Extension of Alaskan structural trends beneath Bristol Bay, Bering Shelf, Alaska

Abstract

Magnetic, gravity, and seismic profiling observations were systematically made 8 km apart over 63,960 km2 in southern Bristol Bay, Alaska. Magnetic and gravity anomalies show a sharp separation between low-frequency, subdued anomalies in the southern half of the area and high-frequency, large magnitude anomalies in the northern half. The strike of this discontinuity curves WSW-NW just north of Unimak Island (Alaska peninsula) and effectively outlines the westward extension of the Goodnews arch and the Bristol Bay basin structures as far as the Pribilof Islands. Seismic profiles suggest that the metamorphosed and intruded rocks of the Goodnews arch are fairly near the surface and are responsible for the high-frequency anomalies in the magnetic data. The data support the concept that the present Aleutian arch-Alaskan peninsula structure transects an older continental margin basin that formerly connected the shelf near Kodiak Island with that in the vicinity of the Pribilof Islands, Bering Sea.