This paper reports on an ice‐wedge pseudomorph that formed and is preserved in metavolcanic host material that was later transformed to metamorphic solid bedrock. It has been dated to 1,895 ± 5 Ma by U–Pb geochronology of zircon in the bedrock, an Early Proterozoic age. Detailed observation of the deformation structures of the wedge points to an ice‐wedge pseudomorph based on typical downbending around the wedge and vertical lamination in the inner part of the wedge due to slumping into the wedge after the ice melted, along with a few remains of lateral pressure structures (such as folds and upturned strata) in the adjacent host sediment. The interpretation of the wedge structure as an ice‐wedge pseudomorph confirms previous work on this topic. This ice‐wedge pseudomorph demonstrates for the first time the existence of permafrost at c. 1.9 Ga. It indicates that permafrost and associated conditions were present in lowlands at low latitude at discrete time intervals early in Earth’s history. Although some caution should be applied, mean annual air temperature appears to have been slightly below the freezing point at that time.

中文翻译：

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瑞典中部古元古代（约1.9 Ga）的多年冻土证据

本文报道了一个冰楔形假晶形，该形晶形成并保留在变火山岩主体材料中，后来被转化为变质的固体基岩。早元古代的基岩中锆石的U–Pb年代学已将其定为1895±5 Ma。对楔形变形结构的详细观察表明，基于典型的楔形周围的向下弯曲和楔形内部的垂直叠层（由于冰融化后塌落到楔形中），楔形变形物呈冰楔形，还有少量的残余物。邻近宿主沉积物中的侧向压力结构（例如褶皱和上倾地层）。将楔形结构解释为冰楔形假晶形，证实了以前有关该主题的工作。这种冰楔形假晶形首次证明了多年冻土的存在。c。1.9 Ga。这表明在地球历史早期，低纬度低地低海拔地区以离散时间间隔存在多年冻土层和相关条件。尽管应谨慎行事，但年平均气温似乎已略低于当时的冰点。