New Mexico Geological Society Annual Spring Meeting
April 13, 2018

Abstract
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Geomorphic Evidence for Episodic Inflation Above the Socorro Magma Body: Timescales and Mechanisms Related to Surface Uplift

Brad Sion1, Gary Axen1, Fred Phillips1 and Jolante van Wijk1

1New Mexico Tech, 801 Leroy Place, Socorro, NM, New Mexico, 87801, United States, bradley.sion@student.nmt.edu

Timescales of processes related to mid-crustal magma intrusion are poorly understood. The Socorro magma body (SMB) in the central Rio Grande rift is one of the largest known active mid-crustal intrusions and offers a unique opportunity to study the timing of processes associated with its emplacement. Surface uplift and seismicity above the SMB demonstrate ongoing magmatic unrest. Nearby Holocene volcanism illustrates the potential for a longer-lived magmatic system that was active during Holocene or pre-Holocene times. Quaternary river terraces preserved at the surface and above the SMB provide paleo-geodetic markers to interrogate the longevity of magmatism. We use high-resolution terrace elevations in the Rio Salado, a Rio Grande tributary that crosses surface-uplift contours, and new 36Cl surface-exposure and 14C ages to document a prehistoric surface-uplift event above the SMB. We observe longitudinal terrace patterns consistent with an arching event that began after 26 ka and ceased before 3 ka which cannot be explained by tectonic or fluvial mechanisms. This late Pleistocene-early Holocene surface uplift is related to a magma-emplacement event that predates modern magmatism and is co-located with geodetic uplift. We interpret the two temporally distinct surface-uplift events as recording episodic intrusion below the Socorro area since late-Pleistocene time. We propose that rejuvenation of magmatic activity occurs via a stationary plumbing system inferred from seismic data. This study shows that the magmatic source-feeder system is stable and active over timescales of 104 yrs and demonstrates the utility of terraces as strain markers of low-amplitude, large-wavelength deformation caused by mid-crustal magmatic activity.

Keywords:

Socorro magma body, surface deformation, river terraces

pp. 71

2018 New Mexico Geological Society Annual Spring Meeting
April 13, 2018, Macey Center, New Mexico Tech campus, Socorro, NM