Calcareous nannofossils across the Eocene-Oligocene boundary

This work presents the stratigraphic distribution of several species of calcareous nannofossil in the middle Eocene early-Oligocene from four Ocean Drilling Program (ODP) sites located between 60° and 65°S paleolatitude in the Southern Atlantic and Indian Oceans. Useful nannofossil datums that should facilitate construction of age-models and contribute to an integrated chronology for the upper Paleogene Southern Ocean sediments from ~42 to 33 Ma are summarized. The distribution patterns of calcareous nannofossils, studied by means of quantitative and semiquantitative methods, provide an improvement of the classical Southern Ocean biozonations, introducing new biostratigraphically useful biohorizons, and testing their reproducibility within and outside the region.本研究阐明了采自古南纬60°至65°的南大西洋与印度洋海域4个大洋钻探计划（Ocean Drilling Program, ODP）站位中，中始新世-早渐新世时期多种钙质超微化石（calcareous nannofossil）的地层分布特征。本文总结了一批实用超微化石基准面，此类基准面可助力年代模型构建，同时为约42 Ma至33 Ma的南大洋古近纪上部沉积物提供综合年代序列。本研究通过定量与半定量方法对钙质超微化石的分布模式开展分析，完善了经典南大洋生物地层分带体系，引入了一批新的具有生物地层学应用价值的生物界面，并检验了这些生物界面在研究区内外的可重现性。