Contribution to the magnetostratigraphy of the Carnian: New magneto-biostratigraphic constraints from Pignola-2 and Dibona marine sections, Italy

Abstract

In an effort to improve the calibration of the Late Triassic time scale, two stratigraphic successions in Italy were investigated for magnetostratigraphy: the Pignola-2 (Southern Apennines) and the Dibona (Dolomites) sections. These sections reveal a sequence of biostratigraphically calibrated (conodonts and palynomorphs) magnetic polarity zones encompassing the Julian/Tuvalian boundary (Carnian). A total of 63 samples have been collected from the Pignola-2 section that helped defining 3 magnetozones. These data are constrained by a published radiometric U/Pb age of 230.91 ± 0.33 Ma from the Aglianico ash-bed (Furin et al. 2006). From the Dibona section, 81 samples have been collected, revealing 2 magnetozones in the Heiligkreuz Fm. (lower part of the succession) and 2 magnetozones in the Travenanzes Fm. (upper part). The Dibona section provided only few high-quality paleomagnetic data in spite of the sampling effort, so we considered only the Pignola-2 section as suitable for the correlation with other Carnian sections from the literature, in order to define the magnetostratigraphy around the Julian/Tuvalian boundary in the Tethys realm. The correlation between the Pignola-2 and the Newark Astrochronological Polarity Time Scale (APTS) provides independent insights on the age of the base of the Newark basin APTS. We found that the U-Pb zircon-dated Pignola-2 level, magnetostratigraphically projected on the Newark APTS, falls within Chrons E5-E4 at around 231 Ma, in agreement with the (extrapolated) astrochronological ages of the Newark APTS.