Subduction zones in the Lachlan Fold Belt of southeastern Australia
The Lachlan Fold Belt is a wide (>700 km) zone of deformed rock in southeastern Australia that makes up part of the Tasman Fold Belt System and formed along the active Palaeozoic, palaeo-Pacific Ocean margin of Gondwana.
The Early Palaeozoic history of the Lachlan Fold Belt is controversial especially given the multiple subduction zones advocated by David Gray and David Foster (e.g. Foster and Gray 2000).
An interpretation of the early history of the Lachlan Fold Belt is given by Fergusson (2003) and incorporates all of the subduction zones outlined by Foster and Gray (2000). Fergusson’s (2003) main ideas are outlined in the three figures below.
|
Major zones of the Lachlan Fold Belt. The green “island arc” in the east is the Ordovician Macquarie arc that Fergusson (2003) related to potential subduction zones to the west and east of the island arc. Just how this tectonic history has developed is incompletely understood.
|
Cross section reconstructions of subduction zones in the Lachlan Fold Belt in the Ordovician to Early Silurian. See Fergusson (2003) for details. Diagrams are drawn to scale using constraints from the regional shortening in the Lachlan Fold Belt and the thickness of crust in modern analogues such as the Izu-Bonin-Mariana island arc.
|
Simplified stratigraphic column showing the Cambrian-Ordovician stratigraphy for the eastern Lachlan Fold Belt (east of the Governor Fault) and exclusive of the Macquarie island arc. For details see Fergusson and Fanning (2002).
|
Steeply dipping thick-bedded turbidites of Early to Middle Ordovician age, Tambo River (Tabberabbera Zone), eastern Victoria. See Fergusson (2003) for more details.
|
Thin-bedded “stripy” turbidites of the Upper Ordovician succession, lower Bungonia Creek (east of Goulburn, southeastern New South Wales). See Fergusson and Fanning (2002) for more details
|
 Pillow lava of inferred Cambrian age at Narooma, south coast of New South Wales. See Fergusson and Frikken (2003) for more details.
|
Upper Cambrian limestone from Burrewarra Point, south of Batemans Bay, south coast of New South Wales (Peter Frikken is under the hat). See Fergusson and Frikken (2003) for more details.
|
 Fragment of greenstone in mud-rich melange, northern headland of Malua Bay, south of Batemans Bay, south coast of New South Wales. See Fergusson and Frikken (2003) for more details.
|
 Fragments of sandstone in mud-rich melange, Garden Bay, near Malua Bay, south of Batemans Bay, south coast of New South Wales. See Fergusson and Frikken (2003) for more details.
|
Small fragments in mud-rich melange, Sunshine Bay, south of Batemans Bay, south coast of New South Wales. See Fergusson and Frikken (2003) for more details.
|
Chert melange from the southern side of Burrewarra Point, south of Batemans Bay, south coast of New South Wales. See Fergusson and Frikken (2003) for more details.
|
Folded disrupted quartzose turbidites from the southern side of Burrewarra Point, south of Batemans Bay, south coast of New South Wales. See Fergusson and Frikken (2003) for more details.
|
 Sandstone fragments in melange, Wonnangatta Fault Zone, southern Tabberabbera Zone, eastern Victoria. See Fergusson (2003) for more details.
|
|
References
(Reprints for articles by Fergusson are available on request – cferguss@uow.edu.au)
Fergusson C. L., Fanning, C. M., Phillips D. and Ackerman B. R. 2005. Structure, detrital zircon U-Pb ages and 40Ar/39Ar geochronology of the Early Palaeozoic Girilambone Group, central New South Wales: subduction, contraction and extension associated with the Benambran Orogeny. Australian Journal of Earth Sciences 52, 137–159.
Fergusson C. L. 2003. Ordovician–Silurian accretion tectonics of the Lachlan Fold Belt, southeastern Australia. Australian Journal of Earth Sciences 50, 475–490.
Fergusson C. L. and Frikken P. 2003. Diapirism and structural thickening in an Early Palaeozoic subduction complex, southeastern New South Wales, Australia. Journal of Structural Geology, 25, 43–58.
Fergusson C. L. and Fanning C. M. 2002. Late Ordovician stratigraphy, zircon provenance and tectonics, Lachlan Fold Belt, southeastern Australia. Australian Journal of Earth Sciences 49, 423–436.
Foster D. A. and Gray D. R. 2000. Evolution and structure of the Lachlan Fold belt (Orogen) of eastern Australia. Annual Reviews of Earth and Planetary Sciences 28, 47–80.
|
|
Back to Chris Fergusson Home Page
|
