GEOMAGNETISM AND AGE STUDY OF TYRRHENIAN SEAMOUNTS

We discuss the results of measurements of the magnetic anomaly field o f several seamounts located on the ocean floor and on the bordering co ntinental slopes of the Tyrrhenian Sea. This geomagnetic study of seam ounts is based on joint 3-D analyses of the magnetic anomalies and the bathymetry, on measurements of the magnetic properties of rock specim ens and on geochronological data. The 3-D analysis of the magnetic ano malies of large volcanoes emplaced in the small oceanic basins of Vavi lov and Marsili serves to shed light on the spatial distribution of th e magnetized bodies by eliminating the effect of topography. A new mag netic anomaly map of the southern Tyrrhenian Sea is obtained by the me rging of shipborne local data, measured on topographic highs, with dat a of regional type. The study of the magnetic patterns and age of the oceanic seamounts indicates that the volcanic activity mainly develope d prior to chron C2 (>2.02 Ma BP) on the Vavilov and Magnaghi edifices (Vavilov Basin), whereas the volcanism of a big oceanic seamount empl aced in the small basin of Marsili took place mainly during the period of chron C1 (0-0.78 Ma BP).