Spectral Stratigraphy of DSDP and ODP Cores from the Equatorial Pacific

最广泛使用的高分辨率海洋地层学方法依赖于三角洲-018的变化记录、古生物学或古地学。不幸的是，这些技术仅限于富含碳酸盐或二氧化硅化石的沉积物，或来自磁性取向岩心的沉积物。赫伯特博士将开发使用GRAPE（伽马射线衰减孔隙度评估器）体积密度测量的技术，以确定赤道东太平洋5个DSDP和ODP岩心的轨道频率。这些“米兰科维奇”信号在新近纪的精度在2%以内，作者打算“调整”沉积速率以适应这些频率。初步工作表明，“移动窗口”方案将获得5%的精度和100凯尔的沉降率分辨率，可恢复到17米。由于这是一个发展实验，他提出了针对现有生物地层学和古地磁校准的几项验证检查，以及站点间一致性检查。如果被证明是有效的，这项技术不仅将大大改进这些岩心和其他岩心的年表，而且还将：1)使CaCO3、cog、SiO2和风积尘的质量积累率估计同样得到改进；2)首次发现超过500凯尔的古海洋周期；3)可以更好地理解回溯到17my的轨道强迫的均值和方差。

The most widely used methods of high-resolution marine stratigraphy rely on the record of changes in delta-018, paleontology or paleomagnetics. Unfortunately, these techniques are limited to sediments either rich in carbonate- or silica- bearing fossils, or from magnetically oriented cores. Dr. Herbert will develop techniques for using GRAPE (Gamma Ray Attenuation Porosity Evaluator) bulk density measurements to identify orbital frequencies in 5 DSDP and ODP cores from the equatorial eastern Pacific. These "Milankovitch" signals are known within 2% precision back through the Neogene, and the author intends to "tune" the sedimentation rates to fit these frequencies. Preliminary work has shaon that a "moving window" scheme will result in 5% precision and 100 Kyr resolution of sedimentation rates back to 17 MY. As this is a developmental experiment, he proposes several validation checks against existing biostratigraphy and paleomagnetic calibrations, as well as inter-site consistency checks. If found to be valid, this technique will not only provide much improved chronologies at these and other cores, but will also: 1) make possible equally improved mass accumulation rate estimates for CaCO3, Corg, SiO2, and aeolian dust; 2) provide the first chance of finding paleoceanographic periodicities longer than 500 Kyrs; and 3) lead to better understanding of the mean and variance of orbital forcings back to 17 MY.