Radiolarian Paleogene biostratigraphy in the southern Indian Ocean, ODP Leg 120

During Ocean Drilling Program Leg 120, an almost complete Paleogene sediment section on the Kerguelen Plateau in the southern Indian Ocean was recovered. The biostratigraphy of radiolarians from these sediments at Sites 748 and 749 is studied. A biostratigraphic framework established in low and middle latitudes is not applicable because of the absence of most zonal marker species. Biogenic opal is present only in middle Eocene to Oligocene sediments, and three new zones-Lychnocanoma conica, Axoprunum (?) irregularis, and Eucyrtidium spinosum zones-are proposed. The Paleogene antarctic radiolarian fauna is different from that in low and middle latitudes. Three new species, Axoprunum (?) irregularis, Eucyrtidium cheni, and Eucyrtidium spinosum, are described.

在大洋钻探计划（Ocean Drilling Program, ODP）第120航次中，科研人员于南印度洋凯尔盖朗高原（Kerguelen Plateau）获取了一套近乎完整的古近纪沉积剖面。本研究针对748和749站位沉积物中的放射虫生物地层特征展开分析。由于绝大多数分带标志种缺失，此前在中低纬度海区建立的生物地层框架无法适用于本研究区域。生物成因蛋白石仅发育于中始新世至渐新世的沉积地层中，据此本文提出3个全新的放射虫生物地层分带：锥状光盔虫（Lychnocanoma conica）分带、不规则轴窗虫（？）（Axoprunum (?) irregularis）分带以及棘状真扇虫（Eucyrtidium spinosum）分带。古近纪南极放射虫动物群与中低纬度海区的放射虫动物群存在显著差异。本次研究还描述了3个放射虫新种：不规则轴窗虫（？）（Axoprunum (?) irregularis）、陈氏真扇虫（Eucyrtidium cheni）以及棘状真扇虫（Eucyrtidium spinosum）。