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Paléo-champs de contrainte tertiaires dans la plate-forme européenne au front de l'orogène alpin

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... Since the end of the Miocene, this stress field is characterized by a fan-shaped distribution of S Hmax along the northern border of the Alpine arc. This gives way to a more consistent NW-SE to NNW-SSE direction of compression further from the chain (Bergerat 1987;Müller et al. 1992). ...
... However, the southward extension of the rift towards the Valencia trough is not accounted for by this model. Moreover, despite the generally compressional stress regime resulting in west Europe from plate collision, rifting occurred during phases of predominating far-field extensional stresses (Bergerat 1987;Lacombe et al. 1993). These phases are integrated by the plate kinematics reconstruction of Le Pichon et al. (1988), showing divergent motion between westernmost Europe and the rest of Eurasia during the Oligocene. ...
... Related to the opening of the Atlantic Ocean, a rifting began during the Eocene as a result of a Pyrenean compression phase. Tectonic faulting and (Bergerat 1987) and was followed by a major compressive phase. An important horst uplift occurred, separating the rift valleys. ...
Article
A distinguished team of Western European scholars has written an advanced, full-length physical geography designed to be a state-of-the-art evaluation of the physical environment of Western Europe, being both retrospective and prospective in its perception of environmental change. The unique natural and regional environments of Western Europe are discussed, as well as the physical geographic framework of the region. Particular emphasis is placed on the impact and responses of human society on the physical environment of the region which is characterized by a very high population density. As an enhanced reference work it will be of enduring value.
... Because it is known that the Pyrenean stresses were transmitted very far into the Pyrenean foreland (in the Paris Basin (Lacombe & Obert, 2000); in eastern France (Bergerat, 1987); and even in the UK (Parrish et al. 2018)), in this study we investigate the effect of the Pyrenean compressive tectonics on the Cévennes Fault System (CFS) and related structures such as the Pic Saint-Loup thrust (Mattei, 1986) or the Dalle des Matelles (Petit & Mattauer, 1995;Fig. 1b). ...
... Since the beginning of Neogene times, the region has been relatively quiet from a tectonic point of view, although Roy & Trémolières (1992) documented Miocene N-S-trending reverse faults in the Alès basin and Bergerat (1987) reported activity of the CFS in a dextral movement during the Aquitanian, associated with a tectonic episode recorded on the whole European platform and interpreted as a resumption of the Africa/Europe convergence. According to Séranne et al. (2002), this major fault was ...
... Finally, the absence of deformation in the CFS associated with the early Miocene event highlighted by Parizot et al. (2021) and Hoareau et al. (2021), respectively on the northern and southern foreland of the Pyrenean belt, could reflect that it is restricted to the belt core, although we suggest here the potential sensitivity of the CFS to such an event. Further exhaustive sampling and dating along the strike of the CFS will probably allow this phase along this inherited structure to be seen, as proposed by Bergerat (1987). ...
Article
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Deformation in intraplate domains is usually considered as a consequence of tectonic events at plate boundaries. Nevertheless, the occurrence of intraplate earthquakes such as the recent Le Teil event in the south of France along the Cévennes Fault System (CFS), on 11 November 2019, Mw = 4.9, questions whether this far-field deformation only occurs during tectonic pulses at plate boundaries, or if it corresponds to low-intensity but regional continuous deformation through time. To address this question, we have coupled U–Pb geochronology of fault-related calcites with structural analysis along a major fault system (the CFS) in the South-East Basin, France. We evidence (1) an Albian activity of the CFS and (2) a continuous compressional activity of the CFS and satellite structures during the whole Eocene and probably during the Late Cretaceous – Palaeocene, including periods (e.g. Lutetian) usually considered as phases of tectonic quiescence. We thus demonstrate that the tectonic reactivation of this intraplate fault system is not restricted to periods of high rates of deformation at plate boundaries.
... La phase tardive miocène, datée à env. 16 (Bergerat 1987;Bergerat 1982) (Bergerat 1987). Les flèches représentent les directions de la contrainte principale σ1 déduites du calcul des tenseurs moyens des contraintes. ...
... La phase tardive miocène, datée à env. 16 (Bergerat 1987;Bergerat 1982) (Bergerat 1987). Les flèches représentent les directions de la contrainte principale σ1 déduites du calcul des tenseurs moyens des contraintes. ...
... Since the beginning of the Neogene times, the region has been relatively quiet from a tectonic point of view, although Roy & Trémolières (1992) documented Miocene N-S trending reverse faults in the Alès basin and Bergerat et al.(1987) reported activity of the CFS in a dextral movement during the Aquitanian, associated with a tectonic episode recorded on the whole European platform and interpreted as a resumption of the Africa/Europe convergence. ...
