sapropels S3 and S1 were clearly recognized here by the high concentrations and good state of preservation of pollen because of the development of anoxia in the bottom water that may be related to more extensive Nile discharge coinciding with high insolation values at 65° N and enhanced westerlies activity. Another wet and warm event is the Bölling-Allerød (14.6–12.3 ka). Cold and dry spells identified by low AP and high steppe elements correspond with Heinrich Events H2–H6, the Last Glacial Maximum, Younger Dryas and the 8.2 ka event. Similar pattern of vegetation trends was observed also in Lake Zeribar Western Iran, Tenaghi Philippon North East Greece and the Alborán Sea. There is a clear general difference between the South East Mediterranean and western and central Mediterranean because of W-E climatic moisture gradient reflected in the dominance of Mediterranean maquis, lower tree population and higher steppe vegetation in the South East Mediterranean.