The last deglaciation in New Zealand ; new 10Be production rates from Misery moraines, Arthur’s Pass, Southern Alps
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Date
2019-07-29
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Publisher
International Union for Quaternary Research (INQUA)
Abstract
Recent debate on mid-latitude New Zealand glaciation has focused on reconstructing paleo-climate conditions leading into the (global) Last Glacial Maximum and subsequent deglaciation dynamics during the last termination. Paleo-environmental evidence coupled with reliable glacial chronologies confirms significant differences from that observed in northern hemisphere signatures of glacial change. The New Zealand glacial record does not show glacial readvance and strong cooling commensurate with Younger Dryas timing (~11.7-12.9 ka) and many lake pollen records suggest a minor cooling or hiatus in warming during the period from ~14.5 – 12.0 ka that is more commonly associated with the Antarctic Cold Reversal (ACR) (~14.7 - 13.0 ka). The Arthur’s Pass Moraine complex at 950 masl, deposited by an alpine glacier advancing out of the Otira Valley splaying east and westward over the divide of the Southern Alps in New Zealand, exhibits a full post-LGM glacial chronology. We have determined paired 10-Be and 26-Al exposure ages from 58 greywacke samples taken from all major moraines. Calculated exposure ages (using accepted local NZ production rates) show that the Arthur’s Pass moraine system spans a period of 19.5 ka to 12.0 ka with mean recessional moraine ages in chrono-stratigraphic sequence. The overall timing of deglaciation after peak LGM conditions is similar to the glacial systems we have dated in the Rakaia, Waimakariri and Rangitata Valleys. The Misery sequence shows ice retreat at the end of the ACR and no major advance during the YD period. Multiple cores from two intermorainal bog (Lances and Misery Tarns), separated by ~1 km and constrained by the terminal Dobson and Misery moraines, have been recovered for paleo-climate study. Basal glacial silts and organic matter have provided radiocarbon ages representing a minimum age for glacial retreat. Combined with the Misery moraine cosmogenic concentrations, new 10Be and 26Al production rate calibrations can be made for New Zealand to improve exposure age accuracy.
Description
Keywords
Glaciers, New Zealand, Climatic change, Environment, Moraines, Beryllium 10, Aluminium 26, Southern Hemisphere, Northern Hemisphere
Citation
Fink, D., Rother, H., Woodward, C., Schilmeister, J., Wilcken, K., Fujioka, T. (2019). The last deglaciation in New Zealand ; new 10Be production rates from Misery moraines, Arthur’s Pass, Southern Alps. Paper presented to the 20th INQUA Congress, Dublin, Ireland, 25th - 31st July 2019. Retrieved from: https://virtual.oxfordabstracts.com/#/event/public/574/submission/1535