Architecture of a Classic Volcanic Rifted Margin: a New Model for the Exmouth - Gascoyne Margin, Western Australia  

Authors / CoAuthors

Direen, N.G. | Stagg, H.M.J. | Symonds, P.A. | Colwell, J.B.

Abstract

This paper presents new interpretations of the distribution of magmatic and pre-rift rock packages in the Exmouth-Gascoyne margin, based on the integrated interpretation of two deep crustal transects with existing seismic reflection, refraction, gravity and magnetic data. Interpretations are constrained by data from sparse ODP and petroleum drilling, and dredging. There is evidence for significant accumulation of magmatic rocks and their clastic derivatives infilling extensional fault-controlled basins developed in a broad volcanic margin transition (VMT) zone between the outer Exmouth Plateau and true oceanic crust. These rocks have distinctive seismic facies in the form of Seaward Dipping Reflector Sequences (SDRS), and are dense and magnetised. Most significantly, these packages give rise to potential field anomalies that have previously been interpreted as due to seafloor spreading. Recognition of these packages in a VMT zone has implications for the recognition of the inboard edge of unequivocal oceanic crust, the Oceanic Volcanic Margin Boundary (OVMB). Notably, in the volcanic margin transition zone off the Exmouth Plateau, the main locus of igneous activity is spatially offset from a previously recognised high velocity zone, suggesting that these two phenomena may not be temporally related. Seismically imaged differences in total thinning and partitioning of thinning between upper and lower crust provide support for models of depth dependent thinning previously proposed for this margin.

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nonGeographicDataset

eCat Id

64862

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Keywords

• External Publication

( Theme )

• continental margins

( Theme )

• geophysics

( Theme )

• gravity

( Theme )

• magnetics

( Theme )

• seismics

• AU-WA

Australian and New Zealand Standard Research Classification (ANZSRC)

• Earth Sciences

• Published_Internal

Publication Date

2006-08-14T00:00:00

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[-21.0, -15.0, 108.0, 115.0]

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