Late Pleistocene and Holocene climate and environmental evolution of a subantarctic fjord ingression basin in the southwest Pacific. (1st February 2021)

• Record Type: Journal Article
• Authors: Gilmer, Greer; Moy, Christopher M.; Riesselman, Christina R.; Vandergoes, Marcus; Jacobsen, Geraldine; Gorman, Andrew R.; Tidey, Emily J.; Wilson, Gary S.
• Is Part Of: Quaternary science reviews. Volume 253(2021)
• Publication Date: 2021-02-01
• Subjects: Subantarctic -- Holocene -- Paleoclimatology -- Southern Ocean -- Fjord -- LGM -- Deglaciation -- Stable isotopes; Geology, Stratigraphic -- Quaternary -- Periodicals; Stratigraphie -- Quaternaire -- Périodiques; 551.79
• DOI: 10.1016/j.quascirev.2020.106698
• Languages: English
• ISSNs: 0277-3791

Abstract

Abstract: Subantarctic islands are located at a critical latitude for reconstructing past changes in ocean-atmosphere interactions. Currently, there is a lack of high-resolution records from the Pacific sector of the Southern Ocean that can be used to reconstruct climate since the Last Glacial Maximum (LGM). Here, we present a reconstruction of environmental change from a fjord ingression basin at New Zealand's subantarctic Auckland Islands (50.5°S) over the last ∼19 ka cal BP. Using sedimentological and geochemical analysis of cores collected along a depth transect in Norman Inlet we find evidence for four different stages of environmental history: deglacial, lacustrine, marine transgression, and marine. Glaciers retreated from their maximum extent before 19.4 ka cal BP during a period of ice retreat that appears synchronous across the Pacific basin, likely due to southward migration of the Subtropical Front. However, in contrast to other glaciated regions, we see no evidence for ice re-advance, and a proglacial lake was present in the basin until 15.7 ka cal BP. Following deglaciation, organic-rich sedimentation dominated the lacustrine environment until post-glacial sea-level rise flooded the depositional basin at 8.8 ka cal BP. Deposition of organic-rich sediment continued during the Antarctic Cold Reversal and we find no evidence for a glacial re-advance. Mixing of terrestrial and marine organic matter during the marine transgression (8.8–6.7 ka cal BP) indicates significant erosion and re-working of sediment in the catchment as seawater overtopped the sill. Modern fjord circulation commenced ∼6.7 ka cal BP when sea level reached its maximum in the early Holocene. This well-dated, high-resolution record constrains the timing of deglaciation, sea-level rise, and subantarctic environmental change following the LGM that expands our understanding of the key drives of climate change in the middle to high southern latitudes. Highlights: Multi-site subantarctic fjord coring yields post-LGM paleoclimate composite record. Glacier retreat was under way prior to 19.4 ka and deglaciation ended by 15.7 ka. There is no evidence for glacial re-advance during the ACR. Post-glacial sea-level rise flooded the basin around 8.8 ka.