The age and origin of the Blakeney esker of north Norfolk: implications for the glaciology of the southern North Sea Basin

摘要

The age and origin of the Blakeney ridge of eastern England have been debated for over a century.The feature is shown to be an esker formed in the late stages locally of a glaciation of MiddleQuaternary age. The weight of evidence indicates that the esker was associated with the ice thatlaid down the Marly Drift of central north Norfolk, although this cannot be demonstrated con-clusively. The flows that formed the Blakeney esker were subglacial. They took place from north-west to southeast along the length of the ridge, with at least the final phase occurring under hydrostaticpressure. It is likely that the esker developed during a glacial stillstand and under steep hydraulicgradients close to the ice sheet terminus. Although the esker conduit appears to have functionedlargely as a Rothlisberger channel, there is evidence of simultaneous incision of the glacial bed. Avalley is cut into bedrock beneath the esker. The esker and the buried valley may form the distalcomponents of one of the broadly north-south aligned subglacial valleys that were trenched acrossthe southern North Sea Basin in Middle Quaternary times. The complex assemblage of proglacialglaciofluvial landforms found to the south of the esker may represent the products of transportalong the subglacial valley. The ice lobe that occupied the southern North Sea Basin may have leftsimilar buried valley-proglacial fan complexes elsewhere along the northern fringe of East Anglia.