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Vasse Shelf

Entity ID: 27029 Compiled by: Bradshaw, B.E. and Pepper, M.R. Year: 2003 Status: Defined

Last Revised: 2014

Rank: subprovince Type: sedimentary Subtype: polyhistory Location: WA On-shore and off-shore

Synonyms: Vasse Terrace Symbol: NA

Minimum age: Recent Age method: inferred, biostratigraphic correlation

Maximum age: Permian Age method: inferred, biostratigraphic correlation

Summary: The Permian to Recent Vasse Shelf is a relatively shallow, narrow, north-south trending structural element that contains up to 3km of predominantly siliciclastic non-marine sedimentary rocks and a substantial, arenaceous, coal-bearing succession.

Attributes:
Area (square kilometres): 4500
State: WA
Minimum present water depth (m): 0
Maximum present water depth (m): 1000
Main rock types: organic-rich sediments and sedimentary rocks
Main rock types: siliciclastic sediments and sedimentary rocks
Main depositional environment: non-marine
Maximum sediment thickness (m): 3000
Resources: Coal - black
Rosabrook Coal Measures have the thickest (up to 4.5 m) and best quality (black, bituminous) seams
Present crustal setting: continental
Country: AUS

Parent: Perth Basin

Child Provinces: No data

Relationships:
Adjoins - Vlaming Sub-basin, Yallingup Shelf

Constituent units: Lesueur Sandstone, Sue Group, Rosabrook Coal Measures, Stockton Group, Sabina Sandstone, Willespie Formation, Ashbrook Sandstone, Woodynook Sandstone, Mosswood Formation, Osmington Seam, Redgate Coal Measures

Events: No data

Mineral Deposits: No data

Key Reference: Iasky, R.P. 1993, A structural study of the southern Perth basin, Western Australia., Geological Survey of Western Australia. Report, 31, 56pp (Refid:43096)

Comments: No data

Overview: The Permian to Recent Vasse Shelf is a relatively shallow, narrow, north-south to north-northwest- to south-southeast trending structural element located on the southwestern margin of the Perth Basin. The Vasse Shelf extends over an area of 4500 sq. km and has significant onshore and offshore components (0 to 1000 m water depth). It contains up to 2000 m of Permian sediments which thicken eastward, overlain by a maximum of 1000 m of Mesozoic sediments which thin to the west. The Vasse Shelf is a shallow footwall block that formed against the Leeuwin Complex on the western margin of the main rift basin in the Bunbury Trough and southern Vlaming Sub-basin during Permian to Early Cretaceous rifting. Seismic data from the offshore northern extent of the Vasse Shelf show that it consists of some small west-dipping half graben formed during Permian rifting. Strike-slip faults and contractional duplex structures are also common. Sedimentary rocks deposited in the Vasse Shelf include Lower Permian glaciogenic argillaceous sediments overlain by a substantial arenaceous, coal-bearing, Permian succession deposited in a fluvial to lacustrine deltaic environment, and Triassic fluvial sandstones. Three hydrocarbon exploration wells have been drilled in the Vasse Shelf (Jan 2004), two onshore and one offshore, with no hydrocarbons recovered. The Permian section of the Vasse Shelf contains good reservoir rocks and potential structural traps. However, hydrocarbon migration from adjacent depocentres is required for traps to be charged as the depth of burial for Permian strata on the Vasse Shelf is insufficient for significant hydrocarbon generation. The Permian Sue Group has been explored for its coal mining potential in the northern Vasse Shelf where coal seams are shallow. The Rosabrook Coal Measures has the greatest potential for economic coal resources as they possess the thickest (up to 4.5 m) and highest quality (black, bituminous) seams.

Images: Perth Basin regional setting and cross-section location map (101 KB), Perth Basin regional cross-section Profile 7 (48 KB)

Other media: No data

Source Information:

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This report was generated on Tuesday, September 30, 2014 8:01:13 PM EST.