Durham Research Online Deposited in DRO: 07 April 2021 Version of attached le: Published Version Peer-review status of attached le: Peer-reviewed Citation for published item: Evans, David J. A. and Roberts, David H. and Bateman, Mark D. and Clark, Chris D. and Medialdea, Alicia and Callard, Louise and Grimoldi, Elena and Chiverrell, Richard C. and Ely, Jeremy and Dove, Dayton and O¡ Cofaigh, Colm and Saher, Margot and Bradwell, Tom and Moreton, Steven G. and Fabel, Derek and Bradley, Sarah L. (2021) 'Retreat dynamics of the eastern sector of the BritishIrish Ice Sheet during the last glaciation.', Journal of quaternary science., 36 (5). pp. 723-751. Further information on publisher's website: https://doi.org/10.1002/jqs.3275 Publisher's copyright statement: Copyright c 2021 The Authors Journal of Quaternary Science Published by John Wiley Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Additional information: Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full DRO policy for further details. Durham University Library, Stockton Road, Durham DH1 3LY, United Kingdom Tel : +44 (0)191 334 3042 | Fax : +44 (0)191 334 2971 https://dro.dur.ac.uk JOURNAL OF QUATERNARY SCIENCE (2021) 1–29 ISSN 0267-8179. DOI: 10.1002/jqs.3275 Retreat dynamics of the eastern sector of the British–Irish Ice Sheet during the last glaciation DAVID J. A. EVANS,1* DAVID H. ROBERTS,1 MARK D. BATEMAN,2 CHRIS D. CLARK,2 ALICIA MEDIALDEA,3 LOUISE CALLARD,4 ELENA GRIMOLDI,5 RICHARD C. CHIVERRELL,6 JEREMY ELY,2 DAYTON DOVE,7 COLM Ó COFAIGH,1 MARGOT SAHER,8 TOM BRADWELL,9 STEVEN G. MORETON,10 DEREK FABEL11 and SARAH L. BRADLEY12 1Department of Geography, Durham University, Durham, UK 2Department of Geography, University of Sheffield, Sheffield, UK 3National Research Centre on Human Evolution (CENIEH), Burgos, Spain 4School of Geography, Politics and Sociology, Newcastle University, Newcastle, UK 5Fugro, Fugro House, Wallingford, Oxford, UK 6School of Environmental Sciences, University of Liverpool, Liverpool, UK 7British Geological Survey, Lyell Centre, Herriot Watt University, Edinburgh, UK 8School of Ocean Sciences, Bangor University, Anglesey, UK 9Biological and Environmental Sciences, University of Stirling, Stirling, UK 10Natural Environment Research Council, Radiocarbon facility, East Kilbride, UK 11Scottish Universities Environmental Research Centre, East Kilbride, UK 12Institute of Geography, University of Cologne, Cologne, Germany Received 21 April 2020; Revised 16 November 2020; Accepted 11 January 2021 ABSTRACT: The findings of BRITICE‐CHRONO Transect 2 through the North Sea Basin and eastern England are reported. We define ice‐sheet marginal oscillation between ~31 and 16 ka, with seven distinctive former ice‐sheet limits (L1–7) constrained by Bayesian statistical analysis. The southernmost limit of the North Sea Lobe is recorded by the Bolders Bank Formation (L1; 25.8–24.6 ka). L2 represents ice‐sheet oscillation and early retreat to the northern edge of the Dogger Bank (23.5–22.2 ka), with the Garret Hill Moraine in north Norfolk recording a significant regional readvance to L3 at 21.5–20.8 ka. Ice‐marginal oscillations at ~26–21 ka resulted in L1, L2 and L3 being partially to totally overprinted. Ice‐dammed lakes related to L1–3, including Lake Humber, are dated at 24.1–22.3 ka. Ice‐sheet oscillation and retreat from L4 to L5 occurred between 19.7 and 17.3 ka, with grounding zone wedges marking an important transition from terrestrial to marine tidewater conditions, triggered by the opening of the Dogger Lake spillway between 19.9 and 17.5 ka. L6 relates to ice retreat under glacimarine conditions and final ice retreat into the Firth of Forth by 15.8 ka. L7 (~15 ka) represents an ice retreat from Bosies Bank into the Moray Firth. Copyright © 2021 The Authors Journal of Quaternary Science Published by John Wiley & Sons Ltd KEYWORDS: British–Irish Ice Sheet; ice‐sheet flow dynamics; MIS2; North Sea Lobe; palaeoglaciology Introduction record of deglaciation in a terrestrial setting, with sub- glacial landscapes overprinted by glacilacustrine, glaci- ‐ This paper reviews the results of the BRITICE CHRONO Transect fluvial outwash and Holocene marine sediments (e.g. Dove 2 through the North Sea Basin and onto the onshore areas of et al. 2017; Roberts et al. 2018). ‐ eastern England in the context of pre existing knowledge on the Recent hypotheses suggest that ice‐sheet coalescence – behaviour of the British Irish Ice Sheet (BIIS) in the