珠江口盆地中中新世韩江组天文调谐地质年代表

利用多种频谱分析方法,对珠江口盆地Langhian阶韩江组三角洲相硅质碎屑岩及浅海相碳酸盐岩韵律性交替地层进行旋回地层学分析,然后选择最新天文周期解决方案中的北纬65°夏半年日照量曲线及斜率曲线作为目标曲线,对自然伽马测井曲线进行天文调谐,得到高分辨率天文调谐地质年代表。结果表明:珠江口盆地中中新世韩江组地层旋回受天文轨道周期变化的驱动;利用天文调谐地质年代表进行的定年结果与前人利用古地磁对南中国海相邻盆地的定年一致;通过天文调谐地质年代表求得的研究层段高分辨率沉积速率变化与天文轨道周期偏心率曲线可以对应,推测沉积速率变化的主要控制因素是405 ka长周期偏心率。

Astronomical time scale of middle Miocene Hanjiang formation in Pearl River Mouth Basin,South China Sea

Cyclostratigraphic analysis was undertaken with several different spectral analysis methods on the Hanjiang formation of Langhian age(middle Miocene) in the Pearl River Mouth Basin of South China Sea,which consists of deltaic siliciclastic and neritic shelf carbonate rhythmic alternations.Within biochronological constraint,a high-resolution astronomical time scale was constructed through astronomical tuning of the natural gamma-ray well-logging record to the 65°N insolation curve and obliquity curve,which are from the most recent astronomically calculated variation of the earth s orbit.The results show that the Hanjiang formation cycles are controlled by variation of the earth s orbital period.The astronomically tuned time scale can be used to calculate astronomical ages for geological events and bioevents recognized throughout the period,and the results are only slightly different from earlier estimates in South China Sea.The astronomical time scale resolves the sedimentation history for the Langhian stage(middle Miocene) with a variation that strongly resembles that of the earth s orbital eccentricity.The main factor controlling the variability of the sedimentation rate in the Hanjiang formation may be related to the 405 ka long period eccentricity.