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Provenance of the Early Permian Nambucca Block (eastern Australia) and implications for the role of trench retreat in accretionary orogens

Uri Shaanan, Gideon Rosenbaum and Richard Wormald
Provenance of the Early Permian Nambucca Block (eastern Australia) and implications for the role of trench retreat in accretionary orogens
Geological Society of America Bulletin (February 2015) 127 (7-8): 1052-1063

Abstract

The New England orogen of eastern Australia is characterized by tight orogenic curvatures (oroclines). Oroclinal bending commenced in the Early Permian during a period of extension that involved crustal melting, widespread emplacement of S-type granitoids, high-temperature metamorphism, exhumation of metamorphic complexes, extensional faulting, and development of rift basins. One of these basins is the Early Permian Nambucca block, which is situated in the "core" of the oroclinal structure, but its origin and time of deposition are poorly constrained. Here, we present new U-Pb ages of detrital zircons from the Nambucca block, which include age populations as young as 299 and 285 Ma, confirming the Early Permian deposition of the succession. Additional Devonian-Carboniferous and Precambrian ages indicate that detritus was mainly derived from the New England subduction complex and cratonic Gondwana. The range of ages suggests that the Nambucca Basin received detritus from both arc and continent and that deposition occurred in a back-arc setting. Given the coeval formation of the Nambucca Basin and the New England oroclines, we propose that this back-arc extensional basin was controlled by trench retreat, which resulted in "Mediterranean-style" orogenic curvatures along the plate boundary of eastern Gondwana. The recognition of a genetic link between oroclinal bending and back-arc extension may explain how accretionary orogens, such as the eastern Australian Tasmanides, were able to obtain an anomalous width without a substantial contribution of accreted exotic terranes. A similar mode of tectonism may have played an important role in other accretionary orogens.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 127
Serial Issue: 7-8
Title: Provenance of the Early Permian Nambucca Block (eastern Australia) and implications for the role of trench retreat in accretionary orogens
Affiliation: University of Queensland, School of Earth Sciences, Brisbane, Queensl., Australia
Pages: 1052-1063
Published: 20150219
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 88
Accession Number: 2015-021932
Categories: Structural geologyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2015094
Illustration Description: illus. incl. 1 table, geol. sketch map
S33°00'00" - S28°00'00", E150°00'00" - E154°00'00"
Secondary Affiliation: James Cook University, AUS, Australia
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201511
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