Plio-Pleistocene magnetic polarity stratigraphies of ODP Leg 177 Sites from the South Atlantic

Magnetite is the principal remanence-carrying mineral. Downcore alteration of magnetite and authigenic growth of iron sulfides introduces a high coercivity diagenetic remanence carrier (pyrrhotite).

The change in pore water sulfate with depth in the sediment tends to be in step with the decrease in magnetization intensity, indicating the link between sulfate reduction and magnetite dissolution. Shipboard pass-through magnetometer data are generally very noisy due to a combination of weak magnetization intensities, drilling-related core deformation, and the influence of authigenic iron sulfides. Post-cruise progressive demagnetization of discrete samples aids the magnetostratigraphic interpretation, as these measurements are less influenced by low magnetization intensities and drilling-related deformation.