A cosmogenic glacial chronology of Lake Judd, southwest Tasmania and latitudinal shifts in the Roaring Forties

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dc.contributor.authorFink, Den_AU
dc.contributor.authorWilcken, KMen_AU
dc.contributor.authorSimon, KJen_AU
dc.contributor.authorSchulmeister, Jen_AU
dc.contributor.authorThackray, GDen_AU
dc.date.accessioned2023-05-29T05:08:42Zen_AU
dc.date.available2023-05-29T05:08:42Zen_AU
dc.date.issued2019-07-27en_AU
dc.date.statistics2023-04-12en_AU
dc.description.abstractLimited attention has been paid to the glacial history of Tasmania (40-44 S). At the northern limits of today’s Westerly storm track (the Roaring Forties), it experiences precipitation changes due to shifts in the Southern Annular Mode and ITCZ. Cosmogenic dating in southwest Tasmania (Kiernan 2010) highlights the marginal nature of its glaciation where small precipitation or temperature changes cause large changes in mass balance. This makes southwestern Tasmania an excellent location to study Westerly flow through the Last Glacial Cycle. The prevailing idea is that during glacial times, Westerlies expand northward to lower Southern Ocean latitudes, delivering increased rainfall to Tasmania, whilst during interglacials, their migration polewards reduces precipitation. Somewhat counterintuitively, from a Tasmanian perspective of increased Westerly circulation and wind strength, maxima glaciation should coincide with peak global glacials. Although well preserved, extensive last glacial cycle moraine sequences are not common, a series of more than 20 terminal moraine ridges have been mapped over 3 km concentric with the southern margin of Lake Judd, in the SW wilderness corner of Tasmania. Morphologically, the Lake Judd sequence is believed to represent three phases; pre MIS-6, MIS 5-3 and MIS 2 (LGM), representing substantially different volumes of ice accumulation. Our first field campaign collected 16 dolerite samples (36Cl) from the three innermost concentric moraines adjacent to lake edge and 4 quartzite (10Be, 26Al) samples from the most distal moraines. Our aim is to test correlation of the long-term glacial history with records of westerly fluctuations from NZ speleothems (Whittaker et al., 2011) to determine whether the latitudinal variation in Westerly winds in the Australasian region are zonal during glacial times as they are demonstrated to be in interglacial intervals (Fletcher and Moreno, 2012). Preliminary exposure age calculations on the full set of 20 samples are in poor agreement with Kiernan’s age associations. The 10Be (and 26Al) ages on the distal moraine indicate a most probable MIS 4/5 affiliation (>50 ka), significantly younger than expected. In contrast, the 16 dolerite samples from the 3 innermost proximal moraines at lake edge gave a complex set of ages that ranged from MIS 3 to MIS 4 affiliation (45-25ka), somewhat older than predicted. To add further complexity, these 16 ages show no intra or inter moraine age trends with respect to their morphologic positions and ice flow direction. These results contrast with those from other Tasmanian glacial records and reveal the need for a concretive effort to apply cosmogenic exposure dating to the numerus glacial deposits already mapped throughout Tasmania.en_AU
dc.identifier.citationFink, D., Wilcken, K., Simon, K., Schulmeister, J., & Thackray, G. (2019). A cosmogenic glacial chronology of Lake Judd, southwest Tasmania and latitudinal shifts in the Roaring Forties. Poster presented to the 20th INQUA Congress, Dublin, Ireland, 25th - 31st July 2019. Retrieved from: https://virtual.oxfordabstracts.com/#/event/public/574/submission/1538en_AU
dc.identifier.conferenceenddate31 July 2019en_AU
dc.identifier.conferencename20th INQUA Congressen_AU
dc.identifier.conferenceplaceDublin, Irelanden_AU
dc.identifier.conferencestartdate25 July 2019en_AU
dc.identifier.urihttps://virtual.oxfordabstracts.com/#/event/public/574/submission/1538en_AU
dc.identifier.urihttps://apo.ansto.gov.au/handle/10238/15046en_AU
dc.language.isoenen_AU
dc.publisherInternational Union for Quaternary Research (INQUA)en_AU
dc.relation.urihttps://virtual.oxfordabstracts.com/#/event/public/574/submission/1538en_AU
dc.subjectGlaciersen_AU
dc.subjectTasmaniaen_AU
dc.subjectAustraliaen_AU
dc.subjectLakesen_AU
dc.subjectMorainesen_AU
dc.subjectGeologic depositsen_AU
dc.subjectTurbulenceen_AU
dc.subjectAmbient temperatureen_AU
dc.subjectIceen_AU
dc.subjectAtmospheric precipitationsen_AU
dc.subjectWinden_AU
dc.titleA cosmogenic glacial chronology of Lake Judd, southwest Tasmania and latitudinal shifts in the Roaring Fortiesen_AU
dc.typeConference Posteren_AU
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