Abstract:
Paleomagnetic recording of Earth magnetic field (EMF) variations plays an essential part in understanding the origin and behaviour of the EMF. As the common recorders like sediments or basalts are all dealing with intrinsic problems like the lock-in-depth-problem or time-gaps, the aim of this thesis is to test the potential and quality of secondary pyrrhotite in contact metamorphic, marly limestones as a new recorder of EMF variations. The advantage of this technique is to combine the rockmagnetic qualities of a TRM record with a continuous recording process. Therefore, the magnetic particle assemblages of samples from four locations (Manaslu, Nepal; Isle of Skye, Scotland; Bourg d'Oisan, France; Elba Island, Italy) were investigated in advance using microscopic (light microscopy, SEM, TEM) and rockmagnetic techniques (IRM, FORC, delta M). In addition, the recording quality (additivity and independence of pTRM) was tested by the means of laboratory pTRM checks and artificial Thellier-Thellier-Experiments. The method was successfully tested on a site from central Elba, where the NRM is a clear secondary TRM consisting of two antiparallel components and a broad transition. The derived paleofield values are similar to the present day field in Elba, but decrease to about 5% of present day field during the transition. The duration of the transition (<20kyr) is estimated by numerical models.