Thesis
En géodynamique, l’essentiel des déformations est accommodé aux limites des plaques tectoniques. Pourtant, la propagation de la contrainte au-delà de ces frontières est à l’origine de déformations dites « intraplaques », d’intensité modérée mais qui contrôlent notamment des circulations de fluides et minéralisations. Ces déformations, et en particulier leur lien avec l’agenda tectonique établi en limite de plaque, sont aujourd’hui encore mal comprises : sont-elles antérieures, contemporaines, postérieures à la formation des orogènes ? S’agit-il d’épisodes uniques ou multiples, et sur quelle durée ? Les travaux présentés tentent de répondre à ces questions en s’appuyant sur la caractérisation du domaine intraplaque situé au Nord de la chaîne Pyrénéenne, dans la région des Corbières, du Languedoc et des Grands Causses. La méthode de datation U-Pb sur calcite de faille, développée en partie au laboratoire GEOPS au cours de ce travail, est couplée à une analyse structurale de chacune des zones afin de dater de manière absolue la déformation compressive dans les divers secteurs. Les résultats obtenus permettent ainsi de (1) préciser/établir les calendriers géodynamiques de chacun des secteurs (2) replacer ces déformations intraplaques dans le contexte géodynamique global et (3) établir le lien entre les déformations dans le domaine intraplaque et celles en bordure de plaque. Les travaux réalisés dans la région des Corbières, au front de l’orogène, mettent en évidence une phase de déformation au Lutétien, en décalage avec le paroxysme d’exhumation de la chaîne à l’Eocène supérieur. La région a également enregistré un évènement tectonique au Miocène, contemporain d’une phase d’exhumation de la chaîne, de la formation des surfaces « perchées » des Pyrénées et d’un épisode de déformation décrit sur le versant espagnol des Pyrénées. Le secteur du Languedoc, et en particulier le système de faille des Cévennes, enregistre une déformation associée à la compression pyrénéenne continue tout au long de l’Eocène. Par ailleurs les données U-Pb indiquent une activité à l’Albien de ce faisceau de failles, contemporaine de l’ouverture des bassins pyrénéens. Enfin, la région des Grands Causses correspondant au secteur d’étude le plus distal à la chaîne enregistre une déformation longue et continue du Crétacé inférieur à l’Eocène supérieur. L’ensemble de ces travaux démontre ainsi que la déformation en domaine intraplaque n’est pas limitée à l’enregistrement des phases paroxysmales de déformation en limite de plaque comme cela a pu être proposé auparavant, mais que le domaine intraplaque présente une grande sensibilité aux déformations en bordure de plaque, et donc une forte déformabilité sur des durées importantes avant, pendant et après la formation des orogènes en limite de plaque.
... Located in southeastern France, the Provence fold-thrust belt has experienced moderate shortening during the Campanian-Eocene N-S Pyrenean-Provence compression and was then deformed by Oligocene-Miocene Ligurian-Provence rifting events and Neogene to present-day Alpine compression (e.g., Tempier, 1987;Bergerat, 1987;Villeger and Andrieux, 1987;Hippolyte et al., 1993;Lacombe and Jolivet, 2005;Bestani et al., 2016;Philip, 2012). This fold-thrust belt superimposed on a Mesozoic passive margin that developed during the opening of the Tethys-South Provence/Pyrenean rift system (Masse and Philip, 1976;Philip et al., 1987;Lemoine and de Graciansky, 1988;Tavani et al., 2018). ...
... The eastern Provence fold-thrust belt belonging east of the Rians, Arc and Beausset basins and west of the Permian depressions and Variscan Maures and Tanneron-Estérel massifs (Figs. 1 and 2) was formed above a thick middle-upper Triassic evaporitic-carbonate layer and complex array of inherited basement structures, explaining its irregular of thrust traces in map view (Bathiard and Lambert, 1968;Baudemont, 1985;Tempier, 1987). This hybrid fold-thrust belt mainly results from the~N trending Campanian-Eocene Pyrenean-Provence compression (Bergerat, 1987;Lacombe and Jolivet, 2005;Bestani et al., 2016). This framework was then deformed by Oligocene extensional faults during the Ligurian-Provence rifting, and by Africa-Europe plate kinematics and the southern propagation of the Castellane compressional arc (Figs. 1 and 2) during Miocene to present-day (Bergerat, 1987;Villeger and Andrieux, 1987;Hippolyte et al., 1993). ...
... This hybrid fold-thrust belt mainly results from the~N trending Campanian-Eocene Pyrenean-Provence compression (Bergerat, 1987;Lacombe and Jolivet, 2005;Bestani et al., 2016). This framework was then deformed by Oligocene extensional faults during the Ligurian-Provence rifting, and by Africa-Europe plate kinematics and the southern propagation of the Castellane compressional arc (Figs. 1 and 2) during Miocene to present-day (Bergerat, 1987;Villeger and Andrieux, 1987;Hippolyte et al., 1993). ...
Article
The Provence Chain incorporated preexisting halokinetic and basement features which have played a key role in the structural evolution of the thrust systems. Field structural data, previously published geological maps and exploration well data have been used to interpret a new ~80 km-long balanced and restored cross section across the eastern Provence fold-thrust belt. The geological data and cross section construction suggest evidence for Mesozoic salt domes and minibasins embedded in the thin-skinned thrusts, and upper Paleozoic extensional structures transported on new thick-skinned thrusts. According to field data, pre-contractional palinspastic restoration suggests that salt domes and minibasins grew mainly during Rhaetien to late Jurassic times and intermittently until the early Santonian. Minibasins are mainly filled by carbonate systems associated with gravitational instabilities in minor normal faulting. Minibasin sinking into middle-upper Triassic evaporitic-carbonate succession has been mainly controlled by sediment loading. However, the initiation of salt movements might have been controlled by the initial geometry of the Triassic strata and probably extensional basement faulting. Preexisting salt structures have controlled thrust emplacements and their kinematics. Synorogenic deposits indicate a classical hinterland to foreland sequence of thrust inversion of the margin during the upper Cretaceous-Eocene Pyrenean-Provence compression. Diapiric structures were mainly eroded during and after the Pyrenean-Provence compression then reactivated during Oligocene extension and Miocene to present-day Alpine compression. Cross section balancing shows a total horizontal shortening of 28.5 km related to the Pyrenean-Provence and Alpine compressions. The eastern Provence fold-thrust belt integrates preexisting halokinetic folding which can be misinterpreted as resulting to compression. This suggests that a significant amount of folding in fold-thrust belts can results from an early halokinetic fold system developed during the pre-contractional passive margin evolution.
