Date of Award

6-2009

Degree Name

Master of Science

Department

Geosciences

First Advisor

Dr. Michelle A. Kominz

Second Advisor

Dr. David A. Barnes

Third Advisor

Christopher J. Schmidt

Access Setting

Masters Thesis-Campus Only

Abstract

Passive margins form by rifting and extension of continental crust. Extension both increases the surface area of and thins continental crust. The area of the Earth remains constant, however, and either the area of continental or more likely oceanic crust must be reduced elsewhere through subduction or collision. A reduction in the area of oceanic crust causes a loss of ocean basin volume and thus impacts sea level. The amount that the continental crust has been extended can be quantified using total tectonic subsidence, which is determined using sediment thickness and water depth data coupled with a model of the rifting process. We calculate total tectonic subsidence, the amount of extension or stretching factor, and thickness of extended continental crust at a 5-minute grid resolution for passive margins between 77°N and 70°S. Our modeled crustal thicknesses correlate well with seismic refraction data from North America and Australia, and can be used to estimate the change in ocean volume and the impact of extension on sea level. The duration of extension is constrained by estimating the onset of rifting and the breakup age, which is when rifting ceased and sea floor spreading began. Our results indicate that extension of continental crust has increased sea level by 20.8 m since the start of Pangea rifting.

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