GEOMAGNETISM AND AGE STUDY OF TYRRHENIAN SEAMOUNTS

We discuss the results of measurements of the magnetic anomaly field of several seamounts located on the ocean floor and on the bordering continental slopes of the Tyrrhenian Sea. This geomagnetic study of seamounts is based on joint 3-D analyses of the magnetic anomalies and the bathymetry, on measurements of the magnetic properties of rock specimens and on geochronological data. The 3-D analysis of the magnetic anomalies of large volcanoes emplaced in the small oceanic basins of Vavilov and Marsili serves to shed light on the spatial distribution of the magnetized bodies by eliminating the effect of topography. A new magnetic anomaly map of the southern Tyrrhenian Sea is obtained by the merging of shipborne local data, measured on topographic highs, with data of regional type. The study of the magnetic patterns and age of the oceanic seamounts indicates that the volcanic activity mainly developed prior to chron C2 (>2.02 Ma BP) on the Vavilov and Magnaghi edifices (Vavilov Basin), whereas the volcanism of a big oceanic seamount emplaced in the small basin of Marsili took place mainly during the period of chron C1 (0-0.78 Ma BP).