Evidence that large scale extension operates at the same time as overall compression during tectonic convergence has been observed in several orogens. The extension is usually at high structural levels while compression is operating at depth, however the relative extent and displacements are not well understood. This project continues, investigation of possible Mesozoic extension in the Bitterroot Mountains of Idaho and Montana that occurred during the Sevier Orogen. Prior results indicate that extension operated in the Funeral Mountains of California during this tectonic episode. This work will help determine the regional extent and importance of this phenomena for the Sevier Orogen. The results should be applicable to understanding the general significance of extension in compressional orogens.
