A major angular unconformity between the Bakhtyari conglomerates and the underlying Agha Jari Formation has long been interpreted as indicating that orogeny in the Zagros Simply Folded Zone took place in Plio-Pleistocene times. This study uses field evidence of unconformities between older units in conjunction with geological maps and cross sections to argue that the front of the Zagros Simply Folded Zone has propagated in time and space. These unconformities indicate that deformation started as early as end Eocene in the northeast of the Simply Folded Zone and propagated progressively to the southwest, where unconformable contacts are only seen between younger units. As shortening continued, the southwest migration of the deformation front drove the foreland basin in front of it to its present position along the Persian Gulf and Mesopotamia. The climax of orogeny took place at end Pliocene time when the most extensive unconformity in the Zagros Simply Folded Zone developed between the (upper) Bakhtyari Formation and older units. Active seismicity and documented present uplift imply that the Simply Folded Zone is still propagating southwestward.

At Iranian longitude, the Arabian plate is moving northward relative to Eurasia (∼20 mm yr−1 according to GPS). To the east, this relative motion is accommodated by northward subduction under the E‐W Makran emerged accretionary prism. To the west, it is accommodated partly by the Zagros fold‐and‐thrust belt and partly by the Alborz/Kopet Dagh deforming zones further north. This work investigates the NNW striking transition zone that connects Zagros and Makran: the Minab‐Zendan fault system. Satellite images, and structural and geomorphic field observations show a distributed deformation pattern covering a wide domain. Five north to NW trending major faults were identified. They exhibit evidence for late Quaternary reverse right‐lateral slip, and correspond to two distinct fault systems: the western one transferring the Zagros deformation to the Makran prism, and the eastern one northward transferring the deformation to the Alborz/Kopet Dagh. Tectonic study and fault slip vector analyses indicate that two distinct tectonic regimes have occurred successively since the Miocene within a consistent regional NE trending compression: (1) an upper Miocene to Pliocene tectonic regime characterized by partitioned deformation, between reverse faulting and en echelon folding; (2) a NE trending σ1 axis transpressional regime homogeneously affecting the region since upper Pliocene. The change is contemporaneous with major tectonic reorganization regionally recorded. Therefore this study provides evidence for active deformation that is not localized, but distributed across a wide zone. It accommodates the convergence and transfers it from collision to subduction by transpressional tectonics without any partitioning process in the present‐day period.

.[1] This paper focuses on the analysis of geomorphic, structural, and behavioral characteristics along the Doruneh Fault System (DFS), east of longitude 56°45′E. Detailed geomorphic and structural analyses of different scale satellite images and digital topographic data, accompanied with field surveys allowed us to establish a fault segmentation model in which three discrete fault zones have been recognized: (1) the western fault zone (WFZ) characterized by reverse left-lateral mechanism with left-handed step-over geometry, (2) the central fault zone (CFZ) which is pure left-lateral strike-slip and comprises nearly parallel faults, and (3) the eastern fault zone (EFZ) that is a trailing imbricate fan fault-termination characterized by reverse faulting and fault-related folding. Each fault zone shows discrete geometry and kinematics implying that deformation is not uniformly accommodated along the DFS. We propose a new kinematic model to explain how the DFS accommodate the Arabia-Eurasia convergence normal to the overall fault orientation. According to this model, the DFS takes up the northward motion between central Iran-Lut block relative to Eurasia by a complex kinematics varying from pure reverse to pure left-lateral strike-slip faulting. The kinematics of the WFZ and EFZ corresponds to the direction of the NE-trending regional compression. While, the partitioning of slip into strike-slip and reverse component of faulting on parallel faults (strain partitioning) allows the CFZ to remain pure left-lateral strike-slip. Such a model propose a way to explain how large strike-slip faults such as the DFS accommodate tectonic block motions perpendicular to strike of the faults.

The NW trending Zagros fold‐and‐thrust belt is affected by two major dextral faults: (1) the NW trending Main Recent Fault that accommodates partitioning of oblique convergence at the rear of the western Zagros and (2) the north trending Kazerun Fault located in the central Zagros. Combined structural and fault kinematics studies and SPOT images analysis have shown a Pliocene kinematic change accompanied by a fault pattern reorganization, which has led to a modification in the accommodation of oblique convergence. Since the late Pliocene, the distributed transpressional deformation operating at the rear of the belt has become partitioned along the newly formed Main Recent Fault. This fault cuts through early Pliocene nappes and transpressional structures by right‐laterally reactivating high‐angle thrusts. The southeastern termination of the Main Recent Fault connects to the northern termination of Kazerun Fault that consists of three fault zones that end in bent, orogen‐parallel splay thrust faults. The Kazerun Fault, together with a series of north to NNW trending inherited basement strike‐slip faults, define an orogen‐scale fan‐shaped fault pattern pointing toward the Main Recent Fault–Kazerun Fault junction. This structural pattern allows slip from along the Main Recent Fault to become distributed by transfer to the longitudinal thrust faults and folds of the Zagros belt, with the fan‐shaped fault pattern acting as a horse‐tail termination of the Main Recent Fault.