The Western Otway Basin — a Tectonic Framework from new Seismic, Gravity and Aeromagnetic Data

Finlayson, D. M.; Cockshell, C. D.; Finlayson, B.; Johnstone, David; Reeves, C.V.; Morse, Michael; Milligan, Peter

doi:10.1071/eg993493

Cited by 7 publications

(3 citation statements)

References 11 publications

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“…Its dimensions are not resolved, but it must have a conductivity of the order of 1 S•m-1, and from Archie's Law this is indicative of a bulk porosity of 40%. The experiment transect intersects the rifted marginal Otway basin, which is a few kilometres wide and deep (Williams and Corliss, 1982;Finlayson et al, 1994). The effect of brinesaturated sediments on the coast effect at subduction zones has been discussed by Kurtz et al (1986Kurtz et al ( , 1990 and Wannamaker et al (1989), but has not been observed at passive margins.…”

Section: Tectonic Interpretationmentioning

confidence: 99%

“…These prejudices include the seismically determined depths to the Moho and asthensophere of 40 and 140 km respectively (Denham, 1992), the globally determined depth ofthe transition zone of 390 km (Akaogi et al, 1989), possible lateral variations in conductivity between the oceanic and continetal lithosphere (Kellett et al, 1991), and the rifted Otway Basin at the continental margin (Finlayson et al, 1994).…”

Section: Two-dimensional Inversionmentioning

confidence: 99%

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Two-Dimensional Electrical Conductivity Structure across the Southern Coastline of Australia.

White

Heinson

1994

J. geomagn. geoelec

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Geomagnetic field measurements have been made at three new seafloor locations off the coast of southern Australia, to extend a magnetometer array deployed by White and Polatayko (1978). Geomagnetic depth sounding (GDS) and vertical gradient sounding (VGS) estimates provide a measure of both the TE and TM mode response of the continent-ocean boundary, which is relatively two-dimensional (2D) over hundreds of kilometres. The seafloor data from the continental shelf, mid-continental slope and at the edge of the abyssal plain show a strong geomagnetic coast effect which can largely be accounted for by the sea-water and a thick wedge of sediments in a rifted marginal basin on the continental shelf. A 2D inversion of the GDS and VGS estimates to determine the sub-seafloor conductivity structure suggests that (a) the oceanic crust and continental crust have conductivities of 0.05 and 0.005 S-m ' respectively to a depth of 10 km, (b) the upper mantle above 140 km has conductivity 0.01-0.003 S-m', (c) the upper mantle between 140 and 390 km has conductivity less than 0.003 S-m ', and (d) the lower mantle below 390 km has conductivity less than 0.3 S•m'. No distinct boundary between oceanic and continental lithosphere conductivity can be discerned. The conductivity structure beneath the coastline of southern Australia is somewhat less conductive than the preferred model ofKellett et al. (1991) for southeastern Australia.

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Section: Tectonic Interpretationmentioning

confidence: 99%

Section: Two-dimensional Inversionmentioning

confidence: 99%

Two-Dimensional Electrical Conductivity Structure across the Southern Coastline of Australia.

White

Heinson

1994

J. geomagn. geoelec

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“…It is a northwest-southeast trending structure and is bound to the southwest by a large northeast dipping listric fault complex known as the Hungerford/ Kalangadoo fault system ( Fig. 1; Finlayson et al, 1993).…”

Section: Regional Geologymentioning

confidence: 99%

A Systematic Fault Seal Evaluation of the Ladbroke Grove and Pyrus Traps of the Penola Trough, Otway Basin

Lyon¹,

Boult²,

Watson³

et al. 2005

The APPEA Journal

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Juxtaposition mapping of lithology onto the Ladbroke Grove Fault plane shows that the Pretty Hill Sandstone reservoir, which hosts a 90 m gas column, juxtaposes massive shale units in the hangingwall. Retention of the column at Ladbroke Grove can thus be attributed to favourable across-fault, reservoir-seal juxtaposition. The free water level (FWL) of the Ladbroke Grove column coincides with an abrupt change in strike of the fault from east–west to northwest–southeast. Fault re-activation risking using the FAST (Fault Analysis Seals Technology) technique indicates that the northwest–southeast striking segment of the fault is critically oriented within the in-situ stress field for reactivation, whereas the more east–west trending segment is associated with a relatively lower risk of fault re-activation. Hence recent slip along the northwest–southeast segment may have created permeable fracture networks along this part of the fault plane and thus limited the extent of the column to that bounded by the east–west trending fault segment. This hypothesis is supported by data on soil gases acquired across the fault which suggest that the fault is leaking CO2 across its northwest–southeast striking segment, but not across its east–west striking segment.The Pyrus Fault is not presently sealing by across-fault, reservoir-seal juxtaposition. The throw on the fault plane is sufficient to juxtapose the Katnook Sandstone in the hangingwall against the Pretty Hill Sandstone reservoir in the footwall, providing a sand-on-sand juxtaposition leak point at the structural apex of the trap. Fault re-activation along this fault is likely to have caused fracturing of any shale gouge veneer that may have been present along this sand-on-sand contact resulting in across-fault leakage of hydrocarbons into the Katnook Sandstone and leakage up the fault along permeable fracture networks. FAST predictions of fault re-activation show that the fault is critically oriented within the in-situ stress field for re-activation and soil gas measurements at the surface suggest the fault is leaking CO2.

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Basement controls on rifting and the associated formation of ocean transform faults—Cretaceous continental extension of the southern margin of Australia

2002

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The Western Otway Basin — a Tectonic Framework from new Seismic, Gravity and Aeromagnetic Data

Cited by 7 publications

References 11 publications

Two-Dimensional Electrical Conductivity Structure across the Southern Coastline of Australia.

Two-Dimensional Electrical Conductivity Structure across the Southern Coastline of Australia.

A Systematic Fault Seal Evaluation of the Ladbroke Grove and Pyrus Traps of the Penola Trough, Otway Basin

Basement controls on rifting and the associated formation of ocean transform faults—Cretaceous continental extension of the southern margin of Australia

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