Towards an Astronomically Calibrated Late Cretaceous to Early Paleocene Time Scale

最近的40Ar/39Ar定年已经通过轨道调谐方法验证了地磁极性时间尺度（GPTS）上新世和更新世部分的变化。因为轨道周期在地质学上以短的增量标记时间，它们可以用来非常精确地测量事件之间的时间间隔，例如地磁反转或生物地层基准面。通过研究大量晚白垩世至早古新世的DSDP/ODP钻孔点，提出了改进和完善GPTS白垩纪和早古新世部分的工作计划，该部分受南大西洋海底模板扩展速率变化的误差影响，这些钻孔点显示了进动（20 kyr重复时间）强迫碳酸盐旋回。高分辨率古磁采样将与采集的数字时间序列（彩色反射光谱）相结合，生成C33R至C27N （83 Ma至62 Ma）磁时线的复合天文年表。GPTS的改进结果将对地球动力学家、生物地层学家和古海洋学家有用。

Gee 95064452 Recent 40Ar/39Ar dating has validated changes made to the Pliocene and Pleistocene portions of the Geomagnetic Polarity Time Scale (GPTS) by orbital tuning methods. Because orbital cycles mark off time in geologically short increments, they may be used to measure elapsed time between events such as magnetic reversals or biostratigraphic datums very precisely. We outline a work plan to improve and refine the Cretaceous and early Paleocene portion of the GPTS, an interval which is subject to errors from spreading rate changes in the South Atlantic sea-floor template by studying a number of DSDP/ODP drill sites of late Cretaceous to early Paleocene age that display precessionally (20 kyr repeat time) forced carbonate cycles. High resolution paleomagnetic sampling will be combined with gathering digital time series (color reflectance spectrometry) to produce a composite astronomical chronology for magnetochrons C33R through C27N (83 Ma to 62 Ma). The resulting improvement in the GPTS will be of use to geodynamicsts, biostratigraphers, and paleoceanographers.