南海ODP1148站中中新世(12～18.3 Ma) 天文调谐的年代标尺

ODP1148站深海沉积岩心的磁化率记录显示出较强的周期性变化规律．研究发现，中新世和渐新世的深海地层物性参数具有很强的斜率周期．Shackletoneta1．利用这一规律，以北半球高纬太阳辐射曲线作为天文调谐的目标，以ODP154航次的深海沉积岩心的磁化率记录作为调谐对象，将磁化率的极大值与北半球天文辐射的极小值相对应，建立了14～34Ma的天文调谐的年代标尺．采用相同的方法，利用南海北部ODP1148站深海沉积岩心的磁化率记录和北半球高纬太阳辐射曲线建立了南海中中新世天文调谐的年代标尺．调谐后的磁化率记录显示了很强的斜率周期和较强的岁差周期，并与太阳辐射在这2个记录上高度相关，此外偏心率周期在磁化率记录中也较显著．调谐后1148站的浮游有孔虫事件年龄与ODP154航次采用相同的天文调谐方法获取的事件年龄异常接近，而与传统方法获取的生物地层事件年龄有较大差距，这在一定程度上证明了利用天文调谐的方法建立中新世深海地层年代标尺的可行性．

Astronomically Tuned Time Scale 12 Ma to 18. 3 Ma,ODP Site 1148, Northern South China Sea

Lithological cyclicity was observed in magnetic susceptibility records of the deep sea sediments from ODP Site 1184 in the northern South China Sea (SCS), which was considered to be related to obliquity cycles in the Miocene and Oligocene. Using recent methodology, an astronomically tuned time scale for the middle Miocene of ODP Site 1148 in the northern SCS was established. After tuning, the magnetic susceptibility (MS) records show strong obliquity and precession cycles as well as prominent eccentricity cycles. The planktonic foraminiferal events identified within the studied interval of ODP Site 1148 show ages very close to those set by Shackleton et al. (1999) for ODP Leg 154, which were obtained by the same astronomical tuning method as this study, but differ substantially from the traditional age. The results lend support to the practicality of the method for establishing a tuned Miocene time scale.