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Northern Victoria Land terranes, Antarctica: far-travelled or local products?

By
Franz Tessensohn
Franz Tessensohn
Bundesanstalt für Geowissenschaften und Rohstoffe, Stilleweg 2, 30655 Hannover, Germany (e-mail: franz.tessensohn@tiscali.de)
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Friedhelm Henjes-Kunst
Friedhelm Henjes-Kunst
Bundesanstalt für Geowissenschaften und Rohstoffe, Stilleweg 2, 30655 Hannover, Germany (e-mail: franz.tessensohn@tiscali.de)
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Published:
January 01, 2005

Abstract

The early Palaeozoic Ross Orogen in northern Victoria Land, Antarctica, consists of three major fault-bounded tectonostratigraphic terranes. Their true nature, far-travelled or local part of the accretionary collage, is under discussion. The inboard Wilson terrane (WT) consists mainly of high-grade metamorphic rocks intruded by the calc-alkaline magmatic arc of the Ross Orogen. The terrane nature of the WT is doubtful, as it appears more like the leading edge of the East Antarctic craton. The Bowers terrane (BT) comprises a mixed sedimentary-volcanic succession, beginning with volcanic rocks of island-arc character, followed by turbidites, mudstones, conglomerates and fossiliferous Middle Cambrian shallow-water sediments. The whole sequence is capped by a fluvial to deltaic quartzitic series several kilometres thick, with strong continental affinity. The combination of primitive forearc to back-arc volcanics at the bottom and mature continental sediments at the top poses a problem. The outer Robertson Bay terrane (RBT) is made up of a thick turbidite succession which, in one area, contains allochthonous blocks of fossiliferous Tremadocian limestones. All terrane boundaries appear to be distinct fault zones. The WT/BT boundary forms a deep-reaching continent-ocean suture associated with strongly sheared rock units, ultramafic lenses and high-pressure rocks. Coesite in eclogites of the Lanterman Range indicates a depth of burial of around 90 km. A green- schist-facies schist belt marks the BT/RBT boundary. The terranes contain evidence for subduction at an active margin setting as well as for accretion processes along major faults. The present changes of the Cambrian time-scale, such as younging of the base of the Upper Cambrian by about 30 Ma since the 1980s, allow separation of arc formation and later terrane accretion events.

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Geological Society, London, Special Publications

Terrane Processes at the Margins of Gondwana

A. P. M. Vaughan
A. P. M. Vaughan
British Antarctic Survey, UK
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P. T. Leat
P. T. Leat
British Antarctic Survey, UK
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R. J. Pankhurst
R. J. Pankhurst
British Geological Survey, UK
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Geological Society of London
Volume
246
ISBN electronic:
9781862394940
Publication date:
January 01, 2005

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