长江中游和尚洞石笋的高分辨率同位素、微量元素记录及古气候研究

Study on High-Resolution Carbon, Oxygen Isotope and Trace Element Records and Paleoclimate from Heshang Cave, the Middle Reach of the Yangtse River

通过对长江中游和尚洞HS 2号石笋的沉积特征及C、O同位素Mg、Sr微量元素相结合分析 ,利用U系法定年 ,获取了长江中游 19.0ka～ 6 .9ka的古气候、古环境信息 (平均分辨率为 17a ,局部分辨率达到 7a)。得出如下结论(1) 19.0～ 16 .6ka ,C、O同位素偏轻 ,气候冷湿 ;(2 ) 16 .6～ 11.1ka ,C、O同位素偏重 ,气温上升 ,降水偏少 ;(3) 11.1～10 .3ka干热时期中的突然回冷事件对应于新仙女木事件 (YoungerDryasEvent) ;(4 ) 10 .3～ 6 .9kaB .Pδ18O及δ13 C值逐渐变轻 ,而Mg/Sr比继续增大 ,表现为气温上升 ,降雨量较大。反映了历史时期湿冷、干热、湿暖交替变化的气候趋势 ,得出了长江中游千年级和百年级的一些气候变化趋势 ,特别是发现了新仙女木事件在长江中游洞穴石笋中完整的记录 。

Through a combined analysis of sedimentary characteristics, C and O isotopes, Mg and Sr trace elements of a stalagmite from Heshang Cave, Hubei, with uranium-series dating, the palaeoclimatic and palaeoenvironmental information from 19.0ka to 6.9ka in the Hubei area is obtained.The average resolution is 17a, and the local resolution is 7a. The following results are obtained: (1) from 19.0～16.6ka B.P.:C and O isotopes were lighter, the climate was cold and wet; (2) 16.6～11.1kaB.P.: C,O isotopes were a little heavy, temperature rose, rainfall was inclined to be little; (3) 11.1～10.3ka B.P.: an excursion during dry and hot period responded to the Younger Dryas Event; (4)10.3～6.9 ka B.P: C,O,Isotopes were lighter, but Mg/Sr value was bigger, showing temperature was continuously rising and rainfall was greater. These reflect the variation tends from humid-cold climate, to dry-hot climate, and to humid, warm climate in history, and some climatic variation trends of thousand years and hundred years cycles are gainned. In particular the authors found out the integrated record of the Younger Dryas Event which means the Younger Dryas Event is a globally climatic sudden change and environmental calamity.