Evidence of permafrost in the Paleoproterozoic (c. 1.9 Ga) of Central Sweden

Jef Vandenberghe*, Gerrit Kuipers, Frank F. Beunk, Keewook Yi, Frederik M. van der Wateren

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

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.

Original languageEnglish
Pages (from-to)169-177
Number of pages9
JournalPermafrost and Periglacial Processes
Volume32
Issue number1
Early online date17 Dec 2020
DOIs
Publication statusPublished - Jan 2021

Keywords

  • Central Sweden, early Proterozoic, ice-wedge cast, paleo-permafrost

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