Browsing by Author "Hemmingsen, M"

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    Comment on Barrell et al. “Reconciling the onset of deglaciation in the Upper Rangitata valley, Southern Alps, New Zealand” (Quaternary Science Reviews 203 (2019), 141–150.)
    (Elsevier, 2019-09-01) Shulmeister, J; Fink, D; Winkler, S; Thackray, GD; Borsellino, R; Hemmingsen, M; Rittenour, TM
    Recently, Barrell et al. (2019) published an article that responded to our article (Shulmeister et al., 2018a) on gradual evacuation of ice from the Upper Rangitata Valley, South Island, New Zealand, during the last glaciation. They base their contrasting interpretation of substantial and rapid ice-lowering of Rangitata glacier shortly after 18 ka on a revision of our 10Be cosmogenic radionuclide (CRN) chronology and by reference to published sources (e.g. Mabin, 1980, 1987). Their interpretation relies on glacial landform features extracted from a geomorphology map of the central Southern Alps by Barrell et al. (2011). Barrell et al. (2019) highlight that rapid ice recession of the Rangitata glacier is compatible to their results from Mackenzie Basin and Rakaia Valley (Putnam et al., 2013a, b). We highlight four points in response to Barrell et al. (2019). © 2019 Elsevier Ltd.
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    Corrigendum to “Evidence for slow late-glacial ice retreat in the upper Rangitata Valley, South Island, New Zealand” [Quat. Sci. Rev. 185 (2018) 102–112]
    (Elsevier, 2019-09-01) Shulmeister, J; Fink, D; Winkler, S; Thackray, GD; Borsellino, R; Hemmingsen, M; Rittenour, TM
    It has been brought to our attention, following a recent publication by Barrell et al. (2019), that the elevations for 12 of 23 boulders reported in our publication, Shulmeister et al., v185, 102–112 (2018) are incorrect. For these 12 samples, the true elevations are higher and hence all exposure ages based on their respective 10Be concentration measurements require a downward correction of between 10 and 15%. This change in age does not alter our main conclusions but does have some implication for the initiation and pace of deglaciation. © 2019 Elsevier Ltd.
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    Evidence for slow late-glacial ice retreat in the upper Rangitata Valley, South Island, New Zealand
    (Elsevier, 2018-04-01) Shulmeister, J; Fink, D; Winkler, S; Thackray, GD; Borsellino, R; Hemmingsen, M; Rittenour, TM
    A suite of cosmogenic radionuclide ages taken from boulders on lateral and latero-terminal moraines in the Rangitata Valley, eastern South Island, New Zealand demonstrates that relatively thick ice occupied valley reaches inland of the Rangitata Gorge until c. 21 ka. Thereafter ice began to thin, and by c. 17 ka it had retreated 33 km up-valley of the Rangitata Gorge to the Butler-Brabazon Downs, a structurally created basin in the upper Rangitata Valley. Despite its magnitude, this retreat represents a minor ice volume reduction from 21 ka to 17 ka, and numerous lateral moraines preserved suggest a relatively gradual retreat over that 4 ka period. In contrast to records from adjacent valleys, there is no evidence for an ice-collapse at c. 18 ka. We argue that the Rangitata record constitutes a more direct record of glacial response to deglacial climate than other records where glacial dynamics were influenced by proglacial lake development, such as the Rakaia Valley to the North and the major valleys in the Mackenzie Basin to the south-west. Our data supports the concept of a gradual warming during the early deglaciation in the South Island New Zealand. © 2018 Elsevier Ltd.