【摘要】 处于高纬度和高海拔地区的内蒙古黄旗海湖泊沉积物δ13Corg的变化反映了气候环境的变化。特殊的自然环境条件造成黄旗海湖泊沉积物δ13Corg偏负段对应暖湿环境,偏正段对应冷干环境。自8.2 kaBP开始,δ13Corg值显著降低,表明本区气候转暖;8.2~4.0 kaBP是全新世大暖期,这一时期黄旗海为高湖面,在7.8 kaBP左右本区气候最为暖湿。4.0~2.2 kaBP,δ13Corg值明显偏正,指示气候变为冷干,全新世大暖期结束。在研究时段内δ13Corg值相对于-23.5‰均值的正负偏移主要反映了湖泊有机质生产率和保存条件的变化。这种变化与当时的气候,尤其是湖泊水位的波动有直接关系。更多还原

【Abstract】 Section（H3） at 1.64 m depth from the south bank of Huangqihai Lake,Inner Mongolia recorded paleoclimatic and paleoenvironmental changes during 8.3 and 2.2 kaBP.Bulk organic carbon isotopic composition((δ¹³C_org)) of H3 section is analyzed and the relation between(δ¹³C_org) record from the shallow closed-drainage lake and environmental evolution is discussed.The positive values of(δ¹³C_org)indicate that the climate in the period of time was cold and dry,while the negative values of(δ¹³C_org) indicate that the climate in the period of time was warm and wet.Results suggest that the climate at Huangqihai Lake was warm and wet during 8.3 and 7.4 kaBP,and(δ¹³C_org) values of the sediments are 0.46‰ lower than the average in the whole period of time of study.There is about 2.66‰ shift in(δ¹³C_org) values in the whole period of time,and it was mostly related to the rapid increase in the organic productivity of the paleo-lake.The substantial fall in(δ¹³C_org) values of the sediments from Huangqihai Lake of 8.2 kaBP provides evidence for an abrupt warming of the regional climate at that time.The period（8.2～4.0 kaBP） is Megathermal Maximum in Holocene and is regarded as the period of high stand of Huangqihai Lake.Thereinto,it was the warmest at about 7.8 kaBP.During 4.0 and 2.2 kaBP,the δ¹³Corg average value is-22.8‰（obviously positive）,which indicates that the climate was quite cold and dry after 4.0 kaBP.The Megathermal Maximum period ended and the climate drastically deteriorated after 4.0 kaBP.Variation in(δ¹³C_org)during the whole period of time is characterized by both negative and positive excursions from the line of the average(δ¹³C_org) value of（-23.5‰.） These excursions may principally reflect the change in productivity and preserving condition of organic matter in the lake,which in some way link to the climate,especially to the lake-level fluctuations.更多还原