中文摘要：

本文对采自西北太平洋某海山的CHA56富钻结壳样品进行了钙质超微化石及生物地层学的研究与分析，并对其所折射的时代意义进行了探讨。该结壳从构造上分为3层：致密型上层、疏松型中层和致密型下层。在研究中对各构造层和各分层有颜色或细微构造变化的层位都进行了取样分析。在识别化石的基础上，确定了该结壳的疏松型中层为晚中新世到晚上新世（0．5～11．9Ma）沉积；致密型下层为晚古新世到晚渐新世（56．3～23．2Ma）沉积。研究发现，在致密型下层和疏松型中层之间存在沉积间断。研究认为，新生代渐新世／中新世（O／M）时太平洋深水海洋环境的变化，可能是导致西北太平洋海山上3层构造结壳下、中层间显微构造、色泽和成分发生变化和沉积间断产生的主要原因，下、中层间的界面成为结壳生长过程中一个特定的时间标识。

英文摘要：

Calcareous nanofossils in CHA56 Co-rich crust from the Northwestern Pacific Seamount were analyzed to estimate their depositional ages. The crust has three structural layers, i. e., compact upper layer, porous middle layer and compact lower layer. Studies show that the porous middle layer was formed in the period from Late Miocene to Late Pliocene （0.5 - 11.9 Ma）, whereas the lower layer from Late Paleocene to Late Oligocene （56.3 - 23.2 Ma）. Sedimentation hiatus was also observed. The environmental change in Pacific was caused by the change of Drake Passage around the O/M boundary, probably corresponding to the changes in structure, color and luster, and elemental composition in the middle and lower layer. The boundary between the middle layer and the lower layer serves as an important message of the growth age.