Age and Nature of Basalts from the Tyrrhenian Abyssal Plain

Abstract

Geochemical and petrological analyses of samples cored in the basement of the Tyrrhenian Abyssal Plain demonstrate that this basin is floored by a sequence of at least 250 meters of basalts with a clear oceanic tholeiitic affinity. The oldest recovered basalts have a K-Ar age of 7.3 ±1.3 m.y. These data strongly favor the hypothesis of an origin by back-arc spreading for the Tyrrhenian Abyssal Plain and imply that the formation of oceanic crust was already active in pre-Messinian times.