STABLE ISOTOPE PALEOALTIMETRY IN COUPLED BASIN-DETACHMENT SYSTEMS OF THE NORTH AMERICAN CORDILLERA

High-elevation orogenic plateaus and mountain ranges exert a strong control on global climate and precipitation patterns and respond to tectonic processes in the lithosphere and even the upper mantle. Reconstructing the history of surface elevation thus provides a critical link in understanding the coupling among erosive, climatic, and tectonic processes. Stable isotope paleoaltimetry allows to determine long-term elevation changes, yet complex terrestrial precipitation and hydraulic patterns necessitate integrative approaches, comprising various isotope systems and mineral proxies. In order to resolve some of the complexities associated with stable isotope paleoaltimetry we present multi-proxy, multi-isotope data from syntectonic basins and kinematically linked extensional detachment zones that record paleotopographic and climatic changes during Cenozoic landscape development of the North American Cordillera.

Combined stable isotope, geochronological and structural data from Eocene to Miocene extensional detachments of the Raft River (UT) and Ruby Mountains (NV) core complexes as well as the adjacent intramontane basins indicate that temporal and spatial variations in topography were closely related to the formation of crustal-scale extensional structures at various lithospheric levels. Embedded in the context of stable isotopic studies in terrestrial basins across and along strike of the Cordillera, we see an emerging picture of major readjustments in surface elevation and relief combined with reorganization of continental drainage systems that accompany the formation of Eocene metamorphic core complexes. For the northern Utah/central Nevada segment of the Cordillera, oxygen and hydrogen isotope data from extensional detachment systems and various proxy materials in the adjacent basins depict a landscape that first responds to mid-crustal flow followed by normal faulting in crustal-scale detachment systems. Understanding the relative timing of changing precipitation and climate conditions as recorded in tectonic (detachments) and sedimentary (basins) archives represents one key parameter for reconstructing long-term elevation histories.