Seismic reflection evidence for the evolution of a transcurrent fault system; the Norumbega fault zone, Maine

A seismic reflection profile in east-central Maine reveals a steeply dipping fault zone that terminates in diffraction hyperbolae that are associated with an offset of the Moho. When combined with data from geologic mapping, the seismic data imply Mesozoic or post-Mesozoic dip-slip reactivation of the Norumbega fault zone, hitherto interpreted as a locus of mid- to late Paleozoic dextral offset. This finding highlights the value of seismic reflection data in determining the history of fault displacement and warns of the complexities that arise in attempts to seismically characterize faults in polygenic tectonic regimes.