The work of several investigators on the magnetic lineations in the northeast Pacific has been re-examined and a new lineation map of the area is presented. These lineations are presumed to have been generated by a process of sea-floor spreading. By adopting a time scale for the lineations we have presented a map of the inferred ages of the basement rocks and a maximum age for the overlying sediments. These ages are expressed in terms of the familiar geologic epochs. It has been postulated that the tectonic evolution of the northeast Pacific was largely dominated by a “Y”-shaped system of migrating ridge axes. The trenches that formed in response to this system of ridges, and the the ridges themselves, were characterized by periods of activity and inactivity. The barrier nature of these features should have had considerable influence on the distribution of terrigenous sediments in the northeast Pacific.
A new group of magnetic lineations has been discovered which trends northwest and is partially bounded by the Shatsky Rise, the Emperor Seamounts and the Hawaiian Arch. The lineations are thought to have been formed by a process of sea-floor spreading prior to the Late Cretaceous. Lineations trending east-northeast in the area just east of Japan are also thought to represent an old era of spread-ing. These two groups of lineations may comprise the two limbs of an ancient magnetic bight now centered in the northwest Pacific near the Shatsky Rise.
Quiet magnetic zones separate the major areas of magnetic lineations, giving rise to a distribution of four zones with distinctive magnetic signatures. These four zones may relate to similar magnetic zones in the North Atlantic.