Structural inversion of the Tamworth Belt: Insights into the development of orogenic curvature in the southern New England Orogen, Australia. (May 2016)

• Record Type: Journal Article
• Authors: Phillips, G.; Robinson, J.; Glen, R.; Roberts, J.
• Is Part Of: Journal of structural geology. Volume 86(2016:May)
• Page Start: 224
• Page End: 240
• Publication Date: 2016-05
• Subjects: Orogenic curvature -- Cross-sections -- Southern New England Orogen -- Tasmanides -- Hunter Bowen Event; Geology, Structural -- Periodicals; Géomorphologie structurale -- Périodiques; Geology, Structural; Periodicals; 551.805
• DOI: 10.1016/j.jsg.2016.03.004
• Languages: English
• ISSNs: 0191-8141

Abstract

Abstract: The middle to late Permian Hunter Bowen Event is credited with the development of orogenic curvature in the southern New England Orogen, yet contention surrounds the structural dynamics responsible for the development of this curvature. Debate is largely centred on the roles of orogen parallel strike-slip and orogen normal extension and contraction to explain the development of curvature. To evaluate the dynamic history of the Hunter Bowen Event, we present new kinematic reconstructions of the Tamworth Belt. The Tamworth Belt formed as a Carboniferous forearc basin and was subsequently inverted during the Hunter Bowen Event. Kinematic reconstructions of the Tamworth Belt are based on new maps and cross-sections built from a synthesis of best-available mapping, chronostratigraphic data and new interpretations of depth-converted seismic data. The following conclusions are made from our study: (i) the Hunter Bowen Event was dominantly driven by margin normal contraction (east–west shortening; present-day coordinates), and; (ii) variations in structural style along the strike of the Tamworth Belt can be explained by orthogonal vs. oblique inversion, which reflects the angular relationship between the principal shortening vector and continental-arc margin. Given these conclusions, we suggest that curvature around the controversial Manning Bend was influenced by the presence of primary curvature in the continental margin, and that the Hastings Block was translated along a sinistral strike-slip fault system that formed along this oblique (with respect to the regional east–west extension and convergence direction) part of the margin. Given the available temporal data, the translation of the Hastings Block took place in the Early Permian (Asselian) and therefore preceded the Hunter Bowen Event. Accordingly, we suggest that the Hunter Bowen Event was dominantly associated with enhancing curvature that was either primary in origin, or associated with fault block translation during the Early Permian. This model differs to previously proposed reconstructions where curvature largely formed by orogen parallel strike-slip transportation during the Hunter Bowen Event. Graphical abstract: Highlights: Kinematic reconstructions of the Tamworth Belt (southern New England Orogen) reveal the dominance of orogen normal extension and contraction. Orogenic curvature around the Manning bend was facilitated by a salient in the pre-Permian continental-arc margin. The structural evolution of the Tamworth Belt during the Hunter Bowen Event can be explained by zones of orthogonal and oblique convergence.