Measuring the depth extent of processes driving the tectonic evolution of North America

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The accretion of rifted continental margin fragments, island arcs, and oceanic plateaus onto the western margin of North America has contributed to its growth since the Mesozoic. However, Precambrian ages of the upper mantle underlying these terranes in the Canadian Cordillera indicate that they are underlain by older lithosphere. It would therefore appear that the orogenic processes associated with the growth of this portion of North America were limited to the shallow crust. Contrasting ages between terranes at the surface and deeper structures represent a clear departure in tectonic style from other orogenic systems where the crust and its underlying mantle possess a similar evolutionary history. The research program proposed here seeks to understand the mechanisms by which terranes combine to form continents and will accomplish this goal by surveying the crust and upper mantle of the western margin of North America. Determining the present-day structure of the crust and upper mantle within suture zones that juxtapose formerly disparate terranes, and comparing their structures to stable continental regions, will clarify the process of continental growth. The