The Antola Unit is a Ligurian Unit occurring at the top of the nappe pile of the Northern Apennines (Italy). The performed structural analysis indicates that the Antola Unit has been involved in a complex polyphase deformation history characterized however by the lacking of any metamorphic overprint. The successive deformation phases belong to both the Alpine and Apenninic orogenic cycles. Therefore the Antola Unit can be regarded as a good example of polyorogenic tectonic unit deformed at very shallow structural level. The older part of the structural evolution can be referred to the “Mesoalpine” tectonic stage and is characterized by two deformation phases (D1 and D2) showing opposite vergences. The D1 and D2 structures were sealed by the middle Eocene-Miocene deposits of the Tertiary Piedmont Basin. The younger part of the deformation history can be instead referred to the Northern Apennine tectonics, and consists of two phases (D3 and D4) both involving the Tertiary Piedmont Basin succession. The structural data indicate that the D1 deformations developed in mostly unlithified rocks, and that these structures can be related to the westward emplacement of the Antola Unit in the Alpine orogenic wedge. The D2 phase is characterized by sub-isoclinal folds and low-angle extensional faults, and is referable to a gravity-driven deformation. Both the D3 and D4 phases, characterized by folds and thrusts, are referable to the compressive regime related to the development of the Northern Apennine. Polyorogenic tectonics; Antola Unit; Northern Apennine; Soft sediment and gravity driven deformations; Shallow structural levels
Polyorogenic deformation history recognized at very shallow structural levels: the case of the Antola Unit (Northern Apennine, Italy)
PANDOLFI, LUCA
2006-01-01
Abstract
The Antola Unit is a Ligurian Unit occurring at the top of the nappe pile of the Northern Apennines (Italy). The performed structural analysis indicates that the Antola Unit has been involved in a complex polyphase deformation history characterized however by the lacking of any metamorphic overprint. The successive deformation phases belong to both the Alpine and Apenninic orogenic cycles. Therefore the Antola Unit can be regarded as a good example of polyorogenic tectonic unit deformed at very shallow structural level. The older part of the structural evolution can be referred to the “Mesoalpine” tectonic stage and is characterized by two deformation phases (D1 and D2) showing opposite vergences. The D1 and D2 structures were sealed by the middle Eocene-Miocene deposits of the Tertiary Piedmont Basin. The younger part of the deformation history can be instead referred to the Northern Apennine tectonics, and consists of two phases (D3 and D4) both involving the Tertiary Piedmont Basin succession. The structural data indicate that the D1 deformations developed in mostly unlithified rocks, and that these structures can be related to the westward emplacement of the Antola Unit in the Alpine orogenic wedge. The D2 phase is characterized by sub-isoclinal folds and low-angle extensional faults, and is referable to a gravity-driven deformation. Both the D3 and D4 phases, characterized by folds and thrusts, are referable to the compressive regime related to the development of the Northern Apennine. Polyorogenic tectonics; Antola Unit; Northern Apennine; Soft sediment and gravity driven deformations; Shallow structural levelsI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
