International audienceThe Early Toarcian is marked by a global perturbation of the carbon cycle and major marine biological changes. These coincide with a general decrease in calcium carbonate production and an increase in organic carbon burial, and culminate in the so-called Toarcian Oceanic Anoxic Event. It is believed that the environmental crisis was triggered by the activity of the Karoo-Ferrar large igneous province. In order to further document the Early Toarcian palaeoenvironmental perturbations, carbon isotope, total organic matter, calcareous nannofossils and phosphorus content of the Amellago section in the High Atlas rift basin of Morocco were investigated. This section is extremely expanded compared to the well-studied European sections. Its position along the northern margin of the Gondwana continent is of critical importance because it enables an assessment of changes of river nutrient input into the western Tethyan realm. The carbon isotope curve shows two negative excursions of equal thickness and amplitude, at the Pliensbachian-Toarcian boundary and at the transition from the Polymorphum to the Levisoni Zone. This confirms the supra-regional nature of these shifts and highlights the possible condensation of the first "boundary" shift in European sections. Phosphorus content is used to trace palaeo-nutrient changes and shows that the two negative carbon isotope shifts are associated with increased nutrient levels, confirming that these episodes are related to enhanced continental weathering, probably due to elevated greenhouse gases in the atmosphere. In the High Atlas Basin, the increase in nutrient levels at the Pliensbachian-Toarcian boundary is moreover likely to be the main factor responsible for the coeval demise of the Saharan carbonate platform. A middle Toarcian event, centered on the boundary between the Bifrons and Gradata Zones, characterized by a positive carbon isotope excursion and nutrient level rise, is documented in the Amellago section

This study employs a novel Discrete-Element Modelling approach to investigate the interplay of sedimentation with rejuvenation of diapirs by shortening. The inherent complexity of salt tectonics, the complications encountered when imaging structures beneath salt, and the lack of outcrop analogues, coupled with its importance to petroleum systems, make salt tectonics one of the most interesting and debated topics in basin studies. Model results successfully reproduce the geometric and dynamic behaviour of active diapirism and show the effects of sedimentation thickness, rate and timing on the generation of distinct diapir geometries, including i) salt tongues and ii) squeezed upright diapirs. Models with late sedimentation or a lower sedimentation rate relative to salt mobility show development of asymmetric diapirs with allochthonous salt tongues; whereas models with earlier sedimentation or a faster sedimentation rate generate upright squeezed diapirs. Early sedimentation at a moderate rate results in a symmetrical hour-glass shaped structure, resembling a tear-drop diapir. Results are fully reproducible and comparable with many natural examples, and include overburden deformation which is difficult to simulate using other numerical techniques. Extending this approach to different problems and basinal contexts could improve our understanding of deformation mechanisms and sediment distribution around salt structures.

a b s t r a c tThe Jeffara escarpment spans 400 km from southeastern Tunisia to sorthwestern Libya, and marks the northern edge of the Berkine-Ghadames Basin. Its horseshoe shape provides a good 3D control of regional-scale depositional architecture. Historically, the political border between Tunisia and Libya hindered the integration of studies over its entirety, which led to the establishment of separate litho-biostratigraphic frameworks. Field-work undertaken on both sides of the border has allowed the unification of lithostratigraphic schemes developed in both countries. Published stratigraphic ages of the different formations and members are compared and integrated in order to propose a unified bio-lithostratigraphic framework. The correlation of serial sections along the Jeffara escarpment shows that two major tectonic unconformities divide the Early Cretaceous sedimentary pattern. The first one is dated as Late Aptian and is commonly associated with the European ''Austrian" tectonic phase. The second, which has previously not been recognized as a regional significant surface in Libya, occurs during the Middle Albian and marks moreover the transition from a siliciclastic to a carbonate-dominated sedimentation regime. These two important regional unconformities form the lower and upper boundaries of the Kiklah-Aïn el Guettar Formations, and can be associated with intra-plate deformation linked with the opening of the central segment of the South Atlantic and the Equatorial Atlantic oceans.

