NEW CONSTRAINTS ON THE FORMATION AND BREAKUP OF PANGEA FROM SOUTHERN NEW ENGLAND: IMAGING OF THE CRUST AND LITHOSPHERE USING THE SEISCONN ARRAY (Invited Presentation)

The eastern margin of North America has been affected by a range of fundamental tectonic processes in the geologic past. Major events include the Paleozoic Appalachian orogeny, which culminated in the formation of the supercontinent Pangea, and the breakup of Pangea during the Mesozoic. The southern New England Appalachians exhibit a particularly rich set of geologic and tectonic structures that reflect multiple episodes of subduction and terrane accretion, as well as subsequent supercontinental breakup. The Seismic Experiment for Imaging Structure beneath Connecticut (SEISConn) was a deployment of 15 broadband seismometers in a dense linear array across northern Connecticut. The array traversed a number of major tectonic boundaries, and also crossed the Mesozoic Hartford rift basin in the central portion of the state. Here we present detailed images of the crust beneath the SEISConn array, which reveal significant variations in crustal thickness and crustal velocity structure across various geologic structures, with particularly thin crust beneath the Hartford rift basin. Of particular note is the identification of a region of high-velocity lower crust beneath the Hartford basin, which likely represents the remnant of magmatic underplating during continental breakup. These results shed light on a number of unresolved questions related to the breakup of the Pangea supercontinent, including the interplay between extension and rifting and the emplacement of the geographically widespread Central Atlantic Magmatic Province (CAMP). Taken together, the evidence for crustal thinning and the emplacement of high-velocity mafic material in the lower crust beneath the Hartford basin sheds light on crustal modification of the eastern North American margin associated with supercontinental breakup, rifting, extension, and magmatism during the Mesozoic.