PALEOMAGNETISM OF PLEISTOCENE VOLCANIC-ROCKS FROM PANTELLERIA-ISLAND (SICILY CHANNEL), ITALY

A paleomagnetic investigation has been carried out an Pleistocene volc anic rocks from Pantelleria, in the Sicily Channel. This island is cha racterised by a bimodal volcanism of peralkaline rhyolite to trachyte and basalt composition. The radiometric data indicate that volcanic ac tivity started around 324 ka BP. Samples have been collected from 30 s ites in 16 volcanic units spanning activity during the last 150 ka. Ma gnetic properties vary systematically with lithotype and indicate high -Ti titanomagnetite to magnetite as the main carriers of magnetisation . Stable characteristic remanent magnetisation (ChRM) directions isola ted by alternating fields (Af) demagnetisation show normal polarity co nsistent with emplacement during the Brunhes chron and vary within the paleosecular Variation (PSV) range. However, the inclinations are low as compared with the geocentric axial dipole (GAD) inclination at Pan telleria, especially for volcanic units younger than 50 ka. The mean C hRM direction computed from 27 sites is D = 358.8 degrees, l = 46.9 de grees (k = 30, alpha(95) = 5.2 degrees), and the inclination anomaly i s Delta l = -8.1 degrees. Both tectonic movements and the presence of large magnetic anomalies around the island of Pantelleria fail to expl ain this low inclination, which may therefore be related to a signific ant long-lived, non-dipolar field contribution in the area over the pa st 150 kyr. (C) 1998 Elsevier Science B.V. All rights reserved.