Intensive chemical weathering in the Arctic during the Miocene Climatic Optimum

Hall, A., Barfod, D. , Gilg, A., Stuart, F. , Sarala, P. and Al-Ani, T. (2024) Intensive chemical weathering in the Arctic during the Miocene Climatic Optimum. Palaeogeography, Palaeoclimatology, Palaeoecology, 634, 111927. (doi: 10.1016/j.palaeo.2023.111927)

Abstract

The Arctic today has shallow, chemically immature, and frost-dominated weathering regimes. At Sokli, Finland (68°N), a 70 m deep palaeo-weathering profile is developed in a Devonian carbonatite pipe that represents fundamentally different past weathering environments. Formation of the apatite-francolite P-ore likely began under Palaeogene warm, humid climates. Later, cryptomelane (K-Mn oxide) crusts developed within the ore that have yielded peak 40Ar/39Ar ages of 16.20 ± 0.13 Ma (2σ)., The crusts formed at the redox front during the Miocene Climatic Optimum (∼16.9–14.7 Ma) under mean annual temperatures ∼12–14 °C warmer than today. The presence of the cryptomelane crust at shallow depth (15 m) indicates very low erosion rates since formation, consistent with its position on a tectonically stable Archaean craton and in the cold-based ice-divide zone of successive Fennoscandian ice sheets. The Miocene Climatic Optimum triggered a pulse of intensive weathering in mid- and low latitudes; the Sokli cryptomelane ages demonstrate that intensive chemical weathering extended into the Arctic.

• Item Type: Articles
• Additional Information: The work described in this paper was supported by the Albert & Maria Bergström Foundation and the NERC funded NEIF Argon Isotope Laboratory.
• Keywords: Miocene Climatic Optimum, weathering, Arctic, cryptomelane, climate change.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Barfod, Dr Dan and Stuart, Professor Fin
• Authors: Hall, A., Barfod, D., Gilg, A., Stuart, F., Sarala, P., and Al-Ani, T.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Palaeogeography, Palaeoclimatology, Palaeoecology
• Publisher: Elsevier
• ISSN: 0031-0182
• ISSN (Online): 1872-616X
• Published Online: 22 November 2023
• Copyright Holders: Copyright © 2023 The Authors
• First Published: First published in Palaeogeography, Palaeoclimatology, Palaeoecology 634:111927
• Publisher Policy: Reproduced under a Creative Commons licence