桂林44kaB.P.石笋同位素记录及其环境解译

Isotopic Records of Stalagmites from Guilin since 44 ka B.P. and Their Environmental Interpretation

通过大气降水多种因素的相关性 ,以及平均温差较大的 2个时段生长的石笋C、O同位素的明显差异性 ,论证了本区石笋碳酸盐的C、O同位素与全球气温变化呈明显的负相关。Pl 1和X 1石笋高分辨率的同位素记录取得了完全一致的结果 ,C、O同位素确定了冰期旋回冰消期的终止点“I” ,其时限为 10 .7kaB .P .。自 4 4kaB .P .以来桂林地区的气候变化可划分为 3个阶段 :4 4～ 2 5.6kaB .P .的冰期 ,寒冷 ,但比盛冰期暖和 ;2 5.6～ 10 .7kaB .P .的盛冰期 ,气候干冷 ,温度最低 ;10 .7kaB .P .至今的全新世 ,气候温暖、潮湿。气候变化的总趋势为自 4 4～10 .7kaB .P .由暖变冷 ,温差变幅由小变大。末次冰期最后一次冷事件 ,发生在 11kaB .P .前后 ,可能是新仙女木事件在本区的表现。这些特点可以与南极东方冰芯及苏禄海同位素记录进行对比。

This paper has studied the correlation between the precipitation and other climatic factors, as well as the oxygen and carbon isotopes in the calcite of the stalagmites deposited in last glaciation and Holocene.The results show that the δ values of the oxygen and carbon isotopes in stalagmite calcite have a negative correlation with the annual mean surface temperature. The parallel high resolution studies of two stalagmites since 44 ka B.P. gave the same results. It is shown the that there are 3 climatic stages, i.e. 10.7ka ～present,25.6～10.7ka B.P. and 44～25.6ka B.P.. Stage 1 is Holocene, which was warm and wet.Stages 2 and 3 mean the last glaciation, which was cold and dry,Stage 2 being the coldest.These three stages can be correlated with the oxygen isotopic records of the deep sea sediments and climatic records of Vostok ice core. The overall trend of climatic changes were from warm to cold, and the temperature varied from low to high in the last glaciation in the study area. Around 11kaB.P., expression of Younger Dryas was obvious in this area. After that period, the air temperature went up rapidly and was close to the pressent level in 10.7kaB.P..