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Tectonic Evolution of the North West Shelf of Australia and southern Southeast Asia
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Christian Heine |
Two papers and several conference contributions have resulted from my work on the geodynamic evolution of the North West Shelf over the past three years. They are all accessible on my Publications page or via the links below:
In addition to the papers above, a plate tectonic animation is available and a set of paleogeographic reconstructions from the Australian J. Earth Sci. paper (Fig. 10). Follow the links above.
The following data and maps are available on request:
Please contact me for details and download instructions.
The Argo and Gascoyne Abyssal Plains off northwest Australia are the only preserved patches of Tethyan ocean floor, containing vital information about the plate tectonic evolution of northeastern Gondwanaland, the eastern Tethys and Southeast Asia. Subduction of the oceanic crust north of Australia has destroyed evidence of the exact configuration of seafloor spreading around northeastern Gondwanaland. In this study magnetic and gravity data from the Argo and Gascoyne Abyssal Plains have been interpreted jointly with compiled geological information from the Northwest Shelf and Southeast Asia to reconstruct Tethyan oceanic lithosphere based on the assumption of symmetrical seafloor spreading. The interpretation of magnetic data has been constrained by modelling synthetic magnetic profiles, sequence stratigraphic analysis, industry well data and ODP/DSDP results.
On the basis of lithological affinities of sequences exposed in the Indo-Burman Ranges, Timor and surveyed by seismic profiles and drilling on the Exmouth /Wombat Plateaus the West Burma Block has been identified as the continental fragment breaking up from the Northwest Shelf in the Late Jurassic. Seafloor spreading off northern Australia separated this block first in northward motion before the drift path became fixed relative to the motions of the Middle Greater India Block (Mihut, PhD Thesis, 1997).
The new interpretation of magnetic data shows that seafloor spreading in the Argo and Gascoyne Abyssal Plains started simultaneously in the Oxfordian with M25A identified as the oldest anomaly. North of the Exmouth Plateau, in the Gascoyne Abyssal Plain, the oldest anomaly sequence M25A - M22A (154.5 - 150.4Ma) suggests that the ``Argo'' spreading ridge continued around the northern margin of Greater India. Similarities between fracture azimuths between the Somali Basin and the Argo / Gascoyne Abyssal Plains suggest that the two basins were part of the same spreading system. At chron M24 (152.1Ma) a single spreading center was active along the entire northeastern margin of Gondwanaland. By the time of M14 (135.8Ma) a southward ridge jump occurred in the Argo Abyssal Plain. After a slight anticlockwise rotation, the ``Argo'' ridge became part of the spreading ridge between India and Australia, associated with a counterclockwise rotation of the ridge strike and the spreading center north of India became extinct.
According to this model the West Burma continental terrane was accreted to the Southeast Asian mainland in Santonian / Coniacian times (85-80Ma) in the vicinity of present day western Thailand. A set of paleogeographic reconstructions is included in the study, accompanied by an animation of the plate tectonic evolution of the Northwest Shelf and southern southeast Asia on the enclosed CD inside the back cover.
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