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Article

Cosmogenic Exposure Dating (36Cl) of Landforms on Jan Mayen, North Atlantic, and the Effects of Bedrock Formation Age Assumptions on 36Cl Ages

1
Department of Natural Sciences and Environmental Health, University of South-Eastern Norway, Gullbringvegen 36, 3800 Bø, Norway
2
Institute of Geological Sciences, University of Bern, Baltzerstrasse 1-3, 3012 Bern, Switzerland
3
Geological Survey of Norway, P.O. Box 6315, Torgarden, 7491 Trondheim, Norway
4
School of Earth and Environmental Sciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK
5
Laboratory of Ion Beam Physics, ETH Zürich, 8093 Zürich, Switzerland
*
Author to whom correspondence should be addressed.
Academic Editors: Ángel Rodés and Jesus Martinez-Frias
Geosciences 2021, 11(9), 390; https://doi.org/10.3390/geosciences11090390
Received: 14 July 2021 / Revised: 31 August 2021 / Accepted: 10 September 2021 / Published: 15 September 2021
(This article belongs to the Special Issue Cutting Edge Earth Sciences: Three Decades of Cosmogenic Nuclides)
Jan Mayen is a small volcanic island situated 550 km north of Iceland. Glacial sediments and landforms are relatively common on the island but, so far, only a few of them have been dated. In this study, we present and discuss 89 36Cl dates of primarily glacial and volcanic events on Jan Mayen. Calculations of sample exposure ages were complicated by young exposure ages, young rock formation age, and high native Cl contents, leading to updates in CRONUScalc to enable accurate exposure age calculations. The samples provide good evidence against an equilibrium assumption when subtracting background production (e.g., 36Cl produced by neutron capture from fission of U or Th) for samples on young bedrock, with younger exposure ages most significantly affected. Exposure ages were calculated with a range of assumptions of bedrock formation ages appropriate for Jan Mayen, including the assumption that the rock formation age equaled the exposure age (i.e., the youngest age it could possibly have), and we found that although the effect on most of the ages was small, the calculated ages of 25 of the samples increased by more than 1 standard deviation from the age calculated assuming equilibrium background production, with a maximum deviation of 6.1 ka. Due to the very young bedrock on Jan Mayen, we consider the nonequilibrium ages to be the most reliable ages from the island and conclude that large-scale deglaciation on the south and central, lower-lying, parts of the island, started around 20 ka and lasted until ~7 ka. On northern Jan Mayen, the slopes of the 2277 m high stratovolcano Beerenberg are currently partly glaciated; however, outside of the Little Ice Age moraines, all but two samples give ages between 14 and 5.7 ka. View Full-Text
Keywords: cosmogenic surface exposure dating; 36Cl; Jan Mayen; background production cosmogenic surface exposure dating; 36Cl; Jan Mayen; background production
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MDPI and ACS Style

Anjar, J.; Akҫar, N.; Larsen, E.A.; Lyså, A.; Marrero, S.; Mozafari, N.; Vockenhuber, C. Cosmogenic Exposure Dating (36Cl) of Landforms on Jan Mayen, North Atlantic, and the Effects of Bedrock Formation Age Assumptions on 36Cl Ages. Geosciences 2021, 11, 390. https://doi.org/10.3390/geosciences11090390

AMA Style

Anjar J, Akҫar N, Larsen EA, Lyså A, Marrero S, Mozafari N, Vockenhuber C. Cosmogenic Exposure Dating (36Cl) of Landforms on Jan Mayen, North Atlantic, and the Effects of Bedrock Formation Age Assumptions on 36Cl Ages. Geosciences. 2021; 11(9):390. https://doi.org/10.3390/geosciences11090390

Chicago/Turabian Style

Anjar, Johanna, Naki Akҫar, Eiliv A. Larsen, Astrid Lyså, Shasta Marrero, Nasim Mozafari, and Christof Vockenhuber. 2021. "Cosmogenic Exposure Dating (36Cl) of Landforms on Jan Mayen, North Atlantic, and the Effects of Bedrock Formation Age Assumptions on 36Cl Ages" Geosciences 11, no. 9: 390. https://doi.org/10.3390/geosciences11090390

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