It is debated whether there was strong climate seasonality during the Eocene, which provides a close geological analogy for near-future scenarios of greenhouse gas emissions. Lithological data suggest the existence of a broad arid zone centered around 30°N paleo-latitude, while a humid climate was supported by palaeobotanic assemblages in East Asia. Here, we report the occurrence of massive primary lacustrine dolomite and magnesite in the central East Asia during the middle Eocene. We provide a novel perspective from magnesium isotopes to link the formation of Mg-carbonates to seasonal dry-wet cycles. Rapid magnesium input during the rainy season and intense evaporation in the dry season likely caused the formation of magnesium carbonates in an enclosed lake. These findings provide insights into hydroclimatic seasonality during the Eocene, contributing to our understanding of the hydrological cycle response to a greenhouse climate.

中文翻译：

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碳酸盐镁同位素揭示中始新世中东地区的季节性气候变化

关于始新世是否存在强烈的气候季节性存在争议，这为近期温室气体排放的情景提供了密切的地质类比。岩性数据表明，存在着以北纬 30° 古纬度为中心的广阔干旱区，而东亚的古植物群则支持湿润气候。在这里，我们报告了始新世中期在东亚中部出现了大量的原生湖相白云石和菱镁矿。我们从镁同位素提供了一种新颖的视角，将碳酸镁的形成与季节性干湿循环联系起来。雨季镁的快速输入和旱季的强烈蒸发可能导致封闭湖中碳酸镁的形成。这些发现为我们了解始新世期间的水文气候季节性提供了见解，有助于我们了解水文循环对温室气候的响应。