1. Tectonic imbrication and foredeep development in the Penokean orogen, east-central Minnesota--an interpretation based on regional geophysics and the results of test-drilling Author/Creator: Southwick, D. L. 1936- (David Leroy) Publication/Creation: Denver, CO : For sale by the Books and Open-File Reports Section, U.S. Geological Survey Resource Type: Book Access & Availability: Loading