The effect of the Gachsaran mobile formation on folding style and tectonic evolution of the Rag-e- Sefid anticline in the southern Dezful Embayment

Plastic behavior and significant thickness of the Gachsaran incompetence formation on top of middle carbonate units in the sedimentary sequence of the southern Dezful Embayment led to the emergence of different styles of folding above and below of this formation. So that the structures in the upper and lower parts of this formation are completely separated and do not match each other. In the upper anticlines, above the Gachsaran horizon, the calculation of the limbs angle, the main thrust slope and the percentage of forelimb thickening indicate the fault detachment fold style. This style marks the geometry of fold at the early stage of the development of this anticline. Also the seismic profiles below the Gachsaran horizon also show the fault-propagation folding style. In the south Dezful Embayment, folding in the Gachsaran Formation occurs with shorter wavelengths in the form of disharmonic folds. This folding acts as the decoupling surface for the lower folds so that the synclines in this moving horizon directly cover the lower anticlines. The rounded folds in the carbonates in lower anticline are the imposed folds associated with steepened up reverse faults, detached on the basal decollement level and ultimately faulted by progressive deformation. The interpretation of seismic sections in the southern Dezful Embayment shows that lateral migration occurs in the salt units of the GS2 and GS4, and the upper and lower units of the Gachsaran Formation do not play a role in salt migration. Lateral migration in Miocene salts of the Gachsaran Formation is accomplished by the growth of sub-anticline during folding and loading of upper formation at the upper Gachsaran Formation.