Summary We investigate the role of detachment faults, oblique extension, and structural and thermal inheritance during the rifting of the eastern Gulf of Aden. Our structural approach integrates new seismic interpretations on academic seismic data, previous geological and geophysical data along two representative onshore-offshore sections through the Socotra-Sharbithat segment. We calculate the stretching factors of the different crustal domains (stretched, necking, hyper-extended, exhumed, proto-oceanic and oceanic domains) of the narrow and asymmetric conjugate margins of Socotra and southern Oman.

The fossil rift in the North Pyrenean Zone, which underwent high temperature‐low pressure metamorphism and alkaline magmatism during Early Cretaceous hyperextension, was studied to explore the geothermal regime at the time of rifting. In this work, we combined Raman lab analysis and thermal numerical modelling to shed light on the distribution of geothermal gradients across the inverted hyperextended Mauléon rift basin during Albian and Cenomanian time, its period of active extension. Data were acquired from a set of 155 samples from densely spaced outcrops and boreholes, analyzed using Raman spectroscopy of carbonaceous material. The estimated paleogeothermal gradient is strongly related to the structural position along the Albian‐Cenomanian rift, increasing along a proximal‐distal margin transect from ~34°C/km in the European proximal margin to ~37–47°C/km in the two necking zones and 57–60°C/km in the hyperextended domain. This pattern of the paleogeothermal gradient induced a complex interaction between brittle and ductile deformation during crustal extension. A numerical model reproducing the thermal evolution of the North Pyrenees since 120 Ma suggests that mantle heat flow values may have reached 100 mW/m2 during the rifting event. This model reveals that above the thermal pulse, the temperature gradient varied within a small range of 55 to 62°C/km, as inferred from RSCM peak temperatures. We demonstrate that the style of reactivation during subsequent convergence influenced the thermal structure of the inverted rift system.

Mountain building in the Al-Hajar Mountains (NE Oman) occurred during two major shortening stages, related to the convergence between Africa-Arabia and Eurasia, separated by nearly 30 Ma of tectonic quiescence. Most of the shortening was accommodated during the Late Cretaceous, when northward subduction of the Neo-Tethys Ocean was followed by the ophiolites obduction on top of the former Mesozoic margin. This shortening event lasted until the latest Santonian - early Campanian. Maastrichtian to Eocene carbonates unconformably overlie the eroded nappes and seal the Cretaceous foredeep. These neo-autochthonous post-nappe sedimentary rocks were deformed, along with the underlying Cretaceous tectonic pile, during the second shortening event, itself including two main exhumation stages. In this study we combine remotely sensed structural data, seismic interpretation, field-based structural investigations and apatite (U-Th)/He (AHe) cooling ages to obtain new insights into the Cenozoic deformation stage. Seismic interpretation indicates the occurrence of a late Eocene flexural basin, later deformed by an Oligocene thrusting event, during which the post-nappe succession and the underlying Cretaceous nappes of the internal foredeep were uplifted. This stage was followed by folding of the post-nappe succession during the Miocene. AHe data from detrital siliciclastic deposits in the frontal area of the mountain chain provide cooling ages spanning from 17.3 to 42 Ma, consistent with available data for the structural culminations of Oman. Our work points out how renewal of flexural subsidence in the foredeep and uplift of the mountain belt were coeval processes, followed by layer-parallel shortening preceding final fold amplification.

Summary The southeastern Oman is located at the articulation of an “older” N20° E strike-slip margin in the East and a “younger” N70°E divergent margin in the South. The Eastern strike-slip margin was initiated in the Late Jurassic during the separation between the African–Arabian plate and the Indian–Madagascar–Seychelles plate ( Rabinowitz et al., 1983 ; Beurrier, 1987 ; Coffin & Rabinowitz, 1992 ; Salman & Abdula, 1995 ; Gnos et al., 1997 ; Marquer et al., 1998 ; Peters & Mercolli, 1998 ; Rodriguez et al., 2016 ). The detail architecture and the evolution of the margin remain unclear. We attempt to improve our knowledge of the area by a detail integrated field and subsurface study based on new sedimentological, paleontological and stratigraphical analysis of the Paleocene–Miocene deposits in the southeastern. Our work provides a detailed tectono-stratigraphic architecture scheme highlighting the evolution of the margin during the Cenozoic. It also provides new insights for the understanding of the relative motion between the Arabian and the Indian plates during this time.

