30 New advances in geological and geophysical research on the Appalachian orogen. (Posters)

We invite contributions that discuss new research on the Appalachian orogen. Submissions should include, but are not limited to, geological or geophysical studies or works comprising a combination of both methods.

Monday, 23 March 2026
1:30 PM - 5:30 PM
CCC, Ballroom C

New Constraints on Crustal Anisotropy and Deformation in the Nashoba Terrane of Eastern Massachusetts, USA, from the GENESIS Seismic Experiment

Paper number: 30-5
Program: Technical Sessions
Time: 1:30 PM – 1:30 PM

Authors

Abstract

The accretion of Avalonia to eastern North America during the Paleozoic left a complex imprint of deformation in the crust and mantle lithosphere, including northwest-dipping shear zones, metamorphic gradients, and partial melting within the Nashoba-Putnam terrane, which represents the trailing edge of Ganderia. These features have been previously interpreted as evidence of channel flow and ductile extrusion, processes that likely generate significant seismic anisotropy within the crust. In this study, we test this hypothesis using a novel seismic imaging approach that enables high-resolution recovery of anisotropic structure from Ps receiver functions, which provides detailed insights into crustal deformation during the Avalonian accretion. Our method investigates the directionally dependent content in P-to-S receiver function data, allowing us to isolate the directional signatures of anisotropy and dipping structure at depth. With dense seismic data, we can incorporate inter-station coherency weighting and residual-based noise suppression, allowing us to robustly resolve complex anisotropic layering.

We apply this approach to data from the recently deployed GENESIS broadband seismic profile across the Nashoba terrane in Eastern Massachusetts, which features dense station spacing (~5 km). The resulting images reveal distinct anisotropic domains in the upper and mid-crust and within the lithospheric mantle. Lateral variations in mid-crustal features align with geological boundaries between Avalonia and Ganderia. The anisotropic structure can be related to two past deformation episodes. A west-dipping structure, consistent with the channel flow hypothesis, is apparently overprinted by a younger east-dipping structure within the Avalonian crust whose origin is enigmatic. Our observations demonstrate the power of high-resolution receiver function imaging to extract crustal deformation signatures that were previously inaccessible, offering new insights into the deep structure of Appalachian terrane accretion.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411349

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