Exploring former subglacial Hodgson Lake, Antarctica. Paper II: palaeolimnology

• Published in: Quaternary Science Reviews
• Main Authors: Hodgson, Dominic A., Roberts, Stephen J., Bentley, Michael J., Carmichael, Emma L., Smith, James A., Verleyen, Elie, Vyverman, Wim, Geissler, Paul, Leng, Melanie J., Sanderson, David C.W.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2009
• Subjects: Glaciology; Biology and Microbiology; Earth Sciences; Chemistry; Antarctic; The Antarctic; Hodgson; Hodgson Lake; Antarc*; Antarctica; Ice Sheet
• Online Access: http://nora.nerc.ac.uk/id/eprint/8453/; https://doi.org/10.1016/j.quascirev.2009.04.014

Direct exploration of subglacial lakes buried deep under the Antarctic Ice Sheet has yet to be achieved. However, at retreating margins of the ice sheet, there are a number of locations where former subglacial lakes are emerging from under the ice but remain perennially ice covered. One of these lakes, Hodgson Lake (72°00.549′S, 068°27.708′W) has emerged from under more than 297–465 m of glacial ice during the last few thousand years. This paper presents data from a multidisciplinary investigation of the palaeolimnology of this lake through a study of a 3.8 m sediment core extracted at a depth of 93.4 m below the ice surface. The core was dated using a combination of radiocarbon, optically stimulated luminescence, and relative palaeomagnetic intensity dating incorporated into a chronological model. Stratigraphic analyses included magnetic susceptibility, clast provenance, organic content, carbonate composition, siliceous microfossils, isotope and biogeochemical markers. Based on the chronological model we provisionally assign a well-defined magnetic polarity reversal event at ca 165 cm in the lake sediments to the Mono Lake excursion (ca 30–34 ka), whilst OSL measurements suggest that material incorporated into the basal sediments might date to 93 ± 9 ka. Four stratigraphic zones (A–D) were identified in the sedimentological data. The chronological model suggests that zones A–C were deposited between Marine Isotope Stages 5–2 and zone A during Stage 1, the Holocene. The palaeolimnological record tracks changes in the subglacial depositional environment linked principally to changing glacier dynamics and mass transport and indirectly to climate change. The sediment composition in zones A–C consists of fine-grained sediments together with sands, gravels and small clasts. There is no evidence of overriding glaciers being in contact with the bed reworking the stratigraphy or removing this sediment. This suggests that the lake existed in a subglacial cavity beneath overriding LGM ice. In zone D there is a transition ...