ACQUISITION OF SUCCESSIVE PARTIAL THERMOR EMANENT MAGNETIZATIONS BY SINGLE-DOMAIN PYRRHOTITE DURING THE COOLING OF THE DAUPHINOISE ZONE (WESTERN ALPS, FRANCE)

The magnetization of the marls and marly limestones from the internal part of the Dauphinoise zone is carried by monoclinic pyrrhotite. Our experiments show the equality of blocking and unblocking temperatures which suggests that magnetic grains are single domain. Thermal demagne tization analysis shows the presence of colinear components of opposit e polarity. They are interpreted as partial thermoremanent magnetizati ons acquired during different polarity periods of the geomagnetic fiel d at the time of the slow cooling of the studied area.