Seafloor geomorphology of the Windmill Islands, Wilkes Land, East Antarctica  

Authors / CoAuthors

Carson, C.J. | Post, A. | Smith, J. | Walker, G. | Waring, P.

Abstract

Studies utilising high-resolution multibeam swath bathymetry datasets to understand the glacial evolution of the previously glaciated Antarctic continental margin are limited, and are particularly meagre for the East Antarctic Continental shelf. Here we present an interpretation of the seafloor geomorphology based on a new swath bathymetry dataset from the shallow-water marine environment of the Windmill Islands, adjacent to the Australian Antarctic research station, Casey. This high resolution (1 m) dataset permits visualisation of geomorphological features preserved on the seafloor in unparalleled detail. The seafloor is dominated by an assemblage of bedrock, glacial and post-glacial features, providing new insight into the behaviour of the ice-sheet in the region during past glacial episodes and its subsequent retreat to present-day conditions. Interpretation of the submarine geomorphology reveals five dominant features: (1) basement fault systems and bedrock `highs (2) meltwater channels, (3) streamlined sub-glacial landforms, (4) moraine ridges and (5) isolated basins and depressions. Distinctive NW-SE trending channels and linear features that represent brittle bedrock fault systems are clearly evident. These sub-parallel basement bedrock faults or joints have been preferentially eroded and widened by glacial action to form narrow channels and preserve typical `U-shaped profiles. A secondary set of SW to WSW trending linear features are characterised by broad eroded channels. The general orientation of the coastline and channels in the region suggest that these linear features fundamentally control the regional coastal and seafloor geomorphology. Regions of bedrock highs, comprised of submarine outcrops of crystalline metamorphic basement, are characterised by complex, rugged and variable topography, forming steep knolls, small shoals and reefs. Numerous channel networks have been incised into crystalline bedrock highs and their meandering nature, orientation and geometry are consistent with meltwater channels formed by subglacial hydrological flow under considerable hydrostatic pressure. They likely formed during a period when the ice-sheet was expanded and grounded over the areas of offshore crystalline bedrock, possibly during the late Pleistocene Glacial Maximum (LGM) or earlier glaciations. Glacial lineations characterised by subdued sub-parallel linear ridges are preserved in basins and appear to have formed from moulding of unconsolidated sediments by overriding ice. The orientation of the lineations are consistent with formation during westward expansion of the Law Dome ice-sheet onto the continental shelf during the LGM. Regular and closely-spaced arcuate moraine ridge sets are preserved mostly within the prominent NW-trending U-shaped channels. These features appear to be a sequence of recessional moraines or push moraine banks recording slow or episodic retreat of channelized valley glaciers or outlet ice-streams which appear strongly controlled by the local bathymetry. There are several enclosed basins and shallow depressions between bedrock highs with varying degrees of post-glacial sedimentary infill. There is little evidence of reworking of sediments by currents and as a result, the glacial features in this dataset are well preserved. Interpretation of submarine glacial landforms using high-resolution swath bathymetry, integrated with existing information of local ice-sheet evolution from terrestrial studies, allows us to enhance our understanding of the ice-sheet dynamics in the Windmill Islands region.

Product Type

nonGeographicDataset

eCat Id

89944

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Keywords

• External PublicationAbstract

( Theme )

• Antartic

( Theme )

• bathymetry

( Theme )

• geomorphology

• AQ

Australian and New Zealand Standard Research Classification (ANZSRC)

• Marine Geoscience

• Published_Internal

Publication Date

2016-01-01T00:00:00

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Australian Government Security ClassificationSystem    

Classification - unclassified

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Creative Commons Attribution 4.0 International Licence    

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asNeeded

Topic Category

geoscientificInformation

Series Information

Lineage

Conference abstract follows analysis of multibeam bathymetry datasets collected during 2014/15 (GA-0348).

Parent Information

Extents

[-66.35, -66.2, 110.35, 110.6]

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Source Information

Windmill Islands region, adjacent to Casey station, Wilkes Land, East Antarctica 110.35 110.6 -66.35 -66.2