Ice sheet confluence and deglaciation: evidence from Orkney and Shetland
New data is presented regarding the character and timing of glaciation in Orkney and Shetland and adjoining continental shelf, and a chronology of deglaciation is reconstructed for this critical area of the North Atlantic sector of the British and Fennoscandian Ice Sheets (BIS & FIS). Specifical...
| Main Authors: | , , , , , |
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| Format: | Text |
| Language: | unknown |
| Published: |
UNESCO
2008
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| Subjects: | |
| Online Access: | http://nora.nerc.ac.uk/id/eprint/7685/ http://www.rgs.org |
| Summary: | New data is presented regarding the character and timing of glaciation in Orkney and Shetland and adjoining continental shelf, and a chronology of deglaciation is reconstructed for this critical area of the North Atlantic sector of the British and Fennoscandian Ice Sheets (BIS & FIS). Specifically seabed morphology is interpreted using the Olex echosounder dataset to determine ice stream tracks and glacial limits. Onshore landscape morphology is interpreted using the NEXTMap high resolution DEM and tested using ground survey, and a landsystems approach is applied in the reconstruction of styles of glaciation across the Northern Isles of Scotland. Crucially using Olex, terminal positions of the confluent BIS-FIS offshore at maximum glacial extent and during retreat are determined, and evidence of ice sheet separation is shown. The seabed and landscape evidence for ice streaming, in both erosive and depositional terrains is highlighted. There is evidence for several phases of ice sheet dynamics during Late Devensian deglaciation: confluent streaming ice from FIS/BIS; separation of the ice sheets and the establishment of a remnant ice cap over Shetland; and finally a readvance phase where ice flowing from the Moray Firth overwhelmed much of Orkney. New cosmogenic surface exposure age data is presented giving the first dated constraints on the timing of ice sheet separation, which combined with evidence from the UK continental shelf and North Sea Basin begin to give a chronology for the decline of the ice sheet systems on the western European margin. Finally, it is argued that the timing of these phase changes in the dynamics of the FIS and BIS are coincident with major changes in wider Earth systems, in particular eustatic sea level rise in response to global warming during the waning phase of the Lateglacial. |
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