Structural evolution of the southern Ecuadorian forearc in the Santa Elena Peninsula region

Description

The southern Ecuadorian forearc system is related to the subduction of the oceanic Farallon/Nazca Plate beneaththe continental South American Plate since the Late Cretaceous, and currently evolves with the dynamic of atectonic block called North Andean Sliver. To explore the structural architecture and processes controlling theUpper Cretaceous-Cenozoic growth of the forearc, we built a ~143 km-long onshore-offshore crustal-scale crosssectionin the Santa Elena Peninsula region using seismic reflection profiles and well and field data. The structureof the Santa Elena Peninsula forearc system is controlled by imbrication of Upper Cretaceous-Palaeocene oceanicbasement and Cenozoic sedimentary units, and underplating of distal Cenozoic sequences stacked at the trenchzone. This led to the progressive construction of an accretionary wedge through time. The forearc substratum ismainly formed by the Upper Cretaceous-Palaeocene basement developed during the docking of oceanic terranes.It is later deformed by NW-trending landward-dipping, normal to strike-slip faults during the Middle Eocene, andrenewed compression by inversion of inherited faults from the Oligocene onwards. Recent deformation consistsin N-trending oceanward-dipping normal faults in the frontal slope domain and fault-controlled uplift of marineterraces along the coastal area. Therefore, the Upper Cretaceous to present-day structural evolution of the SantaElena Peninsula forearc is controlled by the long-lasting subduction dynamics and structural inheritance of theupper plate.

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