Tectonic and stratigraphic evolution of the central Exmouth Plateau, NW Shelf of Australia

Bilal, Awad; McClay, Ken

doi:10.1016/j.marpetgeo.2021.105447

Cited by 14 publications

(18 citation statements)

References 40 publications

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“…Based on: (1) the marine setting inferred for the study area during the latest Middle Jurassic (Bilal & McClay, 2021); (2) its seismic facies character, i.e., laterally continuous, relatively low‐ to moderate‐amplitude reflections; and (3) the fact that syn‐rift stratigraphic successions motifs are typically characterised by an upward‐deepening motif, Unit 3 is interpreted as representing laterally continuous, pelagic and hemipelagic rocks deposited in an overall low‐energy environment (Figures 9i and 10g) (e.g., Gawthorpe & Leeder, 2000; Prosser, 1993; Ravnås et al., 2000). This interpretation is supported by the regional relative sea level rise that characterised the Middle‐Late Jurassic (i.e., J40.0SB horizon; Longley et al., 2002).…”

Section: Resultsmentioning

confidence: 99%

“…Fault‐scarp degradation products typically accumulate as texturally immature deposits at the base of the syn‐rift sequence in the immediate hangingwall basins (Figure 1b; Chiarella et al., 2021; Cullen et al., 2019; Henstra et al., 2016; McLeod & Underhill, 1999). Several subsurface studies identify fault‐controlled syn‐rift wedges that pinch‐out away from the controlling fault (e.g., Barrett et al., 2021; Bilal et al., 2018; Bilal & McClay, 2021; Hoth et al., 2018; Ravnås & Bondevik, 1997; Scarselli et al., 2022); these deposits are typically characterised by chaotic to low‐continuity internal reflections (Figure 1d; Barrett et al., 2021; Bilal et al., 2018; Hoth et al., 2018; Mann‐Kalil et al., 2023). Deposits with such characteristics have been previously referred to as slope aprons (e.g., Henstra et al., 2016), talus wedges (e.g., Bilal et al., 2018), fan deltas (e.g., Lewis et al., 2017), or debris flows (e.g., Henstra et al., 2016), which we collectively refer to by the more generic term fault‐controlled base‐of‐scarp deposits (sensu Chiarella et al., 2021).…”

Section: Introductionmentioning

confidence: 99%

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Syn‐rift tectono‐stratigraphic development of the Thebe‐0 fault system, Exmouth Plateau, offshore NW Australia: The role of fault‐scarp degradation

Martinez,

Chiarella,

Jackson

et al. 2024

Basin Research

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The syn‐rift architecture of extensional basins records deposition from and interactions between footwall‐, hangingwall‐, and axially‐derived systems. However, the exact controls on their relative contributions and the overall variable depositional architecture, and how their sediment volume varies through time, remains understudied. We undertook a quantitative approach to determine temporal and spatial changes in the contribution of fault‐scarp degradation to the syn‐rift tectono‐stratigraphic development of the Thebe‐0 fault system on the Exmouth Plateau (NW Shelf, offshore Australia), using high‐quality 3D seismic reflection and boreholes data. The magnitude of footwall erosion was measured in terms of vertical (VE) and headward (HE) erosion by calculating the volume of eroded material along the footwall scarp. A detailed seismic‐stratigraphic and facies analysis allowed us to constrain the architectural variability of the hangingwall depositional systems and the types of resulting deposits (i.e., fault‐controlled base‐of‐scarp, settling from suspension, and hangingwall‐derived). After addressing the syn‐rift tectono‐stratigraphic framework, we suggest that periods of significant erosion along the Thebe‐0 fault scarp are related to the accumulation of fault‐controlled base‐of‐scarp deposits characterised by comprising a lower wedge with chaotic to low‐continuity reflections. Footwall‐derived deposits characterised by an upward decrease in stratigraphic dip are interpreted as related to periods of reduced fault activity and sustained sediment delivery sourced from the footwall scarp and systems beyond it (e.g., antecedent systems). We then analysed the tectono‐stratigraphic framework and the volumetric comparison between material eroded from the fault‐scarp and accumulated in the basin, aiming to estimate the contribution of fault‐scarp degradation to the hangingwall syn‐rift fill. Our results suggest periods of enhanced fault activity control fault‐scarp degradation variability through time, and we agree with that described by previous researchers—fault throw variability along‐strike regulates the variability in the magnitude of erosion. However, we propose that fault‐scarp degradation timing and its spatial variability are also influenced by the interaction and linkage with adjacent normal faults and by sea level variations. Lastly, we determine broader similarities and differences with a system located in the same fault array (i.e., Thebe‐2 fault system), aiming to give insights into the tectono‐stratigraphic evolution of a broader area and the spatial variability in fault‐scarp degradation.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Syn‐rift tectono‐stratigraphic development of the Thebe‐0 fault system, Exmouth Plateau, offshore NW Australia: The role of fault‐scarp degradation

