Basin and Range Geoscientific Experiment

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This award provides support for an integrated, multi- disciplinary investigation of the earth's continental lithosphere where an abrupt boundary exist between highly extended crust and a tectonically stable block. The main research objective of this study is to use the "natural experiment" of a large strain gradient in the uppermost part of the lithosphere to understand how the Moho and other deep discontinuities respond to extension, thus quantifying how large horizontal strains of the lithosphere relate to vertical motions controlled by isostasy. A number of such regions have been identified by geological mapping in the Basin and Range province. Of these, the western margin of the Colorado Plateau is the best-suited example for accomplishing the research objectives. It has the virtues of (1) abruptness; (2) a geologic setting that indicates a simple pre-extensional crustal structure; and (3) a well understood large-scale extensional kinematic history. Achieving these research goals will require both focus and broad expertise. The principal investigators will integrate geologic, petrologic, paleomagnetic, and geochronologic studies and continuum modeling to unravel the geometry, kinematics and dynamics of the lithosphere's response to severe extensional strain.