Biogeochemical remanent magnetization in pelagic sediments of the western equatorial Pacific Ocean

Abstract

Paleomagnetic data from pelagic sediments are an important source of information on the history of the geomagnetic field. However, fundamental uncertainties about how these sediments acquire their magnetizations remain. Here we address whether biogenic magnetite, formed at depth within the sediments, can contribute to remanent magnetizations. In sediments of the western equatorial Pacific Ocean (ODP Site 805), biogenic magnetite found near the Fe-redox boundary carries a natural remanent magnetization. Because the production of biogenic magnetite is tied to the geochemical zonation of the sediments, we call this magnetization a biogeochemical remanence. These data indicate that some pelagic sediments can continue to acquire remanence significantly after the post-depositional lock-in of detrital magnetic grains.