Abstract: Stratigraphy and Structure of Compressional Continental Margins

William R. Dickinson, Donald R. Seely

Compressional continental margins lie in fore-arc regions of arc-trench systems generated by plate consumption. Each has unique individual characteristics related to past history prior to subduction, and to different structural evolution during subduction. Arc-trench systems may be initiated by contractional activation of previously rifted continental margins, by reversal of subduction polarity following arc collisions, or as island arcs within oceanic regions. Fore-arc flanks of arc-trench systems enlarge during subduction through tectonic and sedimentary accretion of deformed ocean-floor sediments and igneous rocks, uplifted trench and slope sediments, and the sedimentary fills of subsiding fore-arc basins. Trench inner slopes typically are underlain by growing subducti n complexes composed of imbricate underthrust packets of ocean-basin, trench-floor, and slope-basin sediments in thrust sheets, isoclines, and melanges. The structure of subduction complexes is governed by the thickness and nature of oceanic layers rafted into subduction zones, variable thicknesses of trench and slope sediments, and the rate of obliquity of plate convergence. Fore-arc basins, located between migratory trench-slope breaks and the volcanic fronts of magmatic arcs, are composed chiefly of clastic strata derived mainly from arc structures. Facies patterns in fore-arc basins are governed by the depth or elevation of the trench slope break, the rate of sediment delivery to the basin and the nature and dynamic behavior of the crustal substratum beneath the basin.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC