MIDDLE TRIASSIC MAGNETOSTRATIGRAPHY AND BIOSTRATIGRAPHY FROM THE DOLOMITES AND GREECE

Magnetostratigrapic and biostratigraphic data across the Anisian/Ladin ian (Middle Triassic) boundary were obtained from the Frotschbach/Sece da section from the Dolomites region of northern Italy, and the Vlicho s section from the Greek island of Hydra, where the Aghia Triada publi shed section was also resampled. The Frotschbach/Seceda section includ es two radiometrically dated (U-Pb) tuff levels and covers two of the three chief candidates for the position of the base of the Ladinian, n amely at the base of the Secedensis Zone or the subsequent Curionii Zo ne. The Aghia Triada section yields biochronological evidence for the base of the Secedensis Zone, whose significance is, however, criticall y discussed in the light of the magnetostratigraphic correlation with Frotschbach/Seceda. The Vlichos section can be correlated with Aghia T riada and Fratschbach/Seceda by means of magnetic polarity stratigraph y and sparse fossil occurrences. The satisfactory correlation of the m agnetozones allows us to construct a composite geomagnetic polarity se quence tied to Tethyan ammonoid and conodont biostratigraphy for about a 2.4 Myr interval across the Anisian/Ladinian boundary.