尕海湖DG03孔碳酸盐含量及其环境意义

通过对尕海DG03孔岩芯碳酸盐含量的测定,表明碳酸盐含量指标较好地记录了尕海湖地区自冰消期晚期以来的气候环境变化。对阿勒罗德暖期和新仙女木期都有较好的反映,并揭示出早全新世气候变暖且波动明显,中全新世早期暖湿,后期温凉偏干,晚全新世气候明显变干,早期较为寒冷,后期偏暖。碳酸盐含量的变化反映了湖水的浓缩程度,与湖泊所处的沉积阶段相联系,同时与岩性特征所反映的环境也有关。在风成作用堆积的粉砂至中砂层,碳酸盐含量降至很低;在滨湖相沉积的细砂层,碳酸盐含量也较低,因此,碳酸盐含量指示的气候环境意义应与岩性及其他指标相结合进行分析,方可得到可信的结论。

Carbonate Content in the Core DG03 of Lake Gahai and its Paleoenvironmental Significance

Carbonate content determined from the sediment core DG03 depicts climate and environmental evolution in the Lake Gahai area since the late Deglacial period.The core provides evidence of a warm period and then a cold-dry period before Holocene based on the analysis of carbonate content,loss-on-ignition(LOI) and lithology.The two periods correspond with the Allerd period and the Younger Dryas period.In the early Holocene,the climate was unstable with a warming trend.The mid-Holocene was warm and humid in the early period,while cold and dry in the late period.The late-Holocene was also dry with lower temperatures in the early period and a warming trend in the period just before the Little Ice Age(LIA).Carbonate content identifies the density of the lake water and its variation also connects with the environmental changes reflected by sediment lithology.The layer composed of silt and medium particle sand which was deposited by eolation,was found to be very low in carbonate content as well as fine sand layer.