Thierry Adate Philip Allen Martin Appold Stefan Back David Barbeau Catherine Baudon Christian Berndt Richard Berry Claudia Bertoni Giovanni Bertotti Roderic Bosboom Dan Bosence Erdin Bozkurt Marita Bradsaw Douglas Burbank Peter Burgess Sebastien Carretier Alan Carroll Andrew Carter Cristian Carvajal Guillaume Caumon William Cavazza Blaine Cecil David Chapman Ole Clausen Sierd Cloetingh Domenico Cosentino Isabelle Coutand Salvatore Critelli Federico Dávila Gregory Davis Bernard Delcaillau Alex Densmore Claudio Di Celma Enrico Dinelli Rebecca Dorsey Francesco Dramis Brandon Dugan Gregor Eberli Eva Enkelmann Paul Fitzgerald Kerry Gallagher Daniel Garcı́a-Castellanos Beatriz Garcia-Fresca Eduardo Garzanti Annette George Christoph Glotzbach Didier Granjeon Carine Grelaud Richard Groshong Chris Guzofski Gary Hampson Mark Harris Adrian Hartley Peter Haughton William Helland-Hansen George Hilley Gregory Hoke Frank Horvath Mads Huuse Pascale Huyghe Raymond Ingersoll Xavier Janson Cari Johnson Teresa Jordan Flemming Jørgensen Ian Kane Paul Kapp Albert Kettner Eric Kirby Peter Koenigshof Barry Kohn Michelle Kominz Wouter Krijgsman Scot Krueger Gary Lash Daniel Le Heron Mike Leeder Andrew Leier Shaofeng Liu Lidia Lonergan Adriano Mazzini Stefano Mazzoli Paul Meijer Qing-Ren Meng Neil Mitchell Julien Moreau Chris Morley Frederic Mouthereau Cornel Olariu Michael Oskin Chris Paola Ivan Petrinovic Mike Pope Daniel Praeg Nereo Preto David Pyles Jeffrey Rahl Victor Ramos Robert Ratliff

This paper provides an alternative model to explain the structural evolution of the Argana Valley, located in the Western High Atlas of Morocco. Most Triassic basins in the High Atlas have been described as isolated rift basins distributed along an ENE-WSW oriented trough and developed as a series of half-grabens. They are characterised by two main sets of syn-sedimentary faults striking ENE-WSW and NNE-SSW, generally attributed to the Atlantic and Tethys rifting. The Permo-Triassic sediments of the Argana Valley are offset by similar trending faults and, as such, they have been interpreted as typical infill sediments of narrow rift-basins in Morocco, controlled by syn-sedimentary faulting due to the Atlantic rifting. Our study investigates the structural evolution of the area using newly acquired field analysis of the main faults and unconformities. This data, together with published information, has been used to construct a series of structural cross-sections across the valley. Three main unconformities have been recognised. The first unconformity separates Permian sediments from the underlying deformed Palaeozoic rocks. The second is an angular unconformity between Late Permian sediments and the overlying Triassic sequence, attributed to relaxation and orogenic collapse that occurred after the Hercynian Orogeny.The geometry of Late Permian units suggests that the large E-W to ENE-WSW faults occurred after deposition of the Late Permian and before the Triassic, and were associated with a major phase of tectonic activity and associated erosion. The third angular unconformity occurs between the latest Triassic sediments and the overlying basalts or Jurassic sedimentary sequence. Significantly, this study suggests that the ENE-WSW faults and most of NNE faults were not active during sedimentation of the Triassic. We conclude that the Triassic sediments of the Argana Valley were not deposited in a half graben, but within a slowly subsiding domain, such as a sag basin or a wide rift. Comparison with other Permo-Triassic basins on the Atlantic margin and in the High Atlas suggests that the structural evolution in the western part of the High Atlas has been mainly affected by Atlantic rifting. The influence of Tethys rifting is confined to the central part of the High Atlas, the Massif Ancien acting as a structural buffer between the two realms. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.

3D seismic data located in the Gjallar Ridge (Vøring Basin, offshore Norway) reveals a closely-spaced polygonal fault system affecting more than 800 m of homogeneous mud-dominated Quaternary and Tertiary sequences. As some faults reach the modern seafloor, they represent an active polygonal fault system at present day. Even if the processes remain unclear and are still under debate, it is generally agreed that the initiation of polygonal faults is the result of shallow burial dewatering of fine-grained unconsolidated sediments by volumetric compaction. 3D seismic data are commonly interpreted by propagating horizons automatically and by picking faults manually. However, in the case of polygonal fault intervals, this approach is time consuming due to the huge number of faults and because automatic propagation can be misleading. In this study, we applied a new technique of 3D seismic interpretation based on a sequential stratigraphy analysis, using the new PaleoScan© software (Eliis Company). It allowed us to build a 3D geological model computing more than 300 horizons within the faulted intervals. We then used the coherency attribute, depicting anomalies in the shape of seismic waveform like faults, in order to constrain a possible link between fault distribution and stratigraphic levels. Our approach allows fault throws to be calculated in milliseconds on any polygonal fault plane. The result shows that fault segments have been reactivated by dip-linkage. Distribution of faults depends on mechanical units, intervals characterized by different petrophysical properties, which are independent from lithological and diagenetic changes. According to these results, we propose a model showing the evolution of polygonal fault intervals in which faulting stages are separated by a quiescence phase during burial. A first tier of polygonal faults is initiated at a specific depth, according to the Cam–clay model. Then, following a period of quiescence during which mud-rich sediments continued to accumulate, new fault segments are initiated above the first mechanical unit and within this undeformed interval. New nucleated faults then connect downward to pre-existing underlying polygonal fault system, thus progressively increasing the thickness of the faulted interval.

