USING SATELLITE IMAGERY TO PROBE A SUPERERUPTION: A UNIQUE PERSPECTIVE ON MIOCENE-AGED VOLCANIC DEPOSITS IN NW ARIZONA AND SE CALIFORNIA – AN NSF REU STUDY

As part of a three-year NSF REU collaboration, we have been conducting an integrated field and lab-based program to understand the evolution of the Miocene-aged Peach Spring Tuff (PST) supereruption system in NW Arizona and SE California (cf. Claiborne et al., 2014, 2015). One distinctive aspect of this program has been the incorporation of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) multi-spectral satellite imagery into six student projects. ASTER has 14 bands – 3 in visible and near infrared (VNIR) (15 m spatial resolution), 6 in short wave infrared (SWIR) (30 m spatial resolution), and 5 in thermal infrared (TIR) (90 m resolution); a single ASTER image covers 60 km x 60 km making it useful for geologic mapping over large areas in arid regions and provides a unique means of broadly viewing and unravelling the PST-related magmatic system. Specifically, students constructed Red-Green-Blue (RGB) images using various band combinations and band math techniques in the ENVI image processing program so as to maximize spectral (and likely compositional and/or mineralogical and/or possibly welding) differences between various lithologic units that comprise this magmatic system. In turn, this has allowed for distinctive identification, compositional characterization, and areal constraining of, deposits that preceded (Beckens et al., 2014; McGuiness et al., 2014; McCosby et al., 2015; Vidal et al., 2015), occurred during (Gibson et al., 2014), and post-dated (Gomez et al., 2015) the ~18.8 Ma PST eruption. Seemingly critical for correctly interpreting ASTER imagery, however, was field work. Prior to working with ASTER imagery, students all conducted ~two weeks of field work to ground truth various locations that then served as training sites for subsequent lab-based remote sensing analyses, which allowed for understanding the spectral and spatial limitations of ASTER data. Students also collected samples for petrographic work and spectral sampling (courtesy T. Glotch, SUNY Stony Brook), which helped tie together observations and conclusions reached through remotely-sensed, field-based, and classic petrologic approaches.