Seismic-refraction measurements were made in the Gulf of Maine in 1948 and 1951 as a continuation of the program of geophysical exploration of the continental margins. Sections from Portland, Maine, to the northwest edge of Georges Bank, from Matinicus Rock, Maine, to Cultivator Shoal, and from Cape Ann, Mass., to Yarmouth, Nova Scotia, were observed.
Sediments (with velocities of 5030 to 6780 ft/sec) varied in thickness from 0 to 1020 feet. North and east of Cashes Ledge consolidated sediments (with velocities of 12,000 to 13,000 ft/sec) were detected up to 1620 feet thick. These are tentatively identified as Triassic and possibly represent an extension of the Fundy Basin. Basement rocks (with velocities of 15,000 to 18,000 ft/sec) thicken under New England and form a troughlike feature off Nova Scotia. Remarkably uniform subbasement rocks (with velocities of 19,000 to 20,000 ft/sec) underlie the Gulf of Maine.