青藏高原腹地湖泊沉积纪录的“仙女木期”古气候颤动事件

Paleoclimatic Oscillation Events of the Dryas Period: Evidence from the Record of Lake Records of Late Sediments in the Interior of the Qinghai-Tibet Plateau

通过对青藏高原腹地钻孔岩心剖面的最新研究,用层序地层学与年代地层学和气候地层学相结合的方法,分辨出可可西里地区苟弄措湖泊沉积记录(孔深7.25 m)约30 ka BP以来的古气候变化,并在孔深3.32～1.98 m处识别出“仙女本期”的3个气候颤动事件,即:①老仙女术事件(孔深3.32～2.62 m);②中仙女本事件(孔深2.62～2.43 m);③新仙女本事件(孔深2.43～1.98 m)。这3个气候颤动事件都是以冷干时段开始、以冷湿时段结束的,并有越向后期其冷干的时段越长的变化趋势,而其后的冷湿时段却具有等时的变化趋势。岩心沉积物的有机碳、有机氮和磁化率以及化学元素含量的变化,都与仙女本期气候变化具有十分吻合的变化态势。仙女术期气候在湖泊沉积物中的响应,在青藏高原环境演化中还是首次发现,为研究第四纪末次冰期冰消期以来的气候变化提供了新的信息。

In the latest study of a section of the well core from the interior of the Qinghai-Xizang(Tibet) Plateau,the authors found the last 32 ka paleoclimatic change from the record of lake sediments of the Goulong Co in the Hoh Xil area by using the sequence stratigraphic and chronostratigraphic approaches, combined with the cli-matostratigraphic approach and recognized three climatic oscillation event of the Dryas period atdepths of 3. 32 to 1. 98 m of a well core, i. e. (1) the Oldest Dryas event (at well depths of 3. 32 to 2. 62 m), (2) the Older Dryas event (at 2. 62 to 2. 43 m) , and (3) the Younger Dryas event (at 2. 43 to 1. 98 m). All the three climat-ic oscillation events started with the dry and cold interval and ended with the cold and humid interval. The cold and dry interval became longer in the later part of the period, while the dry and humid stage shows a tendency of isochronic change. The variations of organic carbon, organic nitrogen, magnetic susceptibility and geochemi-cal element contents in core sediments all well coincide with the climatic change in the Dryas period. The re-sponse of the climate in the Dryas period in lake sediments is first discovered in the environmental evolution of the Qinghai-Tibet Plateau. This provides new information for the study of the climatic change since the deglaciation of the last glacial stage of the Quaternary.