REMOTE SENSING AND PALEOMAGNETISM OF THE TUFF OF BONELLI HOUSE, NW ARIZONA AND SE CALIFORNIA

The 17.7 Ma Tuff of Bonelli House (TB), a newly described pair of ignimbrites (Ferguson & Cook 2015; Regula et al. 2015), overlies the Peach Spring Tuff (PST) at Kingman, AZ. PST is the product of the largest Miocene eruption in this region, and TB appears to document the first large pyroclastic eruption in its aftermath. To further characterize TB and evaluate its extent, we have performed a combined remote sensing and paleomagnetic study of this unit.

Remote sensing work utilized atmospherically corrected Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery. Outcrops of TB in Kingman are below the spatial end spectral resolution of ASTER imagery, but likely correlative ignimbrite exposures in the Sacramento Mtns, CA, are sufficiently extensive for ASTER investigation and were ground-truthed and used as training data for a supervised classification, which allowed us to predict where additional relevant outcrops may occur.

Anisotropy of magnetic susceptibility on drill core was determined at Scripps Institution of Oceanography while magnetic remanence was determined at Pomona College. Stable remanence following alternating frequency cleaning indicate a preliminary, average remanence direction of 200.9 / -26.4. This direction contrasts the N to NE directions seen in the immediately underlying Peach Springs Tuff (e.g. Wells & Hillhouse 1989 and Varga 2010). AMS directions were determined using a MFK1 kappabridge and were corrected for ~40 km of slip on the Whipple Detachment Fault (Lister & Davis, 1989).

We identified a spectral signature and preliminary remnant paleomagnetic direction for the TB and identified potential, additional outcrops in the geological vicinity. AMS demonstrates that the TB ignimbrites originated from a source in a location close to that of the PST (a tectonically dismembered caldera in Sacramento and southern Black Mtns (Ferguson et al. 2013). The remnant paleomagnetic direction allows us to constrain these possible TB exposures as having been emplaced within a similar timeframe. The contrasting paleodirection of the TB and PST allows us to confidently say that the tuffs erupted at distinctly different times.