REGIONAL SIGNIFICANCE OF KILOMETRIC-SCALE NORTHEAST VERGENT RECUMBENTFOLDS ASSOCIATED WITH EAST TO SOUTH-EAST DIRECTED SHEAR ON THE SOUTHERN BORDER OF THE CENTRAL IBERIAN ZONE (HORNACHOS-OLIVA REGION, VARISCAN BELT, IBERIAN PENINSULA)

On the southern border of the Central Iberian Zone there are two secto rs with different styles of deformation. To the south-west, in the Hor nachos sector, large-scale recumbent folds associated with ductile she aring can be seen. This shearing is characterized by a direction of mo vement parallel to the fold axes and can be correlated for 150 km alon g strike. The K-values of the strain ellipsoid range from 0.8 to 2.0. Stretching in the X direction, parallel to the recumbent fold axes, is more than 100%. To the north-east, in the Oliva sector, first-phase f olds are upright and the strain intensity is lower than in the Hornach os sector. Metamorphic, geometric and kinematic considerations lead us to conclude that the shearing in the Hornachos sector is better expla ined as conjugate to a main shear zone along which the southern border of the Central Iberian Zone is moved onto the Ossa - Morena Zone. Thi s main thrust is at present obliterated by a left-lateral extensional shear zone that affects a high pressure exotic unit located between th e Central Iberian and the Ossa - Morena Zones. This high pressure unit constitutes a suture of the Variscan belt in the Iberian Peninsula.