POSSIBLE CONNECTION BETWEEN THE NORUMBEGA, EASTFORD, AND MISERY HILL FAULTS OF NEW ENGLAND AND EVIDENCE FOR POST-TRIASSIC AND LATE CENOZOIC DEFORMATION

The recent availability of high-resolution LiDAR data in New England, combined with topographic, geologic and aeromagnetic data, suggests that the Norumbega fault system (NFS) continues southwestward an additional 300 km across southern New England as a beheaded basement fault system and that its post-Triassic reactivation at depth has fractured through the overlying terranes to produce a discontinuous series of LiDAR lineaments, some of which coincide with the Eastford fault of southern New England and the Misery Hill fault of southeastern New Hampshire. Its surface trace is expressed locally as linear valleys and changes in river morphology that are collinear with 1:24,000-scale, linear negative aeromagnetic anomalies. In southern Maine, the Mackworth and South Portland fault segments of the NFS are interpreted to extend farther southwest than previously mapped. Elevated terrain along a 1-2-km-wide, left-step offset in the South Portland fault where it traverses the western flank of the Triassic-age Agamenticus pluton in southern Maine suggests that this area is a compressional popup associated with dextral motion on this fault. Interpretation of aeromagnetic data in northeastern Massachusetts suggests that this regional structure also crosscuts the late Paleozoic-age Clinton-Newbury fault. Near Kingston in southeastern New Hampshire is a 12° restraining bend along the proposed fault system. Compression at this bend may have produced a NW-trending thrust fault, displacements along which have been postulated to have produced the 1727 Newbury, MA, earthquake.

The proximity of this regional structure to the Littleton, MA, and Moodus, CT, areas of seismicity, in addition to deep borehole and seismic data near Moodus, suggests that local displacements along this structure have produced these areas of seismicity. A large channel knickpoint and changes in the sinuosity and Holocene floodplain patterns of the Merrimack River near Lowell, MA, as well as increased incision and changes in sinuosity of the Kennebunk, Mousam and other smaller rivers in southern Maine, further suggest that this structure has undergone recent deformation. Because this feature lies relatively close to Boston and Hartford, further studies are needed to determine if it is capable of producing large damaging earthquakes.