History of climate and vegetation in the eastern Mediterranean and the Middle East from the Pleniglacial to the Mid-Holocene

Abstract

Quaternary climates of the Middle East were investigated by reevaluating previous data and by analyzing pollen in radiocarbon-dated sediments. For comparison, assemblages of modern pollen were obtained from desert regions.Chenopodiaceae and Plantago pollen is high in surface samples from Kuwait and S. Iraq. In Jordan pollen of herbaceous dicots is more important probably due to warmer winters which allow growth during the rainy season. In the Rub'al-Khali of Saudi Arabia assemblages are most often dominated by the pollen of Calligonum or Cyperus conglomeratus, characteristic sand-dune plants. In each region low Gramineae pollen reflects the inability of most Gramineae to thrive in regions of severe summer drought. Artemisia, which requires higher precipitation, is also unrepresented.Ecology of the modern vegetation was used to assess pollen fluctuations since 25,000 B.P. The ratio of Chenopodiaceae to Artemisia pollen (C/A) was used to identify moisture trends. Similar C/A curves of pollen diagrams suggest that moisture trends were regional 25,000 to 9000 B.P. with a moist glacial period followed by strong fluctuations after 16,000 B.P.The forest trees of each subregion are shown to be adapted to different climates, explaining their differing responses to similar climatic changes. In the north, glacial-period tree growth was probably curtailed by lack of summer precipitation, while in Iran heavy snow may have been responsible. After 16,000 - 14,000 B.P. aridity would have become a factor, preventing the spread of forests at most sites until after 9000 B.P., when summer precipitation apparently was initiated.Peat deposits which formed about 8000 B.P. in the northern Arabo-Persian Gulf region were high in Gramineae and low in Chenopodiaceae pollen, indicating summer precipitation. Lacustrine sediments of similar age from the Rub'al-Khali, dominated by Chenopodiaceae but relatively high in Gramineae, also indicate summer precipitation. Long-distance pollen types in Pleistocene sediments of the Rub'al-Khali suggest strengthened northwesterly winds during that time.