The central High Atlas (Morocco) constitutes a diapiric province that hosts a complex array of elongated diapirs and minibasins that formed during the Lower Jurassic rift of the Atlas Basin. This paper aims to study the structure and growth evolution of the Tazoult diapiric wall, located in the central High Atlas, by means of structural and sedimentological fieldwork integrated with remote sensing mapping. The Tazoult salt wall is a 20km longx3km wide NE-SW trending ridge that exposes Upper Triassic red beds and basalts along its core. The succession flanking the salt wall ranges from Hettangian to Bajocian ages displaying spectacular sedimentary wedges in the SE and NW flanks. The Hettangian-early Sinemurian carbonates mainly crop out as blocks embedded in the core rocks. The similar to 1km thick Pliensbachian platform carbonates display large subvertical flap structures along the flanks of the Tazoult salt wall with unconformities bounding tapered composite halokinetic sequences. In contrast, the similar to 2.5km thick late Pliensbachian-Aalenian mixed deposits form tabular composite halokinetic sequences displaying small-scale hook halokinetic sequences. Passive diapirism resulted in the lateral extrusion of the evaporite-bearing rocks to form an allochthonous salt sheet toward the adjacent SE Amezrai minibasin. The Bajocian platform carbonates partially fossilized the Tazoult salt wall and thus constitute a key horizon to constrain the timing of diapir growth and discriminate diapirism from Alpine shortening. The Pliensbachian carbonate platform evolved as a long flap structure during the early growth of the Tazoult salt wall, well before the onset of the Alpine shortening.

Summary Evaporite basins are commonly rimmed by a wide range of facies made of complex depositional lithologies later affected by various diagenetic processes along the basin margins in response to recurrent fluctuations of relative sea level and associated water chemistry. The example of the Messinian of SE Spain is presented as a potential reference model for other salt basins.

Abstract The Upper Cretaceous Shilaif intra-shelf basin at the eastern margin of the Arabian platform contains rich source rock sequences in the hydrocarbon generation window, which are targets for ongoing exploration work. Time stratigraphy and sedimentology are key components to unravel the complex development of the hydrocarbon system. This paper presents detailed bio-, chemo- and sequence-stratigraphic data in combination with sedimentological analysis from core, well, seismic and outcrop data to support an analysis of basin architecture and regional time stratigraphic correlations. The Late Albian to Turonian saw the final intra-shelf basin development and infill on the eastern margin of the Arabian plate Cretaceous carbonate platform. Basin development began with the deposition of the Late Albian Mauddud Formation. Mauddud cycles are laterally continuous over large distances but thin in western and central Abu Dhabi in the area of the future intra-shelf basin. Differential aggradation is likely to have been accentuated by unfavorable climatic and water-quality conditions related to the Albian/Cenomanian Oceanic Anoxic Event. The Mauddud is overlain in the west and east of Abu Dhabi by the shallow marine aggrading & prograding carbonates of the Mishrif Formation with a SSW-NNE elongated intrashelf basin forming in central Abu Dhabi. This basin is filled by the Shilaif, Tuwayil and Ruwaydah Formations. Four depositional sequences with organic rich intervals are recognized in the Shilaif Fm corresponding in time to pulses of aggradation, progradation and retrogradation of Mishrif shallow-water platform margin sediments. The Tuwayil is a shaly lowstand/transgressional sequence onlapping onto the Mishrif, which was at this time partially exposed based on erosional channel incisions on the platform top. The Ruwaydah Fm is composed significantly of calcispheres recording continued transgression, increased accomodation space and an increase of carbonate production. The Coniacian Laffan shales unconformably overlie the Cenomanian/Turonian sedimentary sequences. Basin-fill sequences have been age dated with detailed chemo- and biostratigraphy. Based on carbon isotopes the Mauddud predates/coincides with the OAE at the Albian/Cenomanian boundary and is hence late Albian. Other carbon peaks, ammonites, calcispheres and planktonic foraminifera align the Shilaif with the Cenomanian reaching near its top the Cenomanian/Turonian boundary. The Tuwayil and Ruwaydah Fms are Turonian.

