Abstract

We have conducted a palaeomagnetic study of a Permian red sandstone layer intruded by a 70cm wide Plio-Pleistocene basaltic dike, with the ultimate goal of estimating the flow duration of the magma before its solidification. 31 samples were collected at various distances from the dike/sandstone interface and were thermally demagnetized in order to separate the overprinted Plio-Pleistocene magnetization component from the primary Permian one and to determine for each sample the unblocking temperature, Tub, necessary to erase totally the overprint. This temperature can be used to determine the maximum palaeotemperature reached at any distance from the contact, provided the secon-dary magnetization is a (P)TRM and the thermal fluctuation effects and actual cooling rates are taken into account. Examination of various magnetic parameters (NRM intensity, 15 days VRM intensity, initial magnetic susceptibility and hysteresis curves) allowed us to establish the nature of the overprinted magnetization and consequently to exclude samples carrying a CRM overprint. An apparent palaeotemperature profile and two