Belt bending driven by lateral bending of subducting lithospheric slab: geophysical evidences from the northern Apennines (Italy)

Late Miocene remagnetization within the internal sector of the Northern Apennines, Italy

“…Paleomagnetic investigations, combined with other geophysical analytical methods, have provided useful information on the kinematics of orogenic regions such as the distribution and amount of vertical-axis rotation of thrust sheets (e.g., Channell, 1992;Channell et al, 1992), oroclinal bending (e.g., Lucente and Speranza, 2001;Schill et al, 2002), horizontal-axis tilting of intrusive rocks (e.g., Varga et al, 1999) and latitudinal displacements and rotations of allochthonous terranes (e.g., Beck, 1980;Irving et al, 1985;Hagstrum and Murchey, 1993). Partial to complete remagnetization of rocks, however, is common in orogenic settings, and can often obliterate primary components (i.e., remanent magnetizations acquired during or soon after deposition for sedimentary rocks).…”

“…In contrast, directions of primary magnetization for Eocene to Pliocene Epiligurian (syn-and post-orogenic) Units within the easternmost (external) sector of the Northern Apennines show significant and variable counterclockwise (CCW) rotations that were probably the consequence of eastward migration of the compressional front (Muttoni et al, 1998). Moreover, oroclinal bending of the Northern Apennines might have deep roots: Seismic imaging beneath the orogenic chain reveals the apparent shape of a lithospheric slab subducted below the belt (Lucente and Speranza, 2001). At depth (>100 km), the slab shows evidence of lateral bending, which mimics the curved shape of the Northern Apennines.…”

“…At depth (>100 km), the slab shows evidence of lateral bending, which mimics the curved shape of the Northern Apennines. Thus, the oroclinal bending of the Northern Apennines is possibly due to lateral bending of the subducted Adriatic Plate (Lucente and Speranza, 2001).…”

The Ligurian Units of Western Tuscany (Northern Apennines): insight on the influence of pre-existing weakness zones during ocean closure

“…The attribution of the ophiolites of Western Tuscany to the EL is due to their geometrical and tectonic setting rather [60][61][62][63], the structures developed during the same deformation phase do not have the same orientation in the internal (western) and external (eastern) sector of the Northern Apennines (see text for details). Data from the Viano area are from [50].…”

“…Since Messinian all the orientations of the above described structures have been modified by the counterclockwise rotations occurred in the eastern/external sector of the Northern Apennines, as visible also from the clear convex shape [60,61]. During the event that brought to the increasing curvature, all the structures jointly rotated counterclockwise.…”