--> Abstract: Stretching Estimates Across the Browse Basin Continental Margin NW Australia: From 2d Basin-Modelling & 3d Gravity-Inversion, by Alan Roberts, Nick J. Kusznir, Richard Woodfine, Steve Matthews, Andrei Belopolsky, Cheree Stover, and Alexey Goncharov; #90082 (2008)

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Stretching Estimates Across the Browse Basin Continental Margin NW Australia: From 2d Basin-Modelling & 3d Gravity-Inversion

Alan Roberts1, Nick J. Kusznir2, Richard Woodfine3, Steve Matthews4, Andrei Belopolsky4, Cheree Stover4, and Alexey Goncharov5
1Badley Geoscience Ltd, Hundelby, Lincolnshire, United Kingdom
2Liverpool University, Liverpool, United Kingdom
3BP Exploration, Perth, WA, Australia
4BP Exploration, Sunbury, United Kingdom
5Geoscience Australia, Canberra, ACT, Australia

3 regional seismic lines across the Browse Basin and Scott Plateau, NW Australia have been analysed by 2D flexural-backstripping and 2D fault-forward-modelling. 3D satellite gravity inversion has been used to map crustal thickness and lithosphere stretching factors for the full Browse continental margin.

Flexural backstripping of the 2D lines to the Jurassic syn-breakup timestep (~160Ma) was performed to investigate stretching-factors (β) and syn-rift geometries across the margin. Structural forward modelling was performed to determine the magnitude of fault-controlled breakup extension and enabled comparison of results with lithosphere β-factors derived from backstripping.
The validity of the sequential backstripped restorations has been QC’d against available geological data calibrating bathymetry, emergence and erosion through time. In this way each sequential restoration was linked directly to the corresponding regional GDE map.

3D gravity inversion is critically dependent on mapping the sediment thickness across the margin. As there is uncertainty in definition of the sediment thickness a number of sensitivity tests were run applying sediment thickness models mapped by different methods.

Primary results of the combined basin-modelling and gravity-inversion analysis indicate that:
- In the east, the Browse Basin is a normal fault-controlled rift basin (β reaching ~1.5)
- In the west the Scott Plateau is a transitional area of highly-stretched continental crust (β ~3-6)
- The Wilson Spur on the extreme outer margin is a moderately-stretched continental block (β ~2) separated from the continental plate by the failed breakup-basin of the Scott Plateau
- Upper crustal extension/faulting cannot account for the high lithosphere β-factors (3-6) across the Scott Plateau, indicating that depth-dependent lithosphere stretching during continental breakup has occurred.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery