Paleoaltimetry of the American Southwest

Reconstructing the paleo-elevation of the American SouthwestLobo Fm

Context: Current tectonic models for Laramide orogenesis (80-40 Ma) and potential inferences about resulting crustal structure and paleotopography suffer from inadequate information about the Laramide orogen in the southwestern US, specifically as regards timing of structural development, topographic characteristics of the region and organization of the resulting orogenic drainage network, as well as knowledge of orogen lifespan. The paleogeography, crustal structure and paleotopography in Arizona, Sonora, New Mexico and West Texas remain less understood and have not been integrated into a broader model for the Laramide orogeny. Unresolved questions regarding Laramide deformational history and crustal structure in the southern Laramide province include: What was the timing of shortening and possible attendant crustal thickening? Was there a systematic migration of the deformation front? What was the paleotopography of the orogen and when was elevation attained relative to crustal deformation? We propose a program of stable isotopic measurements of pedogenic and lacustrine carbonates and volcanic glass to establish paleoelevation estimates in a temporal context by means of improved depositional ages of synorogenic deposits by U-Pb geochronology. These data will provide a new basis for interpreting the paleotopographic evolution of the Southern Laramide Province.

Collaborators: Jay Quade, Marie de Los Santos (University of Arizona, USA), Pete Copeland (University of Houston, USA), Tim Lawton (New Mexico State University, USA), Kate Huntington (University of Washington, USA).