Seismic geomorphology of the Late Miocene submarine channels in the Southern Taranaki Basin

The Late Miocene submarine channel is proven to be a sand-prone deposit in southern Taranaki, offshore New Zealand. A depositional model of a submarine channel is important to understanding its architecture, geomorphology, and evolution. Identifying sand-prone deposits as potential hydrocarbon reservoirs in submarine channel systems is challenging due to their complex architectures, multi-phase channel histories, and intricate vertical and lateral connectivity. In this study, one high-quality 3D seismic reflection dataset and two exploration wells have been analyzed and interpreted using seismic facies, seismic geomorphology, and a seismic attribute approach (slicing technique), resulting in 18 channels in 4 stratigraphic units during the Late Miocene. In addition, the lithological proportion of sand and shale and its stacking pattern, supported by biostratigraphic data, indicate the presence of a submarine channel in this area. Temporal changes in channel characteristics were observed, including shifts in channel orientation, variations in channel dimensions, and a progressive decrease in sinuosity. These changes reflect the influence of dynamic depositional processes controlled by tectonic activity, seafloor topography, sea-level fluctuations, and sediment supply. Favorable reservoir potential within this submarine channel system is associated with multi-episode cut-and-fill processes, including amalgamated channels and lateral accretion deposits, which collectively contribute to the development of sand-prone facies. The insights from this study contribute to a broader understanding of deepwater channel evolution in tectonically active, sediment-rich settings. The conceptual model developed provides a transferable framework for interpreting similar systems in other continental margin basins worldwide, particularly low-angle slope channel systems within foreland basin settings. This makes it a valuable analog for analyzing channel systems in data-limited or frontier regions. • Eighteen Late Miocene submarine channels transition from sinuous to straight forms. • Tectonic activity, sea-level fluctuations, sediment supply, and paleotopography significantly influenced channel morphology, stacking patterns, and reservoir distribution. • Detailed interpretation of the channel system reveals its internal structure, including channel fills, levees, and sediment waves. • Sand-prone facies, including amalgamated channels and lateral accretion deposits, indicate promising deep-water hydrocarbon reservoirs.