Seismic Stratigraphy of Eocene–Recent Mixed Depositional Systems on the SE New Zealand Continental Margin, Great South Basin

The continental margin of SE New Zealand is strongly influenced by the Southland Current and associated water masses. This new seismic stratigraphic study of the margin has revealed a range of depositional mounds and erosional channels that document the close interaction of turbidity and bottom currents in shaping the margin from the Mid‐Eocene onward. Bottom‐current influence was initiated with the onset of the Antarctic Circumpolar Current, following the opening of the Tasmanian Gateway. Following this event, four stages of evolution are identified: (1) the Mid‐Eocene saw the onset of the first mixed depositional system with a series of levee‐drifts adjacent to downslope channels, alongslope‐oriented contourite‐dominated drifts, and an alongslope contourite moat; (2) the Early to Late Oligocene saw the continued vertical growth and incision of these mixed depositional and erosional elements; (3) the Late Oligocene to Mid‐Miocene saw a significant change to a more turbidite‐dominated mixed system, with a weakened bottom‐current influence; and (4) the Mid‐Miocene to Recent saw a resumption in bottom‐current activity, and development of a more contourite‐dominated system. The changes observed in margin evolution reflect variations in tectonic activity and source area uplift, variation in continental slope topography, and evolving bottom‐current systems.