Continental growth by the accretion of microcontinental terranes is an important but poorly understood orogenic process. The Wrangellia-Alexander superterrane is one of the best documented microcontinents in the western Cordillera, yet little is known of its tectonic and depositional history immediately prior to its Cretaceous accretion. This project is a detailed study of the provenance and sedimentology of the Seymour Canal Formation of the Gravina belt, and Jura-Cretaceous sequence of flysch and volcanic rocks deposited on the inboard slope of the Wrangellia-Alexander microcontinent prior to final closure, in order to constrain the nature of this collision. The project will focus on little-metamorphosed portions of the Gravina belt, and carry out petrographic studies of sandstones and conglomerate clasts, coupled with mineral chemistry studies of plagioclase and clinopyroxene in sandstones and igneous rocks to establish provenance and tectonic setting. It will integrate turbidite lithofacies analysis and ichnofacies and paleo- current studies in order to reconstruct basin history, and refine the temporal framework of deposition by combining new microfossil biostratigraphy with radiometric dating of volcanic and detrital biotite and hornblende grains using Argon 40/39 methods. These studies will help document sedimentologic and tectonic processes operative in this microcontinent collision, and may serve as a pilot study for other, more enigmatic Jura-Cretaceous flysch basins of the Cordilleran.