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Late Triassic continental sediments deposited in an active-rift setting are exposed in the Oukaimeden-Ourika Valley, located in the Central High Atlas Basin of Morocco. The Oukaimeden Sandstone Formation is dominated by ephemeral and perennial braided fluvial facies, and is an outcrop analogue for Triassic sandstone hydrocarbon reservoirs found in Atlantic margin and North African basins. This paper documents detailed analysis of the outcrop data to investigate the influence of tectonics on deposition and the interplay with climatic controls. The geodynamic evolution of the basin is interpreted to be influenced by Atlantic rifting to the west and the formation of the Tethys Sea to the north, which led to the development of ENE and NNE striking normal faults. The present-day fault and outcrop geometry reflects later inversion due to the Alpine compression that led to uplift of the High Atlas and subsequent erosion.The ENE trending rift-basin is bound by normal faults, which are probably in part reactivated older Hercynian structures. The facies distribution was controlled by a complex interplay of tectonic and climatic controls. Evidence for syn-sedimentary movement of both fault sets is observed, with stratigraphic thickening and associated progressive change in bedding dip. These faults controlled the basin dimension, geometry of the half-graben and created the accommodation for sediment deposition. The presence of breccia deposits close to the main ENE bounding faults indicates footwall erosion and deposition of basin margin fans. The location and orientation of the main fluvial system was controlled by these structures, and the main channel belts ran parallel and proximal to the controlling faults, whereas away from the main syn-depositional faults overbank deposits dominate. Smaller contemporaneous NNE oriented faults are generally shorter with less throw, and had only a limited influence on gross sedimentation patterns. These faults are interpreted to be syn-sedimentary, displaying characteristics that suggest basal detachment within the Triassic, and as such provide evidence for the extension direction during late Triassic time. A periodic change from ephemeral to perennial systems, with associated changes in architectural style, is potentially attributed to climatic control, although a structural influence cannot be dismissed.

The provenance of the Numidian Flysch in the western Mediterranean remains a controversial subject which hinders understanding of this regionally widespread depositional system. The Numidian Flysch is a deep marine formation dated as Oligocene to Miocene which outcrops throughout the Maghreb and into Italy. Evidence that is widely used for provenance analysis has not previously been reviewed within the context of the Maghrebian Flysch Basin as a whole. The structural location within the Alpine belt indicates deposition proximal to the African margin, while the uniformity of the Numidian Flysch petrofacies suggests a single cratonic source, in stark contrast to heterolithic and immature flysch formations from the north of the basin. Detrital zircon ages constrain a source region with Pan-African and Eburnian age rocks, unaffected by either Hercynian or Alpine tectonic events, which precludes the European basement blocks to the north of the basin. Palaeocurrent trends which suggest a northern source are unreliable given foreland basin analogues and observed structural complications. An African craton source remains the only viable option once these data are reviewed in their entirety, and the Numidian Flysch therefore represents a major Cenozoic drainage system on the North African margin. Deposition is concurrent with regional Atlas uplift phases, and coincidental with globally cooling climates and high sea levels. The Numidian Flysch is therefore interpreted to represent a highstand passive margin deposit, with timing of deposition controlled primarily by hinterland uplift and climatic fluctuations.

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More than 70 enigmatic discordant seismic anomalies of limited lateral extent, associated with eye-shaped structures and folds, have been imaged on 2D seismic data from the offshore Northern Subbasin of the Senegal Basin, NW Africa. In this paper we define their distribution, characterise their morphology and compare them to similar features imaged by seismic data along the NE Atlantic Margin that have been demonstrated to be igneous sills, hydrothermal vents and intrusion-related forced folds. We propose that the Cretaceous and Paleogene strata in the northernmost part of the offshore Northern Subbasin were heavily intruded by igneous sills during the Miocene. The proposed timing of intrusion is coincident with that previously suggested for the development of the Cayar Seamount located 100 km NNW of Dakar and onshore volcanism in the Cap-Vert area near Dakar and in the Cape-Verde Islands. This stage of Miocene igneous activity is interpreted to be closely associated with the coeval collision between Africa and Europe. The interpreted igneous sills give rise to an unexpected ''soft'' seismic response. The preferred explanation for the ''soft'' appearance of the sills is that the majority of sills are thin (o90 m) and hence their seismic appearance is affected by interference between the acoustic response from the top and base of the sills. The identification of shallow-level igneous intrusives in the offshore Northern Subbasin has important implications for hydrocarbon exploration in the Senegal Basin and possibly more broadly for hydrocarbon exploration in Atlantic basins offshore NW Africa. r