The Eocene‐Oligocene transition (EOT) marks the onset of Antarctic glaciation at 33.7 Ma. Although the benthic oxygen isotope record defines the major continental ice sheet expansion, recent sedimentary and geochemical evidence suggests the presence of earlier ephemeral ice sheets. Sediment cores from Ocean Drilling Program Legs 119 and 188 in Prydz Bay provide an archive of conditions in a major drainage system of East Antarctica. We study biomarker and microfossil evidence to discern how the vegetation and climate shifted between 36 and 33 Ma. Pollen was dominated by reworked Permian Glossopterid gymnosperms; however, penecontemporaneous Eocene pollen assemblages indicate that some vegetation survived the glacial advances. At the EOT, brGDGT soil biomarkers indicate abrupt cooling from 13°C to 8°C and soil pH increases from 6.0 to 6.7, suggesting drying which is further supported by plant wax hydrogen and carbon isotopic shifts of 20‰ and 1.1‰, respectively, and evidence for drying from weathering proxies. Although the terrestrial soil biomarker influx mostly precludes the use of TEX₈₆, we find sea surface temperatures of 12°C in the late Eocene cooling to 8°C at the EOT. Marine productivity undergoes a sustained increase after the glacial advance, likely promoted by enhanced ocean circulation. Between the two glacial surge events of the Priabonian Oxygen Maximum at 37.3 Ma and the EOT at 33.7 Ma, we observe warming of 2–5°C at 35.7 and 34.7 Ma, with increase in penecontemporaneous pollen and enhanced marine productivity, capturing the last flickers of Antarctic warmth.

中文翻译：

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南极东部普里兹湾的晚始新世水文和温度记录

始新世-渐新世过渡（EOT）标志着南极冰期开始于33.7 Ma。尽管底栖氧同位素记录确定了主要的大陆冰盖膨胀，但最近的沉积和地球化学证据表明存在较早的短暂冰盖。来自Prydz湾海洋钻探计划第119条和第188条的沉积物岩心提供了南极东部主要排水系统的状况档案。我们研究了生物标志物和微化石证据，以辨别植被和气候在36到33 Ma之间如何变化。花粉主要由重造的二叠纪Glossopterid裸子植物组成；但是，近新世的始新世花粉组合表明，一些植被在冰川发展过程中幸存下来。在EOT处，brGDGT土壤生物标志物表明温度从13°C突然降到8°C，土壤pH从6.0升高到6.7，提示干燥是由植物蜡氢和碳同位素位移分别为20‰和1.1‰进一步支持的，并有来自风化代理干燥的证据。尽管陆地土壤生物标志物大量涌入，但无法使用TEX_在图86中，我们发现始新世晚期在EOT冷却至8°C时海表温度为12°C。冰川发展之后，海洋生产力持续增加，这可能是由于海洋环流增强所推动的。在两次冰川激增事件中，Priabonian的最大氧为37.3 Ma，EOT的为33.7 Ma，我们观察到在35.7和34.7 Ma时温度升高了2–5°C，同时期花粉增加并且海洋生产力增强，捕获了最后的闪烁南极的温暖。