IGN, University of Copenhagen, Øster Voldgade 10, DK-1350, Copenhagen, Denmark.
Biogeochemistry Research Centre, School of Geography, Earth and Environmental Sciences, Plymouth University, Drake Circus, Plymouth, PL4 8AA, UK.
Nat Commun. 2020 Sep 18;11(1):4713. doi: 10.1038/s41467-020-18558-7.
The early Eocene (c. 56 - 48 million years ago) experienced some of the highest global temperatures in Earth's history since the Mesozoic, with no polar ice. Reports of contradictory ice-rafted erratics and cold water glendonites in the higher latitudes have been largely dismissed due to ambiguity of the significance of these purported cold-climate indicators. Here we apply clumped isotope paleothermometry to a traditionally qualitative abiotic proxy, glendonite calcite, to generate quantitative temperature estimates for northern mid-latitude bottom waters. Our data show that the glendonites of the Danish Basin formed in waters below 5 °C, at water depths of <300 m. Such near-freezing temperatures have not previously been reconstructed from proxy data for anywhere on the early Eocene Earth, and these data therefore suggest that regionalised cool episodes punctuated the background warmth of the early Eocene, likely linked to eruptive phases of the North Atlantic Igneous Province.
早始新世（约 5600 万至 4800 万年前）经历了地球历史上自中生代以来的一些最高全球温度，没有极地冰。由于这些所谓的冷气候指标的意义不明确，有关高纬度地区冰漂漂砾和冷水 Glendonites 的报告在很大程度上被驳回。在这里，我们将凝聚同位素古温度计应用于传统的非生物代理 Glendonite 方解石，以生成北中纬度底层水的定量温度估计。我们的数据表明，丹麦盆地的 Glendonites 形成于 5°C 以下的水中，水深<300 m。以前从未从早始新世地球上任何地方的代理数据中重建过如此接近冰点的温度，因此这些数据表明，区域性的凉爽事件打断了早始新世的背景温暖，可能与北大西洋火成岩省的喷发阶段有关。
