Miocene Sl?nic Tuff, Eastern Carpathians, Romania, in the Context of Badenian Salinity Crisis

摘要

New geochronological investigations for the Sl?nic Formation, correlated with previous bio- and lithostratigaphical information, allow for a better succession of events for the Middle Miocene, including the absolute age of the Badenian salinity crisis in the bend sector of the Eastern Carpathians. Within the green Sl?nic Tuff, white tuff layers were in evidence. The main element distribution of the white and green tuffs indicates a dacitic composition, with higher SiO 2 content for the white tuff. The white tuff has a distinct mineralogical composition with quartz, plagioclase, biotite and clinoptilolite. From such a tuff layer a biotite concentrate gives a 40 Ar/ 39 Ar age of 13.7 ± 0.2 Ma. As above these tuff layers discrete levels of gypsum occur, the age documents the beginning of the restrictive circulation and formation of evaporites in this sector of Carpathians during Badenian times.