Asymmetric fold development in the Variscan nappes of Central Sardinia (Italy).

The Meana Sardo Unit (MSU) shows trains of asymmetric SW-verging folds, developed during the thickening stage and nappe development of the Variscan belt in Sardinia. The geometry of the folds and the finite strain analysis results in the hinge of a kilometric fold give information on the folding mechanisms. The strain and the geometry of the fold have been compared to a 2-D geometrical model of development of homogenous non-coaxial deformation. The results show that initial layer parallel shortening and fold amplification followed by simple shearing or by coeval simple and pure shearing, linked to the overthrust of the Low Grade Metamorphic Complex of Barbagia onto MSU, are able to explain the observed fold geometries and finite strain values.