陆生蜗牛记录的新疆全新世气候变化历史

新疆全新世气候变化历史已有大量研究，但关于该区域的干湿变化模式是“西风模式”还是“季风模式”，尚存不同观点。现有研究主要从湖泊沉积物、泥炭、黄土、石笋、冰芯等地质载体中，提取物理或地球化学代用指标，开展古气候重建研究，而对生物记录(除了孢粉)和古气候参数定量重建(如温度)研究还有待加强。前期考察发现，新疆黄土沉积中良好地保存着大量蜗牛化石，而至今对此尚无系统研究报道。因此，本项目将以黄土中环境变化的“指示性动物”—陆生软体动物蜗牛为研究对象，在南疆和北疆采集四个全新世黄土剖面中的蜗牛化石，利用蜗牛壳体和全样有机质AMS 14C数据建立年代框架，开展蜗牛生物量(干湿指标)、蜗牛壳体团簇同位素(∆47，温度指标)研究，从而探讨新疆全新世温度和干湿变化历史及其可能的驱动因素。同时，基于蜗牛壳体∆47和氧同位素，重建形成蜗牛壳体的水的氧同位素变化历史，并尝试探讨新疆全新世水汽来源的可能变化。

Numerous efforts have been conducted to reveal the Holocene climate history in Xinjiang, however, there are still different opinions concerning the pattern of moisture variations, i.e. the ‘westerlies’ or ‘monsoon’ models. Hitherto, studies mainly focused on physical or geochemical proxies, from archives of lake sediments, peat, loess, speleothem, ice core, to reconstruct paleoclimate. More work should be endeavored in studying biological records (except pollen) and quantitative reconstruction of paleoclimate parameters (e.g. temperature). Our preliminary field survey shows that fossil land snail shells (FS) are abundant and well preserved in loess deposits in Xinjiang, but there are no systematic studies on these records so far. Therefore, this work will study land snails, an indicative animal of environmental changes in loess deposits. FS will be collected from four Holocene loess sections in northern and southern Xinjiang, and the age frames will be established using the AMS 14C data of soil organic matter and snail shells. Then snail biomass (moisture proxy) and clumped isotope of FS (∆47, quantitative temperature proxy) will be analyzed. Collectively, the Holocene temperature and moisture history and their possible forcings in the studied region will be discussed. Furthermore, simultaneous determinations of ∆47 and oxygen isotopes for FS will constrain the δ18O of water from which they grew. This will help us further discuss potential water source changes.