... 3 Geofluids graben as a result of the Africa-Europe collision [43,44]. The first stage of this tectonic activity began during the Late Eocene with N-S compression, which affected the entire European continental platform ( Figure 3) [45]. The primary phase of the opening of the Rhine graben took place during the Oligocene as a result of E-W extension ( Figure 3). ...
... The primary phase of the opening of the Rhine graben took place during the Oligocene as a result of E-W extension ( Figure 3). The direction of the stress axis did not vary, but the σ 1 and σ 2 axes reversed [45]. At this stage, normal faults appeared and blocks tilted (Figure 1(d)). ...
... The subsidence rate in the northern part of the graben differed from that of the southern part, which is bordered by the Erstein high. It constitutes the continuity between the Moldanubian and Saxo-Thuringian Figure 3: Synthesis of main brittle tectonic phases and associated fracture set directions since the Hercynian orogenesis in the Rhine graben and around the area modified after [117,118] based on [37,45,48]. The circles represent the main orientation of fractures related to main stress axis (north on the top, east on the right). ...
Article
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In this paper, we focus on paleocirculation at the Hercynian basement/sedimentary cover interface in the tectonic environment of the Upper Rhine graben. The goal is to increase our understanding of the behavior of the fracture-fault network and the origin of the hydrothermal fluids. We studied orientations, mineral fillings, and fluid origins of fractures that crosscut the Hercynian granitic basement and the Permo-Triassic formations in relation to the major tectonic events. Because the Mesozoic formations and the Hercynian basement on the graben flanks and inside the graben do not have the same evolution after uplift, our study includes 20 outcrops on both graben flanks and cores of the Soultz-sous-Forêts geothermal wells located inside the graben. The Hercynian granitic basement and Permo-Triassic formations were affected by several brittle phases associated with fluid circulation pulses related to graben formation during the Tertiary. We distinguished at least four stages: (1) reactivation of Hercynian structures associated with pre-rift tectonics during the early Eocene and descending meteoric waters, characterized by shearing/cataclasis textures and precipitation of illite and microquartz; (2) initiation of convective circulation of deep hot brines mixed with descending meteoric waters at the Hercynian basement/sedimentary cover interface during this first stage of Eocene rifting, characterized by dolomite and barite fillings in reactivated Hercynian fractures; (3) N-S tension fractures associated with rift tectonics just prior to uplift of the graben shoulders during Oligocene extension and descending meteoric waters, characterized by cataclastic textures and precipitation of quartz, illite, hematite, and barite; and (4) current convective circulation of deep hot brines mixed with descending meteoric waters at the Hercynian basement/sedimentary cover interface, characterized by calcite and barite fillings within the graben. This convective circulation is today present in deep geothermal wells in the western part of the Rhine graben.
... Si un consensus existe sur l'histoire tectonique cénozoïque de la plate-forme ouesteuropéenne (Bergerat, 1987), en revanche les périodes plus anciennes sont moins connues et plus controversées . La première difficulté réside dans le fait que les indices de tectonique mésozoïque ont pu être fortement oblitérés par les derniers événements cénozoïques. ...
... Le contexte géodynamique est conditionné par les 2 orogenèses pyrénéenne et alpine, entre lesquelles s'intercale l'épisode de formation du rift ouest-européen. Durant ces événements tectoniques importants, les structures préexistantes (failles de Vittel et Metz) sont réactivées mais il y a aussi la formation de nouveaux accidents (principalement les rifts ouest européens) (Pomerol, 1971;Cavalier et Pomerol, 1979;Bergerat, 1987;Lacombe et Angelier, 1993). ...
... Du Paléocène à l'Eocène supérieur, s'étend la phase compressive pyrénéenne, dont le paroxysme se produit à la fin de cet intervalle. La contrainte principale est orientée N-S pour la majorité des auteurs (Letouzey et Trémolières, 1980;Villemin, 1986;Bergerat, 1987;Homberg et al., 2002) et plutôt N-S à NE-SW pour une minorité (Steiner, 1980;Rocher et al., 2002). Cet épisode entraîne principalement des jeux décrochants pour les failles, parfois associés à des structures plissées comme l'anticlinal du Bray (Pomerol, 1971). ...
Thesis
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L'enchaînement des épisodes de fracturation et de circulations fluides ainsi que les phases de déformations synsédimentaires a été caractérisé dans les terrains jurassiques de l'Est du Bassin de Paris. L'étude s'appuie sur des observations de terrain et sur la caractérisation isotopique des objets diagénétiques et tectoniques. Sur la base de données de décompaction des séries et de la découverte de filons sédimentaires, un contexte tectonique extensif est défini entre la fin du Dogger et le Malm. Ces déformations précoces s'intègrent dans un calendrier tectonique depuis la fin du Mésozoïque jusqu'à l'Actuel, dont l'enchaînement des paléocontraintes est précisé. L'étude des stylolites stratiformes a confirmé leur rôle pendant la compaction et lors de réactivations tectoniques. L'analyse des signatures isotopiques (d18O et d13C) des calcites de fentes de tension et des encaissants a permis de proposer plusieurs origines pour les paléocirculations depuis le Jurassique jusqu'au Tertiaire.