Permo-Triassic rift basins offer important hydrocarbon targets along the Atlantic margins. Their fill is dominated by continental red beds, comprising braided fluvial, alluvial fan, aeolian, floodplain and lacustrine facies. These relatively lightly explored basins span both the Atlantic and Tethyan domains and developed above a complex basement with inherited structural fabrics. Sparse data in offshore regions constrain understanding of depositional geometries and sedimentary architecture, further impeded by their deep burial beneath younger strata, combined with the effects of later deformation during continental breakup. This paper provides results from a multidisciplinary analysis of basins along the Atlantic margin. Regional seismic and well data, combined with geochemical provenance analysis from the European North Atlantic margins, are integrated with detailed outcrop studies in Morocco and Nova Scotia. The research provides new insights into regional basin tectonostratigraphic evolution, sediment fill, and reservoir distribution, architecture and quality at a range of scales. Regional seismic profiles, supported by key well data, indicate the presence of post-orogenic collapse basins, focused narrow rifts and low-magnitude multiple extensional depocentres. Significantly, Permo-Triassic basin geometries are different and more varied than the overlying Jurassic and younger basins. Provenance analysis using Pb isotopic composition of detrital K-feldspar yields new and robust controls on the sediment dispersal patterns of Triassic sandstones in the NE Atlantic margin. The evolving sedimentary architecture is characterized by detailed sedimentological studies of key outcrops of age equivalent Permian-Triassic rifts in Morocco and Nova Scotia. The interplay of tectonics and climate is observed to influence sedimentation, which has significant implications for reservoir distribution in analogue basins. New digital outcrop techniques are providing improved reservoir models, and identification of key marker horizons and sequence boundaries offers a potential subsurface correlation tool. Future work will address source and seal distribution within the potentially petroliferous basins.

Late Triassic continental sediments deposited to :in active-rift setting are exposed to the Oukaimeden-Ourika Valley, located to the Central High Atlas Basin of Morocco. The Oukaimeden Sandstone Formation is dominated by ephemeral and perennial braided fluvial fades. 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 anti 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 ecometry 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 not oral faults. which are probably in part reactivated older Hercyman structures The fades distribution was controlled by of 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 tan 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 tire interpreted to be syn-sedimentary, displaying characteristics that suggest basal detachment within the. Triassic. and as SLICK provide evidence for the extension direction daring late Triassic time A periodic change from ephemeral to perennial systems, with associated changes in architectural style, is potentially attributed to climatic control. although of structural Influence cannot be dismissed Copyright (C) 2009 John Wiley & Sons. Ltd.

The geometry, throw distribution and kinematics of an array of blind normal faults were investigated using a high resolution 3D seismic dataset located in the Levant Basin, offshore Israel, to establish criteria allowing true blind faults to be distinguished from minor synsedimentary faults. A detailed analysis of throw distribution on the fault planes shows that the displacement exhibits a crudely concentric pattern about a maximum region located centrally on a fault plane, as expected for ideal blind faults. However, vertical displacement profiles do not exhibit classical linear or triangular profiles but are mostly flat-topped or hybrid in type. Comparison of unrestricted blind faults to those that interacted with a mechanical boundary or another structure suggests that such interactions significantly modify the throw spatial distribution on a fault plane. To distinguish small synsedimentary faults from blind faults, we use a combination of three criteria to assess whether a fault grew by blind propagation: (1) plunging upper-tip region and complementary pattern in the throw contours, (2) presence of upper-tip propagation fold, and (3) absence of stratigraphic evidence that the fault interacted with the free surface.

Normal reactivation of extensional faults offsetting Cenozoic clastic sediments is investigated using high quality 3D seismic data from offshore Brazil. These faults form complex crestal collapse grabens and result from elliptical doming of the underlying Cretaceous sequence due to Early Cenozoic uplift. The exceptional quality of this dataset allows an extremely detailed analysis of the throw distribution to be conducted on the faults. This, in addition to a reconstruction of the 3D geometry of the fault network, gives insights into the mechanisms and kinematics of reactivation. Two distinct modes of reactivation are recognised from this dataset. The main mode is a classical reactivation by upward propagation of pre-existing structures. A second mode, termed reactivation by dip linkage, is the propagation of an individual fault segment initiated above the pre-existing faults that hard link in the dip direction. For both mechanisms, reactivation processes are selective and only occur on some portions of faults. Factors controlling the preferential reactivation of some segments include: (1) orientation of the pre-existing fault plane relative to the principal stresses responsible for the reactivation, (2) segmentation of the pre-existing network and (3) maximum dimensions and throw values of pre-existing faults and basal tip line geometry associated with a detachment. Reactivation is an important process that may account for part of the scatter in fault-scaling relationships and should be included in fault-growth models.

The geometry and kinematic evolution of small growth faults were analysed from a high-resolution 3D seismic dataset located at the margins of the Levant Basin, in the eastern Mediterranean. The 3D geometry, segmentation history and throw distribution of one particular fault was reconstructed to evaluate and illustrate the changes in dimension and displacement distribution that occurred during the transition from purely blind propagation to propagation at the free surface. The fault is considered to have grown by blind radial propagation of three main segments that hard-linked prior to surface interaction. The fault subsequently reached the seabed and continued to accrue displacement as a syn-sedimentary fault. Most of the fault surface area formed during the blind propagation phase, but most of the displacement was added during the syn-sedimentary phase of the growth history with little increase in surface area. The interaction of the fault with the free surface led to a change in the position of the point of maximum displacement as well as modifying the vertical throw distribution. The amount of displacement added after this transition from blind fault to growth fault is discussed with respect to existing fault-growth models.