Evidence for slow late-glacial ice retreat in the upper Rangitata Valley, South Island, New Zealand

• Published in: Quaternary Science Reviews
• Main Authors: Shulmeister, J., Fink, D., Winkler, S., Thackray, G. D., Borsellino, R., Hemmingsen, M., Rittenour, T. M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Pergamon Press 2018
• Subjects: Antarctic Cold Reversal; Franz-Josef-Glacier; Rakaia Valley; Calving Retreat; Tasman Glacier; Climate-Change; Alps; Chronology; Maximum; Be-10; 1105 Ecology; Evolution; Behavior and Systematics; 1204 Archaeology; 1907 Geology; 2306 Global and Planetary Change; 3302 Archaeology; Antarctic; New Zealand; Antarc*; Mackenzie Basin
• Online Access: https://espace.library.uq.edu.au/view/UQ:727603

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.