Frontiers and Opportunities in Antarctic Geosciences * Certosa di Pontignano * 29-31 July 2004
The Paleo-Pacific Margin of Gondwana and the Ross Orogeny:
A Northern Victoria Land Perspective
L. FEDERICO*, L. CRISPINI & G. CAPPONI
University of Genova, C.so Europa 26, 16132 Genova (Italy)
*Corresponding author (federico@dipteris.unige.it)
In Cambrian time the paleo-Pacific margin of the Gondwana supercontinent included East Antarctica, Australia,
Tasmania and New Zealand. The Ross orogeny, originally described in Northern Victoria Land (NVL),
Antarctica, affected this margin in late Cambrian. Many tectonic reconstructions of this orogeny (e.g.
Kleinschmidt and Tessensohn 1987; Findlay et al. 1991; Ferraccioli et al. 2002) deal with the amalgamation of
the three terranes currently recognized in NVL, i.e. Wilson, Bowers and Robertson Bay terrane. Most of these
models claim a SW subducting plate beneath the continental margin of the Wilson Terrane; the subducting plate
carried an oceanic island arc sequence (Bowers Terrane) and ongoing subduction caused the Bowers Terrane to
collide with the Wilson Terrane.
However, the Bowers Terrane shows more complex geochemical features than one could expect from an oceanic
arc sequence, and could be better compared to a back-arc and/or a fore-arc sequence (Rocchi et al. 2002).
According to these recent advances in the comprehension of NVL geology, we propose a new tectonic model
which covers the time interval from Lower Cambrian to Upper Ordovician and restore both the Bowers and the
Wilson terranes on the upper plate. It explains the opening of a back-arc basin as a consequence of the oblique
subduction of the Pacific plate under the Gondwana margin and of the collision of a microcontinental block.
By comparisons between sedimentological, magmatic and tectonic events in all the various fragments of the
margin, we make correlations with SE-Australia, New Zealand and Tasmania evolution and discuss the possible
extension of the model to the whole margin.
REFERENCES
Ferraccioli F. et al., 2002, Geophysical Research Letters, 29 n°0: 10.1029/2001GLO14138. 2002
Findlay R.H. et al., 1991, Mem. Soc. Geol. It., 46: 117-133
Kleinschmidt G. & Tessensohn F., 1987, in: "Gondwana Six: Structure, Tectonics, and Geophysics. McKenzie G.D. Ed. pp. 89-105
Rocchi S. et al., 2002 Abstract of the Workshop "Scienze della Terra in Antartide" Certosa di Pontignano (Siena) 30/9-02/10/2002