... The tectono-sedimentary record begins with a Late Cretaceous south-north shortening [3] that was responsible for the early inversion of the Bray [27,34] and possibly of Boulonnais zone [14] (figure 1). In Eocene times, the lower Somme constituted the Lutetian gulf [26], which by Oligocene was subjected to extension (microfaults at Saint-Valery and Montreuil). ...
... In Eocene times, the lower Somme constituted the Lutetian gulf [26], which by Oligocene was subjected to extension (microfaults at Saint-Valery and Montreuil). From the end of the Oligocene, the stress field became N150° [3], with transpressional reactivation of Variscan faults and with a thin skinned tectonism associated with drape folds [28] above the main basement faults ( figure 1). ...
... From Neogene, the shift in stress pattern to N150° [3] reactivated an elongated Variscan zone [19] forming in the western part of the Paris basin a wedge from the Seine fault in the south ( figure 1A) intruding northward the Anglo-Brabant massif. By comparison with the eustatic curve [13] and the preserved Paleogene outcrops, the whole region experienced from the onset of the Neogene, a subsidence (circa 150 m since the Bartonian), also in parallel with the lowering of the global eustatic level. ...
... The investigated area is characterized by weak deformation, with a regional slight dip of 1 to 2% towards the northwest, and main structures inherited from major Hercynian faults and Tertiary troughs ( Fig. 1) [21,[25][26][27]. Regional fracturing [17,22,34] (mainly occurring as joints) shows two perpendicular trends (Fig. 2): a NW-SE one, linked to Oligocene-Pliocene events (Alpine orogen), and a NE-SW one, assumed to derive from Palaeocene-Eocene events (Pyrenean orogen) [1,7,[32][33][34]. ...
... Cette série est structurée en surface par un système de failles héritées (failles de Metz, de la Marne et de Vittel, Fig. 1), ainsi que par des fossés d'effondrement d'âge Tertiaire (fossés de Gondrecourt et Joinville, Fig. 1) [23][24][25]27,28]. Ce domaine intraplaque, réputé comme étant faiblement déformé (ondulations de grande longueur d'onde) [7,12,21,26], est donc favorable aux relevés microtectoniques [17]. Un grand nombre d'études sur l'évolution des paléocontraintes et l'état de fracturation à l'affleurement ont ainsi été menées depuis plus de vingt ans [2,5-7,10,11,16,18-20, Fig. 2A). ...
... Un grand nombre d'études sur l'évolution des paléocontraintes et l'état de fracturation à l'affleurement ont ainsi été menées depuis plus de vingt ans [2,5-7,10,11,16,18-20, Fig. 2A). Ces deux directions sub-orthogonales correspondent vraisemblablement à l'expression des épisodes tectoniques liés à l'orogène pyrénéen (fracturation nord-sud à NE-SW), puis alpin (fracturation WNW-ESE à NNW-SSE) depuis la fin du Crétacé et tout au long du Tertiaire [1,7,17,32]. Dans le détail, les différents états de paléocontraintes se sont succédés depuis le dépôt des terrains [1,2,4,9,12,15,23,32], mais seuls les derniers épisodes d'âge tardi-Crétacé à fini-Tertiaire sont clairement indenti-fiables sur le terrain. ...
Article
Study of fractures along a 490-m vertical section of marl/limestone alternations in the Upper Jurassic (Meuse/Haute-Marne underground research laboratory–eastern Paris Basin) reveals their organization and the different states of palaeostress. Type and extension of tectonic structures seem to be controlled principally by lithology and secondary by depth. Also, it appears deviations of Alpine palaeostresses between Kimmeridgian and Oxfordian formations. These deviations are related to the presence of marl/limestone contacts. The vertical evolution of current horizontal maximum stress shows a similar behaviour, with deviations at the walls of Callovo-Oxfordian argillites. These results allow us to point out and to discuss the impact of lithology, rheology and depth on fracturing occurrence and distribution. Furthermore, this study suggests the role of Callovo-Oxfordian as a barrier for fracture development between the limestones of Dogger and Oxfordian formations. To cite this article: G. André et al., C. R. Geoscience 338 (2006).
... In the study area, the Miocene deposits derive from the second shallowing-upward cycle of the Western Alpine foreland basin overfilled phase (Mid-Oligocene to the Late Miocene; Sinclair and Allen 1992;Ford and Lickorish 2004;Ford et al. 2006). Before the first Miocene marine transgression (i.e. during the Oligocene and the Lower Aquitanian), an extensional phase related to the 'Oligocene Western European Rift' (OWER) occurred (Debelmas 1974;Curial 1986;Bergerat 1987;Ziegler 1988Ziegler , 1990Ziegler , 1994Bergerat et al. 1990), whereas, to the east, the study area was already affected by the Alpine compression (Doudoux et al. 1982). Hence a complex palaeotopography was inherited from the Oligocene, as discussed later in this study. ...
... This suggests that the normal fault was active during the Oligocene and involved the initiation of a depocentre that developed sub-parallel to the normal fault (Fig. 3). This tectonic activity is consistent with the Oligocene extensional phase related to the OWER as described at the European scale (Debelmas 1974;Hirn 1980;Curial 1986;Bergerat 1987;Ziegler 1988Ziegler , 1990Ziegler , 1994Bergerat et al. 1990;Sissingh 2003;Prodehl and Haak 2006). ...
