Stratigraphic and tectonic evolution of the northwestern Bonaparte Basin (North West Shelf of Australia) during the Neogene

Muhammad Mudasar Saqab

    Research output: ThesisDoctoral Thesis

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    The Bonaparte Basin (North West Shelf of Australia) is a long-lived sedimentary basin containing extensive oil and gas reserves. This study focuses on reconstructing the Neogene stratigraphic and tectonic evolution of the basinusing basin-scale 3D seismic, regional 2D seismic and biostratigraphic, lithologicand wireline data from over 50 exploration wells. Deformation along this part ofthe Australian margin did not initiate until ca. 6 Ma (latest Miocene) as a resultof the onset of collision between the Australian Plate and Banda Arc in TimorSea region. Thus, the early and middle Miocene sequences were deposited in apassive margin setting controlled by eustasy and global climate, along a lowgradient carbonate ramp. Isolated carbonate build-ups (ICBs) developed duringthe mid Burdigalian and Langhian, at a time of a relative sea-level highstand andclimate warming (Mid Miocene Climatic Optimum). This period represents aglobal acme for reef development along the North West Shelf and in greater SEAsia. Pliocene and Quaternary sediments were deposited on a margin recordingactive tectonic conditions. Numerous oblique extensional faults developed duringthis phase. The faults generally trend northeast-southwest and form right- andleft-stepping en échelon patterns. Flexural extension, operating obliquely abovepre-existing structures, is probably responsible for this deformation. Neogenefaults cluster above Mesozoic-aged, rift-inherited faults which form the mainpetroleum traps in the region. Locally, the Neogene deformation have reactivatedolder faults resulting in loss of trap integrity (breaching), a major risk forhydrocarbon exploration in the northwestern Bonaparte Basin. Seismic analysis indicates that both the distribution and linkage of the faults varies across thestudy area and mainly depends on the: (i) position and orientation of inheritedstructures, and (ii) distance to the deformation front (i.e. the present-day TimorTrough). Hard linkages develop where the two fault systems are parallel, therefore, increasing the risk of loss of trap integrity. Analyses of fault throw anddifferential thickness variations demonstrate that the extensional faults nucleatedin late Miocene strata, and then propagated laterally and vertically. The development of the modern Timor Trough (as a foreland basin) and the CartierTrough also initiated during the late Miocene. This deformation had a directinfluence on carbonate sedimentation during the late Neogene. Indeed, numerous carbonate build-ups, observed along the shelf-edge at present day, focus on top of the tectonically reactivated structural highs. However, these carbonate build-ups initiated during the mid Quaternary (ca. 0.582–0.8 Ma) with the onset of glacially controlled, high-amplitude (± 120 m), short-term sea-level fluctuations.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    • The University of Western Australia
    • Bourget, Julien, Supervisor
    • Dentith, Mike, Supervisor
    Award date1 Jun 2016
    Publication statusUnpublished - 2016


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