Joint 69th Annual Southeastern / 55th Annual Northeastern Section Meeting - 2020

Paper No. 14-11
Presentation Time: 4:50 PM


LONG, Maureen D.1, BENOIT, Margaret H.2, EVANS, Rob L.3, BYRNES, Joseph4, BEZADA, Maximiliano5, MITTAL, Ved1, KING, Scott D.6, KIRBY, Eric7 and LEVIN, Vadim8, (1)Department of Geology and Geophysics, Yale University, New Haven, CT 06520, (2)National Science Foundation, Earthscope Program, 2415 Eisenhower Avenue, Alexandria, VA 22314, (3)Geology and Geophysics, Woods Hole Oceanographic Institution, Clark South 172, MS 24, Woods Hole, MA 02543, (4)University of Minnesota, Minneapolis, MN 55455, (5)Earth Sciences, University of Minnesota, 310 Pillsbury Drive SE, Minneapolis, MN 55455, (6)Department of Geosciences, Virginia Tech, Blacksburg, VA 24060, (7)College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, (8)Dept. of Earth and Planetary Sciences, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854-8066

Recent results from recent geophysical experiments in eastern North America - including those related to EarthScope, GeoPRISMS, and other efforts - are shedding new light on the structure of the upper mantle beneath the passive margin. Imaging studies have revealed evidence for surprisingly complex structure, which suggests that the deep structure of the passive margin has undergone recent or ongoing modification as it continues to evolve. Among the striking features are the Central and Northern Appalachian Anomalies, localized regions of particularly low seismic wave speeds in the upper mantle. Here we present a suite of results from MAGIC, an EarthScope USArray Flexible Array experiment deployed across the Central Appalachian Anomaly that included both seismic and magnetotelluric (MT) instrumentation. We find evidence for thin lithosphere beneath the Central Appalachian Mountains, based on analysis of seismic travel time residuals, seismic attenuation, S to P wave receiver function imaging, and inferences on electrical conductivity from the MT measurements. The region of thin lithosphere is spatially coincident with unusually young (Eocene) volcanism in western Virginia and eastern West Virginia. We discuss several potential models for lithospheric loss beneath the central Appalachians, and compare and contrast our findings beneath the MAGiC array with recent insights into the Northern Appalachian Anomaly, another region with anomalously low wave speeds. An ongoing deployment of seismic instrumentation in New England (the NEST experiment) will shed additional light on the similarities and differences between the Central and Northern Appalachian Anomalies.