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.

始新世早期（大约 56 - 4800 万年前）经历了自中生代以来地球历史上最高的一些全球气温，没有极地冰。由于这些所谓的寒冷气候指标的重要性不明确，有关高纬度地区冰筏漂流和冷水菱镁矿相互矛盾的报告在很大程度上被驳回了。在这里，我们将团块同位素古温度测量法应用于传统的定性非生物替代品格陵脱石方解石，以生成北部中纬度底层水域的定量温度估计值。我们的数据显示，丹麦盆地的菱镁矿在低于 5 °C 的水域中形成，水深小于 300 m。这种接近冰点的温度以前没有根据早期始新世地球上任何地方的代理数据重建，