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Victoria University Antarctic Research Expedition Science and Logistics Reports 1984-85: VUWAE 29

Blue Glacier area

page 25

Blue Glacier area

The sample line across the Transantarctic Mountain Front started in the Miers Valley area, was picked up at spot height 1430 and extended across the Blue Glacier and up the ridge south or Salient Glacier. Samples were also taken from other ridges to try and tie down structural trends. A vertical sampling profile of 800 m was taken from spot height 1890. Samples were also taken across the north end of the Blue Glacier/Briggs Hills area in an extension of work done in the New Harbour area.

A prominent scarp west of Bettle Peak suggesting a fault downthrown to the west is also seen further south to the west of Williams Peak. This is the Foothills Fault of Gunn and Warren (1962) and defines the eastern margin of the Blue Glacier graben; the western margin being defined by the Lister Fault running along the end of ridges which come down off the Royal Society Range lying to the west. However, there exists another fault between the Lister Fault and the Royal Society Range. This is seen in ridges underneath Chaplins Tableland just north of Mt Lister where the basement dolerite sill is downfaulted approximately 200 m to the east. It continues south to Armitage Col and north to the Ferrar Glacier, however no evidence of it is seen north of the Ferrar. Numerous notches in these ridges suggest the presence of more faults in the Southern Foothills running parallel to this fault but no slickensides were seen in what in some cases were possibly poorly indurated crush zones.

In summary: The upper Blue Glacier appears to lie in a graben, its western boundary defined by a number of normal faults. Its eastern boundary is delineated by what appears to be a single block, consisting of the Miers-Marshall-Salmon Valleys and probably also including a small block to the north of the lower Blue Glacier. The block is bounded on its western side by a large normal fault and most probably on its eastern side by a number of step faults similar to those seen further north along the Wilson Piedmont. This graben is terminated to the north by the Ferrar Glacier.

Samples taken for fission-track dating will be processed at the University of Melbourne and representative samples of granitoid rocks from the area covered will be studied in detail at Victoria University to determine mineralogy and geochemistry.