NOAA/WDS Paleoclimatology - Sibaki Cave, Iran U/Th Age Model and Stable Isotope Data from the Last Glacial Maximum to the Early Holocene

Glacial periods and their terminations are useful for assessing the full scale of natural climate variability in the diverse climate regions of West Asia (i.e. deserts, mountains, alluvial plains, coastal zones). In this study, we report the first stalagmite stable isotope (d18O and d13C) records from the southern Zagros Mountains in southwest Iran. The records partially span the period from the Last Glacial Maximum (LGM) to the early Holocene, 24.2–9.6 thousand years before the present. The southwest Iran stalagmite d18O and d13C records indicate that climate and environment in the area differed substantially between the LGM and early Holocene. High stalagmite d13C values are found at the LGM (7‰ greater compared to the early Holocene), and are attributed to sparse vegetation and reduced soil bio-productivity, and possibly a greater degree of prior calcite precipitation in the epikarst, as a result of a cold and dry climate. Stalagmite d18O values are also high at the LGM (4‰ greater compared to the early Holocene), and are attributed to lower temperatures (larger water–calcite isotope fractionation) and higher d18O values of the moisture sources (Mediterranean and Red Seas). Through the deglaciation, stalagmite d18O, d13C and/or growth features coincide with the North Atlantic Heinrich Stadial 1, the Bølling–Allerød warm period and the Younger Dryas cold event, supporting a relationship between southern Zagros climate and the North Atlantic millennial events.

冰期及其终止事件是评估西亚（涵盖沙漠、山地、冲积平原与海岸带等多样气候区）自然气候变率完整幅度的有效研究载体。本研究首次报道了伊朗西南部扎格罗斯山脉南部的石笋（stalagmite）稳定同位素（stable isotope，δ¹⁸O与δ¹³C）记录，该记录的时间跨度部分覆盖了末次冰盛期（Last Glacial Maximum, LGM）至早全新世的24.2~9.6千年时段，即距今24.2至9.6千年。伊朗西南部石笋的δ¹⁸O与δ¹³C记录显示，该区域气候与环境在末次冰盛期与早全新世之间存在显著差异。末次冰盛期的石笋δ¹³C值较高（较早全新世偏高7‰），这被归因于寒冷干燥气候下的植被稀疏、土壤生物生产力降低，以及表层岩溶带中更强的前期方解石沉积作用。末次冰盛期的石笋δ¹⁸O值同样较高（较早全新世偏高4‰），这被归因于更低的温度（更大的水-方解石同位素分馏效应）以及水汽源区（地中海与红海）更高的δ¹⁸O值。在冰消期过程中，石笋δ¹⁸O、δ¹³C及/或生长特征与北大西洋海因里希冷期1、博令-阿勒罗德暖期以及新仙女木冷事件相吻合，这支持了扎格罗斯南部气候与北大西洋千年尺度事件之间存在关联的结论。