Aeromagnetic investigation of crustal structure for a strip across the western United States

This report represents part of a larger study undertaken to interpret the gross features of the earth's crust by aeromagnetic methods. The larger survey covers a 100-mile-wide strip along a great circle arc from Washington, D.C., to San Francisco, California. The area considered extends from about 200 miles east of the Rocky Mountains to 150 miles west of the coast of the Pacific Ocean. Inferences on gross structure and lithology are made from the magnetic patterns and trends shown on the map.

At the continental margin, the magnetic data strongly suggest that the oceanic crust becomes much more deeply buried as the continent is approached.

A large magnetic anomaly extending northwestward along the center of the Great Valley is probably caused by mafic intrusive rocks.