柴达木盆地第四纪古气候变化在自然伽马测井曲线上的记录

QUATERNARY PALAEOCLIMATIC CHANGES RECORDED BY NATURAL GAMMA LOGGING CURVE IN QAIDAM BASIN

利用物理测井曲线分析古气候变化是近年发展起来的新的研究领域。本文在对柴达木盆地取心井涩中 6井多种气候指标分析的基础上 ,建立了涩中 6井GR曲线古气候反演模式 ,将该模式引进到盆地东部唯一贯穿第四系的钻孔———达参 1井 ,利用该井高分辨率自然伽马曲线 ,建立了盆地东部地区 2 .85MaBP以来的时间标尺 ,据此讨论了盆地东部地区 2 .85MaBP以来的古气候变化。此外还与盆地西部大浪滩ZK336井进行了对比。结果表明 :盆地气候变化在大阶段上明显受到天文轨道周期的控制 ,但也具有明显的区域性特征 ;柴达木盆地同时包含了高原隆升与全球性气候变化的信息 ,是古环境变迁的良好的信息载体 ;自然伽马曲线是反映内陆干旱盆地气候与环境变化良好的代用指标。

Using natural gamma logging (GR) curves to analyse palaeoclimatic changes is a newly developed research field. Based on the analyses of a variety of palaeoclimatic indicators of the core samples from Well Sezhong 6,the model of inverse modeling of palaeoclimatic changes has been established. This model has been further introduced into Well Dacan 1 — the only well drilling through the Quaternary in the eastern Qaidam Basin. The high resolution GR curve of Well Dacan 1 has been used to reconstruct the time scale of a period of 2.85 Ma BP in the eastern Qaidam Basin. The palaeoclimatic changes in the eastern Qaidam Basin since 2.85 Ma BP are also discussed. In comparison with the record of Well ZK336 in Dalangtan area of the western Qaidam Basin, it is suggested that the palaeoclimatic changes of the Qaidam Basin were controlled by the astronomic orbital periods, and these changes tended to behave obvious regional characteristics. It is showed that the current Qaidam Basin is one of the best carriers of information such as the uplifting history of the Qinghai—Tibet Plateau, the global climatic and environmental changes. It is also indicated that GR curve can be a good indicator of the environmental and climatic changes of the inland arid basin.