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The mixed‐bed glacial landform imprint of the North Sea Lobe in the western North Sea
Author(s) -
Roberts David H.,
Grimoldi Elena,
Callard Louise,
Evans David J.A.,
Clark Chris D.,
Stewart Heather A.,
Dove Dayton,
Saher Margot,
Ó Cofaigh Colm,
Chiverrell Richard C.,
Bateman Mark D.,
Moreton Steven G.,
Bradwell Tom,
Fabel Derek,
Medialdea Alicia
Publication year - 2019
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.4569
Subject(s) - geology , glacial period , geomorphology , ice sheet , oceanography , ice stream , sea ice , paleontology , cryosphere
During the last glacial cycle an intriguing feature of the British‐Irish Ice Sheet was the North Sea Lobe (NSL); fed from the Firth of Forth and which flowed south and parallel to the English east coast. The controls on the formation and behaviour of the NSL have long been debated, but in the southern North Sea recent work suggests the NSL formed a dynamic, oscillating terrestrial margin operating over a deforming bed. Further north, however, little is known of the behaviour of the NSL or under what conditions it operated. This paper analyses new acoustic, sedimentary and geomorphic data in order to evaluate the glacial landsystem imprint and deglacial history of the NSL offshore from NE England. Subglacial tills (AF2/3) form a discontinuous mosaic interspersed with bedrock outcrops across the seafloor, with the partial excavation and advection of subglacial sediment during both advance and retreat producing mega‐scale glacial lineations and grounding zone wedges. The resultant ‘mixed‐bed’ glacial landsystem is the product of a dynamic switch from a terrestrial piedmont‐lobe margin with a net surplus of sediment to a partially erosive, quasi‐stable, marine‐terminating, ice stream lobe as the NSL withdrew northwards. Glaciomarine sediments (AF4) drape the underlying subglacial mixed‐bed imprint and point to a switch to tidewater conditions between 19.9 and 16.5 ka cal BP as the North Sea became inundated. The dominant controls on NSL recession during this period were changing ice flux through the Firth of Forth ice stream onset zone and water depths at the grounding line; the development of the mixed‐bed landsystem being a response to grounding line instability. © 2018 John Wiley & Sons, Ltd.