The Mountain Frontal Flexure shows a single step along the front of the Pusht-e Kuh Arc with about 3 km of structural relief. This front has been interpreted as being formed by a basement monocline above a blind crustal-scale and low-angle thrust with a ramp–flat geometry (the ramp dips 12–15° towards the inner part of the orogen and cuts the entire crust). The Anaran anticline on top of the Mountain Frontal Flexure shows an irregular geometry in map view and consists of four segments with diverse directions of which the SE Anaran, the Central Anaran and the NW Dome are culminations. The North–South Anaran segment may form a linking zone developed during the rise and amplification of single culminations, the NW Dome and the Central Anaran, above the Mountain Frontal Flexure. The asymmetric Anaran anticline is characterized by the existence of multiple normal faults, some of them with significant dip-slip displacements of up to 1000 m. These faults limit grabens located along the crests of the anticline segments. Cross-cutting relationships show that the normal faults along the Central Anaran are older than along the North–South Anaran, reinforcing the temporal constraints on the later growth of this segment of the anticline. The geometry of the Anaran anticline is asymmetric with the subvertical forelimb very little exposed. This forelimb is cut above and below by a thrust system that seems to develop along the fold hinges. The lower thrust, with a ramp–flat geometry, carries the entire anticline towards the foreland on top of slightly deformed rocks in the footwall. The thrust flattens in the Gachsaran evaporitic level forming a typical triangular zone filled with evaporites, which produce a strong fold disharmony between the overburden (Passive Group) and the underlying rocks (Competent Group). The growth of the Anaran anticline lasted for about 6 Ma and was the consequence of detachment folding that was subsequently thrust, rotated and uplifted above the Mountain Frontal Flexure with coeval reactivation of earlier crestal layer-parallel extension normal faults to accommodate the large increase of structural relief between the foreland and the tectonic arc. Three main results from analogue modelling have been combined with field data to resolve the geometry of the Anaran anticline as well as its evolution: (1) a thickening of intermediate evaporites (Gachsaran Formation) is produced above the flat segment of the thrust carrying the anticline on top of foreland strata; (2) growth strata deposited in the adjacent syncline modify the geometry of the anticline by increasing the dip and the length of its forelimb; (3) coeval erosion to anticline growth, as well as thick growth strata deposition, increases fold amplification rather than foreland propagation of deformation. The proposed fold model may be applied to other anticlines on top of this major basement-related thrust, such as the Siah Kuh and Khaviz anticlines in the Pusht-e Kuh Arc and Dezful Embayment domains.

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The integration of biostratigraphy, strontium isotope stratigraphy, and magnetostratigraphy allowed for the precise dating of the >3.0-km-thick marine to non-marine foreland sedimentary succession within the Dowlatabad growth syncline along the Frontal Fars arc in the Zagros Fold Belt that extends from eastern Turkey to southern Iran. This area was the missing link to complete the dating of syntectonic deposits in the Fars arc and quantify the migration of sedimentary belts as well as the propagation of folding across the entire Mesopotamian foreland basin. Both are essential for defining the interplay of basin evolution and sequence of folding. Deposition of the foreland marine marls in the Mishan Formation started at ca. 11.5 Ma. The transition to a non-marine basin infill occurred at 4.9 Ma by the progradation of thick fluvial deposits of the Aghajari Formation with a fast accumulation rate of 63 cm/k.y. The beginning of growth strata deposition and thus the onset of folding in the Dowlatabad syncline is dated at 4.65 Ma. The first appearance of carbonate conglomerates sourced from the Guri limestone at 2.8 Ma marked the progressive dismantling of the nearby growing anticlines. The tectonic deformation in the front of the Fars arc was active for at least 2.85 m.y. and ceased at 1.8 Ma before the deposition of the discordant and slightly folded Bakhtyari conglomerates characterized by a clast composition derived from the Zagros hinterland. The compilation of magnetostratigraphic ages reveals that both the migration of the Aghajari-Bakhtyari sedimentary belts and the propagation of the folding front was in-sequence toward the foreland at a rate close to 20 mm/yr in the Fars arc and 15 mm/yr in the Lurestan arc, in the last 20 m.y. These high rates of folding propagation are about one order of magnitude larger than age equivalent shortening rates (∼4 mm/yr in Fars arc and ∼2 mm/yr in Lurestan arc) and thus imply an efficient detachment level at the base of the deformed Arabian sedimentary cover. Numerical experiments on both the cover and basement sequences are designed to test the influence of inherited basement structures on the deformation propagation within the cover sequence, providing clues on the partly coeval in-sequence deformation of the Zagros Simply Folded Belt and the local out-of-sequence Mountain Frontal Fault system as illustrated by regional and local geology.