Article
The Miocene of the Western Alpine foreland basin were deposited in a North-South seaway along the active alpine orogenic front. In the subalpine massifs and the southern Jura mountains, the revised Miocene stratigraphy documents a detailed chronology of thrust propagation at the western alpine front, where tectonic activity had a primary influence on seaway palaeogeographical evolution. Here we propose nine palaeogeographical maps during the Miocene, the first of which depicts the initial Miocene transgression at ∼21.0 Ma. Between ∼18.05 Ma and ∼12.0 Ma, a westward retreat of the Miocene Sea occurred in response to the activation of the basal thrust of the Belledonne massif, which in turn triggered successive fault zones from east to west. At ∼10.0 Ma, a major uplift phase intervened and induced a rapid southward retreat of the Miocene Sea. The reconstructed palaeogeographical maps outline the main controls on the foreland basin seaway evolution: (i) the timing of the main thrusts, (ii) the inherited palaeotopography and (iii) eustatic sea-level changes during the Miocene. These reconstructions are integrated at the basin scale, highlighting the southward to westward-directed seaway migration in response to the Belledonne thrust activity that deeply shaped the palaeogeographical evolution during the early to middle Miocene.
... This tectonic regime could be related to the N-S "Pyre nean1' compression, which started in Western Europe during the Eocene (Arthaud & Choukroune, 1972;Bergerat & Geyssant, 1980;Arthaud & Seguret, 1981;Villemin, 1986;Letouzey, 1986;Bergerat, 1987;Blés et ai, 1989) and/or to the "Helvetic" phase which continued until Early Miocene times (Ziegler, 1982). These events are thought to have been part ly interrupted by an extensional period during the Oligocène in the Central European shelf (Bergerat & Geyssant, 1980;Villemin, 1986;Bergerat, 1987). ...
... This tectonic regime could be related to the N-S "Pyre nean1' compression, which started in Western Europe during the Eocene (Arthaud & Choukroune, 1972;Bergerat & Geyssant, 1980;Arthaud & Seguret, 1981;Villemin, 1986;Letouzey, 1986;Bergerat, 1987;Blés et ai, 1989) and/or to the "Helvetic" phase which continued until Early Miocene times (Ziegler, 1982). These events are thought to have been part ly interrupted by an extensional period during the Oligocène in the Central European shelf (Bergerat & Geyssant, 1980;Villemin, 1986;Bergerat, 1987). This last extension is not expressed in the North Sea (Ziegler, 1987c). ...
Article
This microtectonic study has been carried out in the central and northern parts of England and in southernmost Wales. It has allowed us to point out several tectonic stages during the Permian-Cenozoic period. These have been tentatively correlated with the tectonic evolution of offshore basins. (1) The Permian/Early Triassic tectonic phase is characterized by a NNW-SSE trending extension. (2) During the Late Triassic to Early Malm, an E-W to ENE-WSW trending extension was acting. (3) The following tectonic event probably started during the Malm and was particularly active during the Early Cretaceous; it was characterized by a N-S to NNE-SSW trending extension. (4) Prior to the next tectonic regime, some local sites registered NW-SE trending compression. (5) The later tectonic event which affects a Paleocene dyke (Cleveland dyke) is characterized by a N-S trending compression and is supposed to be partly synchronous with the so called "Pyrenean' and/or "Helvetic' compressional events of the Eocene to Early Miocene. -from Authors
... L'histoire tectonique de l'Ouest européen est marquée par les périodes de convergence, durant les crises tectoniques du Paléogène et du Néogène (orogènes pyrénéen et alpin s.s.), et par un important épisode extensif lors de la formation du rift oligocène ouesteuropéen [e.g., Bergerat, 1987 ;Rocher et al., 2003]. A la lumière de cette histoire de la déformation (Fig. 5), il est possible de replacer les chronologies relatives affectant les filons sédimentaires et ainsi d'en contraindre l'âge. ...
... La direction générale NNE-SSW des filons synsédimentaires est parallèle à celle des fentes de tension associées aux épisodes pyrénéo-provençaux s.l., datés de l'Eocène à l'Oligocène (σ3 E-W à NW-SE d'après Bergerat, 1987et Rocher et al., 2003, ce qui pourrait amener à les rattacher à ces événements. Cependant, les réactivations et les recoupements des filons sédimentaires par des failles ( Fig. 1 B) ou par des stylolites ( Fig. 1 C), attribués aux épisodes tectoniques tardi-crétacé et tertiaires, amènent à proposer un âge plus ancien (Fig. 5). ...
Article
Vertical fractures in Oxfordian limestones of the eastern part of the Paris Basin are interpreted as resulting from synsedimentary extensional deformations which occurred during the Mesozoic. These NNE-SSW striking fractures are 10 to 20 meters in height, and filled with microgranular material. The fractures mainly affect crinoidal and oolitic grainstones. Their micritic to microsparitic, lithoclast-bearing infills may have resulted from the solidification of an ancient mud injected from non-lithified, overlying layers of marine sediments. They should therefore be referred to as sedimentary dykes. Graded layering suggests deposition under turbulent flow conditions, whereas later plastic deformation and breccia formation indicate a syndiagenetic reworking. Such observations are consistent with a predominance of the sedimentary dykes in grainstones, which are more rapidly lithified and therefore subject to early fracturing. On the contrary, these dykes are rare in mudstones which may constitute the source of the material for the infills in the grainstones. Both the analysis of the wall geometry and the reconstruction of the diagenetic history of the infills make possible to distinguish two types of sedimentary dykes. The first type corresponds to a fracturation characterized by irregular walls around the rock-constituting grains (i.e. crinoidal debris or ooids), whereas the walls in the second type are cross-cutting the grains and present a fringe of sparite predating the microsparite infill. The following scenario is proposed for the first type of sedimentary dykes: i) syntaxial cementation of crinoidal debris and early cementation of ooids; ii) fracturing along grain boundaries under low burial strain; iii) filling of fractures and open porosity by the mud. The second type of sedimentary dykes was formed under deeper burial conditions, which is indicated by both pre-existing bedding-parallel stylolites and the precipitation of sparite on the walls before the sedimentary infill. This early fracturation and the availability of a sedimentary filling, non-lithified material point to a late Jurassic age for these sedimentary dykes. The δ¹⁸OSMOW isotopic signatures measured for the infilling sparite and microsparite materials indicate that these were precipitated from meteoric waters, either early during the formation of the sedimentary dykes or during a later recrystallization event. The sedimentary dykes have recorded an E-W extension during the Oxfordian-Kimmeridgian period, which is in good agreement with the late Jurassic tectonic history of the western European platform. This early Oxfordian-Kimmeridgian fracturing and its associated fluid paleocirculations is of major interest in the context of the tectonic history of the Paris Basin, since most of these N-S to NNE-SSW tension gashes have been previously attributed to the Eocene Pyrenean shortening and Oligocene rifting stages.
