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Development of the Australian‐Antarctic depth anomaly

Citation

Whittaker, J and Muller, RD and Gurnis, M, Development of the Australian‐Antarctic depth anomaly, Geochemistry Geophysics Geosystems, 11, (11) pp. Q11006. ISSN 1525-2027 (2010) [Refereed Article]


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Copyright Statement

Copyright 2013 The American Geophysical Union

DOI: doi:10.1029/2010GC003276

Abstract

The oceanic Australian‐Antarctic Discordance (AAD) contains two unusual features: (1) N–S trending anomalously deep bathymetries and (2) rough basement morphologies in young (<∼20 Ma) crust between 120°E and 128°E. Models generally attribute AAD formation to underlying cold and/or depleted upper mantle, but no model adequately accounts for all the anomalous attributes. We quantify anomalous basement roughness and basement depths utilizing new seismic reflection data, in combination with all available geophysical and geological observations. We find that the interaction of negative dynamic topography and crustal thickness variations results in the observed complex patterns of residual basement depths. Downwelling, caused by a sinking Mesozoic slab, is the most likely cause of the broad N–S trending residual depth anomalies, while overprinting by westward flowing, buoyant Pacific mantle resulted in the distinctive V‐shaped eastern boundary of the AAD. The particularly large residual depths proximal to the Australian and Antarctic margins may be due to negative dynamic topography combined with thinned oceanic crust caused by ultraslow (<10 mm/yr) half‐spreading rates and sampling of depleted subduction wedge contaminated mantle. Only oceanic basement aged <20 Ma is anomalously rough, a result of sampling of cool/ depleted upper mantle material. Although oceanic crust older than 43 Ma may have sampled depleted mantle, the resulting oceanic basement is not anomalously rough likely because a melt volume controlled threshold of accretion‐related roughness had already been reached due to ultraslow spreading rates. Our analysis reveals that the enigmatic roughness of the Diamantina Zone is mainly related to >45° spreading obliquities.

Item Details

Item Type:Refereed Article
Keywords:Australia, Antarctica, geodynamics, plate tectonics
Research Division:Earth Sciences
Research Group:Geology
Research Field:Marine Geoscience
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
Author:Whittaker, J (Dr Jo Whittaker)
ID Code:84437
Year Published:2010
Web of Science® Times Cited:14
Deposited By:IMAS Research and Education Centre
Deposited On:2013-05-14
Last Modified:2013-09-03
Downloads:0

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