INTEGRATED FIELD- AND REMOTE SENSING-FOCUSED INVESTIGATIONS OF A MIOCENE-AGED SUPERVOLCANIC SYSTEM: RESULTS FROM A THREE YEAR NSF REU PROGRAM IN THE SOUTHERN BLACK MOUNTAINS OF NW ARIZONA

The Southern Black Mountains Volcanic Center (SBMVC; McDowell et al., 2016) of NW Arizona records the ~2 myr evolution (~19-17 Ma) of a supervolcanic system associated with the Peach Spring Tuff (PST; ~18.8 Ma, Ferguson et al 2013). Nine undergraduate students over three years of an NSF REU program addressed questions related to this magmatic system through combined integration of ~two weeks of field work and analysis of aerial and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) multispectral satellite imagery. This approach allowed for effective identification and reconnaissance mapping of geologic units associated with this supereruption system. Monotonous and aerially extensive trachytic lavas (McGuinness et al 2014) with interbedded sediments (McCosby et al 2015) mark the early stages of this system. Eruption of the Cook Canyon Tuff (CCT) and PST followed, which are separated by a mafic lava ~15 m thick (Beckens et al 2014); the CCT is ~20x smaller in its extent than the PST (Vidal et al 2015), which in turn, is more extensive in the southern Blacks than previously identified (Gibson et al 2014). The PST also exhibits three distinct spectral zones in ASTER imagery that correspond with PST zones mapped by Ferguson and Cook (2015) and suggests ASTER imagery is sensitive to either ignimbrite welding and/or phenocryst abundance. Post-dating PST emplacement were two smaller tuffs – the Tuff of Bonelli House (Ferguson and Cook 2015) is seemingly the most abundant in the Sacramento Mountains of SE CA (Gomez et al 2015); the Sitgreaves Tuff (SGT) is fairly continuous between 35.13 N, 114.39° W and 35.03° N, 114.35° W where its distribution was topographically controlled, has a minimum volume of 3-5 km³ (Thompson et al 2016), and is divisible into multiple members (Schwat et al 2016). The SGT near 35.13 N, 114.39° W interfingers with, and pinches out in, ~17.5 Ma (Lang 2001) rhyolite breccias. The last stages of the system include mafic intrusions that cut the SGT and may have a syn-extensional relationship with Miocene crustal lengthening (Helfrich et al 2016). Integration of remote sensing into analysis of magmatic systems allows for ‘bigger picture’ perspectives. However, critical to this is field work, which provides detailed ground training sites on which to base remote sensing-derived interpretations.