16ka以来青海湖湖相自生碳酸盐沉积记录的古气候

研究了青海湖沉积物碳酸盐的组成、来源及其同湖水物理化学性质的关系，建立了文石饱和指数同温度和湖水Mg/Ca比值（可指示盐度）的关系，利用碳酸盐的组成探讨了青海湖16ka B.P.以来的古气候环境演化过程。结果表明，青海湖沉积碳酸盐大都是自生的，16ka B.P.以来沉积碳酸盐以文石为主。文石的高含量时段同暖湿气候相对应，低含量则同冷干气候相对应。15.2ka B.P.为末次冰期盛冰阶进入晚冰期的界限，晚冰期气候的冷暖波动频繁，幅度较小，13.4-13ka B.P.,11.6-12ka B.P.和11-10.4ka B.P.之间的冷颤动分别相当于老仙女木、中仙女木和新仙女木事件，12－13ka B.P.和11.6-11ka B.P.之间的暖期则分别对应于博令和阿勒罗得暖期。全新世初期（10.4-10ka B.P.)白云石含量的突然增高和文石的消失，可能同淡水快速补给前期盐度较高的湖水有关，反映了全新世开始时气温和降水的增加具有突变性的特点。全新世大暖期的鼎盛期，即6.7ka B.P.左右时湖水的盐度较低。6.7-4ka B.P.为气候转型过程中的冷暖和干湿的快速波动期。4ka B.P.以后碳酸盐含量急剧降低，气候逐步向冷干化方向发展。

A 16 000-Year Paleoclimatic Record Derived from Authigenetic Carbonate of Lacustrine Sediment in Qinghai Lake

The compositions and sources of carbonates and their relation to the physical and chemical characteristics of lake waters for Qinghai Lake were studied；the relationship between the saturation index of aragonite and temperature， Mg/Ca ratio was established； and the paleoclimatic evolution of Qinghai Lake since 16 ka B．P．was discussed．The results indicate that the carbonates in the sediments of Qinghai Lake are mostly authigenetic and are mainly composed of aragonite since 16 ka B．P．．The stage of high aragonite content reflects warm-humid climate，while that of low aragonite content reflects the cold．dry climate． The Paleoclimate and Paleoenvironment of Qinghai Lake since 16 ka B．P．recorded by carbonates are as follows：The boundary betwen the Last Glacial and the Lateglacial is at 15.2 ka B．P．．During the Lateglacial，the climate fluctuated frequently，but with small amplitude．There cold events in the periods of 13.4～ 13 ka B．P．．11.6～ 12 ka B．P．an d 11～ 10.4 ka B．P．correspond to the Oldest Dryas， Older Dryas and Younger Dryas event， respectively， whereas the two warm periods between them ，12～ 13 ka B．P．and 11.6～ 11 ka B．P．, correspond to Bo11ing and Allerod period ，respectively．During the early stage of the Holocene (from 10.4 ka B．P．to 10ka B．P．)，the aragonite disappeared and much dolomite emerged ，which may be related to more fresh water flowage into the saline lake．This indicates that the temperature an d rainfall increased abruptly in the early Holocene．The Holocene warm climatic optimum culminated at 6.7 ka B．P．when the salinity of lake water was lower．The climate fluctuated fast as it turned from warm to cold and from hum id to dry between 6.7 ka B．P．and 4 ka B．P．．The climate tended to be cold and dry since 4 ka B．P．．Qinghai Lake