... The stress field may be locally deformed according to the graben geometry and •rl may change from horizontal to vertical when approaching the graben. Segall and Pollard [1980] have demonstrated that strike-slip faults forming releasing geometries induce a complex stress pattern, with curved trajectories for •rl and •r3 and with •rl inferred to locally rotate to vertical in the stepover region (Figure 9a) Several models have been proposed to explain the formation of the West European Rift system [Ahorner, 1975;Tapponnier, 1977;Illies and Baumann, 1982;Bergerat, 1985Bergerat, , 1987Dewey and Windley, 1988;Vogt, 1991;Ziegler, 1992]. Most of them call for compressional stresses emanating from the Pyrenean and Alpine collisional fronts with succession of a north (Eocene-Oligocene) and a NNW striking (since middle Miocene) directed compression. ...
... At a prerift stage during the late Eocene, the continental block located east of the breaking line may have began to slightly move ENE, relatively to the western block (Figure 10a). Due to this horizontal block movement, all the faults were mainly transcurrent, in a strike-slip regime [Villernin and Bergerat, 1987]. ...
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From analysis of gravimetric data, comparisons of levelings, seismic profiling, paleostress analysis, and seismicity together with remotely sensed and morphological data, the Rhinegraben may be divided into several rhomb-shaped basins, separated by ENE trending basement highs. These data express neotectonic movements and slight spatial differences in the subsidence rate. These basins are asymmetrical: on one side they are bounded by a large normal fault zone; on the opposite side there is a megaflexure, cut by smaller normal faults shaping tilted blocks. Since the middle Miocene, extensional directions are subparallel to the ENE trending basement highs that consequently may be interpreted as strike-slip fault zones of transfer type. Across the Erstein basement high, there is a reversal in the rift asymmetry (major bordering fault on the western side to the south, on the eastern side to the north). When considered in the context of the West European Rift, the Rhinegraben is interpreted in terms of a pull-apart depression formed during the horizontal movement of blocks guided by large ENE trending transcurrent faults. The normal faults that are curved shaped in map view may mark the boundaries between areas where the maximum component (sigma-1) of the paleostress field developed in pull-apart patterns was changing from horizontal to vertical.
... The largest oceanic plateau on Earth, Ontong Java Plateau (OJP), located in the southwestern part of the Pacific plate, approached the subduction zone and resisted tectonic downwelling into Earth's mantle (Cox and Engebretson, 1985a,b;Mahoney and Coffin, 1997;Neal et al., 1997). As a result, the Pacific plate rotated 5 • -15 • clockwise, triggering a swarm of short-lived tectonic, volcanic, and structural events worldwide, such as the separation of the Mediterranean from the Atlantic, the formation of topographic divides, and the formation of ecological niches across continents (Figures 1, 2; citations for the events: Vogt, 1972Vogt, , 1979Hsü et al., 1973;Duncan and McDougall, 1974;Ryan and Cita, 1978;Matsubara and Seno, 1980;Leakey, 1981a,b;Hay and Leakey, 1982;Cox and Engebretson, 1985a,b;Sarewitz and Karig, 1986;Bergerat, 1987;Fitton, 1987;Joffe and Garfunkel, 1987;De Ribet and Patriat, 1988;Dewey et al., 1989;Patriat and Parson, 1989;Cloetingh et al., 1990;Pollitz, 1991;Coffin and Eldholm, 1994;Cande et al., 1995;deMenocal, 1995deMenocal, , 2004Rusby and Searle, 1995;Harrison et al., 1997Harrison et al., , 2004McNutt et al., 1997;Tebbens and Cande, 1997;Csontos and Nagymarosy, 1998;Kempler, 1998;Gutscher et al., 1999;Krijgsman et al., 1999;Ebinger et al., 2000;Krijgsman and Langereis, 2000;Wessel and Kroenke, 2000;Allen et al., 2002;Bruguier et al., 2003;Lodolo et al., 2003Lodolo et al., , 2013Bell, 2004;Cande and Stock, 2004;Duggen et al., 2004;Faccenna et al., 2004;Rankenburg et al., 2004;Ben-Avraham et al., 2005;Domínguez-Rodrigo et al., 2005;Eagles et al., 2005;Lu et al., 2005;Tassone et al., 2005;Wang et al., 2007;Croon et al., 2008;Woolley and Kjarsgaard, 2008;White et al., 2009;Cande and Stegman, 2011;Chauvel et al., 2012;Hilgen et al., 2012;Iaffaldano et al., 2012;Baristeas et al., 2013;Colli et al., 2014;Ghiglione et al., 2014Ghiglione et al., , 2016Ben-Avraham and Katsman, 2015;Maslin et al., 2015;Simon et al., 2015;Balázs et al., 2016;Capella et al., 2017;Macchiavelli et al., 2017;Leroux et al., 2018;Vibe et al., 2018;Rozenbaum et al., 2019). The tectonic and environmental disruption was profound and widespread, but shortlived. ...
