Structural development of the Devono-Carboniferous plays of the UK North Sea

Decades of oil and gas exploration across the North Sea have led to a detailed understanding of its Cenozoic–Mesozoic structure. However, the deeper basin architecture of Paleozoic petroleum systems has been less well defined by seismic data. This regional structural overview of the Devono-Carboniferous petroleum systems incorporates interpretations from more than 85 000 line-kilometres of 2D seismic data and 50 3D seismic volumes, plus a gravity, density and magnetic study, from the Central Silverpit Basin to the East Orkney Basin. A complex picture of previously unmapped or poorly known basins emerges on an inherited basement fabric, with numerous granite-cored blocks. These basins are controlled by Devono- Carboniferous normal, strike-slip and reverse faults. The main basins across Quadrants 29–44 trend NW–SE, influenced by the Tornquist trend inherited from the Caledonian basement. North of Quadrants 27 and 28, and the presumed Iapetus suture, the major depocentres are NE–SW (e.g. the Forth Approaches and Inner Moray Firth basins) to east–west (e.g. the Caithness Graben), and WNW–ESE trending (e.g. the East Orkney Basin), reflecting the basement structural inheritance. From seismic interpretation, there are indications of an older north–south fault trend in the Inner Moray Firth that is difficult to image, since it has been dissected by subsequent Permo-Carboniferous and Mesozoic faulting and rifting

Les reliques téthysiennes en Méditerranée orientale: les bassins Ionien, d'Hérodote et du Levant

National audienc

Évolution tectonique et structure de la marge en Cyrenaique, Libye (Méditerranée Orientale)

En Méditerranée orientale, la paleo-marge sud de la Téthys a subit des épisodes polyphasés d'extension pendant le Paléozoïque et le Mésozoïque. Cette marge a été postérieurement inversée pendant des épisodes compressifs et discontinus depuis le Crétacé supérieur liés à la convergence entre l'Afrique et l'Eurasie.La marge Cyrénaïque (nord-est Libye) a enregistré ces épisodes extensifs et compressifs. Elle permet donc l'analyse des inversions et de leurs relations avec les évènements ayant eu lieu le long de la frontière de la plaque Africaine (i.e. subduction Hellenique).Le bassin de Sirte, adjacent à la Cyrénaïque montre une direction oblique, ne présente pas la même déformation et est caractérisé par une subsidence continue depuis le Mésozoïque.Des données de sismique (réflexion) combinées à des rapports et des corrélations de puits, nous ont permis d'examiner et de discuter les interactions entre la Cyrénaïque, le bassin de Sirte et les domaines profonds (i.e. bassin Ionien).Ce travail permet de mieux préciser les différents épisodes d'extension, de contraindre les évènements compressifs enregistrés par la région Cyrénaïque, d'observer les structures du bassin de Sirte et de clarifier en partie son évolution.Finalement cette partie de la marge est intégrée dans le cadre géodynamique régional de la Téthys sud et permet de discuter l'âge ainsi que le mécanisme d'ouverture pour la branche orientale de la Méditerranée.In the Eastern Mediterranean, the South-Tethys paleo-margin experienced poly-phased rifting episodes during Paleozoic and Mesozoic times. This margin has been subsequently inverted by discontinuous events occurring since the Late Cretaceous as a consequence of the Africa-Eurasia convergence.The Cyrenaica margin (northeast Libya) has recorded these extensional and compressional events. It thus gives the opportunity to analyse these inversion and their possible causal links with events occurring along the plate boundary (i.e. within the Hellenic subduction).The adjacent Sirt Basin, follows an oblique direction, did not suffer the same deformation as Cyrenaica and has recorded a continuous subsidence since the Mesozoic.Offshore seismic data combined with well correlations have permitted us to investigate and discuss the interactions between Cyrenaica, Sirt Basin and the deeper domains (i.e. Ionian Basin).We were able to document the different rift episodes, better constrain the compressional events on Cyrenaica, observe characteristics of the architecture of the Sirt Basin and clarify part of its evolution.Finally we integrate this part of the margin, in the regional geodynamic frame of the East Mediterranean branch of the Neo-Tethys by discussing the timing and mechanism which led to its opening

Comment on Geophysical evidence for a large impact structure on the Falkland (Malvinas) Plateau

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Transition from collision to subduction in Western Greece: the Katouna–Stamna active fault system and regional kinematics

International audienceTransition from subduction to collision occurs in Western Greece and is accommodated along the downgoing plate by the Kefalonia right-lateral fault that transfers the Hellenic subduction front to the Apulian collision front. Here we present an active tectonic study of Aitolo-Akarnania (Western Greece) that highlights how such a transition is accommodated in the overriding plate. Based on new multi-scale geomorphic and tectonic observations, we performed an accurate active fault trace mapping in the region, and provide evidence for active normal and left-lateral faulting along the Katouna–Stamna Fault (KSF), a 65-km-long NNW-striking fault system connecting the Amvrakikos Gulf to the Patras Gulf. We further show that the Cenozoic Hellenide thrusts located west of the KSF are no longer active, either in field observation or in GPS data, leading us to propose that the KSF forms the northeastern boundary of a rigid Ionian Islands-Akarnania Block (IAB). Cosmic ray exposure measurements of 10Be and 36Cl were performed on a Quaternary alluvial fan offset along the KSF (~50 m left-lateral offset). A maximum abandonment age of ~12–14 ka for the alluvial fan surface can be determined, giving an estimated KSF minimum geological left-lateral slip rate of ~4 mm year−1, in agreement with high GPS slip rates (~10 mm year−1). Despite this high slip rate, the KSF is characterized by subdued morphological evidence of tectonic activity, a gypsum-breccia bedrock and a low level of seismicity, suggesting a dominantly creeping behavior for this fault. Finally, we discuss how the IAB appears to have been progressively individualized during the Pleistocene (younger than ~1.5 Ma)