The Atlas Mountains are classically regarded as a failed Mesozoic rift arm subject to Alpine inversion, folding and thrusting. Here, we present new integrated structural and sedimentological studies that have revealed numerous Early–Middle Jurassic diapiric ridges and minibasins, characterized by distinctive halokinetic structures. Diachroneity in halokinesis is observed across the Central High Atlas, waning first in the SW during the Early–Middle Jurassic (Jbel Azourki and Tazoult ridges) and continuing to late Middle Jurassic towards the NE (Imilchil region). The halokinetic structures are readily differentiated from the effects of later Alpine deformation, allowing a new picture of the Central High Atlas to emerge. The most pervasive deformation in the Central High Atlas is associated with Early–Middle Jurassic diapirism, whereas the impact of Alpine inversion is mostly focused at the basin margins. This new understanding helps explain previously problematic aspects of the Atlas Mountains, which we now recognize as an exceptionally well exposed natural laboratory for understanding the interactions between halokinesis, tectonics and sedimentation.

New U-Pb SHRIMP zircon ages from the Bou Azzer-El Graara onlier constrains the Neoproterozoic evolution of the Anti-Atlas during Pan-African orogenesis. Within the Central Anti-Atlas, the Bou Azzer-El Graara inlier exposes a dismembered ophiolite, long considered to mark a late Neoproterozoic suture between the West African Craton in the south, and Neoproterozoic arcs to the north. From north to south, this inlier includes four main geological units: a volcanic-arc, an ophiolite, a metamorphic complex and a continental platform. Several plutons intrude the volcanic-arc, the ophiolite, the metamorphic complex, and post-orogenic volcanic and sedimentary deposits unconformably cover these terranes.The age of the volcanic-arc is reported here for the first time. Analyses of zircon of two rhyolites provide ages of 761 +/- 7 Ma and 767 +/- 7 Ma. Zircons from two gneisses provide dates of 755 +/- 9 Ma and 745 5 Ma. Both dates are considered best estimates of the crystallization ages of their igneous protoliths. Analyses of zircon from two granitic bodies, which crosscut gneisses, provide younger dates of 702 +/- 5 Ma and 695 +/- 7 Ma. The age of an aplitic body of the ophiolite is reported here for the first time, as 658 8 Ma (SHRIMP U-Pb on zircons). Theses ages suggest the existence of three distinct orogenic events during Cryogenian times: (i) 770-760 Ma Tasriwine-Tichibanine orogeny with rollback of the subducting oceanic plate, leading to the formation of back-arc basins; (ii) 755-695 Ma Iriri-n'Bougmmane orogeny; and (iii) the 660-640 Ma Bou Azzer orogeny involving the formation and the emplacement of the Bou Azer ophiolite.During Ediacaran times, the Bou Azzer-El Graara inlier is characterized with the development of a continental volcanic arc between 630 and 580 Ma (Bou Lbarod Group, 625 +/- 8 Ma; Bleida granodiorite, 586 +/- 15 Ma), and strike-slip pull-apart basins (Tiddiline Group, 606 +/- 4 Ma and 606 +/- 5 Ma). These volcanic and sedimentary Lower Ediacaran sequences are deformed before the felsic pyroclastic deposits of the Ouarzazate Group (567 +/- 5 Ma and 566 +/- 4 Ma). Finally, the Ouarzazate Group is overlain by early Cambrian volcanic deposits of the Jbel Boho Formation (541 +/- 6 Ma). (C) 2014 Elsevier Ltd. All rights reserved.

