Diatom biostratigraphy of the Kerguelen Plateau and Prydz Bay, Southern Ocean

Samples were examined for diatoms from 22 holes at 11 sites cored by ODP Leg 119 on the Kerguelen Plateau and in Prydz Bay, East Antarctica. Diatoms were observed in Oligocene through Holocene sediments recovered from the Kerguelen Plateau. The diatom flora from the Kerguelen Plateau is characterized by species such as Azpeitia oligocenica, Rocella gelida, Rocella vigilans, and Synedra jouseana in the Oligocene and Crucidenticula nicobarica, Denticulopsis hustedtii, Nitzschia miocenica, and Thalassiosira miocenica in the Miocene. This somewhat cosmopolitan assemblage gives way to a Pliocene and Holocene assemblage characterized by species such as Nitzschia kerguelensis, Thalassiosira inura, and Thalassiosira torokina, which are endemic to the Southern Ocean region. Samples examined from Prydz Bay are generally devoid of diatoms. The exception is Site 739, where diatoms occur sporadically in lower Oligocene and upper Miocene through Quaternary sediments.
The Leg 119 diatom biostratigraphic results allow the development of a stratigraphic framework for the Indian sector of the Southern Ocean. This diatom zonation integrates diatom zonations developed previously for other sectors of the Southern Ocean. The zonation proposed here is based on biostratigraphic events of both geographically widespread and endemic species calibrated to the paleomagnetic stratigraphy. As such, this zonation has application throughout the Southern Ocean and allows correlation from the southern high latitudes to the low latitudes.

本研究对东南极洲普里兹湾与凯尔盖朗海台区域内，由大洋钻探计划（Ocean Drilling Program, ODP）第119航次钻取的11个站位共计22个钻孔的沉积物样品中的硅藻（diatom）展开了分析。凯尔盖朗海台所获取的渐新统至全新统沉积物中均有硅藻产出。该区域的渐新统硅藻组合以Azpeitia oligocenica、Rocella gelida、Rocella vigilans及Synedra jouseana为典型代表，中新统硅藻组合则以Crucidenticula nicobarica、Denticulopsis hustedtii、Nitzschia miocenica及Thalassiosira miocenica为特征分子。这套广布性组合逐渐被上新统至全新统的组合所替代，后者以仅局限于南大洋区域的Nitzschia kerguelensis、Thalassiosira inura及Thalassiosira torokina为标志性物种。普里兹湾的绝大多数钻孔样品均不含硅藻，仅739站位为例外：该站位的下渐新统及上中新统至第四系沉积物中零星可见硅藻产出。

大洋钻探计划第119航次的硅藻生物地层学研究成果，可为南大洋印度洋扇区构建一套地层格架。本次建立的硅藻分带序列整合了此前针对南大洋其他扇区提出的硅藻分带方案。本研究提出的硅藻分带以经古地磁地层校准的广布性与地方性物种的生物地层事件为依据，因此可适用于整个南大洋区域，能够实现南极高纬度区域与低纬度区域的地层对比。