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When early hominids began walking upright around 6 Ma, their evolutionary course took a sharp turn. The new posture enabled physical and mental developments that had not been possible before. The factors driving the transition from quadrupedalism to bipedalism remain open. Most studies have linked this fundamental transition to environmental, topographical, geomorphological, and climatic changes that progressively transformed jungle- and forest-dominated areas of southern and eastern Africa into vast savannas, thus partitioning ecological niches. During the same timeframe, major tectonic events occurred worldwide within a relatively short geological period, due to a significant and sudden shift in the motion of the Pacific plate. In our previous work, we coined the term ripple tectonics to link a major tectonic impact to the short-term local events it caused worldwide. The ripple tectonic cascade in the Pacific around 6 Ma instigated significant environmental transformations in Africa, which ultimately catalyzed the biological evolution of early hominids towards a bipedal posture.
... (F) Growth strata relationships at approximately 20 and 30 m above the river level, corresponding to S2b or S3 deposits according to regional correlation lines. wells, Fig. 15B, and ∼ 50-70 m for S3 sequence between SLF-1, MO-1, MO-2, and MO-3 wells, Fig. 15C), despite the presence of the FZ5 thrusts within transect C and possibly B. On the western edge of the Bas-Dauphiné basin, the absence of S2a-S2b deposits (to the northwest of PA-1, VAF-2, and MO-3 wells, Fig. 15A, B, C) and the thickness vari-ations of the S3 sequence to the west of the Montmiral high (Fig. 15B, C) are attributed to a complex inherited paleotopography (Kalifi, 2020) along the Oligocene western European Rift (Debelmas, 1974;Curial, 1986;Bergerat, 1987;Ziegler, 1988Ziegler, , 1990Ziegler, , 1994Bergerat et al., 1990;Sissingh, 2003). East of the Montmiral high, significant variations in depositional thickness are observed for the S4 sequence with a maximum located in the footwall of FZ4. ...
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After more than a century of research, the chronology of the deformation of the external part of the western Alpine belt (France) is still controversial for the Miocene epoch. In particular, the poor dating of the foreland basin sedimentary succession hampers a comprehensive understanding of the deformation kinematics. Here we focus on the Miocene molasse deposits of the northern subalpine massifs, southern Jura, Royans, Bas-Dauphiné, Crest, and La Bresse sedimentary basins through a multidisciplinary approach to build a basin-wide tectono-stratigraphic framework. Based on sequence stratigraphy constrained by biostratigraphical, chemostratigraphical (Sr isotopes), and magnetostratigraphical data between the late Aquitanian (∼ 21 Ma) and the Tortonian (∼ 8.2 Ma), the Miocene molasse chronostratigraphy is revised with a precision of ∼ 0.5 Ma. The Miocene molasse sediments encompass four different paleogeographical domains: (i) the oriental domain outlined by depositional sequences S1a to S3 (∼ 21 to ∼ 15 Ma), (ii) the median domain characterized by sequences S2 to S5 (∼ 17.8 to ∼ 12 Ma), (iii) the occidental domain in which sequences S2a to S8 (∼ 17.8 to ∼ 8.2 Ma) were deposited, and (iv) the Bressan domain where sedimentation is restricted to sequences S6 to S8 (∼ 12 to ∼ 8.2 Ma). A structural and tectono-sedimentary study is conducted based on new field observations and the reappraisal of regional seismic profiles, thereby allowing the identification of five major faults zones (FZs). The oriental, median, and occidental paleogeographical domains are clearly separated by FZ1, FZ2, and FZ3, suggesting strong interactions between tectonics and sedimentation during the Miocene. The evolution in time and space of the paleogeographical domains within a well-constrained structural framework reveals syntectonic deposits and a westward migration of the depocenters, allowing for proposing the succession of three deformation phases at the western Alpine front. (i) The first is a compressive phase (P1) corresponding to thrusting above the Chartreuse oriental thrust (FZ1), which was likely initiated during the Oligocene and rooted east of Belledonne. This tectonic phase generated reliefs that limited the Miocene transgression to the east. (ii) The second is a ∼ WNW–ESE-directed compressive phase (P2) lasting between 18.05 ± 0.25 Ma and ∼ 12 Ma, with thrusts rooted in the Belledonne basal thrust. Thrusts were activated from east to west: the Salève (SAL) and Gros Foug (GF) thrusts and then successively FZ2, FZ3, FZ4, and FZ5. Along two WNW–ESE balanced cross sections the amount of horizontal shortening is of ∼ 6.3 to 6.7 km, corresponding to average shortening rates of ∼ 1.2 km Myr-1 and migration of the deformation toward the west at a rate of ∼ 2.9 km Myr-1. During ∼ 6 Myr, the Miocene Sea was forced to regress rapidly westwards in response to westward migration of the active thrusts and exhumation of piggyback basins atop the fault zones. Phase P2 thus deeply shaped the Miocene paleogeographical evolution of the area and appears as a prominent compressive phase at the scale of the western Alps from the Swiss molasse basin to the Rhodano–Provencal one. (iii) The third is a ∼ 300 m phase of uplift in the Bas-Dauphiné (P3) of probable Tortonian age (∼ 10 Ma), which would have induced southward sea retreat and been coeval with the folding of the Jura in the north and possibly with back-thrusting east of the Chartreuse massif.
