Tectonic History of the Osbourn Spreading Center and Dynamic Subsidence of the Congo Basin

Author: Downey, Nathan John

Year: 2009

Degree: Dissertation (Ph.D.)

Advisors: Stock, Joann M.; Gurnis, Michael C.; Clayton, Robert W.; Simons, Mark

Committee Members: Avouac, Jean-Philippe; Helmberger, Donald V.; Heaton, Thomas H.; Tromp, Jeroen

Option: Geophysics

DOI: 10.7907/MXQF-GY83

Abstract

This is a thesis in two parts. First is the presentation of a new technique by which it is possible to constrain tectonic models of oceanic regions which are devoid of magnetic reversal anomalies. I applied this technique to the Osbourn region of the Southwest Pacific and determined the tectonic history of the Cretaceous Osbourn spreading center. The results of this analysis showed that the Osbourn Trough, although an extinct spreading center, was not part of the Cretaceous Pacific-Phoenix spreading center. The second part of this thesis involves study of the cratonic Congo sedimentary basin. I created instantaneous dynamic models of the Congo basin that are strongly constrained by observation and which demonstrate that the most recent subsidence event of the basin has a mantle dynamic origin. These models constrain the density structure of the upper mantle beneath the Congo. In addition, I examined geologic data that constrain the time-dependent history of the Congo basin in an attempt to determine the subsidence mechanism of cratonic sedimentary basins.

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