Late Pleistocene deglaciation history of the SW British Isles: new evidence from Lundy and the outer Bristol Channel

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dc.contributor.authorRolfe, Cen_AU
dc.contributor.authorHughes, PDen_AU
dc.contributor.authorBrown, Ten_AU
dc.contributor.authorBateman, Men_AU
dc.contributor.authorGibbard, Pen_AU
dc.contributor.authorFink, Den_AU
dc.date.accessioned2024-02-23T00:34:34Zen_AU
dc.date.available2024-02-23T00:34:34Zen_AU
dc.date.issued2019-07-27en_AU
dc.date.statistics2023-04-12en_AU
dc.description.abstractThe SW British Isles was glaciated by the British-Irish Ice Sheet during the Late Pleistocene. Glacial deposits are widely preserved in the Bristol Channel and are revealed in boreholes and geophysical data. Lundy, an island in the Outer Bristol Channel, displays unique terrestrial evidence of glaciation in the Outer Bristol Channel. The evidence is dominated by erosional evidence of ice-scouring, although there are wide spreads of erratic cobbles and pebbles several of which contain evidence of striae and faceting. In addition, subsurface thick silt-clay deposits are common on the island with clay mineralogy indicating limited weathering, in contrast to occasional pockets of strongly weathered granite (growan). These deposits are interpreted as subglacial in origin. Offshore of Lundy, especially to the E and NE, geophysical data reveals the presence of thick glacial deposits and dense fields of boulders. This suggests that an ice limit occurred between Lundy and the mainland. This allowed the drainage of the proto-Severn to drain between this ice limit and the mainland in Devon, and the course of this palaeochannel can be traced in bathmetry and geophysical survey data. Periglacial activity after deglaciation is recorded by the presence of coversands, loess, ventifacts, scree slopes and associated colluvial deposits. Luminescence ages from colluvial sands on Lundy date to 24-26 ka indicating that this island was deglaciated by marine isotope stage (MIS) 2. This is consistent with deglaciation and exposure of the island in MIS 3 following glaciation in MIS 4 or possibly earlier. Previously obtained exposure ages from ice-scoured bedrock surfaces have been recalculated using the most recent production rate models and support this interpretation. In addition, a new programme of cosmogenic exposure dating of glacially-transported boulders and displaced tors will further test the previously obtained exposure age data from glaciated bedrock surfaces. In contrast to other weathered granite surfaces in the British Isles, Lundy has not experienced a prolonged weathering history through multiple glacial cycles. Whilst the precise timing of deglaciation is undergoing further testing, the current evidence overwhelmingly indicates that Lundy was eroded by an ice sheet during the Late Pleistocene. Morphometric analysis of weathering pits in the ice-moulded granite bedrock on Lundy supports this exposure history as do the OSL ages from sands overlying the bedrock surfaces. Evidence from elsewhere around the Celtic Sea indicates that the glaciation of Lundy most likely occurred in MIS 4 with ice retreating in MIS 3. However, during MIS 2 ice reached to the continental shelf in the Celtic Sea. This apparent paradox may be explained by a highly mobile Irish Sea Ice Stream which changed its configuration in response to fluctuating marine incursions in MIS 3 before exploiting the exposed continental shelf to the southwest during MIS 2. ©The Authors.en_AU
dc.identifier.articlenumberP-1485en_AU
dc.identifier.citationRolfe, C., Hughes, P., Brown, T., Bateman, M., Gibbard, P., & Fink, D. (2019). Late Pleistocene deglaciation history of the SW British Isles: new evidence from Lundy and the outer Bristol Channel. Paper presented to the 20th INQUA Congress, 25th - 31st July 2019, Dublin, Ireland, (P-1485). Retrieved from: https://virtual.oxfordabstracts.com/#/event/public/574/submission/701en_AU
dc.identifier.conferenceenddate2019-07-31en_AU
dc.identifier.conferencename20th INQUA Congressen_AU
dc.identifier.conferenceplaceDublin, Irelanden_AU
dc.identifier.conferencestartdate2019-07-25en_AU
dc.identifier.otherP-1485en_AU
dc.identifier.urihttps://virtual.oxfordabstracts.com/#/event/public/574/submission/701en_AU
dc.identifier.urihttps://apo.ansto.gov.au/handle/10238/15406en_AU
dc.language.isoenen_AU
dc.publisherInternational Union for Quaternary Research (INQUA)en_AU
dc.subjectQuaternary perioden_AU
dc.subjectGlaciersen_AU
dc.subjectIceen_AU
dc.subjectUnited Knigdomen_AU
dc.subjectErosionen_AU
dc.subjectWeatheringen_AU
dc.subjectGranitesen_AU
dc.subjectGeologic depositsen_AU
dc.subjectGeophysical surveysen_AU
dc.titleLate Pleistocene deglaciation history of the SW British Isles: new evidence from Lundy and the outer Bristol Channelen_AU
dc.typeConference Posteren_AU
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