新疆地区黄土-古土壤序列石英释光信号特征对物源的指示

Arid central Asia was mainly influenced by the Westerlies circulation. The paleoclimate evolution information of arid central Asia was documented in the loess-paleosol sequence. The study of provenance in this area is helpful to reconstruct the evolution history of desertification and atmospheric circulation in this area. However, the study of provenance in this area is focused on the spatial location of dust sources. The study on provenance changes between interglacial period and glacial period in orbital scale of continuous loess-paleosol sequence is rarely discussed in Xinjiang area. Big differences exist in climate evolution history between the Westerlies-dominated region Monsoon-dominated region. For instance, the out-of-phase relationship of precipitation in interglacial period between these two areas. To understand the paleoclimate evolution history of Xinjiang area, it is necessary to comprehend the dust source information of a loess-paleosol sequence. The luminescence characteristics of quartz grains can reflect sediment provenance and transporting process. In this study, the typical loess-paleosol profiles from the northern of Tianshan Mountains and in Yili area of Xinjiang were chosen to investigate the provenance of interglacial-glacial loess-paleosol layers, including the last interglacial-glacial cycles (S1-L1-S0) and the differences in the interglacial periods(S1-S0) in light of the luminescence characteristics of quartz signals (signal sensitivity and contribution of different signal compositions).

主要受西风环流影响的中亚干旱区陆相黄土-古土壤序列沉积中记录了西风区环境演变的关键信息。对中亚干旱区物源的研究有助于了解亚洲内陆干旱化过程和重建大气环流演变历史，但目前该区物源的研究集中在空间尺度源区区位的厘定，对于轨道尺度间冰期-冰期旋回沉积物物源变化研究很少。西风区与季风区气候演化存在很大差异，如间冰期内两个区域湿度变化存在错位相等。要理解西风区气候不同于季风区的演变历史，对其黄土-古土壤序列沉积物源的研究至关重要。黄土中主要矿物石英的释光信号特征可以反映沉积物物源和搬运历史。本研究拟选择新疆天山北麓和伊犁河谷地区末次间冰期以来典型黄土-古土壤剖面，利用石英的释光信号特征（信号灵敏度和不同组分贡献率）来区分轨道尺度间冰期-冰期（S1-L1-S0）以及间冰期之间（S1-S0）风成黄土的物源差异。

本项目由于疫情的影响，虽未按照原计划进行，但仍然取得了一定进展。成果主要体现在释光年代方法学和以年代学为基础的古环境变化对古人类活动的影响两方面的进展。研究区域主要集中在河西走廊与青藏高原地区。在释光年代方法学方面，一是对青藏高原的碳酸钙温泉沉积进行研究，以方解石矿物作为测年材料，对方解石的热释光特征和测年潜力进行了探究，并对钙华的辐射因子α系数进行了厘定；二是对已有新疆黄土样品中较老样品（＞70ka）的钾长石测年可靠性进行了探究，通过一系列条件实验证明钾长石多步法（MET-pIRIR250）和pIRIR（200，290）对于老的风成沉积样品更为可靠。古环境变化和人类活动方面：1）对敦煌附近的西沙窝（XSW）剖面年代学进行研究，以光释光方法结合碳十四测年方法对石英样品进行测试，建立了该剖面的年代学序列，结合沉积物粒度数据，确定了西沙窝剖面所在的丝绸之路上发生两次沙漠化事件的时间，并以此展开沙漠化事件对历史上丝路贸易和文明发展的影响。2）对青藏高原钙华上的手脚印研究进行综述，评估了20万年前的手脚印创作者的认知水平，并阐述了手脚印艺术研究的重要意义。本项目成果主要表现为对重要科学问题的理解、基本分析方法的突破，有重要的科学价值。