Subduction and Tectonics. Discussion on the Results of the IPOD Program in Active Margins

Abstract

Since the advent of plate tectonics the active margins of the oceans have been studied according to a model whose basis is a piling up of imbrications of oceanic material units, in front of the upper plate, forming a great tectonic accretionary prism. This model is broadly the same for all the authors; it has been largely used for alpine-type or paleo-oceanic mountain chain, all around the world. The authors have directly taken part in the drillings on western and eastern Pacific active margins (Legs 60 and 67) and they have worked on the tectonics of alpine (paleo-oceanic) chains of the peri-mediterranean, peri-caribbean, and peripacific belts. They compare the geological data acumulated from these tow direct sources. The tectonic constraints constraints regime is specified and the consequences of the subduction are looked for. The notions of collison and obduction are discussed in relation to subduction and tectonics. Finally, an anlaysis of the temporal evolution of active margins and of chains, shows the necessity of thinking in terms of superimposed tectonics