Martinez,

Chiarella,

Jackson

et al. 2024

Basin Research

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“…Rifting of the Exmouth Plateau began in the Late Triassic-to-Jurassic, forming an array of ~N-S striking, large (often >1 km throw) normal faults within pre-rift, fluvio-deltaic sedimentary rocks of the Mungaroo Formation (Figs 2B and C) (e.g., Bilal & McClay, 2022, Bilal et al, 2018, Stagg et al, 2004. The Exmouth Plateau was sediment-starved during this phase of rifting, thus contains a relatively condensed (≲100 m thick), late Triassic-to-Early Jurassic marine succession (e.g., Figs 2B and C) (e.g., Exon et al, 1992, Karner & Driscoll, 1999.…”

Section: Geological Settingmentioning

confidence: 99%

Quantifying dyke-induced graben and dyke structure using 3D seismic reflection data

Magee¹,

Love²,

Fayez³

et al. 2022

Preprint

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During dyke intrusion, tensile stresses concentrated within the overlying rock may lead to the formation of normal faults. These faults typically form graben-bounding pairs that are sub-parallel to, and dip toward, the upper tip of their underlying dyke. Many studies use geometric properties extracted from the surface expression of such dyke-induced faults to estimate the geometry of subsurface dykes. These methods assume dyke-induced faults are planar and nucleate at the surface. However, recent investigations of the 3D structure of dyke-induced faults using seismic reflection data confirm they can be non-planar and have complex growth histories. Here, we use 3D seismic reflection surveys from offshore NW Australia to: (1) examine how the surface expression of dyke-induced faults relates to subsurface dyke geometry and depth; and (2) test whether subjective bias may influence the quantitative analyses of dyke-induced faults. We show displacement and dip vary across dyke-induced faults, supporting previous suggestions that faults nucleate between dyke upper tips and the free surface. We also find that depths of dyke upper tips predicted using graben width and area of loss measurements, whilst sensitive to fault dip variations and interpretation biases, are often similar to measured dyke depths. Both measured and predicted dyke depths vary by several hundred metres along-strike, which we relate to the preservation of dyke heads, segmentation, and/or magma density changes. Overall, we show reflection seismology provides a better understanding of the 3D structure of dyke-induced faults and their relationship to the geometry and emplacement dynamics of their causal dykes.

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“…To understand the geological and tectonostratigraphic evolution, deposition history and to identify the principal uplifting events, we used well completion reports, stratigraphic tops, lithological descriptions, bibliographic information (Bradshaw et al, 1988;Blevin et al, 1994;Müller et al, 1998;Polomka et al, 1999;Kaiko and Tait, 2001;Chongzhi et al, 2013;Geoscience Australia, 2014;Rohead-O'Brien and Elders, 2018;Dempsey et al, 2019;Bilal and McClay, 2022). Because few wells reached deeper than the top of the Mungaroo Formation, the thickness of the underlying units were taken from Goncharov et al (2006).…”

Section: Geochemical Modellingmentioning

confidence: 99%

Geochemical and geomechanical evaluation of the Mungaroo Formation, offshore northwestern Australia

2022

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The geochemical characterization of the Mungaroo Formation rocks shows the presence of kerogen type II/III and III which characterizes the Exmouth Plateau sub-basin as a gas prone basin. Using 13 burial histories constructed from well data, we identified three tendencies: One with high sedimentation rates between the Middle Triassic and Upper Triassic (69.3-95.3 m/Ma), another one with high sedimentation rates between the Lower and Upper Cretaceous (67-158 m/Ma), and the last one with low sedimentation rates (18-40 m/Ma) during the Upper Cretaceous until present time. All these trends defined active generation zones (or gas kitchens) between 2,000 and 4,400 km2. High sedimentation rates during the Cretaceous and Triassic times were key to the burial history of the Mungaroo Formation because they allowed these rocks to reach the required depths to transform its organic matter. In contrast, in the area with low sedimentation rates, radiogenic heat flow was the trigger for the transformation of the organic matter. The generation/expulsion of hydrocarbons from these shales occurs since 100 My, consequently explaining the large gas accumulation found in the sub-basin. Currently, the Mungaroo formation is in the gas generation window at depths of 4,500 to 5,500 m below sea level. The shales of this formation show TOC% values higher than 2% reaching the gas generation zone (Ro% >1.3) and suggesting its potential as an unconventional gas reservoir. However, geomechanical features such as low fragility, under pressure, and thickness, condemns its unconventional potential.

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Tectonic and stratigraphic evolution of the central Exmouth Plateau, NW Shelf of Australia

Cited by 14 publications

References 40 publications

Syn‐rift tectono‐stratigraphic development of the Thebe‐0 fault system, Exmouth Plateau, offshore NW Australia: The role of fault‐scarp degradation

Syn‐rift tectono‐stratigraphic development of the Thebe‐0 fault system, Exmouth Plateau, offshore NW Australia: The role of fault‐scarp degradation

Quantifying dyke-induced graben and dyke structure using 3D seismic reflection data

Geochemical and geomechanical evaluation of the Mungaroo Formation, offshore northwestern Australia

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