The carrier of the natural magnetization of deep sea sediments was characterized by mineralogical, electron microscopic, and rock magnetic investigations. Magnetic single domain (SD) and pseudo single domain (PSD) particles which are most important for the stable remanent magnetization were separated from the magnetic »coarse fraction« and concentrated as magnetic »fine fraction«. The magnetic coarse fraction consists of lithogenic magnetite and titanomagnetite, which often contains exsolution-lamellae of ilmenite. Both minerals are partially maghematized and occur isolated in the sediment or embedded in rock particles, in regionally different concentrations. The magnetic fine fraction consists of lithogenic magnetite and titanomagnetite and biogenic magnetite (magnetofossils = fossil bacterial magnetosomes), the latter generally maghematized.

A graphical method is described which allows the classification and characterization of the magnetic fine fraction by demagnetization of the anhysteretic remanent magnetization (ARM) of whole sediment samples. Three groups with different magnetic properties can be distinguished, characterized by three ARM type-curves: Type A curves are associated with sediments from abyssal plaines. They show nearly identical ARM properties and are typical for magnetofossils.

Type B curves are produced by sediments from the vicinity of volcanic regions. Their shapes are variable to a certain degree and indicate two lithogenic magnetic phases.

Type C curves are found for sediments from submarine ridges and regions with input of terrigenous detritus. These curves have the largest deviations among each other indicating a magnetic multi-phase assemblage including magnetofossils.