Evolution of submarine channel system and mass transport deposits in the Taranaki Basin, Offshore New Zealand

Abstract

The marine sedimentary record can provide valuable information related to the tectonic evolution of a basin, patterns of sediment transportation and deposition, and paleo-oceanographic changes. Major deposits in the deep-water setting include submarine channel and fan systems, landslides, slumps, turbidites, and contourites. Turbidity current, submarine channels, and mass transport can mobilize substantial sediments into the deeper waters. They also feedback with the seabed topography resulting in its dynamic changes. Understanding the deep-water sedimentation patterns is also critical to assess submarine hazard potential, such as landslides that can trigger a tsunami. Three-dimensional (3D) seismic data is helpful to understand the sedimentation patterns and changes in sediment transportation processes in the deep-water system. In this work, I analyze 3D seismic data from the Taranaki Basin, offshore western New Zealand. The 3D seismic data helped to understand the sequence of depositional events, deposition style, and changes on the paleo-seabed. I mainly focus on the Neogene record of the margin that is represented by mass transport deposits and slope channel complexes. Seismic attribute analysis, horizon mapping, spectral decomposition, and color blending enhance 3D seismic interpretation. The submarine channel system shows differential compaction-related anticlinal structure since less compactable sand filled the channel. The channel was forced to alter its course due to a mass transport deposit that obstructed the flow. A submarine landslide shows the initiation of gravity glide and subsequent cessation. The kinematic indicators within the landslide suggest that the gliding process can be halted by dynamic modification in frictional resistance at the basal shear surface. The basal shear surface lies in an underlying older mass transport complex, which is represented by over-pressured mud. The localized increase in frictional resistance at the basal shear surface was likely caused by megaclast blocks within the mass transport complex and loss in pore fluid through the extensional faults shortly after the glide initiation, causing limited translation of the slide and its confinement behind a frontal ramp.