Seismic Evidence for Crustal Modification Beneath the Hartford Rift Basin in the Northeastern United States

Abstract

Extensive Mesozoic rifting along the eastern North American margin formed a series of basins, including the Hartford basin in southern New England. Nearly contemporaneously, the geographically widespread Central Atlantic Magmatic Province (CAMP) was emplaced. The Hartford basin provides an ideal place to investigate the roles of rifting and magmatism in crustal evolution, as the integration of the dense SEISConn array and other seismic networks provides excellent station coverage. Using full‐wave ambient noise tomography, we constructed a detailed crustal model, revealing a low‐velocity (Vs = 3.3–3.6 km/s) midcrust and a high‐velocity (Vs = 4.0–4.5 km/s) lower crust beneath the Hartford basin. The low‐velocity midcrust may correspond to a layer of radial anisotropy due to extension and crustal thinning during rifting. The high‐velocity crustal root likely represents the remnant of magmatic underplating resulting from the CAMP event. Our findings shed light on crustal modification associated with supercontinental breakup, rifting, extension, and magmatism.

High‐Resolution Ps Receiver Function Imaging of the Crust and Mantle Lithosphere Beneath Southern New England and Tectonic Implications

“…Interestingly, while there are lateral variations in the depth of the Moho converter across the SEISConn line, the amplitude of the converter appears to be relatively constant across the array (Figures 4 and 7). This finding is somewhat puzzling in light of previous results on the crustal velocity structure beneath SEISConn obtained via full-waveform ambient noise tomography (Gao et al, 2020). The model of Gao et al (2020) includes a high-velocity region in the lower crust beneath the Hartford Basin, which they attributed to the presence of high-density, high-velocity, likely mafic material in the lower crust, emplaced during the rifting that accompanied the breakup of Pangea, and associated with the Central Atlantic Magmatic Province (CAMP).…”

“…Gao et al. (2020) suggested that significant mafic magmatic underplating may have occurred beneath Hartford basin associated with the eruption of CAMP magmatism. We speculate that this addition of lower crustal material may have accompanied, and/or played a role in, alteration of the geometry of the crustal shear zone locally beneath Hartford basin.…”

Lithospheric Formation and Evolution of Eastern North American Continent

“…Our model reveals strong structural variations within eastern North America. It has been demonstrated that more data and/or a more accurate methodology result in stronger velocity contrasts (e.g., Hung et al., 2004; Becker, 2012; Gao & Shen, 2014; Gao, 2018; Gao et al., 2020; Savage et al., 2017; Yang & Gao, 2020). Furthermore, we ignore seismic anisotropy and attenuation in wave simulation and inversion.…”

SKS Splitting and Upper Mantle Anisotropy Beneath the Southern New England Appalachians: Constraints From the Dense SEISConn Array

“…The Hartford basin (Figure 1) in central Connecticut formed in response to extension and exposes Mesozoic sedimentary, volcanic, and shallow intrusive rocks (Olsen, 1997). The volcanic and intrusive units are part of the geographically extensive Central Atlantic Magmatic Province (CAMP; e.g., Marzoli et al., 1999), and their emplacement was likely associated with modification of lower crustal structure beneath the Hartford basin (Gao et al., 2020). Parts of New England have been affected by post‐CAMP magmatic activity (e.g., Kinney et al., 2020), including the White Mountain Magma Series (WMMS) and Cretaceous magmatism in and around New Hampshire that may reflect the passage of the Great Meteor Hot Spot.…”

“…The Seismic Experiment for Imaging Structure Beneath Connecticut (SEISConn; Gao et al., 2020; Long & Aragon, 2020) was a deployment of 15 seismic stations across northern Connecticut and Rhode Island (Figure 2). SEISConn was designed as a high‐density array, with an average interstation distance of ∼10 km, and it enables the characterization of variations in shear wave splitting over short length scales beneath northern Connecticut, and the interrogation of the possible spatial relationships between anisotropy in the mantle lithosphere and major geologic and tectonic boundaries.…”