Basement fault influence on fold geometries within the Fars Zone, Zagros Orogen, Iran

Fold geometry can be a useful indicator of folding mechanism, especially in the frontal regions of young orogens where a major component of the shortening is accommodated by folding. In turn, fold mechanism is related to the characteristics of the basal detachment and the presence of basement faults. This contribution presents a spatial analysis of fold types across the Fars Zone of the Zagros Simply Folded Belt, characterizing variations in the geometry and kinematics of folding. We use surface geometrical parameters to separate folds into symmetric and asymmetric detachment folds, fault-propagation folds, and fault-bend folds. The parameters used are hinge length, aspect ratio and an index known as fold symmetry index. Fault bend and detachment folds are two endmembers of these fold types, which can be represented on a ternary diagram. Azimuth analysis of anticline axes in the Fars Folded domain is used to define three specified sub-domains, bounded by NE-SW oriented basement faults. We attribute these domain variations to changes in the characteristics of the detachment, and the location and persistence of the basement faults, suggesting that NE-SW oriented basement faults are important in this part of the Central Tethyan Orogen as well as in N Iraq. Finally, we demonstrate a correlation between basement fault location, fold type, and hydrocarbon pool location.

کلیدواژه ها:

Zagros ، Fars Zone ، fault-bend fold ، fault–propagation fold ، detachment fold ، basement faults