We propose that a very oblique or transpressional tectonic regime was dominant during the early (pre‐collisional) orogenic evolution of the Northern Apennines (Late Cretaceous to Early Oligocene). This hypothesis resolves many inconsistencies in the previous reconstructions of this orogenic belt, which were based on a classic model of orthogonal convergence between the European and Adriatic plates. The crucial lines of evidence that point to a major role of oblique tectonics in the structuring of the Northern Apennines are: (1) the plate tectonics framework, that indicates left‐lateral oblique convergence along the Europe/Adria plate margin; (2) the lack of a magmatic arc during the entire pre‐collisional convergent history of the chain (a time span >45 m.y., from Late Cretaceous to Early Oligocene); (3) the long (20 m.y.) residence time of turbidite sequences in the trench (the “dormant” trench); (4) the multiple source areas of turbidites from both sides of the basin, and the associated coarse gravity deposits; (5) the opposite vergence of deformations in some oceanic units; (6) the unmatching stratigraphic features, distinct deformation and metamorphic histories between adjacent overthrust oceanic units (Ligurids), here interpreted as tectonostratigraphic terranes. Specific aspects of Apennine stratigraphy and tectonics and the geometry and structure of the contacts between the Ligurid Units suggest the existence of a number of terranes juxtaposed by transpression during the early (Late Cretaceous to Early Oligocene) orogenic evolution of the chain.
Hidden Terranes in the northern Apennines, Italy: a record of Late Cretaceous-Oligocene transpressional tectonics
MARRONI, MICHELE;
1998-01-01
Abstract
We propose that a very oblique or transpressional tectonic regime was dominant during the early (pre‐collisional) orogenic evolution of the Northern Apennines (Late Cretaceous to Early Oligocene). This hypothesis resolves many inconsistencies in the previous reconstructions of this orogenic belt, which were based on a classic model of orthogonal convergence between the European and Adriatic plates. The crucial lines of evidence that point to a major role of oblique tectonics in the structuring of the Northern Apennines are: (1) the plate tectonics framework, that indicates left‐lateral oblique convergence along the Europe/Adria plate margin; (2) the lack of a magmatic arc during the entire pre‐collisional convergent history of the chain (a time span >45 m.y., from Late Cretaceous to Early Oligocene); (3) the long (20 m.y.) residence time of turbidite sequences in the trench (the “dormant” trench); (4) the multiple source areas of turbidites from both sides of the basin, and the associated coarse gravity deposits; (5) the opposite vergence of deformations in some oceanic units; (6) the unmatching stratigraphic features, distinct deformation and metamorphic histories between adjacent overthrust oceanic units (Ligurids), here interpreted as tectonostratigraphic terranes. Specific aspects of Apennine stratigraphy and tectonics and the geometry and structure of the contacts between the Ligurid Units suggest the existence of a number of terranes juxtaposed by transpression during the early (Late Cretaceous to Early Oligocene) orogenic evolution of the chain.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
