THE ORIGIN AND PRESERVATION OF MAGNETIZATION IN PLATFORMAL CARBONATE MUDS, ANDROS ISLAND, BAHAMAS
As part of a larger project designed to study sedimentary and hydrological processes on the wind-dominated northwestern edge of Andros Island, Bahamas, we conducted a magnetic survey of peritidal, often microbially bound carbonate muds. All oriented samples of carbonate mud exposed at the surface preserve a stable natural remanent magnetization (NRM) indistinguishable from the local geomagnetic field observed over the last five years. Vertical cores through the entire interval of Holocene mud (0.5-3.0 m) revealed abrupt changes in rock magnetic properties and NRM at mean tide level, where a visible Fe-redox boundary and a major increase in bioturbation is apparent. We evaluate the preservation potential of paleomagnetic records in ancient carbonates by examining the affect of bioturbation and redox changes on the size, composition, organization and magnetism of magnetic minerals in surface and core environments.