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British-Irish Ice Sheet during the Devensian Stage in the Vale of York

British-Irish Ice Sheet during the Devensian Stage in the Vale of York

Current understanding of dynamics of the British-Irish Ice Sheet (BIIS) in eastern England during the Devensian Stage is that ice lobes in the Vale of York and North Sea Basin were asynchronous. New sedimentological and geochemical data from four cores through the basin fill in the central part of the Vale of York, together with six, three-dimensional geological models developed from 3050 core logs of superficial deposits in the region, have provided critical new insights into the terrestrial response in central eastern England to climate forcing during the Devensian Stage.

A new, high-resolution age model, determined from sediment colour, optically-stimulated luminescence dating and magnetic properties indicates that the basin-fill sediments were deposited from 41.00 to 15.80 ka. Glacial Lake Humber was initiated in the Vale of York at ~40.00 ka from meltwater flowing eastwards from an ice lobe situated in the eastern Pennines. Variations in sediment redness (a* reflectance and 570–560 nm) and end-member modelling have enabled glacially- and periglacially-derived inputs into Lake Humber to be differentiated. Between 38.20 and 33.00 ka, the dominant processes were periglacial, indicated by variations in the a* reflectance records that were broadly synchronous with the Dansgaard-Oeschger cycles recognised in the Greenland ice-core δ18O records. End-member modelling has demonstrated that Ca/Sr records provide a proxy for incursions of the North Sea Basin ice lobe of the BIS onto Holderness. These records indicate that this ice lobe first advanced westwards to Holderness at 33.00 ka, with three significant readvances at 22.51, 21.36 and 20.80 ka. In the Vale of York, ice extended no further south than the Escrick moraine ridge, attaining its maximum extent between 23.50 and 21.60 ka. The dynamics of the eastern sector of the BIIS between 41.00 to 15.80 ka were strongly coupled with movements of the North Atlantic Polar Front.

Hemingbrough quarry in the Vale of York.

Hemingbrough quarry in the Vale of York. The lithostratigraphy comprises laminated silty clay with interbedded silt and silty sands. X-ray radiographs and high-resolution, line-scan digital images were taken of a core drilled through the basin-fill sediments. CIELAB reflectance data and X-ray fluorescence data were used to analyse the composition of the sediments. An example of the variation in a* reflectance, which describes the redness of the sediments, is shown for one Hemingbrough core section.