Conrad, Clinton P. and Gurnis, Michael (2003) Seismic tomography, surface uplift, and the breakup of Gondwanaland: Integrating mantle convection backwards in time. Geochemistry, Geophysics, Geosystems, 4 (3). 2001GC000299. ISSN 1525-2027 http://resolver.caltech.edu/CaltechAUTHORS:CONggg03
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Mantle density heterogeneities, imaged using seismic tomography, contain information about time-dependent mantle flow and mantle structures that existed in the past. We model the history of mantle flow using a tomographic image of the mantle beneath southern Africa as an initial condition while reversing the direction of flow and analytically incorporating cooling plates as a boundary condition. If the resulting (backwards integrated) model for structures is used as a starting point for a forwards convection model, today's mantle can be adequately reconstructed if we do not integrate backwards more than than about 50–75 Ma. Flow can also be reliably reversed through the Mesozoic, but only if instability of the lower boundary layer can be suppressed. Our model predicts that the large seismically-slow and presumably hot structure beneath southern Africa produced 500–700 m of dynamic topography throughout the Cenozoic. Since ~30 Ma, uplift has moved from eastern to southern Africa, where uplift rates are ~10 m/Myr, consistent with observations. During the Mesozoic, the modeled topographic high is situated near Gondwanaland rifting, raising the possibility that this buoyant structure may have been involved with this breakup.
|Additional Information:||Copyright 2003 by the American Geophysical Union. Received: 31 December 2001; Revised: 8 November 2002; Accepted: 25 January 2003; Published: 29 March 2003. This work was supported by National Science Foundation grants EAR-9814577 and EAR-9910387, and by an O. K. Earl Fellowship and a National Science Foundation Postdoctoral Research Fellowship for Conrad. We thank D. Komatits and J. Tromp for help in the design and assembly of the Beowulf computer cluster, L. Han for help in altering the “CitComS” code for use in this work, and M. Billen for helpful discussions. This manuscript was improved thanks to reviews by B. Steinberger, J. X. Mitrovica, R. J. O'Connell, and an anonymous referee.|
|Subject Keywords:||Time-dependent convection; mantle structure; dynamic topography; continental uplift; Gondwanaland breakup; African superswell; 8121 Tectonophysics: Dynamics, convection currents and mantle plumes; 8109 Tectonophysics: Continental tectonics—extensional (0905); 8180 Tectonophysics: Evolution of the Earth: Tomography; 9305 Information Related to Geographic Region: Africa|
|Official Citation:||Conrad, C. P., and M. Gurnis, Seismic tomography, surface uplift, and the breakup of Gondwanaland: Integrating mantle convection backwards in time, Geochem. Geophys. Geosyst., 4(3), 1031, doi:10.1029/2001GC000299, 2003.|
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|Deposited On:||19 Dec 2005|
|Last Modified:||26 Dec 2012 08:42|
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