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 i ntensity and circulation pattern of ocean currents south of New Zealand. Ne w marine geophysical data show heterogeneous sedimentary environments on Ma cquarie seafloor that reflect interaction of highly variable bathymetry wit h the Antarctic Circumpolar Current and north flowing Antarctic Bottom Wate r. Acoustic backscatter, bathymetry, and seismic reflection data collected aboard RN Rig Seismic in 1994 show five bathymetrically constrained sedimen tary provinces flanking the ridge complex: (1) northwest Macquarie hemipela gic drifts, (2) current-modified Solander submarine fan complex, (3) southw est Macquarie manganese nodule province, (4) Emerald Basin pelagic drift pr ovince, and (5) sediment-free oceanic crust related to the 53.5 degrees S p assage 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 t he intensity of ocean current circulation, sediment reworking, and erosion in all sedimentary provinces.