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Submarine glacial landforms and interactions with volcanism around Sub-Antarctic Heard and McDonald Islands

Citation

Watson, S and Fox, JM and Post, A and Whittaker, J and Lucieer, VL and Carey, RJ and Coffin, MF and Hodgson, D and Hogan, K and Graham, AGC and Picard, K, Submarine glacial landforms and interactions with volcanism around Sub-Antarctic Heard and McDonald Islands, AGU Fall Meeting Abstracts, 11-15 December 2017, New Orleans, USA (2017) [Conference Extract]


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Abstract

Unravelling the glacial history of Sub-Antarctic islands can provide clues to past climate and Antarctic ice sheet stability. The glacial history of many sub-Antarctic islands is poorly understood, including the Heard and McDonald Islands (HIMI) located on the Kerguelen Plateau in the southern Indian Ocean.

The geomorphologic development of HIMI has involved a combination of construction via hotspot volcanism and mechanical erosion caused by waves, weather, and glaciers. Today, the ~2.5 km2 McDonald Islands are not glacierised; in contrast, the ~368 km2 Heard Island has 12 major glaciers, some extending from the summit of 2813 m to sea level. Historical accounts from Heard Island suggest that the glaciers were more extensive in the 1850s to 1870s, and have retreated at least 12% (33.89 km2) since 1997. However, surrounding bathymetry suggests a much more extensive previous glaciation of the HIMI region that encompassed ~9,585 km2, likely dating back at least to the Last Glacial Maximum (LGM) ca. ~26.5 -19 ka.

We present analyses of multibeam bathymetry and backscatter data, acquired aboard RV Investigator in early 2016, that support the previous existence of an extensive icecap. These data reveal widespread ice-marginal and subglacial features including moraines, over-deepened troughs, drumlins and crag-and-tails. Glacial landforms suggest paleo-ice flow directions and a glacial extent that are consistent with previously documented broad scale morphological features. We identify >660 iceberg keel scours in water depths ranging from ~150 - 530 m. The orientations of the iceberg keel scours reflect the predominantly east-flowing Antarctic Circumpolar Current and westerly winds in the region.

40Ar/39Ar dating of volcanic rocks from submarine volcanoes around McDonald Islands suggests that volcanism and glaciation coincided. The flat-topped morphology of these volcanoes may result from lava-ice interaction or erosion by glaciers post eruption during a time of extensive ice-sheet cover and/or wave base erosion during sea level low stands.

The prevalence and range of glacial landforms around HIMI suggest extensive past glaciation, and that glaciers have exerted a major influence on submarine geomorphology.

Item Details

Item Type:Conference Extract
Keywords:submarine geology
Research Division:Earth Sciences
Research Group:Geology
Research Field:Marine Geoscience
Objective Division:Environment
Objective Group:Ecosystem Assessment and Management
Objective Field:Ecosystem Assessment and Management of Marine Environments
Author:Watson, S (Ms Sally Watson)
Author:Fox, JM (Ms Jodi Fox)
Author:Whittaker, J (Dr Jo Whittaker)
Author:Lucieer, VL (Dr Vanessa Lucieer)
Author:Carey, RJ (Dr Rebecca Carey)
Author:Coffin, MF (Professor Mike Coffin)
ID Code:124924
Year Published:2017
Deposited By:Ecology and Biodiversity
Deposited On:2018-03-20
Last Modified:2018-03-20
Downloads:0

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