FORMATION OF BASEMENT-INVOLVED FORELAND ARCHES: INTEGRATED STRUCTURAL AND SEISMOLOGICAL RESEARCH IN THE BIGHORN MOUNTAINS, WYOMING

摘要

The mechanism for the formation of mountain ranges within continental interiors, far from tectonic boundaries where differential motion between plates causes focused crustal deformation, is in some respects just as mystifying today in the 21st century as when Plate Tectonic Theory became the accepted unifying model for geological processes on Earth in the 1960s (Oreskes and LeGrand, 2005). The foundations of geological knowledge of foreland mountain ranges comes from the Rocky Mountains of the western USA, and particularly the ranges of central Wyoming where the term Laramide orogeny originated (e.g., Coney, 1976). The structural geology of the Laramide mountain ranges is world-renowned because of the inspiring grand-scale fold form of sedimentary cover rocks upon Precambrian crystalline basement. In such a quintessential example as the Bighorn Mountains of Wyoming (Figures 1, 2), cover strata define the shape of an elongate arch upon a barrel-roll of crystalline basement rock.