Le volcanisme du “Biarritziano” de Vénétie (Italie): Ages KAr sur basalte, pasalte, plagioclase et céladonites

Abstract

In the Monte Baldo area of the Southern Alps basalts have been deposited below fossiliferous neritic limestones. Large foraminifers gave a “Biarritziano” age to the limestones immediately overlying the basalts. These sediments are followed by a Priabonian sequence. Some of the basalts are rich enough in celadonite for this component to have been used by Roman artists as a cheap painting pigment. This celadonite gave several KAr apparent ages of ∼ 30 and 23.5 Ma, clearly younger than the time of deposition of the basalts. One basalt gave a KAr apparent age of 36.5 ± 2.0 Ma, significantly younger than a plagioclase, selected from a basalt of apparently similar stratigraphic location, measured at 40.4 ± 0.8 Ma. The age of ∼ 40 Ma is an indication of the maximum time of deposition of the sediments of “Biarritziano” age.