(Table 1) Ostracode assemblage parameters in sediments of ODP Hole 113-689

During the late Paleocene thermal maximum (ca. 55.50 Ma) mid-bathyal ostracodes at Maud Rise in the Southern Ocean (Ocean Drilling Program Site 689) underwent a sudden, dramatic turnover synchronous with a global extinction in deep-sea benthic foraminifers and with large-scale, short-lived negative excursions in the stable isotope record of foraminiferal calcite. A previously stable and long-lived ostracode assemblage, dominated by heavily calcified, chiefly epifaunal taxa, was replaced within ~10 k.y. by a taxonomically novel association of small, thin-walled opportunistic and generalist forms that persisted for ~25-40 k.y. Thereafter, ostracode faunas recovered and common bathyal forms returned, although species were smaller and/or less-heavily calcified than before the turnover. The complex fabric of change in ostracode shell morphology and assemblage composition and structure reflects both long-term and sudden perturbations in seawater chemistry at this site. Ostracode data are in agreement with the hypothesis that the latest Paleocene extinctions in the deep sea were caused by a change in the dominant source area of intermediate water mass from high altitudes to the subtropics. These data also suggest that warm saline waters persisted at Maud Rise for the next 100 k.y.

古新世晚期热极大事件（late Paleocene thermal maximum）发生于约5550万年前，此时南大洋毛德海隆（Maud Rise）的大洋钻探计划（Ocean Drilling Program, ODP）689站位的中半深海介形类（ostracode）经历了突发性剧烈更替，该事件与全球深海底栖有孔虫绝灭事件、以及有孔虫方解石稳定同位素记录中的大规模短期负偏移完全同步。此前以厚壳、主要为表生类群占主导的稳定且持久的介形类组合，在约1万年的时间尺度内被替换为分类学上全新的小型薄壁机会主义与广食性类群组合，该组合持续了约2.5万至4万年。此后，介形类动物群逐步恢复，常见的半深海类群重新出现，但物种个体相较于更替前更小，且/或壳体钙化程度更低。介形类壳体形态、组合组成与结构的复杂变化特征，反映了该站位海水化学环境所经历的长期与突发性扰动。介形类数据支持了"深海古新世末期绝灭事件由中间水团主要源区从高海拔到亚热带转变所引发"这一假说。同时，这些数据还表明，在随后的10万年中，毛德海隆区域持续存在暖盐水体。