The timing and consequences of the blockage of the Humber Gap by the last British−Irish Ice Sheet

Mark D Bateman,David H Roberts,Jeremy Ely,Alicia Medialdea,David J A Evans,Chris D Clark

doi:10.1111/bor.12256

Mark D Bateman, David H Roberts + Show 4 more

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https://doi.org/10.1111/bor.12256

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Journal: Boreas	Publication Date: May 15, 2017
Citations: 33	License type: CC BY 4.0

Affiliation: Durham University, University of Sheffield

Abstract

The eastern England terrestrial glacial sequences are critical to the spatial and temporal reconstruction of the last British−Irish Ice sheet (BIIS). Understanding glacial behaviour in the area of the Humber Gap is key as its blockage by ice created extensive proglacial lakes. This paper maps the glacial geomorphology of the Humber Gap region to establish for the first time the extent and thickness of the North Sea Lobe (NSL) of the BIIS. Findings establish the westerly maximal limit of the NSL. Ten new luminescence ages from across the region show the initial Skipsea Till advance to the maximal limits occurred regionally at c. 21.6 ka (Stage 1) and retreated off‐shore c. 18 ka (Stage 2). Punctuated retreat is evident in the south of the region whilst to the immediate north retreat was initially rapid before a series of near synchronous ice advances (including the Withernsea Till advance) occurred at c. 16.8 ka (Stage 3). Full withdrawal of BIIS ice occurred prior to c. 15 ka (Stage 4). Geomorphic mapping and stratigraphy confirms the existence of a proto Lake Humber prior to Stage 1, which persisted to Stage 3 expanding eastward as the NSL ice retreated. It appears that proglacial lakes formed wherever the NSL encountered low topography and reverse gradients during both phases of both advance and retreat. These lakes may in part help explain the dynamism of parts of the NSL, as they initiated ice draw down and associated streaming/surging. The above record of ice‐dammed lakes provides an analogue for now off‐shore parts of the BIIS where it advanced as a number of asynchronous lowland lobes.

Highlights

In eastern England, Cretaceous Chalk forms the north– south aligned Lincolnshire and Yorkshire Wolds, which respectively extend up to 168 m above sea level
The new data facilitate a much better spatial understanding of the pattern and chronology of ice advance and retreat within the region. This yields a better connection between the records of off-shore and on-shore ice dynamics of the NSL of the BIIS
Ages that directly date the Skipsea Till ice advance or require ice-damming in the Humber Gap show a high level of correspondence across the whole region and yield an average age of 21.6Æ1.3 ka (Stage 1, Table 2, Fig. 12)

Summary

Introduction

In eastern England, Cretaceous Chalk forms the north– south aligned Lincolnshire and Yorkshire Wolds, which respectively extend up to 168 m above sea level Arguably the Humber Gap is of greatest significance having been initiated by the pre-Devensian fluvial exploitation of WNW faults located in the Brough-North Ferriby area (Fig. 1; Gaunt et al 1992). This eroded a 2-km-wide gap (at its narrowest) in the Chalk downs to at least À30 m a.s.l.

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