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Benambran Orogeny in the Eastern Lachlan Orogen, Australia


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Glen, RA, Meffre, S and Scott, RJ 2007 , 'Benambran Orogeny in the Eastern Lachlan Orogen, Australia' , Australian Journal of Earth Sciences, vol. 54, no. 2-3 , pp. 385-415 , doi: 10.1080/08120090601147019.

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The Benambran Orogeny reflects the accretion of the intra-oceanic Macquarie Arc to the Gondwana
Plate. The ultimate cause was the northwards strike-slip transport of the allochthonous Bega Terrane
along the eastern margin of Gondwana, into a forearc position outboard of the Macquarie Arc.
Ensuing oblique compression in the outboard part of the Gondwana Plate drove the Macquarie Arc
into and under its backarc Wagga Basin, represented by the Girilambone –Wagga Terrane, and led to
a combination of thrusting and major strike-slip faulting within, inboard and outboard of the arc over 10
million years. In this time frame, the Benambran Orogeny in the Eastern Subprovince of the Lachlan
Orogen in New South Wales consists of two phases of exhumation – deformation, at ca 443 Ma (late
Bolindian to early Llandovery) and ca 430 Ma (late Llandovery), separated by a relaxation/extensional
event. Both phases involved deformation and exhumation of the Macquarie Arc and coeval quartz-
rich turbidites and black shales of the Adaminaby Superterrane. Closure of the former backarc basin
was facilitated by limited east-dipping subduction that generated the short-lived Fifield arc. The second
phase of the Benambran Orogeny also involved deformation and exhumation of overlying Llandovery
strata (e.g. the Yalmy Group) and syn- to post-tectonic emplacement of granitoids. In both phases,
deformation of Adaminaby Superterrane rocks was more intense than deformation of arc rocks.

Item Type: Article
Authors/Creators:Glen, RA and Meffre, S and Scott, RJ
Keywords: arc accretion, Benambran Orogeny, Lachlan Orogen, Ordovician, plate tectonics, Tasmanides.
Journal or Publication Title: Australian Journal of Earth Sciences
ISSN: 0812-0099
DOI / ID Number: 10.1080/08120090601147019
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