Structure of continental margins along the strike-slip and compresional plate boundaries of the Gulf of Alaska

Abstract

Tectonic mechanisms along the eastern and western Gulf of Alaska continental margins are inferred to be strike-slip (transform) and compressional (converging) plate boundaries in tectonic models of the North Pacific. Recent field observations are consistent with the overall plate geometry; however, the crustal configuration observed departs significantly from the simplistic diagrams and models used by some authors. Along the strike-slip plate boundary, a large buried trench requires that another process beside simple lateral shear is operating at the oceanic-continental crustal juncture. Along. the eastern Aleutian Trench an absence of large thrust faults requires other mechanisms of transmitting the shear of the Benioff zone to the earth's surface. ln this area it seems that the Benioff zone may be a sub-crustal feature and that extensive plastic deformation occurs in the lower crust just above the Benioff zone. This may in turn be expressed in the overlying sedimentary section as a wide zone of folding.

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