COLLABORATIVE RESEARCH: Towards a Milankovitch-Scale Stable Isotope Stratigraphy For the Late Oligocene to Early Miocene

小行星9725311 利用大洋钻探计划（ODP）第154航次至西赤道大西洋塞阿拉海隆的岩心，建立第一个渐新世晚期至中新世早期（21-27.5 Ma）的天文调谐稳定同位素时间序列。 该时间序列将是一个复合记录，由塞阿拉海隆三个孔（站点926、928和929）底栖有孔虫的碳和氧同位素记录构成。 通过拼接，复合层将在6.5 m.y长的间隔上具有地层连续性。 因此，它将是有史以来最长的高分辨率同位素时间序列之一。 初步工作证明了拟议办法的可行性。 事实上，现在正在努力将磁化率和现有的稳定同位素记录调整到这个时间段的轨道光谱（与N. J.沙克尔顿合作）。 通过天文调谐的同位素记录，我们将能够（1）估计渐新世/中新世边界的相对年龄，（18 O最大值Oi 2a，Mi 1，Mi 1a（以及所有小事件），（2）以前所未有的细节描述渐新世晚期/中新世早期气候变化的演变（冰量/温度）。 从这项调查的结果中将得到几个重要的好处。 首先，建议的天文调谐同位素时间序列将作为一个全球标准参考部分，所有其他晚渐新世-早中新世海洋序列进行比较。 使用稳定同位素地层学，将有可能将沉积剖面的长段或短段与这一记录进行对比和校准，从而大大提高年龄模型的准确性。 更重要的是，通过为重建气候、深海环流和化学变化提供框架，调整后的塞阿拉海隆同位素记录将大大加强这一时期的古海洋学和古气候学研究。 总之，米兰科维奇标度记录的提出将代表新生代地层学和地球历史的重大进展。

9725311 Flower We propose to develop the first astronomically tuned stable isotope time series for the late Oligocene to early Miocene (21-27.5 Ma) with cores collected during Ocean Drilling Program (ODP) Leg 154 to Ceara Rise, western Equatorial Atlantic. This time series will be a composite record, constructed with the carbon and oxygen isotope records of benthic foraminifers from three Holes on Ceara Rise (Sites 926, 928, and 929). Through splicing, the composite will be stratigraphically continuous over a 6.5 m.y long interval. As such, it will be one of the single longest high-resolution isotope time series ever assembled. Preliminary work has demonstrated the feasibility of the proposed approach. In fact, efforts are now underway to tune the magnetic susceptibility and existing stable isotope records to orbital spectra for this interval (in collaboration with N.J. Shackleton). With the astronomically tuned isotope record we will be able to (1) estimate the relative ages of the Oligocene/Miocene boundary, (18O maxima Oi2a, Mi1, Mi1a (as well as all minor events), and (2) characterize in unprecedented detail the evolution of late Oligocene/early Miocene climate variability (ice-volume/temperature). Several important benefits will be derived from the results of this investigation. For one, the proposed astronomically tuned isotope time series will serve as a global standard reference section by which all other late Oligocene-early Miocene marine sequences are compared. It will be possible, using stable isotope stratigraphies, to correlate and calibrate either long or short segments of sedimentary sections to this record, thereby significantly improving the accuracy of age models. More importantly, by providing the framework for reconstructing changes in climate, deep ocean circulation and chemistry, the tuned Ceara Rise isotope records should greatly enhance paleoceanographic and paleoclimatic research on this interval. In sum, the proposed Milankovitch-scale records will rep resent a significant advance in Cenozoic stratigraphy and Earth history.