HR: 0800h
AN: T51D-1390    [Abstracts]
TI: Assessing the Practicality and Viability of Basalt Vesicle Paleoaltimetry in Solving Regional Tectonic Problems in the Basin and Range
AU: * Niemi, N
EM: niemi@gps.caltech.edu
AF: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 United States
AU: Sahagian, D
EM: dork.sahagian@lehigh.edu
AF: The Environmental Initiative, Lehigh University, Bethlehem, PA 18105 United States
AU: Proussevitch, A
EM: alex.proussevitch@unh.edu
AF: Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH 03824 United States
AU: Carlson, W
EM: wcarlson@mail.utexas.edu
AF: Department of Geological Sciences, University of Texas, Austin, TX 78712 United States
AB: Understanding the paleoelevation history of orogens is fundamental to answering a number of significant questions about continental deformation. Most paleoaltimeters rely on proxies for measuring paleoelevation that may be affected by factors other than elevation, such as climate. The basalt vesicle paleoaltimeter avoids problems associated with such proxies by directly measuring the paleo-atmospheric pressure recorded by vesicle size-distributions in basalt lava flows. Comparison of "paleoelevation" determinations from recent lava flows with their actual modern elevations on Hawaii has demonstrated the potential of this technique. Application to a study of the evolution of Cenozoic topography in the Basin and Range has revealed some of the practical limitations to the technique. Mafic lavas in the Basin and Range are more silicic than the basalts erupted on Hawaii. As a result, typical mafic lava flows in the Basin and Range are thicker, have less well-defined flow stratigraphy, and are less well-preserved than basaltic lava flows on Hawaii. Each of these factors increases the difficulty of locating a suitable sampling site for basalt vesicle paleoaltimetry. In an attempt to ameliorate these difficulties, a number of guidelines for sampling for basalt paleoaltimetry can be applied. Where available, stacks of flows offer the best opportunity for finding preserved flow tops and bottoms. The suitability of the flow for sampling is inversely proportional to SiO₂ content, where samples with SiO₂ < 50% are best, and samples with SiO₂ > 54% are unsuitable. Samples in between this range display vesicles in the field, but the vesicle sizes are near the resolution of CT scans. Paleoelevation determination from young mafic lava flows of a variety of compositions will be presented to assess the viability of this technique to a wider range of lithologies, and thus a wider range of potential tectonic problems.
DE: 8175 Tectonics and landscape evolution
DE: 8178 Tectonics and magmatism
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8499 General or miscellaneous
DE: 9350 North America
SC: Tectonophysics [T]
MN: Fall Meeting 2005