岗日嘎布玉东曲末次冰消期冰川演化及其 ¹⁰Be 暴露测年研究

The Last Glacial Termination marks the transition from the global Last Glacial Maximum(LGM)to the interglacial Holocene. This transition is the most striking climate reorganization on Earth, over the past 100 ka. The global LGM termination has been widely regarded as nearly synchronous around the world, yet, proposed mechanisms behind this synchroneity remain contentious. Mountain glaciers in the mid-latitude regions, such as those in the Tibetan Plateau(TP), are highly sensitive to climate change, and hence can provide invaluable information for clarifying this conundrum. However, glacial chronologies as regards the LGM termination remain extremely limited in the TP and its surrounding mountains. This impedes a full understanding of potential climatic mechanisms forcing glacial fluctuations in the vast TP. In this study, we examined the lateral moraine remnants formed near the valley-mouth of the Yudongqu valley, Gangrigabu Range, southeast TP, using ¹⁰Be surface exposure dating. Apparent ¹⁰Be exposure-ages(n=14)obtained from four out of six lateral moraine relics there range from(13. 3±1. 0)ka to(19. 3±1. 4)ka. On the basis of statistical test, we identified six potential outliers with the aid of probability density function plots. We then examined whether the clustering of remaining ¹⁰Be exposure-ages were merely caused by measurements or not using the reduced chi-square test and P value. After excluding the potential outliers, the two geomorphologically younger moraines were robustly dated to(17. 0±0. 5)ka and(18. 4±1. 0)ka, representing two glacial culminations that correspond well to the LGM termination. We then compared the ¹⁰Be-based moraine chronologies with climatic proxies, such as Northern Hemisphere summer solar insolation, ice-volume equivalent sea level, stalagmite δ¹⁸O record, chironomidinferred mean July temperature record, sea surface temperature(SST), and atmospheric CO₂ concentrations. We conclude that the two glacial events identified in the Yudongqu Valley were in response to changes in summer air temperature connected with SSTs in the Indo-Pacific Warm Pool(IPWP).