The tectonic significance of lower Permian successions in the Texas Orocline (Eastern Australia)

Abstract

The Texas Orocline is a prominent orogenic curvature that developed during the early Permian in the southern New England Orogen. Outliers preserving lower Permian sedimentary successions (Bondonga, Silver Spur, Pikedale, Terrica, Alum Rock and Ashford beds) approximately outline the oroclinal structure, but the tectonic processes responsible for the development of these basinal successions, and their relationships to the Texas Orocline, are unclear. Here we address this shortcoming by providing new U–Pb detrital and primary zircon ages from these successions, as well as detailed stratigraphic and structural data from the largest exposed succession (Bondonga beds). Field observations and U–Pb geochronological data suggest that the lower Permian successions in the Texas Orocline are remnants of a single, formerly larger basin that was deposited after ca 302 Ma. Time constraints for formation of this basin are correlative with constraints from the lower Permian Nambucca Block, which was likely deposited in response to regional back-arc extension during and/or after the development of the Texas Orocline. The conclusion that the lower Permian sedimentary basins in the Texas Orocline belong to this back-arc extensional system supports the suggestion that oroclinal bending in the New England Orogen was primarily controlled by trench retreat and associated overriding-plate extension.

KEY WORDS:

• New England Orogen
• oroclines
• Texas Orocline
• early Permian
• U–Pb geochronology
• zircon
• depositional age
• provenance

ACKNOWLEDGEMENTS

This work was funded by the Australian Research Council (grant DP130100130). We thank Paul Donchak and Chris Fergusson for providing comments on the manuscript. We also wish to thank Llyam White and Travis Klein for assistance in the field, and Derek Hoy, Karine Moromizato and Abbas Babaahmadi for technical support and guidance.

Disclosure statement

No potential conflict of interest was reported by the authors.

SUPPLEMENTAL DATA

U–Pb detrital zircon geochronology and trace element data

Supplemental data is available alongside the online version of the article, at http://dx.doi.org/10.1080/08120099.2015.1111259