Magnetic anisotropy of Plio–Pleistocene sediments from the Adriatic margin of the northern Apennines (Italy): implications for the time–space evolution of the stress field

• Published in: Tectonophysics 1999-09, Vol.311 (1), p.139-153
• Main Authors: Sagnotti, Leonardo, Winkler, Aldo, Montone, Paola, Di Bella, Letizia, Florindo, Fabio, Mariucci, Maria Teresa, Marra, Fabrizio, Alfonsi, Laura, Frepoli, Alberto
• Format: Article
• Language: English
• Subjects: Apennines; Italy; magnetic susceptibility anisotropy; Pleistocene; Pliocene; stress field
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/S0040-1951(99)00159-6

The anisotropy of magnetic susceptibility (AMS) of the marine fine-grained Plio–Pleistocene sediments that crop out at the eastern (Adriatic) front of the central–northern Apennines (Italy) indicates a prevalent sedimentary-compactional magnetic fabric with variable overprint of the tectonic strain. The degree of anisotropy and the geometry of the AMS ellipsoids suggest a subdivision of the studied sediments in two distinct ages: Early–middle Pliocene and Late Pliocene–Early Pleistocene. The Early–middle Pliocene sediments show a weak but well defined magnetic lineation parallel to the main fold and thrust axes throughout the region, analogously to the Messinian sediments located in a more internal (western) position of the Apenninic chain. Since the Late Pliocene, the AMS data are not regionally coherent and indicate a reduced and locally variable tectonic influence on the magnetic fabrics. The AMS data have been integrated with the available geophysical information of the present-day stress in the region, with the aim to reconstruct the time–spatial evolution of the stress field in the Adriatic margin of the central-northern Apennines, during the past 5 Ma. The present-day stress field was evaluated using borehole breakout in deep wells (about 50 wells), focal mechanisms of crustal earthquakes (2.5< M d