Hercynian transpressional tectonics at the southern margin of the Central Iberian Zone, west Spain

Abstract

The boundary between the Central Iberian and Ossa-Morena zones, in south-central Spain, occurs within the Badajoz–Cordoba shear zone. The spatial and temporal relationships of structures across the La Codosera syncline, located within the Central Iberian zone just to the north of the shear zone, demonstrate a progressive increase in strike-slip shear towards the Badajoz shear zone. Within the region of the La Codosera syncline, Precambrian to Cambrian rocks were subject to pre-Ordovician tilting and open folding, accompanied by local faulting and veining, but no cleavage. These, together with overlying Palaeozoic rocks were subsequently affected by Hercynian ductile deformation, which produced steeply inclined folds, cleavage and faulting. Intense left-lateral shearing on the southern limb of the La Codosera syncline produced augen, shear bands, sub-horizontal stretching lineation, boudinage, variably oriented folds and steep faults, whereas the northern limb of the syncline is characterized by folding and thrusting in a transpressional regime, with limited net northward transport. Late Hercynian faulting produced N–S and NE–SW faults which overprint the early structures and granites. These rotate to a NW-SE trend and increase in right-lateral displacement as a result of domino or bookshelf faulting which can be attributed to continued left-lateral motion along the Badajoz shear zone.