关键词: 湿地, 元素比值, 全新世, 气候环境, 区域对比, 新疆

Abstract:

Climate change during the Holocene epoch in the arid Central Asia (ACA) has been one of the research hotspots in paleoclimate and global change research communities. Compared with the Asian monsoon region, 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 records taken from the Wenquan wetland of western Tianshan Mountains in Xinjiang, China. The core was collected in September 2017 using a Russian peat corer. The dated AMS ¹⁴C ages were calibrated to calendar years before 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 element 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 Holocene 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 moisture 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.

Key words: wetland, element ratio, Holocene, climatic environment, regional comparison, Xinjiang