Insights into terrestrial climate conditions of the high-latitude Southern Hemisphere during the Eocene greenhouse world: An integrated palynological and organic geochemical approach

在项目的第一阶段，我们研究了IODP遗址U1156 （Wilkes Land, Antarctica）下始新世至中始新世的陆生孢子（花粉和孢子）。这导致了(1)认识到在始新世早期在威尔克斯地沿海地区盛行的包括棕榈树和Bombacoideae在内的副热带雨林生物群落；（ii）南极从始新世峰值温室条件到中始新世降温的第一次定量的、季节性的气候重建。我们的孢粉学和MBT/CBT古测温数据的整合产生了内部一致的图像。年平均气温可能高达20°C；值得注意的是，那里的冬天非常温和（约10°C），而且没有霜冻。虽然第一个项目阶段提供了从新生代温暖高峰到始新世中期冷却的南极洲陆地气候和环境条件的新见解，但我们建议在项目的最后一年，将重点放在从古新世最冷区间到早始新世温室条件高峰（~60 ~ ~54 myr）的南极洲陆地气候和环境的重建上。作为研究地点，我们推荐位于塔斯马尼亚高原古纬度65°S的ODP site 1172。1172D孔具有良好的年代地层年龄控制能力，前人对恐龙囊的研究表明，其演替具有较高的孢子体丰度。最重要的是，由于地表水流的配置，陆地地貌的源区可以被限制为主要代表来自东南极洲的高纬度信号。该项目将首次对南极洲从古近纪温室世界的兴起到黎明的气候进行定量重建。

During the first project phase, we have studied terrestrial palynomorphs (pollen and spores) from the Lower to Middle Eocene of IODP Site U1156 (Wilkes Land, Antarctica). This has resulted in (i) the recognition of a paratropical rainforest biome including palms and Bombacoideae that prevailed in the coastal region of Wilkes Land during the early Eocene; and (ii) the first quantitative, seasonally resolved climate reconstructions for Antarctica from peak Eocene greenhouse conditions to mid-Eocene cooling. The integration of our palynological and MBT/CBT paleothermometry data yields an internally consistent picture. Mean annual temperatures may have been as high as 20°C; notably, winters were extremely mild (>10°C) and frost-free. While the first project phase has provided new insights into the terrestrial climate and environmental conditions on Antarctica from peak Cenozoic warmth to mid-Eocene cooling, we propose for the final project year to focus on the reconstruction of terrestrial climate and environments on Antarctica from the coolest interval of the Paleocene into the peak of early Eocene greenhouse conditions (~60 to ~54 myr) using the same methodologies. As study site, we propose ODP Site 1172, located on the Tasmanian Plateau at a paleolatitude of 65°S during the Paleogene. Hole 1172D has excellent chronostratigraphic age control, and previous work on dinocysts has shown that its succession exhibits a relatively high abundance of sporomorphs. Most importantly, due to the configuration of surface-water currents, the source area of terrestrial palynomorphs can be constrained to predominantly represent a high-latitude signal from East Antarctica. The project will yield the first quantitative climate reconstructions for Antarctica from the rise into the dawn of the Paleogene greenhouse world.