Interaction Of Basin Floor Submarine Channels with Normal Faults: Examples from the Taranaki Basin, Offshore New Zealand

Seafloor deforming faults influence submarine channels in various ways; however, most studies have focused on basin margin normal faults, or intra-basinal convergent structures. As such, the effects of extensional structures on channel propagation and resulting architecture within basins is poorly understood. Here, 3D seismic data with well control, from the Taranaki Basin, has been analyzed to document the interplay of structures and sediment conduits.

Mapping identified two families of fault networks that were active in the Miocene: faults with large throws striking N–S, and minor faults with smaller throws trending NE–SW. Two mid-Miocene channel systems were mapped, with an overall NW flow direction. Abrupt (often >90°) localized deviations of the channel paths occur in relation to the faults. Although some instances of channels eroding over normal faults were observed, several other styles of channel–fault interaction were recorded, including: deflection, ‘chevron style’ diversion, and capture and confinement along hangingwalls. Furthermore, the architecture of the channel-fills shows distinct relationships with the fault network. In areas of heavy faulting, channels demonstrate narrow, erosional profiles, dominated by bypass facies. As faulting diminishes, channels develop lower aspect ratios, becoming more sinuous and demonstrating more conventional channel-fills.

The channel–fault interactions documented here represent more complex behaviors than have previously been recognized in relation to intra-basinal normal faults. Faulting is seen to influence channel propagation, geometry, architecture, and evolution. The relationships between faults and channels have implications for sediment transport and reservoir architecture, both for conventional resources and carbon reduction initiatives.