Emergence Model for Formation of Aleutian Arc: ABSTRACT

Abstract

It is generally believed that the Aleutian arc has been formed as a result of a North Pacific crustal plate being thrust into the Aleutian Trench and beneath the Aleutian Ridge. Several bathymetric and magnetic features along and south of the Aleutian arc conflict with that model of convergence between crustal plates. A new model is proposed which calls for the development of the Aleutian arc by the emergence of material from the underlying mantle as the North Pacific plate is pulled away. The pattern of magnetic anomalies suggests that an ancestral Aleutian Ridge may have been the source for Late Cretaceous and early Tertiary southward sea-floor spreading. The present Aleutian Ridge was built during the Cenozoic by uplift and the accumulation of volcanogenic material. The Aleutian Terrace and Trench are half-grabens which have been collecting sediments since their probable late Tertiary formation. Tensional first motions of earthquakes beneath the trench may reflect its continuing formation, although there is no evidence of appreciable horizontal motion associated with its development. Basins at t e bottoms of submarine canyons that cut into the Aleutian Ridge suggest that the Aleutian Terrace is still opening. The Aleutian and Bowers basins have been collecting thick sedimentary deposits since the formation of the ancestral Aleutian Ridge. Bowers Ridge probably was pushed up from the Aleutian basin during late Tertiary deformation of the Aleutian Ridge. End_of_Article - Last_Page 2501------------