Origin of basin-scale syn-extensional synclines on the southern margin of the Northern Carnarvon Basin, Western Australia

Abstract

Fault geometry exerts a dominant structural control on the deformation of hanging wall sequences during extension and contraction. Numerical, kinematic and sandbox modelling studies have demonstrated that characteristic anticline–syncline pairs are produced during the extension of ramp-flat faults. These features are commonly recognized in smaller fault-scale structures, but remain underappreciated in larger, basin-scale settings. The Lewis Trough, situated within the Northern Carnarvon Basin, Western Australia, is a basin-scale, largely unfaulted syncline with an associated anticline along its western flank, rather than the fault-related graben typical of the region. We present kinematic models demonstrating that a SE-dipping, ramp-flat fault geometry can produce relative highs and lows in Jurassic strata as well as honouring the asymmetrical onlap pattern within the Lewis Trough. This study indicates that the Lewis Trough formed during the Early Jurassic, a period typically associated with high rates of extension and not during the Late Triassic Fitzroy Compression Event. This study also highlights the importance of the Locker Shale in partitioning deformation of the Permian and Mesozoic fault systems and as a diffuse zone that variably partitions displacement between stacked Permian and Mesozoic fault systems.

Sediment dispersal and redistributive processes in axial and transverse deep‐time source‐to‐sink systems of marine rift basins: Dampier Sub‐basin, Northwest Shelf, Australia

“…We tied stratigraphic surfaces to the seismic data and mapped these surfaces throughout the seismic data to construct a tectono‐stratigraphic framework (Figure 2). This framework enables observations on the temporal evolution of the basin and interpretation of the key rift stages (Longley et al., 2002; Marshall & Lang, 2013; McHarg et al., 2019b). Most of the wells on the Rankin Platform and Madeleine Trend penetrate the Jurassic strata, whereas very few penetrate the equivalent interval in the Kendrew and Lewis troughs (Figure 3a).…”

“…The Dampier Sub‐basin is a Jurassic‐to‐Early Cretaceous marine rift basin in the Northern Carnarvon Basin, Northwest Shelf of Australia (Longley et al., 2002; Marshall & Lang, 2013; McHarg, Elders, & Cunneen, 2019a, 2019b; Thomas et al., 2004; Figure 1a). This study focuses on the late syn‐rift succession in the north‐western part of the Dampier Sub‐basin, the entirety of which is imaged by the Fortuna 3‐D seismic survey (Figure 1a,b).…”

“…Late-Mesozoic rifting started in the Early Jurassic (Pliensbachian) and continued to the end of Early Cretaceous (Valanginian), and is interpreted to comprise three stages: (i) early syn-rift stage (J20 interval), (ii) main syn-rift stage (J30-J40 interval) and iii) late syn-rift stage (J50 interval) (Longley et al, 2002;McHarg, Elders, & Cunneen, 2019b;Stagg, 2004; Figure 2). During the early syn-rift stage, structurally high blocks developed along the Enderby Trend and Rankin Platform, with marine clays and silty sands of the Athol Formation and Legendre Formation, respectively, in the Dampier Sub-basin (Longley et al, 2002;Marshall & Lang, 2013;McHarg et al, 2019b; Figure 2). The early main syn-rift stage (Callovian to Kimmeridgian) marks continental break-up and the onset of seafloor spreading, with deposition of transgressive shallow marine sands of the Calypso Formation (McHarg et al, 2019a(McHarg et al, , 2019bStagg, 2004; Figure 2).…”

“…During the early syn-rift stage, structurally high blocks developed along the Enderby Trend and Rankin Platform, with marine clays and silty sands of the Athol Formation and Legendre Formation, respectively, in the Dampier Sub-basin (Longley et al, 2002;Marshall & Lang, 2013;McHarg et al, 2019b; Figure 2). The early main syn-rift stage (Callovian to Kimmeridgian) marks continental break-up and the onset of seafloor spreading, with deposition of transgressive shallow marine sands of the Calypso Formation (McHarg et al, 2019a(McHarg et al, , 2019bStagg, 2004; Figure 2). Following the transgression, localized basin-floor fans of the Eliassen Formation were deposited (e.g., Fullerton, , & Handschumacher, 1989;Hill, 1994;Stagg, 2004; Figure 2).…”

“…Note the interval of interest in this study is the J50 interval which developed in the late syn-rift stage. Abbreviation: MSR, Main syn-rift; Fm, Formation on the temporal evolution of the basin and interpretation of the key rift stages (Longley et al, 2002;Marshall & Lang, 2013;McHarg et al, 2019b). Most of the wells on the Rankin Platform and Madeleine Trend penetrate the Jurassic strata, whereas very few penetrate the equivalent interval in the Kendrew and Lewis troughs (Figure 3a).…”