Paleoproterozoic metamorphic and igneous rocks, Tonian (?)-lower Cryogenian passive margin sedimentary rocks, Neoproterozoic dolerites, and Upper Ediacaran volcaniclastic, volcanic and pyroclastic rocks are exposed in the Agadir Melloul, Iguerda and the southern edge of the Sirwa inliers. A recent field mapping program of the Ediacaran Ouarzazate Group in these areas allow to distinguish three principal volcanic sequences. The first sequence (Adrar-n-Takoucht Formation) outcrops mainly south of the Sirwa inlier, and is composed of felsic pyroclastic deposits and local basaltic lavas with ages ranging between 572 and 570 Ma. The second sequence (Anammar and Tadoughast formations) occurs primarily in the Agadir Melloul-Jbel Iguiguil inlier. The Anammar Formation contains essentially volcano-detrital sediments, with fine airfall pyroclastic deposits. The Tadoughast Formation is composed of felsic pyroclastic deposits and rhyolitic domes with ages ranging between 567 and 564 Ma. The third sequence (Fajjoud Formation) contains felsic pyroclastic deposits, with an age of 556 Ma, associated with porphyritic basalts. The magmatism of the Ouarzazate Group was not continuous between 572 and 556 Ma, but related to distinct pyroclastic pulses.Geochemical data indicate that the pyroclastic rocks of the Ouarzazate Group have a highly potassic calc-alkaline to shoshonitic affinity. However, the basaltic facies associated with the Adrar-n-Takoucht Formation demonstrate a calc-alkaline affinity whereas those associated with the Fajjoud Formation have a tholeiitic affinity. Rhyolitic domes were derived from hyperaluminous leucogranites. In sum, the typology of zircons defines three poles: (i) subalkaline granites; (ii) calc-alkaline monzogranites and granodiorites frequently associated with basic rocks; and (iii) aluminous leucogranites.In addition, the volcaniclastic deposits of the Ouarzazate Group are submitted to a syn-sedimentary tectonic. The Adrar-n-Takoucht Formation is folded and unconformably overlain by the Anammar and Tadoughast formations. The Anammar and Tadoughast formations were deposited and deformed in a transtensional rift basin as indicated by basaltic lava flows. Hence, the Upper Ediacaran Ouarzazate Group formed in a wrench tectonic regime with extensional and local compressional deformation. (C) 2014 Elsevier Ltd. All rights reserved.

The present study brings new insights on the small-scale characteristics of relatively distal turbidite deposits (classically defined as depositional lobes or sheets) from the deep-water clastic slope system of the Annot Sandstones (Grès d'Annot), in the Trois Evêchés area. This “seismic scale” outcrop has been studied in detail to characterize sedimentary geometries and facies associations within and between sheet-like sandstone-bodies. In terms of facies, their internal architecture is dominated by numerous erosional features, variable scale cross-bedding and dewatering structures. Facies range from gravelly sandstones to fine-grained sandstones and their spatial distribution inside sandstone-bodies is provided, allowing us to discuss the spatial changes in flow behaviour. A detailed dataset, made of very high-resolution correlations in thick to thin-bedded sheet-like sandstone-bodies, enables to identify five main types of architectural elements, composed of both channelised and unchannelised depositional bodies. Gravelly-filled channel-elements, laterally stacked channel-elements (interpreted as being related to sinuous channel migrations) and wing-like channel-elements constitute the channelised sheet systems whereas tabular sandstones (sheets sensu stricto), prograding and/or dome-shaped units constitute layered sheet systems. Sinuous channels are represented by the association of erosive-based, laterally stacked bedsets and very coarse-grained, low-angle cross-bedded facies. These latter facies are interpreted as the result of flow deconfinement and overbanks above channel margins. The stratigraphic relationships between these architectural elements permit establishing a conceptual model of the distribution and organisation of the components. This distribution scheme is based on the longitudinal differentiation of gravity processes, which are directly linked with architectural element types. This model is composed of proximal confined units where channelization processes, amalgamation and bypass dominate, to more distal and less confined units where compensation, constructive structures and high deposition rates control sedimentary architectures. The Trois Evêchés sub-basin may be considered as a good example of a channelised lobe to unchannelised lobe transitional environment, which explains the lateral and vertical high variability during its infill. The widespread apparition of residual facies, such as cross-stratified sandstones as well as basal lags, suggests significant bypass. The appearance of both channelised and unchannelised units is consistent with this transitional environment. The provided detailed dataset in this paper displays the associated wide range of architectural elements in these settings, and highlights the significant heterogeneities of sand-rich confined turbidite sheet systems. These heterogeneities are under the seismic resolution and may influence fluid migration in sand-rich deep-water reservoirs.