region. It is a between the BIIS and FIS over the central North Sea occurred critical region for palaeoglaciological reconstruction because it throughout the Last Glacial Maximum (LGM; 30–23 ka), but was characterised by confluence between the BIIS and the was followed by regional decoupling and rapid flow instability Fennoscandinavian Ice Sheet (FIS), where ice flow was highly of the BIIS (Sejrup et al. 2000; Graham et al. 2007, 2010; ‐ dynamic (and possibly surge influenced) and ice streams appear Bradwell et al. 2008, 2019). This was triggered first by the to have switched on and off through the last glacial cycle (cf. retreat of the Norwegian Channel Ice Stream (NCIS) and Balson & Jeffrey 1991; Eyles et al. 1994; Carr et al. 2006; second by the catastrophic northerly drainage of the Dogger Hubbard et al. 2009; Sejrup et al. 2009, 2016; Boston Lake complex between 19 and 17.5 ka in the southern North et al. 2010; Graham et al. 2011; Clark et al. 2012). In the Sea (Sejrup et al., 2016). However, despite many years of north and central North Sea, subglacial landforms and work, several key questions remain unanswered. Working in deposits are overlain by glacimarine sediments that record the North Sea region, Transect 2 of the BRITICE‐CHRONO marine inundation following deglaciation. In contrast, in project specifically aimed to explore several key questions: 1) the south, the shallow seas of the Dogger Bank and offshore how far did the BIIS extend at the LGM?; 2) how, when and areas of Yorkshire, Lincolnshire and Norfolk contain a where did the BIIS and FIS uncouple?; 3) did marine inundation of the northern North Sea destabilise the BIIS and *Correspondence: David j. A. Evans, as above. ‐ ‐ E‐mail: [email protected] thereby trigger rapid east to west retreat?; and 4) what were the Copyright © 2021 The Authors Journal of Quaternary Science Published by John Wiley & Sons Ltd This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. 2 JOURNAL OF QUATERNARY SCIENCE major BIIS controls on North Sea ice flow dynamics and ice‐dammed lakes such as Lake Tyne, Lake Wear and Lake Tees deglaciation patterns? during phases of ice‐marginal recession (Agar 1954; Smith 1981; The findings of Transect 2 are summarised here based upon Plater et al. 2000; Davies et al. 2009, 2019; Livingstone new data from a number of localised case studies that were et al. 2012, 2015; Yorke et al. 2012). Around the North Yorkshire designed to further interrogate the existing glacial geomorphol- Moors, ice‐dammed lakes were created in Kildale and the Vale of ogy, Late Quaternary stratigraphy and geochronology in key Pickering by onshore flow of the NSL at its maximum extent locations around the British sector of the North Sea Basin (Evans during MIS 2 (Kendall 1902; Evans et al. 2017; Lincoln et al. 2017; et al. 2017, 2018, 2019; Bateman et al. 2018; Roberts Fig. 2). In the Vale of Pickering, the NSL plugged the valley et al. 2018, 2019), as well as concurrent reports on glacial mouth with substantial morainic topography (Filey and Flambor- reconstructions prepared outwith, but at the same time com- ough moraines; Kendall 1902; Farrington & Mitchell 1951), plementary to, the BRITICE‐CHRONO project (e.g. Murton thereby permanently reversing the flow of the River Derwent et al. 2009; Bateman et al. 2008, 2015; Fairburn & Bate- (King 1965; Evans et al. 2017). The most substantial lake created man 2016; Dove et al. 2017; Fig. 1). The findings reported in between the Pennine‐sourced ice and the NSL existed in the Vale these case studies are now critically reviewed in the context of of York/Humber lowland region, where the 125 km long Vale of the regional reconstructions of BIIS palaeoglaciology as it York ice lobe flowed from the Stainmore Gap and Tees lowlands pertains to the eastern margins of the ice sheet. The North to terminate within 10 km of the onshore‐flowing NSL, plugging Sea is subdivided into two sectors: the northern sector, the Humber Estuary to construct the Ellingham/Ferriby/Horkstow extending from the Firth of Forth to the Moray Firth and east moraine complex and thereby creating Glacial Lake Humber to Fladen Ground and Viking Bank/Plateau; and the south- (Gaunt 1974, 1981; Straw 1979; Bateman et al. 2000, ern sector, extending from the Firth of Forth to Great Fisher 2008, 2015, 2018; Fig. 2). Although Lake Humber highstands Bank and southwards into the southern North Sea Basin of up to ~30 m OD (Ordnance Datum) have been proposed (e.g.