FROM FINITE STRAIN DATA TO STRAIN HISTORY - A MODEL FOR A SECTOR OF THE LIGURIAN ALPS, ITALY

Bulk strain measurements were made in a Penninic sector of the Liguria n Alps. Previous detailed mapping, supported by petrographic and struc tural analyses, had shown that the oldest (Dl), complex Alpine episode produced km-scale sheath-like folds, involving basement and cover, be fore the activation of a set of thrusts leading to nappe superposition . By combining all data, a kinematic model has been developed into whi ch the subsequent deformation steps have been set. In particular, tota l strain constraints led to the :es suggestion of a combination of rel atively low values of pure sheer and simple shear for the genesis of t he sheath-like folds. A computer simulation has proved that this sugge stion is tenable. The model was then used to Factor the bulk strain in to increments-starting from the diagenetic compaction of the cover, up to the last 'late D-1' phase-necessary to obtain results that compare well with the finite strain data. Some theories were also deduced on the possible attitude of the pre-Alpine schistosity in the basement ro cks at the beginning of Late Variscan times. (C) 1998 Elsevier Science Ltd. Ail rights reserved.