Magnetostratigraphy of the Salto del Cieco section (Northern Apennines, Italy) from the Pliensbachian to Jurassic/Cretaceous boundary
Satolli, Sara; Turtù, Antonio; Donatelli, Ugo
Newsletters on Stratigraphy Volume 48 Number 2 (2015), p. 153 - 177
published: Apr 1, 2015
ArtNo. ESP026004802001, Price: 29.00 €
In this paper, we report on a new magnetic stratigraphy from the Jurassic Salto del Cieco section (Italy), which is barely known in the literature and has not been previously investigated for magnetostrati graphy. This approximately 130-m-thick section is the most temporally extended section that has ever been studied for the Jurassic magnetostratigraphy in the Tethyan realm and is the third section spanning the Jurassic/Cretaceous boundary in the Apennines. Our main goals are to document magnetic polarities and to investigate the Jurassic/Cretaceous boundary. A total of 435 cylindrical samples have been collected with a sampling resolution of 30 cm as low sedimentation rate and high frequency polarity reversals were expected. After thermal cleaning, 89% of the samples show a primary component of magnetization that is isolated in temperature ranges depending upon lithologies. The succession of normal- and reverse-polarity magnetozones matches the Geomagnetic Polarity Time Scale in the M19–M25n, while it was inferred in the Toarcian-Aalenian intervals due to the presence of a slump. A total absence of correlation characterizes 17 Myr between the Early Kimmeridgian and Early Bajocian. Instead, the Carixian interval only correlates with other condensed successions known from the literature. The Jurassic/Cretaceous boundary is constrained with the Calpionella alpina explosion and located at 60% of the M19n.2n. We found two possible polarity subchrons that have not been previously referred in the literature: one in the middle of M20r and one at the top of M21n. Finally, the comparison with the GPTS yields to a detailed estimate of sedimentation rates and enables to evaluate the diachronicity of Maiolica onset between different land sections.