Style, timing and distribution of tectonic deformation across the Exmouth Plateau, northwest Australia, determined from stratal architecture and quantitative basin modelling

Abstract

By combining a kinematic and flexural model for the deformation of the lithosphere with sequence stratigraphy, the distribution amplitude, depth-partitioning and interaction of the tectonic events responsible for the formation of the Exmouth Plateau, northwest Australia, have been determined. The style of deformation varied continually as a function of space and time. Initially, the deformation was characterized by a broadly distributed late Permian event. During late Triassic-middle Jurassic time, deformation became more localized and formed a series of sub-basins; the Exmouth, Barrow and Dampier Sub-basins. This localized phase of deformation was followed by a substantially more regional deformation event in the Tithonian-Valanginian that generated large, post-Valanginian regional subsidence across the Exmouth Plateau, with only minor accompanying brittle deformation and erosion. After the initiation of seafloor spreading, a phase of inversion occurred, which correlated with the reorganization of the Indo-Australian plates during magnetic anomaly M0-34 time. This inversion induced minor reactivation of fault systems within the sub-basins and adjacent areas.The style and distribution of each tectonic event are recorded by a diagnostic stratal architecture. For example, the late Permian event is recorded by the deposition of the broadly distributed and monotonous sequences of the Locker Shales and Mungaroo Formation. These units are more appropriately described as intracratonic in character. In contrast, the localized early Triassic and Callovian rifting events are characterized by regressive packages of thick shales (the upper and lower Dingo claystones). Crucial in the development of the upper and lower Dingo claystones was the segmented nature of the border faults that delineated the Exmouth, Barrow and Dampier Sub-basins. En echelon fault patterns and a basin synform structure, within which the pre-rift stratigraphy dips subparalM to or away from the fault trace, strongly implies a wrench influence in the development of the northern sub-basins (central Barrow and Dampier Sub-basins). This wrenching is consistent with the difference in regional trend of both the central Barrow and Dampier Sub-basins relative to the spreading fabric within either the Argo and/or Cuvier oceanic crust.The regional distribution and amplitude of the post-Valanginian subsidence is not consistent with the minor amounts of Tithonian-Valanginian brittle upper crustal extension observed on the margin. Facies and microfossil analyses suggest that, prior to extension, large portions of the platform were emergent, or at shallow water depths. To match the distribution and magnitude of the post-Valanginian thermal-type subsidence requires significant lower crustal and mantle extension across the Exmouth Plateau Basin. Such a distribution of extension implies the existence of an intracrustal detachment having a rampflat-ramp geometry that effectively thinned the lower crust and lithospheric mantle. A large injection of heat should accompany t...

Cretaceous–Tertiary inversion history of the Dampier Sub-basin, northwest Australia: Insights from quantitative basin modelling

“…The 'Quantitative Basin Analysis' (QBA) approach of Driscoll and Karner (1998) and Karner and Driscoll (1999) used in this study integrates seismic stratigraphic interpretations (Cathro et al, 2003), palaeo-water depth estimates (Moss et al, 2004), and forward kinematic basin modelling to simulate the development and modification of accommodation space as a function of space and time across the margin and, thus, the time-line stratigraphy of the basin. Geoscience Australia line 101r_09 ( Fig.…”

“…2). The fine-grained, transgressive, Muderong Shale covers much of the NWS, forming the regional seal for hydrocarbons (Hocking et al, 1988;Driscoll and Karner, 1998;Karner and Driscoll, 1999). The overlying regional but condensed Windalia Radiolarite is downlapped by the Albian-Santonian Gearle Siltstone in the Barrow Subbasin, and its equivalent, the Haycock Marl, was deposited in the Dampier Sub-basin ( Fig.…”

“…We combine seismic sequence stratigraphy, sequence biostratigraphy and forward kinematic basin modelling to determine: (1) the distribution and history of Cretaceous-Late Tertiary inversion across the Dampier Sub-basin, and (2) the distribution and magnitude of inversion developed across preexisting structural trends. This analysis, coupled with significantly improved palaeo-bathymetric estimates and high resolution multi-channel reflection seismic data, builds on earlier quantitative basin analyses that examined the general geological development of the Exmouth, Barrow and Dampier sub-basins and in particular, the lateral and vertical distribution of Early Cretaceous extension Karner, 1996, 1998;Karner and Driscoll, 1999). The ultimate goal of our modelling is to investigate the interaction of depositional or accommodation-forming processes responsible for the stratigraphic development of the NCB, as represented in the depthconverted seismic reflection and well data.…”

“…Cretaceous inversion features in the NCB include ( Fig. 1): (1) a forced fold in the Exmouth sub-basin, (2) Barrow Island, and (3) Rosemary-Legendre Trend in the Dampier Sub-basin (Driscoll and Karner, 1996;Tindale et al, 1998;Bradshaw et al, 1998;Karner and Driscoll, 1999). Tertiary reactivation is identified along the entire North West Shelf (NWS) (Keep et al, 1998) from the northern Bonaparte Basin (O'Brien et al, 1999) to the NCB along the Rosemary-Legendre Trend, and the Giralia and Cape Range anticlines ( Fig.…”

Imaging, mapping and modelling continental lithosphere extension and breakup: an introduction

“…For margins exemplified by well developed pre-, syn-and post-rift stratigraphies, the polyphase faulting history is known and is minor (e.g. Karner & Driscoll 1999).…”