The eastern and western continental margins of the Gulf of Alaska are simple plate boundaries separating the Pacific and North American Plates. On the east is the Queen Charlotte–Fairweather transform fault system, along which the Pacific Plate moves northwest with respect to the North American Plate. On the west is the Aleutian Trench, along which the Pacific Plate converges against the North American Plate and produces a subduction zone (Fig. 1). Between the transform and convergent plate boundaries is a tectonically complicated area including the Yakutat Terrane (Jones and others, 1982), which migrated northwest on the Pacific Plate until it collided with the North American Plate. This collision occurred where the transform and thrust fault boundaries meet to form a 90° change in the trend of the plate boundary (Fig. 1). The general transform and convergent plate motion pattern has existed during the Cenozoic history of the Gulf, but variation in rate of plate motion, collision of features on the plate with North America, and subduction of oceanic crust of different age and physical properties have produced variations in the tectonic history. The tectonics produced by the subduction of thousands of kilometers of ocean crust shaped the geologic record of the convergent margin, but only the rudiments of that record are known because of the reconnaissance level of geological knowledge of the submerged margins around the Gulf of Alaska.
Figures & Tables
This new synthesis includes a section on plate kinematics, documenting the basis for a new interpretation of the magnetic anomaly patterns. It also includes: six chapters on various aspects of tectonics, petrologic characteristics, and hydrothermal processes of active ridges from the Galapagos Rift to the Juan de Fuca Ridge; a section on mid-plate volcanism, including the Hawaii-Emperor chain; five chapters on various aspects of northeastern Pacific sedimentary regimes; and nine chapters on the geology of the Pacific continental margin from the Aleutians to Guatemala, seen from the perspective of marine geology. Three separate oversize plates illustrate the bathymetry of the northeast Pacific; two more on the same base show distribution of sediment samples and types and magnetic anomaly data and tectonic interpretations; and others include a synthesis of the geology and bathymetry of the Hawaiian Islands, details of bathymetry along parts of the East Pacific Rise, and a major seismic profile across the Pacific margin of Guatemala.