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Sedimentary basins adjacent to plate boundaries contain key tectonic and stratigraphic elements to understand how stress is transmitted through plates. The Levant Basin is a place of choice to study such elements because it flanks the Levant Fracture System and the Africa/Anatolia boundary. This paper uses new high-quality 3-D seismic reflection data to unravel the tectonic evolution of the margin of this basin during the Cenozoic, the period corresponding to the formation of the Levant Fracture System, part of the Africa/Arabia plate boundary. Four major groups of structures are identified in the interpreted Cenozoic units: NW-SE striking normal faults, NNE-SSW striking thrust-faults, ENE-WSW striking dextral strike-slip faults, and NNE trending anticlines. We demonstrate that all structures, apart of the NW-SE striking normal faults, are inherited from Mesozoic faults. Their reactivation and associated folding started during the late Miocene prior to the Messinian salinity crisis due to a NW-SE compressional stress field. No clear evidence of shortening at present-day offshore Lebanon and no large NNE-SSW strike-slip faults parallel to the restraining bend are found indicating that the Levant Fracture System is mainly contained onshore at present day. The intermittent activity of the interpreted structures correlates with the two stages of Levant Fracture System movement during late Miocene and Pliocene. This paper provides a good example of the impact of the evolution of plate boundaries on adjacent basins and indicates that any changes in the stress field, as controlled by the plate boundary, will affect immediately the preexisting structures in adjacent basins.

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Based on an analysis of 8000 minor fault-slip data in the Jura Mountains (France), we discuss the influence of pre-existing discontinuities on the development of fold-and-thrust belts. We present palinspastic maps showing the stress fields and active faults during the Cenozoic pre-orogenic events in the Jura belt prior to the main Late Miocene fold-and-thrust tectonics. During the Eocene, a N -S strike-slip regime produced a few NNE -SSW sub-vertical strike-slip faults in the central external Jura and a few E -W reverse faults in the eastern Jura near the future frontal thrust. During the Oligocene, an average WNW -ESE extension, with irregular stress trajectories, resulted in normal faulting along N -S to NE -SW trends in the external part of the belt, WNW -ESE trends along the future northern and northeastern frontal thrust, and NW -SE trends in the internal Jura. The Late Miocene tectonics began with a strike-slip regime with a fan-shaped compressional trajectory. It was followed by a stress field with similar stress direction, but local r 2 /r 3 stress permutation resulted in strike-slip regime domains contrasting with reverse regime domains. Stress deflections and permutations occurred near inherited cover and basement discontinuities. Major deformation zones, like the Jura frontal thrust onto the foreland, the thrust of the internal central Jura onto the external Jura, and the narrow deformation bands within the flat-lying plateaus formed close to the inherited faults. The structural style of the Jura belt thus partly mimics the pre-orogenic fault pattern. Stress deflections point to the pre-orogenic faults, express the indentation process of the Jura by its hinterland, and highlight successive slip events along major faults during the fold-and-thrust tectonics. This case study illustrates the relevance of minor fault-slip studies for characterizing both the pre-orogenic tectonics and the kinematics of the deformation. D

Layer-bound normal faults commonly form polygonal faults with fine-grained sediments early in their burial history. When subject to anisotropic stress conditions, these faults will be preferentially oriented. In this study we investigate how faults grow, evolve and interact within regional-scale layer-bound fault systems characterized by parallel faults. The intention is to understand the geometry and growth of faults by applying qualitative and quantitative fault analysis techniques to a 3D seismic reflection dataset from the Levant Basin, an area containing a unique layer-bound normal fault array. This analysis indicates that the faults were affected by mechanical stratigraphy, causing preferential nucleation sites of fault segments, which were later linked. Our interpretation suggests that growth of layer-bound faults at a basin scale generally follows the isolated model, accumulating length proportional to displacement and, when subject to an anisotropic regional stress field, resembling to a great extent classical tectonic normal faults.

[1] 3D numerical modeling has been used to investigate how the variations of mechanical properties in sedimentary layered sections affect the development of normal faults. We calculated the distribution of the Coulomb stress to assess the proximity of the layers to failure through an elastic layered section. The simulation of various combinations of rock properties allowed us to compare the effect of the stiffness and strength contrasts, which promote or inhibit faulting in the stiff layer, respectively. For rock systems showing little variation in strength, nucleation of the fault occurs in the stiff layer (e.g., limestones or sandstones), whereas it occurs in the compliant layer (e.g., clay-rich rocks) if the stiff layer has a high cohesion. Considering a mean strength profile of the carbonate sequences, nucleation occurs in limestones if the ratio of Young's moduli between the limestone and clay-rich rock is greater than 2; otherwise, clay-rich layers fail first. We also showed that nucleation is promoted in sandstones or limestones if these layers are thinner than the clayey layers. In a second set of simulation, using a slip on a fault, we examined the conditions needed to overcome the restriction of the fault propagation. Our results suggest that the lateral propagation of the fault, within a layer, produces increasingly favorable conditions for vertical propagation. A maximum aspect ratio of width to height of 13 is predicted for faults in limestone-clay sequences, and this maximum aspect ratio is expected to decrease as the contrast in the rock properties decreases.Citation: Roche, V., C. Homberg, and M. Rocher (2013), Fault nucleation, restriction, and aspect ratio in layered sections: Quantification of the strength and stiffness roles using numerical modeling,

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