Paleogene benthic foraminifera from the Kerguelen Plateau

Benthic foraminifers were studied from lower Paleocene through upper Oligocene sections from Sites 747 and 748. The composition of the benthic foraminifer species suggests a middle to lower bathyal (600-2000 m) paleodepth during the Neogene and a probable upper abyssal (2000-3000 m) paleodepth during the Paleocene at Site 747. Site 748 is thought to have remained at middle to lower bathyal paleodepths throughout the Cenozoic. Principal component analysis distinguished four major benthic foraminifer assemblages: (1) a Paleocene Stensioina beccariiformis assemblage at Sites 747 and 748, (2) an early Eocene Nuttallides truempyi assemblage at lower bathyal Site 747, (3) an early through middle Eocene Stilostomella-Lenticulina assemblage at middle bathyal Site 748, and (4) a latest Eocene through Oligocene Cibicidoides-Astrononion pusillum assemblage at both sites. Major benthic foraminifer changes, as indicated by the principal components and first and last appearances, occurred at or close to the Paleocene/Eocene boundary, and in the late Eocene close to the middle/late Eocene boundary.

本研究对747与748两个站位的古新统下部至渐新统上部剖面中的底栖有孔虫（Benthic foraminifers）展开了系统研究。747站位的底栖有孔虫物种组成表明，其在新近纪时期的古水深为中-下半深海相（600~2000米），而古新世时期的古水深大概率为上深渊相（2000~3000米）；748站位在整个新生代时期均维持在中-下半深海的古水深环境。通过主成分分析（Principal Component Analysis），研究识别出四类主要的底栖有孔虫组合：（1）分布于747与748站位的古新世*Stensioina beccariiformis*组合；（2）见于下半深海相747站位的早始新世*Nuttallides truempyi*组合；（3）分布于中半深海相748站位的始新世早期至中期*Stilostomella*-*Lenticulina*组合；（4）在两个站位均有产出的始新世晚期至渐新世*Cibicidoides*-*Astrononion pusillum*组合。结合主成分分析结果以及底栖有孔虫物种的首现与末现层位，其重大群落演替事件均发生于古新世/始新世界限附近，以及始新世晚期接近中始新世/晚始新世界限的时段。