The timing of deglaciation from mountain summits to cirques in Wales: 10Be and 26Al exposure dates from Cadair Idris

Simple item page
dc.contributor.authorHughes, PDen_AU
dc.contributor.authorGlasser, NFen_AU
dc.contributor.authorFink, Den_AU
dc.contributor.authorDortch, Jen_AU
dc.contributor.authorFülöp, RHen_AU
dc.contributor.authorWilcken, KMen_AU
dc.contributor.authorFujioka, Ten_AU
dc.date.accessioned2023-03-30T21:35:00Zen_AU
dc.date.available2023-03-30T21:35:00Zen_AU
dc.date.issued2021-04-19en_AU
dc.date.statistics2023-03-27en_AU
dc.description.abstractCosmogenic 10Be and 26Al exposure ages from 20 erratic samples collected from Cadair Idris (893 m), a mountain in southern Snowdonia, Wales, provide evidence for the timing of deglaciation from summits to cirques at the end of the Late Pleistocene. The summit of the mountain is characterised by intensely modified frost-shattered surfaces that have long been identified as a representing a former nunatak. Numerous glacially-transported quartz boulders on the highest ground indicate that ice overran the summit at some point in the Pleistocene. Two quartz boulders, one with preserved striations, sampled at c. 856 m near the summit of Cadair Idris yielded consistent 10Be and 26Al paired exposure ages of 75 ka to 60 ka (using anuhigh-latitude sea level 10Be spallation production rate of 4.20 at/g/y, scaled by the Lal/Stone scheme). A glacially polished bedrock quartzite outcrop at 735 m gave an age of 17.5 ka. Immediately below this, cirque and down-valley recessional moraine ages, covering an elevation of 480 m to 350 m ranged from 10 to 15 ka respectively. These results confirm that Cadair Idris was overridden by the Welsh Ice Cap during marine isotope stage (MIS) 4, when ice was thicker than at the global last glacial maximum (LGM) in MIS 2. This is consistent with findings from northern Snowdonia. The highest Welsh summits, including Cadair Idris, emerged above a thinning Welsh Ice Cap (British Irish Ice Sheet) during the transition from MIS 4 to 3. The summit area above ~800 m then stood as nunataks above the LGM ice sheet surface in MIS 2. The Welsh Ice Cap then rapidly thinned over Cadair Idris at ~20-17 ka based on ages from high-level ice-moulded bedrockThis is supported by more new ages from high-level paired erratics and bedrock samples on several other mountains throughout Snowdonia, leading to a phase of alpine-style deglaciation. Valley glaciers initiated their retreat up-valley from ~17 to 14 ka after Heinrich Event 1. A later phase of glacier stabilisation or still stand formation produced classic cirque moraines near the rim of a present cirque lake basin (480 m elevation) yielding 10Be ages of 13-10 ka during the Younger Dryas.en_AU
dc.identifier.citationHughes, P., Glasser, N., Fink, D., Dortch, J., Fülöp, R., Wilcken, K., & Fujioka, T. (2021). The timing of deglaciation from mountain summits to cirques in Wales: 10Be and 26Al exposure dates from Cadair Idris. Paper presented to the EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10398. Retrieved from: https://doi.org/10.5194/egusphere-egu21-10398en_AU
dc.identifier.conferenceenddate30 April 2021en_AU
dc.identifier.conferencenameEGU General Assembly 2021en_AU
dc.identifier.conferenceplaceOnlineen_AU
dc.identifier.conferencestartdate19 April 2021en_AU
dc.identifier.otherEGU21-10398en_AU
dc.identifier.urihttps://doi.org/10.5194/egusphere-egu21-10398en_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/14757en_AU
dc.language.isoenen_AU
dc.publisherCopernicus GmbHen_AU
dc.subjectBeryllium 10en_AU
dc.subjectAluminium 26en_AU
dc.subjectMountainsen_AU
dc.subjectSurfacesen_AU
dc.subjectMorainesen_AU
dc.subjectLevelsen_AU
dc.subjectFrosten_AU
dc.subjectValleysen_AU
dc.titleThe timing of deglaciation from mountain summits to cirques in Wales: 10Be and 26Al exposure dates from Cadair Idrisen_AU
dc.typeConference Paperen_AU
Files
License bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
license.txt
Size:
1.63 KB
Format:
Item-specific license agreed upon to submission
Description:
Download
Collections
Conference Publications