Sedimentary regimes at the Macquarie Ridge Complex: Interaction of Southern Ocean circulation and plate boundary bathymetry

Seafloor structure at the Macquarie Ridge Complex strongly influences the intensity and circulation pattern of ocean currents south of New Zealand. New marine geophysical data show heterogeneous sedimentary environments on Macquarie seafloor that reflect interaction of highly variable bathymetry with the Antarctic Circumpolar Current and north flowing Antarctic Bottom Water. Acoustic backscatter, bathymetry, and seismic reflection data collected aboard RN Rig Seismic in 1994 show five bathymetrically constrained sedimentary provinces flanking the ridge complex: (1) northwest Macquarie hemipelagic drifts, (2) current-modified Solander submarine fan complex, (3) southwest Macquarie manganese nodule province, (4) Emerald Basin pelagic drift province, and (5) sediment-free oceanic crust related to the 53.5 degrees S passage in the Macquarie Ridge Complex. The late Miocene-Pliocene opening of a 53.5 degrees S passage in the ridge complex caused a major increase in the intensity of ocean current circulation, sediment reworking, and erosion in all sedimentary provinces.