Peru Basin sediments: Diagenetic implications of a low coercivity overprint of the NRM

Two coexisting populations of magnetite that vary by at least 320kyr in age characterize the magnetomineralogy in oxic through suboxic Peru Basin sedi ment (7 degrees 04'S /88 degrees 28'W). 1) Primary magnetite barely underwe nt post-depositional alteration and yields a straightforward magnetostratig raphy (Brunhes Chron - top of Olduvai Subchron). 2) A stable, low-coercivit y overprint of the NRM resides in secondary, slightly oxidized SD magnetite that recorded the Brunhes Chron direction. The secondary magnetite appears at the modern Fe-redox boundary (2.6 mbsf) and continues downhole to abrup tly disappear at 5.3 mbsf in the Matuyama Chron. It can be discerned by com bined analyses of directional data and the Verwey transition in low-tempera ture remanence measurements (20-300K) that appears concomitant with the ove rprint.