Crust of eastern North America preserves a record of the supercontinent cycle

The northeastern North American lithosphere, integral to supercontinent cycles and the Wilson Cycle concept, remains largely inaccessible at depth. Employing innovative P-wave receiver function methods, we unveil the upper ∼60 km of the lithosphere, focusing on the Appalachian Front (AF). Three distinct lithospheric blocks emerge, revealing a central 150 km wide region of thick (45+ km) crust with a gradational Moho and elevated P-to-S velocity ratio (κ), flanked by thinner (35–40 km) crust regions with lower κ and a sharp Moho. Abrupt changes align with Proterozoic (St. Fulgence Shear Zone (SFSZ)) and Paleozoic (Baie Verte–Brompton Line (BVBL)) tectonic boundaries, but not with the AF and the Red Indian Line (RIL), two of the first-order structural boundaries in the region. An elevated κ area coincides with the ∼450 Ma Charlevoix impact crater. Lithosphere NW of the BVBL retains Neoproterozoic supercontinent assembly structures, while the lithospheric affinity of the SE region remains unclear. Despite the RIL marking the Pangaean suture, connecting Paleozoic Laurentian and Gondwanan rocks, no changes are observed at depth. This suggests a thin-skinned tectonic regime and/or significant lateral transport. We propose either Gondwanan lithosphere extension to the BVBL or a subsurface Laurentia–Gondwana suture SE of its surface trace.