Burial claystones remagnetization and some consequences for magnetostratigraphy

Abstract: We investigate the broad lines of magnetic mineral formation for non-metamorphic claystones. More particularly, we focus on the formation of magnetite from c. 20 day-experiments aiming to reproduce burial conditions. It is shown that the sole action of temperature from 50 8C to 250 8C leads to the formation of magnetite. The neoformed magnetites carry a chemical remanent magnetization which equates at least the natural remanent magnetization. We propose a schematic of burial with three magnetic windows where a chemical remanent magnetization superimposed the natural remanent magnetization. These are the greigite window (subsurface), the magnetite window (depth. 2 km) and the pyrrhotite window (depth. 6 km). The formation of magnetic minerals has profound consequences for the magnetostratigraphy record. We propose a conceptual model that shows that the continuous production of magnetite during burial may result in magne-tozones that have no relation to the age of the sediment. Widespread remagnetization is a common process in sedimentary rocks (Kligfield & Channell 1981