河西走廊花海古湖泊全新世白云石的发现及其环境意义

通过对河西走廊花海古湖泊沉积物的X衍射分析发现,全新世期间有明显的白云石沉积.岩性、沉积过程、石膏以及Fe3+含量的变化表明,花海湖全新世白云石沉积环境以还原环境为主,即还原环境利于白云石的形成,为白云石的成因研究提供了新的证据.白云石作为碳酸盐矿物,可以反映湖水盐度,但并非直接指示了湖水的咸化.随着湖水盐度的进一步增加,在硫酸盐型湖泊中,白云石含量随盐度的增加而相应减少,表明利用白云石分析湖水盐度时需要结合其他矿物进行分析.结合石膏含量的变化,花海湖全新世时期白云石含量的变化可以揭示该区域湖水盐度的变化.在10.478.87 cal ka B.P.早全新世时期,湖水的盐度较高,气候由干向湿转变;8.87 cal ka B.P.时期,有大量石膏沉积,显示了湖水盐度的进一步升高,气候干旱;随后湖水相对淡化,气候湿润;5.50 cal ka B.P.至今,沉积出现间断,气候逐渐干旱.

Discovery of dolomite deposition during the Holocene and its environmental significance in Lake Huahai,Hexi Corridor

Obvious dolomite deposition during the Holocene was found by using X-ray diffraction analysis in Lake Huahai,Hexi Corridor.The dolomite deposition was in deoxidizing environment during the Holocene according to the lithology,sediments characteristics, gypsum and the changes of Fe³⁺.It provided new evidence for the research of dolomite formation.Dolomite,as a kind of carbonate mineral,can indicate the lake water salinity.However,it can not indicate the salinity increase directly.The decrease of dolomite content is corresponded with the increase of salinity in sulfate lake.Dolomite and gypsum changes in Lake Huahai can be used to reconstruct lake salinity during the Holocene.During 10.47 8.87 cal ka B.P.,lake salinity was high,implying the climate change from arid to humid.During 8.87 cal ka B.P.,a mount of gypsum deposition revealed increase in water salinity and arid climate.After that,water salinity decreased and the climate was humid.After 5.50 cal ka B.P.,hiatus indicated arid climate.