Transfer zones are ubiquitous features in continental rifts and margins, as are transform faults in oceanic lithosphere. Here, we present a structural study of the Hadibo Transfer Zone (HTZ), located in Socotra Island (Yemen) in the southeastern Gulf of Aden. There, we interpret this continental transfer fault zone to represent a reactivated pre-existing structure. Its trend is oblique to the direction of divergence and it has been active from the early up to the latest stages of rifting. One of the main oceanic fracture zones (FZ), the Hadibo–Sharbithat FZ, is aligned with and appears to be an extension of the HTZ and is probably genetically linked to it. Comparing this setting with observations from other Afro-Arabian rifts as well as with passive margins worldwide, it appears that many continental transfer zones are reactivated pre-existing structures, oblique to divergence. We therefore establish a classification system for oceanic FZ based upon their relationship with syn-rift structures. Type 1 FZ form at syn-rift structures and are late syn-rift to early syn-OCT. Type 2 FZ form during the OCT formation and Type 3 FZ form within the oceanic domain, after the oceanic spreading onset. The latter are controlled by far-field forces, magmatic processes, spreading rates, and oceanic crust rheology.

The Paleogene deposits on the northern passive margin of the Gulf of Aden record the transition from the pre-rift to the syn-rift stages of the southern Arabian plate margin. In southern Oman (Dhofar Region), the relative continuity of the sedimentary record offers the possibility to investigate the early deformation phases of the Aden rift system. A new detailed sedimentological and biostratigraphic analysis of the Cuisian to Rupelian deposits of the Dhofar region allows to define a second-order transgressive–regressive cycle, that can be further subdivided into four third-order sequences between the Late Cuisian and the Early Rupelian time. The sequence stratigraphy established in this study has major implications for the understanding of the time equivalent deposits described in the eastern Arabian plate and illustrates the polyphased history of the initiation of the Aden Gulf rift system. The first two depositional sequences are controlled by a phase of deformation that only affects the eastern Oman margin, in relation with the tectonic activity at the Arabian–Indian plate boundary, during the Late Cuisian–Middle Lutetian. The last two depositional sequences record a westward migration of the deformation within the eastern realm of the proto-Gulf of Aden from the Bartonian. Priabonian uplift resulted in the basinward shift of the depositional system followed by a phase of tectonic subsidence that is recorded by the aggradation of lacustrine deposits in localized fault bounded basins. A subsequent major regional relative sea level fall related to domal uplift is recorded by terrigenous deposits (lower part of the Ashawq Formation) prior to the main phase of syn-rift tectonic subsidence (upper part of the Ashawq and Mughsayl formations) in Rupelian–Chattian times.

The Late Jurassic to Early Cretaceous sequences of the Arabian Platform form a key petroleum province with super-giant carbonate reservoirs. Despite this economic importance and an excellent database the stratigraphy still contains ambiguities with possible alternative interpretations of far-reaching implications.

The integration of subsurface and outcrop data has allowed to build a 200 km NW-SE correlation transect across 7 oil fields in Abu Dhabi. It reveals new possible concepts on the stratigraphic organization of the Late Jurassic-Early Cretaceous systems in the U.A.E.

The Lekhwair/Habshan/Salil (or LHS) system is a carbonate succession that prograded by 300 kmtoward the northeast across the eastern part of the Arabian Plate (Rayda Basin) from Berriasian to EarlyBarremian. The system is organized as a series of large prograding clinoforms with amplitudes rangingfrom 200 to 350 m.