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Title: Devensian Ice-Sheet history of the western North Sea
Author: Grimoldi, Elena
ISNI:       0000 0004 7426 8667
Awarding Body: Durham University
Current Institution: Durham University
Date of Award: 2018
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The ice masses of present-day Greenland and Antarctica are characterised by marine-terminating ice streams and outlet glaciers, which deliver the majority of ice to the surrounding ocean and have a large impact on the ice sheet stability and sea-level. Understanding the break-up of palaeo-ice sheets and ice streams is thus considered crucial for understanding contemporary ice sheet behaviour and ice sheet response to global climate change. The history of the former eastern margin of the last British and Irish Ice Sheet (BIIS) is still poorly understood, particularly in the western North Sea. The BIIS is known to have overrun the eastern coasts of England and Scotland at different times during the Pleistocene and to have extended offshore. It was drained by numerous ice streams, which experienced different phases of activity during the Last Glacial Maximum (LGM). However, despite recent improvements in the understanding of the onshore glacial history of the region, still little is known about the offshore sector. In particular, significant gaps remain in the knowledge of the deglacial history of the BIIS from the western North Sea, and of the dynamic behaviour of the North Sea Lobe (NSL) ice stream as it retreated from the offshore region. This research incorporates different bathymetric, seismic and sedimentological datasets collected in the western North Sea, to investigate the geomorphological and sedimentary imprint left on the seafloor by the passage of the BIIS and by the NSL during the last glacial phase. The findings provide new insights on the seafloor geomorphology and on the stratigraphic architecture of the Quaternary sediments of the area, and better reconstruct the advance and retreat behaviour of the NSL in the region. The results demonstrate that the geomorphological imprint found on the seafloor of the western North Sea can be ascribable to the action of the NSL, which was flowing from NW to SE. The presence of Grounding Zone Wedges and of glaciomarine sediments characterised by cold temperature foraminifera species, known to be indicators of extreme glacial marine environments, indicates that the NSL was a marine-terminating ice lobe in the investigated area during retreat and that its decay was episodic, punctuated by phases of temporary stability. Bedrock strata, which is present at or very close to the seabed, is thought to have provided pinning points that facilitated periods of ice stillstand. In addition, new radiocarbon ages constrain ice retreat towards southern Scotland between ~19 - 16 ka BP, and suggest that deglaciation of this sector of the North Sea started earlier than previously thought.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available