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 站点 U1156（南极洲威尔克斯地）下始新世至中始新世的陆地孢粉型（花粉和孢子）。这导致 (i) 认识到始新世早期在威尔克斯地沿海地区盛行的副热带雨林生物群落，包括棕榈树和 Bombacoideae； (ii) 首次定量、季节性解析南极洲气候重建，从始新世温室条件高峰到始新世中期降温。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，冬季极其温和（>10°C）且无霜。虽然第一项目阶段为南极洲从新生代温暖高峰到始新世中期降温的陆地气候和环境条件提供了新的见解，但我们建议最后一个项目年重点关注使用相同的方法重建从古新世最冷时期到始新世早期温室条件高峰（约60至约54林吉特）的南极洲陆地气候和环境。作为研究地点，我们建议 ODP 地点 1172，位于古近纪古南纬 65° 的塔斯马尼亚高原。 1172D 洞具有出色的年代地层年龄控制能力，之前对恐龙囊的研究表明，其演替表现出相对较高丰度的孢子体。最重要的是，由于地表水流的配置，陆地孢粉型的源区可能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兴起到黎明的时期进行定量气候重建。

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.