Lake sediment records give valuable insight into the dynamic events that characterized the last deglaciation in Iceland. Here, we focus on the well-dated sediment record from Hestvatn, a low-elevation lake in south Iceland, that features six graded bedding events deposited by outburst floods from glacial lakes dammed by the decaying Iceland Ice Sheet (IIS) in the time period of the Vedde Ash and the G10ka Series tephra. Using climate proxies preserved in the sediment cores, in conjunction with regional glacial geomorphology, we reconstruct the retreat of the IIS in south Iceland, from a marine-based glacier during the Younger Dryas to a land-based glacier during the Preboreal. As the ice sheet margin withdrew to the central highlands, ice-dammed lakes formed along glacier margins. The ice-dams were occasionally breached, generating large-scale jökulhlaups (catastrophic outburst floods) that deposited thick turbidite sequences preserved in the sediment record of Hestvatn. The high concentration of volcanic material incorporated within deglacial sediments indicates that along with IIS retreat, subglacial volcanic activity may have helped initiate some of the jökulhlaups. Onset of more stable Holocene conditions was reached after the final turbidite at ~10 ka bp, when the IIS had withdrawn from most of the highlands of Iceland. © 2021 John Wiley & Sons, Ltd.
Bibliographical noteFunding Information:
The Hestvatn sediment cores were obtained using the DOSECC GLAD‐200 coring system with financial support from the US National Science Foundation (OPP‐0138010) and the Icelandic Centre of Research, RANNIS (No. 040233021). Additional support was provided by the VAST (Volcanism in the Arctic System) Project, through NSF‐ARC 0714074 and RANNIS No. 0070272011 and RANNIS project grant No. 100233021. Thanks to DOSECC personnel, Thorsteinn Jónsson, Sveinbjörn Steinthórsson and Doug Schnurrenberger for their assistance in the field, and to the people at the LRC, University of Minnesota and the Hu Laboratory at University of Illinois at Urbana‐Champaign, for laboratory assistance and analyses. We thank Alex Wolfe, Department of Biological Sciences, University of Alberta, for the diatom analysis and the SEM images. We thank Jan Mangerud and an anonymous reviewer as well as the editor, Martin Melles, for helpful and constructive comments on the manuscript.
© 2021 John Wiley & Sons, Ltd.
- lake sediments
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