Surface exposure chronology of the Waimakariri glacial sequence in the Southern Alps of New Zealand: Implications for MIS-2 ice extent and LGM glacial mass balance

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dc.contributor.authorRother, Hen_AU
dc.contributor.authorShulmeister, Jen_AU
dc.contributor.authorFink, Den_AU
dc.contributor.authorAlexander, Den_AU
dc.contributor.authorBell, Den_AU
dc.date.accessioned2016-02-01T22:06:41Zen_AU
dc.date.available2016-02-01T22:06:41Zen_AU
dc.date.issued2015-11-01en_AU
dc.date.statistics2016-02-02en_AU
dc.description.abstractDuring the late Quaternary, the Southern Alps of New Zealand experienced multiple episodes of glaciation with large piedmont glaciers reaching the coastal plains in the west and expanding into the eastern alpine forelands. Here, we present a new 10Be exposure age chronology for a moraine sequence in the Waimakariri Valley (N-Canterbury), which has long been used as a reference record for correlating glacial events across New Zealand and the wider Southern Hemisphere. Our data indicate that the Waimakariri glacier reached its maximum last glaciation extent prior to ∼26 ka well before the global last glaciation maximum (LGM). This was followed by a gradual reduction in ice volume and the abandonment of the innermost LGM moraines at about 17.5 ka. Significantly, we find that during its maximum extent, the Waimakariri glacier overflowed the Avoca Plateau, previously believed to represent a mid-Pleistocene glacial surface (i.e. MIS 8). At the same time, the glacier extended to a position downstream of the Waimakariri Gorge, some 15 km beyond the previously mapped LGM ice limit. We use a simple steady-state mass balance model to test the sensitivity of past glacial accumulation to various climatic parameters, and to evaluate possible climate scenarios capable of generating the ice volume required to reach the full local-LGM extent. Model outcomes indicate that under New Zealand's oceanic setting, a cooling of 5 °C, assuming modern precipitation levels, or a cooling of 6.5 °C, assuming a one third reduction in precipitation, would suffice to drive the Waimakariri glacier to the eastern alpine forelands (Canterbury Plains). Our findings demonstrate that the scale of LGM glaciation in the Waimakariri Valley and adjacent major catchments, both in terms of ice volume and downvalley ice extent, has been significantly underestimated. Our observation that high-lying glacial surfaces, so far believed to represent much older glacial episodes, were glaciated during the LGM, challenges the conventional geomorphic model of glaciation in New Zealand where the vertical arrangement of glacial landform-associations is used to assign successively older glaciation ages. © 2015, Elsevier B.V.en_AU
dc.identifier.citationRother, H., Shulmeister, J., Fink, D., Alexander, D., & Bell, D. (2015). Surface exposure chronology of the Waimakariri glacial sequence in the Southern Alps of New Zealand: implications for MIS-2 ice extent and LGM glacial mass balance. Earth and Planetary Science Letters, 429, 69-81. doi:10.1016/j.epsl.2015.07.033en_AU
dc.identifier.govdoc6425en_AU
dc.identifier.issn0012-821Xen_AU
dc.identifier.journaltitleEarth and Planetary Science Lettersen_AU
dc.identifier.pagination69-81en_AU
dc.identifier.urihttp://dx.doi.org/10.1016/j.epsl.2015.07.033en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/6579en_AU
dc.identifier.volume429en_AU
dc.language.isoenen_AU
dc.publisherElsevieren_AU
dc.subjectSurfacesen_AU
dc.subjectNew Zealanden_AU
dc.subjectGlaciersen_AU
dc.subjectQuaternary perioden_AU
dc.subjectDataen_AU
dc.subjectClimatesen_AU
dc.titleSurface exposure chronology of the Waimakariri glacial sequence in the Southern Alps of New Zealand: Implications for MIS-2 ice extent and LGM glacial mass balanceen_AU
dc.typeJournal Articleen_AU
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