Sediment qualities resulting from postdepositional iron diagenesis in the seafloor, such as reversible increases of the silicate lattice Fe(II)/Fe(III) ratio, may undergo drastic changes even within the short time intervals of archive storage. Consequently, those qualities must be studied on fresh materials, subsampled immediately after core retrieval, and handled with the necessary care. It does not seem helpful to use archive materials for the respective scientific aims. However, the "primary" signal of the solid phase Fe(II)/Fe(III) record survives the archive storage because the diagenetic overprint to this pattern is essentially reversible (König et al., 1999). Therefore, even older cores retain information in the Fe(II)/Fe(III) record that may be of use with respect to, for example, correlations based on deposition cyclicity and astronomical age models (compare the variation in Figure F2B with the age given in Table T1).
As nearly the entire Fe(II) fraction in Site 1062 sediments is structural iron in silicates, iron oxidation during storage occurred within the silicate lattice structure, and the mineral assemblage remained unaltered. Consequently, modification of the magnetic signal during storage is unlikely in this case, whereas the reversible shift in the Fe(II)/Fe(III) ratio suggests that magnetic overprints might have occurred in the seafloor. Moreover, our findings imply that iron oxidation during storage, at least as intense as in the reported case, would probably occur in sediment cores containing significant amounts of authigenic Fe(II)-bearing carbonates or sulfides. With such other types of sediment core, Fe(III) oxides and oxyhydroxides would form, and a magnetic study parallel to Mössbauer investigations (of the changes that occur during archive storage) would be worthwhile to also observe and document alterations of the magnetic signal or properties.