松辽盆地晚白垩世古气候变化的测井替代指标

Well logging proxy of the Late Cretaceous palaeoclimate change in Songliao Basin

寻求指示古气候变化的测井替代指标是近年来古气候研究的重要途径和方向。测井曲线是地层岩石学、岩石物理学、岩石地球化学特征的综合反映,具有连续性好、纵向分辨率高的特点,为反演古气候变化提供了新的手段。松科1井作为专门为研究松辽盆地晚白垩世重大地质事件与古气候变化而部署的一口科学探索井,具有系统的岩心资料和较完整的测井系列资料。文中在对松科1井南孔自然伽马能谱测井资料进行统计的基础上,结合放射性元素地球化学分析结果,论证了钍/钾比(Th/K)可以作为指示气候变化良好替代指标的可行性,并据此对松辽盆地青山口组—嫩江组沉积时期的气候干湿变化进行了反演。结果表明:松辽盆地从泉头组3段—嫩江组2段沉积时期气候总体表现为从潮湿向半干旱转化的趋势,垂向上可划分为3个完整的干湿变化旋回。这一研究结论与前人在松辽盆地南部采用古生物学以及元素地球化学分析得出的结论相吻合,表明根据自然伽马能谱资料统计得出的Th/K值可以作为反演古气候变化的替代指标。

To seek the logging proxies of palaeoclimate change has been a vital way and orientation in recent years.The well logging curves,with good continuity and high longitudinal resolution,are the comprehensive reflection of stratigraphic petrology,petrophysics and petrochemistry.They can provide a new approach for the research of palaeoclimate change inversion.Well SK 1,as a scientific exploration well for studying important geological events and palaeoclimatic change in the Songliao Basin,has systematic core data and integrated well logging suites.According to the statistics of spectral gamma-ray log in the south hole of Well SK 1 and the analysis of radioactive element geochemistry,the feasibility of Th/K ratio as a proxy of palaeoclimate changes is verified,and also the climate humidity changes are inverted from the Quantou Formation depositional period to the Nenjiang Formation depositional period of the Songliao Basin.The results show that the climate trends from humid to semi-arid between the third stage of Quantou Formation depositional period to the second stage of Nenjiang Formation depositional period in the Songliao Basin.Vertically,the climate tendency can be divided into three arid-humid cycles,which perfectly coincide with the paleontology and geochemistry analyses in the southern Songliao Basin.