Timing and consequences of Bering Strait opening: new insights from 40Ar/39 1 Ar dating 2 of the Barmur Group (Tjörnes beds), northern Iceland

Hall, J. R., Allison, M. S., Papadopoulos, M. T., Barfod, D. N. and Jones, S. M. (2023) Timing and consequences of Bering Strait opening: new insights from 40Ar/39 1 Ar dating 2 of the Barmur Group (Tjörnes beds), northern Iceland. Paleoceanography and Paleoclimatology, 38, e2022PA004. (doi: 10.1029/2022PA004539)

Abstract

The Barmur Group (informally Tjörnes beds) sedimentary succession of northern Iceland is key to reconstructing the opening of the Bering Strait oceanic gateway because these rocks record migration of bivalve molluscs from the Pacific to the Atlantic via the Arctic. However, the timing of the migration event is poorly constrained owing to a lack of reliable absolute ages. To address this problem, we present the first Ar-Ar radiometric dates from four basaltic lavas that underlie, are intercalated with, and overlie the Barmur Group, and integrate them with existing paleomagnetic records. We show that the Barmur Group has a latest Miocene to early Pliocene age range (c. 6.0–4.4 Ma; C3r–C3n.2n), older than all previous age models. Thus, the Barmur Group does not record the mid-Piacenzian Warm Period, contra some previous suggestions. Abundant Pacific bivalve molluscs appeared in the Barmur Group during subchrons C3n.4n–C3n.3r at 5.235–4.896 Ma, over 1.3 million years earlier than previously suggested. Appearance of Pacific bivalves in the northern Atlantic occurred shortly after the 5.6–5.4 Ma age previously inferred for first appearance of Arctic bivalves in the Pacific. Thus, our data suggest that first opening of the Bering Strait gateway by the latest Miocene (c. 5.5 Ma) was soon followed by bidirectional trans-Arctic faunal exchange, and argue against a hypothesized two-stage faunal exchange process spanning c. 2 million years. Our results also confirm that first opening of the Bering Strait gateway was not directly associated with the growth of large northern hemisphere icesheets, which occurred several million years later.

• Item Type: Articles
• Additional Information: This work was supported by the Natural Environment Research Council (NERC Grant NE/M00578X/1). We thank the NERC Isotope Geosciences Facilities Steering Committee for awarding funding to undertake rock preparation and 40Ar/39Ar dating at the SUERC Argon Isotope Facility (NIGL Grant IP-1855-1118).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Barfod, Dr Dan
• Authors: Hall, J. R., Allison, M. S., Papadopoulos, M. T., Barfod, D. N., and Jones, S. M.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Paleoceanography and Paleoclimatology
• Publisher: American Geophysical Union
• ISSN: 2572-4517
• ISSN (Online): 2572-4525
• Published Online: 28 March 2023
• Copyright Holders: Copyright © 2023 The Authors
• First Published: First published in Paleoceanography and Paleoclimatology 38:e2022PA004539
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher