The principal objective of this paper is to summarize the large data set gathered in the last few years on the Early-Middle Jurassic diapiric evolution in the well-exposed Central High Atlas in Morocco. Field data on both structural geology and sedimentology of halokinetic sequences, significant remote sensing mapping using good quality satellite images, thermal modeling and subsidence analysis, balanced and restored cross sections, and analog modeling allowed us to construct an integrated tectono-sedimentary interpretation of a salt-related rift basin. Three characteristic regions are summarized here to show the tectonic and diapiric evolution of the study region: Tazoult, Azourki, and Imilchil. Salt ridges (Tazoult, Jbel Azourki, and Tassent salt walls) above blind basement faults developed a polygonal array bounding thick synclines (minibasins) with different orientations. The Imilchil minibasins show diachronous age of their infill, which is a typical characteristic of diapiric regions. The Tazoult and Jbel Azourki salt walls developed an allochthonous salt body starting during the Late Pliensbachian-Aalenian time. Although only Lower and Middle Jurassic halokinetic sedimentary sequences are preserved in most of the Central High Atlas, younger synclines (minibasins) along the northern boundary of the Atlas (Demnate region) show development of Late Jurassic and Early Cretaceous minibasins. At the larger scale, the diachronous evolution of the extension and diapirism along the Atlas Basin suggests that diapirism and salt withdrawal play an important role during the development of the High Atlas in Morocco, Saharan Atlas in Algeria, and Tunisian Atlas in a similar way as it is fabulously imaged across the onshore and offshore Atlantic Moroccan basins.

The Zagros orogeny took place during a protracted period of time, and its complete evolution is difficult to ascertain due to the multiple stages starting with oceanic obduction related processes and culminating with arc-continent and continent-continent collision. We document the geometries and ages of the Zagros foreland basin with a large number of dated samples along 16 stratigraphic successions, and hinterland denudation history with AFT ages on both bedrock and detrital samples. We integrate these data together with a crustal cross-section across the Lurestan region to constrain the total shortening amounts using extrapolations of rates of shortening as well as crustal reconstructions based on area balance from the Late Cretaceous times to present. The orogenic history of the Zagros is much longer and shortening probably much higher. The crustal area balance assuming shallow marine deposition at the onset of flexural basin formation could form with crustal thicknesses of about 27 km in the NW Arabian margin. Comparing to present day thickness of the crust underneath the internal Zagros Mountain presupposes a crustal shortening of about 150 km. This amount fits well will independent extrapolations of rates of shortening calculated in the Late Cretaceous-Eocene foreland basin in Lurestan.

Abstract The Barremian–Aptian upper Khami Group and Albian–Campanian Bangestan Group have been studied at outcrop in Lurestan, SW Iran. The upper Khami Group comprises a thin deltaic wedge (Gadvan Fm) transgressively overlain by shelfal carbonates (Dariyan Fm). The Dariyan Fm can be divided into lower and upper units separated by a major intra-Aptian fracture-controlled karst. The top of the Daryian Fm is capped by the Arabian plate-wide Aptian–Albian unconformity. The overlying Bangestan Group includes the Kazhdumi, Sarvak, Surgah and Ilam formations. The Kazhdumi Fm represents a mixed carbonate-clastic intrashelf basin succession, and passes laterally (towards the NE) into a low-angle Orbitolina-dominated muddy carbonate ramp/shoal (Mauddud Mbr). The Mauddud Mbr is capped by an angular unconformity and karst of latest Albian–earliest Cenomanian age. The overlying Sarvak Fm comprises both low-angle ramp and steeper dipping (5–10°) carbonate shelf/platform systems. Three regionally extensive karst surfaces are developed in the latest Cenomanian–Turonian interval of the Sarvak Fm, and are interpreted to be related to flexure of the Arabian plate margin due to the initiation of intra-oceanic deformation. The Surgah and Ilam Fm represent clastic and muddy carbonate ramp depositional systems respectively. Both The Khami and Bangestan groups have been affected by spectacularly exposed fracture-controlled dolomitization. Dolomite bodies are 100 m to several km in width, have plume-like geometry, with both fracture (fault/joint) and gradational diagenetic contacts with undolomitized country rock. Sheets of dolomite extend away from dolomite bodies along steeply dipping fault/joint zones, and as strata-bound bodies preferentially following specific depositional/diagenetic facies or stratal surfaces. There is a close link between primary depositional architecture/facies and secondary dolomitization. Vertical barriers to dolomitization are low permeability mudstones, below which dolomitizing fluids moved laterally. Where these barriers are cut by faults and fracture corridors, dolomitization can be observed to have advanced upwards, indicating that faults and joints were fluid migration conduits. Comparisons to Jurassic–Cenozoic dolomites elsewhere in Iran, Palaeozoic dolomites of North America and Neogene dolomites of the Gulf of Suez indicate striking textural, paragenetic and outcrop-scale similarities. These data imply a common fracture-controlled dolomitization process is applicable regardless of tectonic setting (compressional, transtensional and extensional).

Late burial dolomite of hydrothermal origin replaces Cretaceous carbonate shelf sediments of Albian to Turonian age (Sarvak Formation) in the NW closure of the Anaran Anticline, Zagros Mountains, Simply Folded Belt, Iran. The outcrops, spectacularly exposed along deep river canyons, offer the possibility for a 3D reconstruction of the geobodies, combining both field data (sedimentary logs, cross sections and samples for diagenetic and petrophysical studies) and LIDAR derived photorealistic model of the most representative dolomite bodies. The aim is to quantify the impact of hydrothermal dolomitisation on the reservoir quality. The hydrothermal origin of the dolomitising fluids will be discussed integrating different geochemical data (fluid inclusions, stable and radiogenic isotopes, minor and trace elements). Dolomite replaces carbonate rocks characterised by different facies, showing different geometries: 1) massive plus stratabound (Lower Sarvak); 2) pipes (Upper Sarvak). Dolomite distribution decreases vertically with at least three discrete breaks corresponding to two main aquitard intervals: 1) Ahmadi Shales, separating massive dolomite form from plume-like bodies; 2) Turonian Mudstones; 3) Surgah Fm., above, which no dolomite has been observed. Fractures and faults play a major role in controlling the distribution of the dolomite bodies, in particular the ENE-WSW and WNW-ESE conjugate fault systems, which are often associated with dolomitic halos. A geological conceptual model is built taking into account different fracture and matrix porosity models for limestone and dolomite.

Abstract 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.

Spectacular outcrops of dolomite of hydrothermal origin are described from the Anaran Anticline, in the Simply Folded Belt of the Zagros Mountains, Ilam province, SW Iran. Dolomite replaces Cretaceous carbonates of the Upper and Lower Sarvak formation (Albian to Turonian). The typical paragenetic association includes a matrix replacing dolomite phase followed by a void-filling saddle dolomite. Both are interpreted to be of hydrothermal origin. The contact between dolomite and precursor lithology is typically sharp on the scale of the outcrop, with contacts being both stratigraphically, structurally and diagenetically (reaction front) controlled. Dolomite bodies in both the Lower Sarvak and Upper Sarvak have been described and sampled systematically in order to constrain lateral and vertical textural and poro-perm variations. Systematic collection of structural data has also been undertaken to evaluate the possible control of fractures (joints faults) on fluid flow, and to place constraint on the timing of the dolomitisation event within the geological evolution of the Zagros Mountain belt. Comparison between fracture pattern inside and outside the dolomite bodies is taken into account to evaluate a possible impact on reservoir modelling.

We report here the presence of fold growth strata in lower Paleogene beds across Lurestan. Those are associated with a compressional phase much older than the typical Zagros folding which affected the eastern side of the Simple folded zone 12 Ma ago (Emami, 2008) and spread to the mountain front, on the western edge of the Simple Folded Zone around 8 Ma ago (Homke et al., 2006) with the deposition of Agha Jari-Bakhtyari and Quaternary sediments. Early folding accounts there for up to half of the total shortening measured in cross section and corresponds to a shortening of around 10%.