The Timing and Nature of the Last Glacial Cycle in New Zealand

• Main Authors: Shulmeister, James, Thackray, Glenn D., Rittenour, Tammy M., Fink, David, Patton, Nicholas R.
• Other Authors: Pergamon Press
• Format: Text
• Language: unknown
• Published: Hosted by Utah State University Libraries 2018
• Subjects: Otiran glaciation; New Zealand; Glacial advances; Westerlies; Paleoclimate; CRN; Luminescence dating; Earth Sciences; Geology; Physical Sciences and Mathematics; Antarctic; Antarc*
• Online Access: https://digitalcommons.usu.edu/geology_facpub/515

This paper constitutes a review of the last (Otiran) glaciation in New Zealand, spanning marine isotope stages (MIS) 4-2. We highlight the nature of glaciation, which is characterised by exceptional sedimentation, relatively mild maritime climatic conditions and the widespread presence of water associated with proglacial settings. These conditions produce glacial systems characterised by extensive outwash fans and relatively small terminal moraines. Extensive recent geochronological work allows us to recognise at least eight glacial advances during the Otiran. These occurred at 65 ± 3.25ka, 47.5 ± 3 ka, 38.5 ± 2 ka, 31.5 ± 3 ka, 26.5 ± 2 ka, 20.5 ± 2 ka, 17 ± 2 ka and 13 ± 1 ka, which we term the Otira 1 to 8 advances, respectively. Though the analytical uncertainty ranges for some of these advances overlap, all are independently distinguished through moraine morphologic relationships and/or stratigraphic relationships in outcrop. Major advances appear to be associated with climate influences such as periods of Southern Hemisphere insolation minima (65ka, and 31.5 ka advances), the last glacial maximum cooling (LGM) (20.5 ka) and periods of Antarctic cooling (13ka). The timing of greatest glacial extent in the last glacial cycle is not simultaneous across New Zealand. The MIS 4 advance was the greatest in the southern South Island, while the MIS 3/2 advances (26.5 ka) were greatest in the central South Island. In the northern South Island and the North Island, MIS 4, MIS 3/2, and the last glacial maximum appear to be equivalent in extent. We attribute these spatio-temporal variations in the timing of maximum glaciation to precipitation changes related to a northward shift in the track of the westerlies.