Controls on magnetic grain-size variations and concentration in the Argentine Basin, South Atlantic Ocean

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Measurement of two magnetic parameters, magnetic susceptibility (ξ) and anhysteretic remanent moment (ARM), was performed on 192 core-top samples from the Argentine Basin of the South Atlantic Ocean. Susceptibility indicates the concentration of magnetic grains in the sediment sample, while ARM estimates changes in magnetic mineral grain size: large ARM values indicate finer grain sizes. ARM normalized for magnetic concentration variation (ARM/ξ) increases precision in magnetic grain-size estimation. In the Argentine Basin, the magnetic characteristics reflect broad changes in magnetic mineral concentration rather than a substantial change in magnetic grain size across the basin. Data variations are consistent with deep-water circulation and sediment sources in the basin. The center of the basin acts as a sediment sink and is characterized by uniform magnetic grain concentrations and small grain sizes. Localized sediment input to abyssal depths from the South American continental margin dramatically modifies the magnetic pattern along the western margin of the basin. The data also show a marked downstream decrease in bulk magnetic grain content of the sediment as Antarctic Bottom Water enters the basin to the southeast and moves first westward and then northward along the margin of the basin. © 1988.

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Deep Sea Research Part A, Oceanographic Research Papers

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