ABSTRACT: Tectonic Histories of Some Well-Explored Convergent Margins of the Pacific
Roland Von Huene
Cenozoic tectonic histories of convergent margins are characteristically discontinuous involving periods of accretion and erosion. Growth along the seaward edges of continents from subduction accretion is well understood and documented by the ages and volumes of the attached materials. Less clear is the role of subduction erosion whereby formerly attached material as well as large parts of the continental framework are removed.
A change in tectonics from an accretionary to an erosional regime is sometimes coeval with changes in the plate convergence vector. Much of the Cenozoic margin seaward of the Cretaceous Andean volcanic arc is missing, and subsidence of the Peruvian fore arc since the Oligocene is best explained as a result of erosion along the plate boundary. The margin off northern Honshu, Japan, has subsided since latest Oligocene time, and the landward trench slope retreated at least 80 km with respect to the Cretaceous arc. Within the Pacific basin, the Oligocene was a time of major changes in plate motion. This correspondence suggests linkage between margin tectonics and plate convergence rate. However, many tectonic events along convergent margins have no plate tectonic counterpart and could res lt from collision of features that are now subducted. The collision of small topographic highs affects tectonic processes temporarily and the collision of larger features causes long-term changes. Convergent margin and plate tectonic histories, when compared at 1-m.y. precision, will provide a better understanding of convergent-margin tectonic mechanisms.
AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990