Successive Rifting Events in Marginal Basins: The Example of the Coral Sea Region (Papua New Guinea)

Reactivation of extensional structures is commonly inferred during rift evolution. In that context, we present original seismic interpretation to explore the geometry and interactions of three successive rifting events in the Coral Sea region, Papua New Guinea. The first event (R₁), poorly documented, occurred during the Triassic along an older N-S Permian structural fabric. During the Jurassic, extensional faults were reactivated through a second extensional episode (R₂), which formed small ( 10/20 km) basins bounded by N-S, NE-SW, and E-W listric faults. Extension prolonged during the Lower Cretaceous with seafloor spreading in the Owen Stanley Oceanic Basin, now incorporated in the Papuan fold and thrust belts. A third Late Cretaceous extensional phase (R₃) gently reactivated some of the faults with very limited landward tilt in most basins and deformation located along the present continent-ocean transition. Seafloor spreading in the Coral Sea followed from Danian to Ypresian. This extensional system is sealed by unequally preserved Eocene strata that mark the onset of postrift thermal subsidence prior to the margin inversion from Oligocene onward. This overall evolution suggests various extensional systems that are geographically and temporarily defined the one another. The early rifting of the crust is controlled by preexisting continental features resulting in the local Pangaea breakup. In contrast, the Coral Sea propagator cuts through the rifted margin and is controlled by a subduction complex in accordance with the Tasman Sea opening. This evolution underlines the interactions existing between two extension modes in agreement with variations of the regional geodynamical setting around Australia.