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Paleoclimate reconstruction based on the timing of speleothem growth and oxygen and carbon isotope composition in a cave located in the rain shadow in Israel |
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| Authors: | Anton VaksMiryam Bar-Matthews Avner AyalonBettina Schilman Mabs GilmourChris J Hawkesworth Amos FrumkinAaron Kaufman Alan Matthews |
| Institution: | a Geological Survey of Israel, 30 Malchei Israel Street, Jerusalem 95501, Israel b Department of Earth Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK c Department of Earth Sciences, The University of Bristol, Bristol, UK d Department of Physical Geography, The Hebrew University of Jerusalem, Jerusalem 91905, Israel e Department of Environmental Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel f Department of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem 91905, Israel |
| Abstract: | High-resolution 230Th/234U ages and δ18O and δ13C compositions of speleothems in Ma’ale Efrayim Cave located to the east of the central mountain ridge of Israel enable us to examine the nature of the rain shadow aridity during glacial and interglacial intervals. Speleothem growth occurred during marine glacial isotopic periods, with no growth during the two last marine isotope interglacial intervals and during the peak of the Last Glacial Maximum. This contrasts with speleothem growth in caves located on the western flank of the central mountain ridge, in the Eastern Mediterranean semiarid climatic zone, which continued throughout the last 240,000 yr. Thus, during glacial periods water reached both sides of the central mountain ridge. A comparison of the present-day rain and cave water isotopic compositions and amounts at the Ma’ale Efrayim Cave site with those on the western flank shows that evaporation and higher temperatures on the eastern flank are major influences on isotopic composition and the lack of rainfall. The δ18O and δ13C profiles of the speleothems deposited between 67,000 and 25,000 yr B.P. match the general trends of the isotopic profiles of Soreq Cave speleothems, suggesting a similar source (eastern Mediterranean Sea) and similar climatic conditions. Thus, during glacial periods the desert boundary effectively migrated further south or east from its present-day location on the eastern flank, whereas interglacial periods appear to have been similar to the present, with the desert boundary at the same position. The decrease in overall temperature and a consequent reduction in the evaporation to precipitation ratios on the eastern flank are viewed as the major factors controlling the decay of the rain shadow effect during glacial periods. |
| Keywords: | Speleothems δ18O δ13C Paleoclimate Eastern Mediterranean Rain shadow Effective precipitation |
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