Publication Name: PESA Journal No. 24
Authors: S.M. Polomka and N.M. Lemon
Publication Volume: 24
Date Published: December 1996
Number of Pages: 12
Reference Type: Journal Article
Abstract:
Phanerozoic sedimentary basin subdivision in the NorthWest Shelf area is refined, based on a re-appraisal of the
sedimentary history from detailed seismic and oil well
interpretation of the Barrow Sub-basin and Peedamullah and
Lambert Shelves. The underlying concept is derived from
the observation that different structural elements were active
at different times during the history of a region. The
proposed new basins and sub-basins are described in terms
of five time slices: Palaeozoic, Triassic, Early Jurassic, Late
Jurassic to Early Cretaceous and late Early Cretaceous to
Recent. Each interval is separated by major unconformities
developed during the re-organisation of stress fields and as
such can be linked to sequence stratigraphic subdivisions.
An intracratonic fracture style appears to extend from the
western margin of southern Western Australia into the
northern margin and spanned a period from the Silurian to
the Permian. This suggests redefinition of the base of the
Westralian Superbasin from the Late Carboniferous to the
Early Triassic. A different basin style, an intracratonic sag,
developed over the whole North West Shelf in the Triassic,
associated with a change in tectonic style and sedimentary
fill. The Rankin Platform and Alpha Arch did not come into
being until the Jurassic. Initial rifting in the Early Jurassic
produced a narrow central graben which was a precursor to
the Barrow Sub-basin. This rifting was followed by the
development of the proto-Barrow Sub-basin in the Late
Jurassic. The onset of a new period of rifting, combined
with thermal sag in the Barrow Sub-basin in the Late
Jurassic-Early Cretaceous, resulted in the migration of the
depocentre from its Jurassic location westwards, to an Early Cretaceous depocentre, that is also defined by a present-day
syncline. By the late Early Cretaceous, Hauterivian time
when the deposition of the Winning Group commenced, the
North West Shelf area had become a passive margin basin.