Sedimentary Record of Multiple Mesozoic Arc Events in Western Guerrero Terrane, Mexico

The western margin of Mexico is ideally suited for testing two opposing models for the growth of continents along convergent margins. In the first model, the continent grows through accretion of exotic island arcs by the consumption of entire ocean basins at multiple subduction zones with varying polarities. In the second model, protracted extensional processes in the upper plate of a subduction zone produce numerous arc-related basins, some rifted off the continental margin and others formed of new oceanic lithosphere; these continent-fringing basins become filled with detritus derived from arcs or the continent margin, and later become accreted to the edge of the continent during compressional, transpressional or transtensional phases of subduction. In some cases, renewed upper plate extension/transtension rifts or slivers these terranes off the continental margin once more, and are latter accreted to the continental margin again.

Prior to this study, all Mesozoic rocks in western Guerrero terrane were considered part of a single arc. However, we divide it in six distinctive tectonstratigraphic assemblages by integrating detrital zircon data, Ar/Ar ages and our new stratigraphic data. I) Paleozoic North America-derived turbidites (continent-slope assemblage). II) Triassic-Early Jurassic accretionary complex. III) mid-Jurassic volcanic arc assemblage. IV) Early Cretaceous extensional arc assemblage. V) Cenomanian retroarc assemblage. VI) Campanian-Maestrichtian intra-arc assemblage. Inherited zircons from a previous event into the following assemblages indicate that a series of deformational events, uplift and erosion occurred throughout the Mesozoic.