ILLUMINATING THE PAST IN MIDDLE EARTH: APPLICATION OF LUMINESCENCE DATING TO GLACIAL SEQUENCES IN THE SOUTHERN ALPS OF NEW ZEALAND

Records of glacial ice buildup and recession from the Southern Alps of New Zealand (NZ) are important indicators of Southern Hemisphere ocean-atmosphere climate conditions; only the southern Andes of Chile/Argentina occupy a similar latitude (41-45 S) to supply analogous reconstructions. Our understanding of the timing and sequence of glacial advances in NZ has been enhanced by the application of cosmogenic radionuclide (CRN) dating of glacial moraines and over 500 CRN ages have been obtained thus far (e.g Darvill et al. 2016). In contrast, the application of luminescence dating to glacial sequences in NZ has been viewed with less enthusiasm due to early reports of problems with luminescence properties rooted in the source rock characteristics and high exhumation and weathering rates on the West Coast of NZ (e.g. Preusser et al., 2005, 2006). However, more recent applications of newer methods of optically and infrared stimulated luminescence (OSL, IRSL) dating of quartz and feldspar from eastern Southern Alps drainages have yielded promising results (e.g. Rowan et al. 2012; Shulmeister et al. 2018) and a recent literature review has tallied over 250 luminescence ages from the region (Shulmeister et al., in review). Luminescence dating offers a complimentary approach to CRN surface exposure dating of moraines by expanding age control to depositional sequences related to glacial margins that may not have geomorphic expressions, despite potential incomplete solar resetting in near-ice environments. We report on the newly developed luminescence-derived glacial chronology from the Rangitata valley in the central Southern Alps. The luminescence results provide age control for six periods of ice advance in the last 70kyr and are supported by geomorphic and sed/stratigraphic evidence in outcrop. These results are also consistent with limited CRN dating of boulders deposited during the most recent ice retreat (Shulmeister et al. 2018; cf Barrell et al 2019). Results from the Rangitata valley are compared with glacial chronologies from across NZ to discuss regional correlations and temporal-spatial influences of past climate change.