(Table 1) Strontium isotope ratios of planktonic foraminifera and ostracoda from ODP Hole 120-748B on the Kerguelen Plateau, Indian Ocean

Stable and radiogenic isotopic and sedimentological data from sub-Antarctic deep sea sediment cores reveal a temporal link between changes in seawater 87Sr/86Sr ratios and major episodes of late Eocene-early Oligocene climate change. The 87Sr/86Sr records show two major inflections, one at 38-39 Ma near the middle/late Eocene boundary, followed by another at 33.4 Ma. Similarly, the oxygen isotope, ice-rafted debris, and clay assemblage records indicate two important climatic events: the appearance of alpine glaciers and/or small ice-sheets on Antarctica in the late Eocene at 38-39 Ma, followed by a rapid transition to larger and more permanent temperate ice-sheets in the early Oligocene at 33.4 Ma. Moreover, during the early Oligocene 30-33 Ma. three to four inferred peaks in glacial activity appear to coincide with subtle steps in the 87Sr/86Sr record. The coupled variations in climate and seawater Sr isotope ratios during the Eocene/Oligocene imply a strong causal link between the two. Either changes in climate directly influenced patterns of continental weathering and hence seawater chemistry, and/or a tectonic event e.g., uplift.as reflected in weathering and seawater chemistry triggered relatively abrupt changes in global climate.本数据集包含亚南极深海沉积岩芯的稳定同位素、放射成因同位素及沉积学数据，揭示了海水87Sr/86Sr比值变化与始新世晚期-渐新世早期主要气候变化事件之间的时序关联。87Sr/86Sr记录存在两个显著拐点：其一位于38~39 Ma，接近始新世中晚期界线；其二位于33.4 Ma。与之对应，氧同位素（oxygen isotope）、冰筏碎屑（ice-rafted debris）及黏土组合（clay assemblage）记录也反映出两起重要气候事件：始新世晚期38~39 Ma时，南极境内出现高山冰川及/或小型冰盖；随后在渐新世早期33.4 Ma时，快速过渡为规模更大且更稳定持久的温型冰盖。此外，在渐新世早期30~33 Ma期间，推断出的3~4次冰川活动峰值似乎与87Sr/86Sr记录中的细微阶跃变化相吻合。始新世/渐新世期间气候与海水锶同位素比值的协同变化表明，二者之间存在极强的因果关联：要么是气候变化直接影响了大陆风化模式，进而改变海水化学组成；要么是构造事件（如抬升作用）通过影响风化作用与海水化学组成，触发了全球气候的相对突变。