Late Devensian deglaciation of the Tyne Gap Palaeo‐Ice Stream, northern England

Stephen J Livingstone,David H Roberts,David J A Evans,Colm Ó Cofaigh,Delia M Gheorghiu,Bethan J Davies

doi:10.1002/jqs.2813

Abstract

ABSTRACTThe deglacial history of the central sector of the last British–Irish Ice Sheet is poorly constrained, particularly along major ice‐stream flow paths. The Tyne Gap Palaeo‐Ice Stream (TGIS) was a major fast‐flow conduit of the British–Irish Ice Sheet during the last glaciation. We reconstruct the pattern and constrain the timing of retreat of this ice stream using cosmogenic radionuclide (10Be) dating of exposed bedrock surfaces, radiocarbon dating of lake cores and geomorphological mapping of deglacial features. Four of the five 10Be samples produced minimum ages between 17.8 and 16.5 ka. These were supplemented by a basal radiocarbon date of 15.7 ± 0.1 cal ka BP, in a core recovered from Talkin Tarn in the Brampton Kame Belt. Our new geochronology indicates progressive retreat of the TGIS from 18.7 to 17.1 ka, and becoming ice free before 16.4–15.7 ka. Initial retreat and decoupling of the TGIS from the North Sea Lobe is recorded by a prominent moraine 10–15 km inland of the present‐day coast. This constrains the damming of Glacial Lake Wear to a period before ∼18.7–17.1 ka in the area deglaciated by the contraction of the TGIS. We suggest that retreat of the TGIS was part of a regional collapse of ice‐dispersal centres between 18 and 16 ka.

Highlights

The investigation of palaeo-ice sheet beds is critical to the assessment of recent and future changes in contemporary ice sheets and for understanding the controls that influence their behaviour
This paper focuses on the Tyne Gap Ice Stream (TGIS), which flowed eastwards towards the mouth of the River Tyne through a predominantly bedrock-floored, 15–30-km-wide mountainous pass located between the Cheviot Hills and English Pennines (Figs 1 and 2)
In this paper we present a simple chronological model based on single 10Be surface exposure and 14C radiocarbon ages, which provide the first constraints on deglaciation of the Tyne Gap Palaeo-Ice Stream (TGIS) corridor

Summary

Introduction

The investigation of palaeo-ice sheet beds is critical to the assessment of recent and future changes in contemporary ice sheets and for understanding the controls that influence their behaviour. Livingstone et al, 2008, 2010a, 2012; Evans et al, 2009; Davies et al, 2009, 2012), the timing and rate of its retreat are poorly constrained (Chiverrell and Thomas, 2010; Hughes et al, 2011; Clark et al, 2012). This is significant as the development of a robust geochronology is essential for correlating complex ice-flow phasing across different sectors of the last BIIS and for relating ice-dynamic behaviour to internal and external forcing mechanisms. This is reflected in the geological record, which indicates complex, multi-phase ice-flow behaviour and repeated marginal fluctuations (Livingstone et al, 2008, 2012; Evans et al, 2009)

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Discussion

Conclusion