MODIFICATION OF LITHOSPHERIC STRUCTURE BENEATH CONNECTICUT VIA SUBDUCTION, TERRANE ACCRETION, AND RIFTING: INSIGHTS FROM THE SEISCONN EXPERIMENT

The bedrock geology of Connecticut expresses the juxtaposition of a variety of terranes, of both continental and volcanic arc affinity and from across the Laurentian and peri-Gondwanan realms, that were brought together via subduction and terrane accretion during Appalachian orogenesis. Later Mesozoic rifting modified (and was likely influenced by) these pre-existing structures and formed the Hartford Rift Basin in the central portion of the state. This region therefore represents a unique opportunity to study a range of fundamental tectonic processes, and their effects on the evolution of the continental lithosphere, within a compact area that can be efficiently sampled with a modest number of seismic stations. The Seismic Experiment for Imaging Structure beneath Connecticut (SEISConn) is an ongoing (2015-present) deployment of 15 broadband seismic stations in a dense linear array across northern Connecticut. We aim to understand how past tectonic episodes of have affected present-day structure of the crust and mantle lithosphere, as well as how the lithosphere was deformed during episodes of subduction, terrane accretion, and rifting. Here we present results from SEISConn that constrain the structure and deformation of the crust and lithospheric mantle using a variety of imaging techniques, including Ps and Sp receiver functions (RFs), full waveform ambient noise tomography, and SKS splitting analysis. Taken together, these analyses suggest complex and laterally variable (isotropic and anisotropic) structure across Connecticut in both the crust and lithospheric mantle, including a sharp step in the Moho in the western portion of the state, and high lower crustal velocities beneath the Hartford Basin that may suggest mafic underplating. Ongoing work focuses on the testing of specific hypotheses for the tectonic evolution of southern New England derived from geologic observations.