Thin-skinned thrust-fault complex in the Phu Quoc Basin, SW Vietnam

The Phu Quoc Basin is a Late Jurassic to Early Cretaceous foreland basin located SW of Vietnam in the eastern part of the Gulf of Thailand. A structural model for the basin is provided based on the interpretation of a commercial 2 D digital multichannel reflection seismic survey in a rectangular open grid with an approximate distance between the lines of 8 km. The survey consists of 29 profiles totalling about 1500 km with a range of 7 sec TWT depth. The aim of this investigation is to present a structural model for a virgin area, which has not been subjected to exploration drilling. For any future investigation of the potential of this basin it is of crucial importance to know the structural framework, without which all further investigations will be waste of investments. The deformation of the Phu Quoc Basin took place during the orogenic build-up of the Kampot Fold Belt (Fyhn et al. 2010) in the early to middle Cretaceous, which resulted in the formation of a thin-skinned thrust-fault complex. The main thrust fault elements are flats and ramps. In the distal part of the complex piggyback basins occur with a translation of more than 3 km. The main part of the complex is concealed under Neogene marine deposits. The magnitude of displacement of thrust sheets with an average thickness of 300 m varies from 3 to 8 km. The number of ramps increases towards the proximal part of the complex, and an increasing number of hanging-wall anticlines occur, some of which developed into antiformal stacks. Duplex structures initially lifted the top of the tectonic complex to a higher level, which resulted in a deeper level of erosion into the tectono-stratigraphic units. An example of this is the Hon Mau island in the Nam Du archipelago, where the thrust deformation elevated Permian pyroclastic rhyolites up to a surface-near position. The thin-skinned thrust-fault model is based on a detailed balanced cross-section analysis. The structural information can be provided for future investigations of the Phu Quoc Basin, either commercial or scientific.