Sedimentological, geochemical, micropaleontological and palynological sediment record of TT Lake, southern-central Tibetan Plateau

A sedimentological, geochemical, micropaleontological, and palynological study of a lacustrine sediment record from the small TT Lake (southern-central Tibetan Plateau) shows that the background sedimentation was frequently interrupted by event-related deposits. These event-related deposits are interpreted as the result of hydrologic events that are triggered by above-average precipitation events. In total, 11 events were recorded in the TT Lake sequence. Two types can be differentiated: fluvial runoff events caused by precipitation that carried sediment in suspension into the lake and a sediment mass transport caused by torrential precipitation. The hydrologic events appear to be decoupled from long-term climate and environmental variations, but there is evidence that anthropogenic impact, in terms of pastoralism, might have favored the runoff events. The multi-proxy approach proved to be valuable and allowed for a detailed study of sedimentary processes within the lake and its watershed in order to assess their triggering processes and dynamics. The findings show the complexity of these sedimentary processes and their controlling factors, and the study aims to improve their understanding. This study is the first effort to investigate event-related deposits and sedimentary processes on the Tibetan Plateau and its triggering processes and dynamics by utilizing lacustrine sediment records.

针对藏中南部小型TT湖的湖相沉积记录所开展的沉积学、地球化学、微古生物学与孢粉学研究显示，背景沉积作用频繁被事件成因沉积所中断。这些事件成因沉积被认为是由极端降水事件触发的水文事件的产物。TT湖沉积序列中共记录到11次此类事件，可划分为两类：一类是由携带悬浮沉积物入湖的降水引发的河流径流事件，另一类是由强降雨引发的沉积物质量搬运事件。这些水文事件似乎与长期气候及环境变化解耦，但有证据表明，以畜牧业为代表的人类活动可能促进了径流事件的发生。多代用指标方法被证实极具应用价值，其助力我们对湖泊及其流域内的沉积过程开展精细研究，以解析其触发机制与动力学特征。本研究结果揭示了此类沉积过程及其控制因素的复杂性，研究旨在加深学界对这些过程的认知。本研究是首次利用湖相沉积记录，针对青藏高原地区的事件成因沉积、沉积过程及其触发机制与动力学特征展开的探索性研究。