THE NEW YORK–ALABAMA LINEAMENT: A BURIED RIGHT-SLIP FAULT BORDERING THE APPALACHIANS AND MID-CONTINENT NORTH AMERICA

The New York-Alabama lineament is a magnetic anomaly recognized in 1978 that delineates a fundamental though historically enigmatic crustal boundary in eastern North America that lies deeply buried beneath the Appalachian basin. ‘Holes’ in the original aeromagnetic dataset, particularly the lack of any information available at the time to constrain its southern continuation southwest of Tennessee, left the source of the lineament open to conjecture. We use modern digital aeromagnetic maps to fill in these data holes and, for the first time, constrain the southern termination of the New York-Alabama lineament. Our analysis indicates that the lineament reflects a crustal scale, right-lateral strike-slip fault that has displaced anomalies attributed to Grenville orogenesis by ~220 km. Palinspastic restoration of this displacement rearranges the trace of the Grenville belt in southern Rodinia and implies only passive influence on later formed Appalachian structures. The precise timing of dextral movement on the New York-Alabama structure is not resolvable from the existing dataset, but it must have occurred during one or combinations of the following events: (1) a late, post-contractional (post-Ottawan) stage of the Grenville orogeny; (2) late Neoproterozoic to Cambrian rifting of Laurentia; or (3) right-slip reactivation during the late Neoproterozoic –Cambrian rifting, or during Appalachian movements. Our palinspastic reconstruction also implies that the host rocks for modern earthquakes in the Eastern Tennessee Seismic Zone are metasedimentary gneisses, and it provides an explanation for the spatial location and size of the seismic zone.