Late Cretaceous-Miocene diachronous onset of back thrusting along the South Caribbean deformed belt and its importance for understanding processes of arc collision and crustal growth

The Venezuelan basin is obliquely subducted to the east‐southeast beneath the continental South American plate at the east‐west‐trending South Caribbean deformed belt (SCDB), a 50–100‐km‐wide wedge of accreted sedimentary rocks derived both from offscraping of the 0.5 to 1 km‐thick sedimentary cover of the subducting Venezuelan basin and from incorporation of clastic sediments derived from the continental margin of South America. In this paper we describe the structure and sequence stratigraphy of five Late Cretaceous to recent sedimentary sequences overlying a 230,000 km2 area of the southern Venezuelan basin and Beata Ridge. The data set includes 5900 km of 2D seismic reflection data that are tied to lithologic and age data taken from DSDP sites 146/149 and 150 in the central part of the Venezuelan basin. We use observed patterns of wedging in mapped and dated sedimentary sequences adjacent to the SCDB to determine the age of the diachronous west‐to‐east initiation of thrusting and subduction at the SCDB. The onset of subduction in the SCDB corresponds with the cessation of thrusting from west to east along the zone of collision between the intraoceanic Caribbean arc and the South American continent. This correlation in the age of deformation indicates that collision between the Caribbean arc and the South American continent led to subduction polarity reversal, a process that is commonly observed at various stages of tectonic evolution in other areas of active, arc‐continent collision including Japan and Sunda. Key Points Describe structure and stratigraphy in Venezuelan basin and Beata Ridge Determine the age of the initiation of thrusting and subduction at the SCDB Subduction polarity reversal as a result of correlation in age of deformation