Abstract In the Zagros Fold–Thrust Belt (ZFTB) of Iran it is firmly established that the basement is involved in the deformation. The strongest line of evidence for this assertion comes from the relatively intense mid-crustal seismic activity. On one hand, the main basement structures such as the Main Zagros Fault (MZT) and High Zagros Fault (HZF) reach the surface and are therefore well identified. On the other hand, basement faults south of the HZF are hidden by sedimentary cover and their location is uncertain. In the Eastern Zagros, basement control on surface structures occurred only at a late stage of the tectonic evolution. In other words, the current thick-skinned style of Zagros deformation succeeded a more general thin-skinned phase of orogeny. This chronology is particularly well illustrated by spectacular interference patterns, in which early detachment folds are cut by late oblique basement faults. We present a combined morphological and structural analysis of such structures, and we explore their impact on the river network. We confirm that basement involvement occurred at a late stage of deformation and we show that thick-skinned deformation progressively propagated towards the foreland. An overview of basement steps throughout the Zagros based on published cross-sections allows us to conclude that although basement deformation is concentrated on two major faults in the Central Zagros, it is distributed on several segmented faults in the Fars Arc. This segmentation increases to the SE towards the so-called Oman line and the transition to the Makran accretionary prism.

Abstract Reservoir appraisal is commonly a difficult task in fold and thrust belts. Thrust-related folding leads to the development of meso- to microscopic brittle structures that can significantly alter the porosity and permeability properties of reservoir rocks, thus influencing fluid migration and accumulation. The aim of this chapter is to describe at different scales the deformation associated to the development of the Chaudrons thrust-related anticline (Corbières, France) and to discuss its influence on reservoir quality. Pervasive solution cleavage sets at high angle to bedding (ATB) were found and measured along the fold. In addition, collected core samples were used to measure the rock physical properties (anisotropy of magnetic susceptibility and anisotropy of the P-wave velocity). The distribution of deformation in the anticline was used to identify three different deformational panels: crest, rounded forelimb, and constantly steeping forelimb. The crest is characterized by the lowest cleavage intensity. Nonpenetrative solution cleavages and the magnetic foliation are orthogonal to bedding. In the rounded forelimb, bedding dip progressively rotates from 0 to 60°. Cleavage intensity progressively increases, and cleavage and magnetic foliation ATBs progressively increase from 80 to 120° and then remain constant in the steep forelimb. The timing of the development of mesoscale structures, as well as changes of physical properties occurring before and during folding, is also discussed.