(Table 1) Stable-isotope and eolian grain size data across the Paleocene/Eocene boundary from DSDP Hole 22-215

Deep Sea Drilling Project (DSDP) Site 215 provides an expanded section across the Paleocene/Eocene boundary, the most complete mid-latitude sequence from a Southern Hemisphere location in the Indo-Pacific area. The events of this transition occurred during a span of about 1.2 m.y. Oxygen isotope values derived from benthic foraminiferal calcite decrease by about 1.0 per mil, a decrease most likely related to warming of deep ocean waters. Turnovers of benthic foraminifera accompany d18O changes and culminate in the predominant extinction event at the end of the Paleocene Epoch. Carbon isotope ratios also shift dramatically toward lighter values near the end of the Paleocene, beginning about 0.45 m.y. after oxygen isotope values start to change. The intensity of Southern Hemisphere atmospheric circulation as recorded by grain sizes of eolian particles shows a large and rapid reduction beginning another 0.45 m.y. later. A significant reduction of zonal wind strength at the Paleocene/Eocene boundary, until now observed only at Northern Hemisphere locations, appears to have been a global phenomenon related to decreased latitudinal thermal gradients occasioned by more effective poleward heat transport via the deep ocean.

深海钻探计划（Deep Sea Drilling Project, DSDP）215号站位获取了横跨古新世/始新世边界（Paleocene/Eocene boundary）的增厚沉积剖面，是印度-太平洋区域（Indo-Pacific area）南半球点位中最为完整的中纬度沉积序列。此次气候跃迁事件的持续时长约为120万年。从底栖有孔虫方解石（benthic foraminiferal calcite）中提取的氧同位素值（Oxygen isotope values）降低了约1.0‰，该同位素负偏大概率与深层海水升温相关。底栖有孔虫（benthic foraminifera）的群落更替伴随d18O值变化，并在古新世末期的主要灭绝事件中达到峰值。碳同位素比值（Carbon isotope ratios）同样在古新世末期发生显著的轻值偏移，这一偏移始于氧同位素值开始变化后的约45万年。由风成颗粒（eolian particles）粒度记录的南半球大气环流强度，在该偏移发生后又过了45万年，出现了大幅且快速的减弱。此前仅在北半球点位观测到的古新世/始新世边界处纬向风速（zonal wind strength）显著减弱现象，如今被证实为全球性现象，其与深层海洋更高效的极向热输送（poleward heat transport）引发的纬度温度梯度（latitudinal thermal gradients）降低密切相关。