Igneous Intrusions in the Carnarvon Basin, NW Shelf, Australia

Kenneth McClay, Nicola Scarselli, Sukonmeth Jitmahantakul

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Many rifts and passive margin basins are characterised by
dykes and sills that intrude the both pre-rift and syn-rift strata.
In the southern part of the northern Carnarvon Basin sills
and dykes are well imaged in a number of 3D seismic surveys.
This paper focuses on the igneous features in the Coverack
3D seismic survey in the southern part of the Exmouth Subbasin
of the Northern Carnarvon Basin, North West Shelf of
Australia. The sills typically occur at present day depths of
2–3 km in the domino-style faulted Upper Jurassic and Lower
Cretaceous strata beneath the prominent Valanginian and
Aptian unconformities. The sills are commonly 2–10 km across
with wing-like apotheses at their edges. Many sills link to dykes
that have intruded pre-existing Jurassic to Early Cretaceous age
extensional faults. The sills and dykes do not occur above the
Aptian unconformity and in several places extrusive flows were
found at the Aptian unconformity indicating a Valanginian to
Aptian age for the intrusions in this area. The emplacement
of sills and dykes was strongly controlled by the pre-existing
extensional faults as well as the stratal dips in the rift halfgraben
systems. The structural geometries of these NW shelf
sill complexes are analysed and evolutionary models for sill and
dyke emplacement are proposed.
Original languageEnglish
Title of host publicationProceedings of the Western Australian Basins Conference
Number of pages20
Publication statusPublished - 31 Aug 2013

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