A drowned Holocene barrier spit off Cape Ann, Massachusetts

Seismic profiles and bathymetric contours reveal a drowned barrier spit on Jeffreys Ledge off Cape Ann, Massachusetts. Seaward-dipping internal reflectors indicate that a regressive barrier formed during the early Holocene low sea-level stillstand. Preservation of the barrier spit may have been favored by its large size (as much as 20 m thick), by an ample sediment supply from unconsolidated glacial drift, and by the subsequent rapid sea-level rise. The barrier spit is present in water depths of 50 to 70 m and indicates a low relative sea-level stand of −50 m. This value confirms the low relative sea-level stand of −47 m postulated by Oldale et al. (1983) for northeast Massachusetts and New Hampshire on the basis of the submerged delta of the Merrimack River, and it indicates that the barrier and delta were contemporaneous (Oldale et al., 1983).