Structural and Stratigraphic Evolution of Late Cretaceous Convergent Margins of Southern Alaska and California: ABSTRACT

The most prominent and well-preserved remnants of the convergent margins are present in southern Alaska and California. The southern Alaska convergent margin appears to have developed in response to northward-directed subduction of the Kula plate and the California margin in response to eastward-directed subduction of the Farallon plate. The chief elements of the southern Alaska convergent margin, on the basis of paleomagnetic data, appear to have subsequently migrated northward and rotated in the post-Cretaceous. The chief elements of the California margin have been disrupted by Neogene strike-slip displacements on the San Andreas fault system and accretion of younger terranes to the west. In both southern Alaska and California, the forearc-basin deposits are well preserved and produce major amounts of gas. The principal reservoirs in Alaska are Tertiary nonmarine deposits and in California are Late Cretaceous and Tertiary deep marine and deltaic deposits. The accretionary wedge in southern Alaska forms a remarkably well-preserved assemblage of trench and trench-slope deposits that extend for about 2000 km along the Gulf of Alaska, flanked oceanward by younger accreted terranes. The accretionary wedge in California consists of a great variety of older and younger terranes, including some fragments of ocean crust that originated in southernmore » latitudes. Comparative structural and stratigraphic analyses of the two Late Cretaceous margins reveals the complexity of tectonic, depositional, and stratigraphic patterns associated with subduction of very large oceanic plates at the margins of very large continental plates.« less