西太平洋富钴结壳超微化石与分子化石地层划分及对比

STRATIGRAPHY DIVISION AND COMPARISON OF WESTERN PACIFIC COBALTRICH CRUST BASED ON CALCAREOUS NANNOFOSSIL AND MOLECULAR FOSSIL

对具典型三层构造的西太平洋海山群富钴结壳样品进行了钙质超微化石地层学研究,获取了富钴结壳从内层致密层、中间疏松层到外层较致密层的生长时代:CM1D03为晚古新世-早始新世、始新世中期、中中新世-更新世;CM3D06分为晚古新世-早始新世、中始新世-晚中新世、上新世-更新世。对富钴结壳壳层的甾烷系列分子(C27、C28、C29)进行了检测并计算了相对含量,结果表明,两块富钴结壳的甾烷分布构型在结壳生长时代上具有一致性:晚古新世-早始新世,呈反"L"型分布;中始新世呈C27优势的"V"型分布;中新世-更新世呈C29优势的"V"型分布。甾烷分布构型的变化与古海洋环境演化造成的海底甾烷输入波动有关,具有一定的时代特征钙质超微化石和分子化石地层学划分方法在富钴结壳层主要生长时代及生长间断的界定上具有一致性,可以用于富钴结壳的地层划分和对比。

Calcareous nannofossil stratigraphy of two cobalt-rich crust samples in typical three-layered(dense-loosedense) structure from a seamount in the western Pacific was studied based on nannofossils and molecular fossil(sterane) using scanning electronic microscope and mass spectrometry. Results show that the three layers were formed during late Paleocene to early Eocene, middle Eocene, and middle Miocene to Pleistocene for CM1D03, and late Paleocene to early Eocene, Eocene to late Miocene, and Pliocene to Pleistocene for CM3D06, respectively. C27, C28, and C29 sterane in the samples were detected, and the relative abundance calculated. The two cobalt-rich crust samples were found consistent in sterane abundance and variation in geological history, and believed to be resulted from the fluctuation of paleoceanographical environment, indicating the input change of sterane at sea bottom. Thus, sterane distribution can be used for stratigraphic subdivision as the stratigraphic subdivision schemes in chemical imprint and in calcareous nannofossil paleontology agreed well for the cobalt-rich crust.