Extension of the Exmouth Plateau, offshore northwestern Australia; deep seismic reflection/refraction evidence for simple and pure shear mechanisms

The response to extensional stresses that deformed and finally ruptured the northwest Australian passive margin was achieved by an interplay of simple and pure shear mechanisms. The results of a two-ship seismic reflection and refraction experiment show that the outer Exmouth Plateau is dominated by...

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Bibliographic Details
Published in:Geology (Boulder) 1989-01, Vol.17 (1), p.15-18
Main Authors: Mutter, John C, Larson, Roger L, Buhl, Peter, Diebold, John B, Alsop, Joyce, Lorenzo, Juan M, Mithal, Rakesh, Hopper, John, Falvey, David A, Williamson, Paul E, Brassil, Frank
Format: Article
Language:English
Subjects:
applied (geophysical surveys & methods)
Australasia
Australia
block structures
bottom features
continental margin
Cretaceous
decollement
deep seismic sounding
Exmouth Plateau
extension
faults
Geology
geophysical methods
geophysical profiles
geophysical surveys
Geophysics
Indian Ocean
Jurassic
Marine
mechanics
Mesozoic
normal faults
oceanography
Oceans
passive margins
plate tectonics
plateaus
reflection methods
refraction methods
seismic methods
seismic profiles
shear
solid Earth (tectonophysics)
structural geology
surveys
tectonics
tectonophysics
Western Australia
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Summary:The response to extensional stresses that deformed and finally ruptured the northwest Australian passive margin was achieved by an interplay of simple and pure shear mechanisms. The results of a two-ship seismic reflection and refraction experiment show that the outer Exmouth Plateau is dominated by large rotated blocks bounded by deeply penetrating normal faults, some of which are heavily intruded. Magmatic underplating attended this extension but is absent in the central region where a set of prominent, subhorizontal, mid-crustal arrivals are interpreted to be detachment surfaces. Extensive exploration seismic coverage, drilling, and sampling suggest that deformation on the outer plateau postdates that in the central plateau. We propose that initial deformation of the region was dominated by a simple shear detachment system along low-angle fault planes. This passed laterally and temporally into a region of pure shear deformation characterized by high-angle normal faults and magmatism, and this became the locus of final rupture.
ISSN:0091-7613
1943-2682
DOI:10.1130/0091-7613(1989)017<0015:EOTEPO>2.3.CO;2