西天山温泉地区全新世沉积物元素地球化学记录及其古环境意义

Holocene sediment element geochemical records and their paleoenvironmental significance in Wenquan area of western Tianshan Mountains

通过对西天山温泉湿地钻孔沉积物Rb/Sr、Sr/Ca、Ti/Sr、Mg/Ca、Zr/Sr 5种特征元素比值综合分析与对比研究,识别温泉湿地全新世气候变化驱动模式。结果表明:(1)温泉湿地沉积物提供了新疆全新世气候变化的可靠记录,其全新世气候经历了暖干(10300—7700 cal a BP)-暖干向温湿过渡期(7700—7000 cal a BP)-温湿(7000—4200 cal a BP)-温干(4200—2900 cal a BP)-冷湿(2900—81 cal a BP)5个阶段变化过程。(2)与邻近区域其他替代性指标所指示的气候变化相吻合,验证了新疆地区全新世早期暖干、中晚期冷湿的气候变化模式,表明新疆地区全新世气候类似于西风模式。(3)温泉湿地沉积物化学元素比值在7700—7000 cal a BP期间指示的降温过程是8200 cal a BP全球变冷事件的响应;4200—2900 cal a BP期间指示的升温过程或许与3000—2900 cal a BP敦德冰芯反映的全新世次高温事件相关。同时,与周边区域其他替代性指标对比发现,新疆地区逐渐湿润的变化趋势可能是全新世温度降低与降水增加共同作用的结果。

Climate change during the Holocene epoch in the arid Central Asia(ACA)has been one of the re-search hotspots in paleoclimate and global change research communities.Compared with the Asian monsoon re-gion,the history of the change in humidity and the combination of moisture-temperature in the ACA region in the Holocene epoch are still controversial.In this study,we present the results of sediment element geochemical re-cords taken from the Wenquan wetland of western Tianshan Mountains in Xinjiang,China.The core was collect-ed in September 2017 using a Russian peat corer.The dated AMS 14C ages were calibrated to calendar years be-fore present using the IntCall3 calibration dataset.Concentrations of Rb,Ti,Sr,Zr,Mg,and Ca were determined using an inductively coupled plasma atomic emission spectrometer,and the error of parallel analysis was<±5%.Holocene environmental evolution was reconstructed using the Rb/Sr,Sr/Ca,Ti/Sr,Mg/Ca,and Zr/Sr chemical el-ement ratios.Through comprehensive analysis of the climatic and environmental indicators of the five ratios,and contrastive analysis with adjacent areas,this paper provides a useful information for a better understanding of the Holocene moisture-temperature relationship,and to identify patterns that drove the Holocene climate change in the Wenquan wetland.The results show that the Wenquan wetland is able to provide a reliable record of the Holo-cene climate change in Xinjiang.Based on analyses of the chronology records,the five element ratios reveal that the climate of the Wenquan wetland region during the last 10300 cal a BP has experienced a warm dry period(10300-7700 cal a BP),a warm dry period to warm wet period(7700-7000 cal a BP),a warm wet period(7000-4200 cal a BP),a warm dry period(4200-2900 cal a BP),and a cold and wet period(2900-81 cal a BP).This process is consistent with the climate change records and model simulations of neighboring regions,which verifies the warm/dry and cold/wet climate change patterns in Xinjiang during the Holocene.This indicates that the climate environment change in Xinjiang is similar to the westerly domination pattern and exhibits an“out-of-phase”relationship with the pattern of monsoonal evolution in eastern monsoonal Asia.Moreover,the cooling process indicated by the ratio of the core elements in the Wenquan wetland sediments during 7700-7000 cal a BP may correspond to the global cooling event of 8.2 cal ka BP.The warming process observed during 4200-2900 cal a BP may be consistent with a Holocene sub-high-temperature event reflected by Dunde ice cores from 3.0 to 2.9 cal ka BP.In recent years,an increasing number of researches has concentrated on ACA region mois-ture changes and the possible mechanisms responsible for these changes,based on a westerly dominated regime.Compared with other proxy indexes in the surrounding region,it was found that the trend of gradual wetting in Xinjiang may be the result of the combined effect of decreasing temperature and increasing precipitation in the Holocene.