New constraints on the timing of flexural deformation along the northern Australian margin: Implications for arc-continent collision and the development of the Timor Trough Muhammad Mudasar Saqab a,b, ⁎ ,1 , Julien Bourget a,b , Julie Trotter b , Myra Keep b a Centre for Energy Geoscience, The University of Western Australia, 35 Stirling Highway, Crawley 6009, WA, Australia b School of Earth and Environment, The University of Western Australia, 35 Stirling Highway, Crawley 6009, WA, Australia abstract article info Article history: Received 29 May 2016 Received in revised form 9 December 2016 Accepted 19 December 2016 Available online 21 December 2016 Numerous extensional faults offset the passive margin strata of the northern Bonaparte Basin. This extensional de- formation has been attributed to lithospheric flexure of the descending Australian Plate, in an overall convergence setting. Here we use an extensive 2D and 3D seismic dataset calibrated with well biostratigraphy and strontium (Sr) isotope age data to constrain the timing of deformation along the northern Australian margin during the Neogene. Analysis of fault throw and differential thickness variations give new insights on the propagation and slip history of the faults. Along-dip throw profiles exhibit ‘D’ shape distributions, skewed towards the top. Positive throw gradients above the throw maxima, coinciding with intervals of growth strata, indicate multiphase fault activity. Results indicate that post-rift extensional deformation initiated during the latest Miocene (ca. 6 Ma). The development of the modern Timor Trough (as a foreland basin) and Cartier Trough also commenced during this period. A second episode of increased tectonic activity occurred around the Pliocene–Quaternary boundary (ca. 3 Ma), and the deformation continued intermittently to the present-day. These new results are in agreement with the timing of initiation of collision between the Australian Plate and the Banda Arc and uplift of the Timor Island, recently derived from stratigraphic analysis in Timor. These regional tectonic events have profoundly affected the paleogeography of the Timor Sea and may explain major changes in oceanic circulation and climate during the Neogene. © 2016 Elsevier B.V. All rights reserved. Keywords: Arc-continent collision Flexural extension Syn-kinematic growth faulting Timor Sea Paleoceanography 1. Introduction Arc-continent collision zones form geologically complex areas where parameters such as deformation mechanisms and timing of collision are generally difficult to understand (e.g. Bowin et al., 1980; Snyder et al., 1996; Brown et al., 2011; Harris, 2011). A commonly cited example of arc-continent collision is the Neogene collision between the Australian continent and the Banda Arc (Bowin et al., 1980; Richardson and Blundell, 1996; Hall and Wilson, 2000; Brown et al., 2011; Harris, 2011; Metcalfe, 2011; Hall, 2012; Kearey et al., 2013). In this system the locus, age and mode of collision is still debated (Crostella, 1977; Hamilton, 1979; Johnston and Bowin, 1981; McCaffrey et al., 1985; Audley-Charles, 2004; Keep and Haig, 2010; Harris, 2011; Benincasa et al., 2012; Haig, 2012). Estimates for the start of collision vary from late Miocene (9.8–5.7 Ma; Berry and McDougall, 1986; Haig and McCartain, 2007; Keep and Haig, 2010; Haig, 2012; Tate et al., 2015) to late Pliocene and Quaternary (4–2 Ma; Bowin et al., 1980; Abbott and Chamalaun, 1981; Audley-Charles, 2004; Spakman and Hall, 2010; Hall, 2012). These differences are mainly due to: (i) different interpretations of stratigraphic data from Timor, (ii) absence of a clearly recognisable subduction trench, and (iii) limitations of availability and resolution of seismic and biostratigraphic data from the northern Australian margin (Richardson and Blundell, 1996; Snyder et al., 1996; Audley-Charles, 2004; Keep and Haig, 2010; Haig, 2012). The Timor Sea sedimentary succession including the foreland basin (Timor Trough; Audley-Charles, 2004; Haig, 2012) and the adjacent areas dominated by lithospheric flexure (e.g. the northern margin of Australia; O'Brien et al., 1999; Londoño and Lorenzo, 2004; Fig. 1) consti- tute unique archives of the tectonic evolution of the region (Dickinson, 1974; Beaumont, 1981; Sinclair, 1997; O'Brien et al., 1999; Londoño and Lorenzo, 2004). On the northern Australian margin (Browse and Bonaparte basins; Fig. 1) flexural extension, mainly due to thrust loading in Timor Island, triggered a new phase of deformation associated with the reactivation of pre-existing (Mesozoic) rift structures (Patillo and Nicholls, 1990; Shuster et al., 1998; O'Brien et al., 1999; De Ruig et al., 2000; Keep et al., 2002; Harrowfield et al., 2003; Gartrell et al., 2006; Langhi et al., 2011; Saqab and Bourget, 2015). Paleozoic rifting in the Bonaparte Basin, which produced NW–SE structural grain (e.g. Mory, 1991; Longley et al., 2002), developed inboard of the flexural hinge Tectonophysics 696–697 (2017) 14–36 ⁎ Corresponding author. E-mail address: mmsaqab@gmail.com (M.M. Saqab). 1 Present address: Irish Centre for Research in Applied Geosciences, School of Earth Sciences, University College Dublin, Belfield, Dublin 4, Ireland. http://dx.doi.org/10.1016/j.tecto.2016.12.020 0040-1951/© 2016 Elsevier B.V. All rights reserved. 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