Early Cretaceous magnetostratigraphy of the Salto del Cieco section (Northern Apennines, Italy)

This study documents the Early Cretaceous magnetic stratigraphy from the Salto del Cieco section (Italy), from the Jurassic/Cretaceous boundary to the early Aptian. Our main goals are the correlation of the section to the M-sequence of oceanic anomalies, the detection of eventual subchrons and the investigation of a weak intensity zone documented in other land sections mainly during the Valanginian. A primary component of magnetization was successfully isolated in 70% of the 281 samples collected from Maiolica and Marne a Fucoidi Formations, providing a detailed record of polarity chrons from M19 to M15 and from M10 to M0r, while the weak intensity zone is detected in the M14n to M11 interval. This interval is characterized by lower NRM and susceptibility values and a lower content of magnetite, which is the main magnetic carrier in Maiolica samples. A comparison with other sections from the literature shows that the weak intensity zone peaks in correspondence to the Late Valanginian positive C-13 excursion event. However, its association to the isotopic excursions is not straightforward. The Maiolica/Marne a Fucoidi boundary and the Faraoni level within the Maiolica Fm. have been constrained in chrons M0r and M5n, respectively. The sedimentation rate is higher in the lower part of the section and allows recognizing both the M19n-1 subchron, here documented for the seventh time in a land section, and a possible geomagnetic excursion at 70% (from the bottom) of M17r. © 2016 Gebrüder Borntraeger, Stuttgart, Germany.