Structural styles in the Zagros Simple Folded Zone, Iran

Arabia-Eurasia convergence is achieved in the NW Zagros by a combination of shortening on NW-SE-trending folds and thrusts, mainly in the Simple Folded Zone, and by right-lateral strike-slip on the NW-SE-trending Main Recent Fault. A balanced and restored cross-section across this part of the range indicates c. 49 km of shortening. This probably occurred since c. 5 Ma, providing an estimate of the long-term shortening rate across the Simple Folded Zone of c. 10 turn a(-1). The geometries of exposed structures suggest both basement thrusts and thin-skinned decollement levels, with major folds possibly nucleated above basement faults. Fold geometries indicate several decollement horizons; shale units are candidates, as well as evaporites in the Neogene, Mesozoic, Lower Palaeozoic and upper Proterozoic successions. The SE part of the Simple Folded Zone deforms by north-south shortening on broadly east-west-trending folds and thrusts. The link between these regions occurs via a set of fault blocks c. 400 km wide in total, each bounded by north-south right-lateral faults. Incremental changes in the strike of some of the folds occur across these right-lateral faults, with more east-west orientations to the east.