New Mexico Geological Society Annual Spring Meeting — Abstracts

The Jemez lineament is a NE-SW alignment of late Tertiary volcanic rocks, stretching from southwest Arizona into northeast New Mexico. Ideas for the origin of the lineament include a Proterozoic accretionary structure, but this interpretation is ambiguous because of poorly understood lithospheric structure in the region. Slow seismic P-wave velocities at 50-160 km depth under the Jemez lineament and adjacent to the Colorado Plateau suggest anomalous upper mantle under these features. Constraints from crustal geology and existing seismic data will be applied to constrain long wavelength (>700 km) 2.5-D forward gravity models across the Jemez Lineament and Colorado Plateau region in order to provide insight into the structure of the lithosphere. Xenolith data will also play an important role in the models by constraining the physical properties and composition of lower crustal and upper mantle rocks. Preliminary gravity modeling suggests that topography in parts of our study area is supported by low-density upper mantle, not by Airy model crustal thickness variations.