... The Limagne Basin corresponds to a north-south oriented half-graben, the largest of the Massif Central Rift (35 km large, Fig. 1A). This basin formed during the Tertiary (Bergerat, 1987) and belongs to the European Cenozoic Rift System (Merle et al., 1998;Michon and Merle, 2001;Sissingh 2001;Dèzes et al., 2004). The basin is divided into the "Limagne Bourbonnaise" in the north, the "Limagne de Clermont" in the central part and the "Limagne d'Issoire" in the south (Fig. 1B). ...
... In the northern part of the Massif Central, this extension led to the formation of the Limagne basin, bounded by N-S trending normal faults [ Figure 1A, e.g. Bergerat, 1987]. Later, from the upper Miocene, the stress field came progressively back to a meridian position [today ca N170°E in Western Europe; Heidbach et al., 2016] with the continuation of the plate convergence between Africa and Europe. ...
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The macroseismic and instrumental observations accumulated by the Bureau Central Sismologique Français and other national agencies over the last 100 years show that the northwestern part of metropolitan France is affected by an apparently diffuse and moderate intraplate seismicity. Far from any plate boundary, well-documented inherited structures, such as the Armorican shear zone network, the Sillon Houiller, and the normal faults related to the Atlantic ocean margin, likely exert significant control on the regional seismicity pattern. However, in the absence of a clearly measurable strain field, processes other than far-field tectonic stress loading such as erosion, gravitational potential energy, and/or hydraulic loadings can co-exist, but their respective influence on the current seismicity is debated and remains to be fully addressed. Reliable detection/location of low-to-moderate magnitude events is one of the most important challenges in the near future to better understand the processes that control this intraplate seismicity. As shown here for a limited region, this issue can be achieved positively, thanks to the new Résif-Epos network, in conjunction with sophisticated algorithms for both earthquakes’ detection and discrimination.
... The Limagne Basin corresponds to a north-south oriented half-graben, the largest of the Massif Central Rift (35 km large, Fig. 1A). This basin formed during the Tertiary (Bergerat, 1987) and belongs to the European Cenozoic Rift System (Merle et al., 1998;Michon and Merle, 2001;Sissingh 2001;Dèzes et al., 2004). The basin is divided into the "Limagne Bourbonnaise" in the north, the "Limagne de Clermont" in the central part and the "Limagne d'Issoire" in the south (Fig. 1B). ...
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The Limagne Basin (Massif Central, France) originated during a major, European-scale, extensive event (European Cenozoic Rift System), which led to the formation of several rift systems in the foreland of the Alps between the Upper Eocene and Pliocene. A fluvio-lacustrine system emplaced in the basin and resulted in a mixed carbonate-siliciclastic sedimentation in which microbial and metazoan buildups occupy an important place. However, microbial deposits are not exclusive to the Cenozoic history of the Limagne Basin; nowadays, in the basin, they still form in association with thermal spring systems. A fieldtrip was carried out in the Limagne Basin as part of the Microbialites: formation, evolution and diagenesis (M-Fed) meeting (October 2019). The objective of this excursion was to assess the diversity of modern and fossil (Chattian to Aquitanian) microbial sediments and structures in three prime locations (the Jussat and Chadrat outcrops and the Grand Gandaillat quarry). A detailed description of the morphologies and fabrics of the buildups and their associated biotic components can be used to discuss the spatio-temporal distribution pattern. Different margin models are proposed based on the changes in the distribution, morphology and size of the microbial and metazoan-rich deposits through time. The Jussat outcrop offers novel perspectives to unravel the evolution of the lacustrine/palustrine cycles over time and to establish a long-term paleoenvironmental history of the western margin of the basin during the Aquitanian. These cycles are composed of (i) lacustrine sedimentation comprising microbial and metazoan buildups and organic matter-rich marls reflecting a period of high accommodation, and (ii) palustrine deposits made of mudstones and clayey paleosoils, indicative of a period of low accommodation. It is suggested that climatic, tectonic, volcanic and local parameters (physiography, substrate) control the deposition of the buildups in each of the different cycles. In addition, the modern microbial mats of the Sainte-Marguerite and La Poix outcrops offer an opportunity to approach the controlling processes at the origin of the mineralization involved in the formation of the microbialites and their preservation in the fossil record.
... Considering the tectonic history of the area, the large E-W fault zone crossing the quarry could be in relation with the Saalian tectonic phase which has an ESE-WNW to NW-SE-oriented stress field (Bergerat, 1987). This constitutes the last Hercynian compression phase during the Saxonian before the formation of Permo-Triassic basins, such as the Villé basin. ...
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Defining the fracture network and the active fluid pathways are fundamental to characterizing a fractured reservoir. With this goal, we chose the Saint Pierre Bois quarry (Vosges Massif, France) as a natural analogue for the Permian-Stephanian cover (arkoses)/Hercynian basement (granite) transition that serve as geothermal reservoirs, for example at Rittershoffen, Landau and Insheim, where geothermal plants exploit this kind of reservoir within the Upper Rhine Graben (URG). During our study, along walls of the quarry, we measured fracture orientation on multiple 1D scanlines, sampled fracture fills and associated wall rock, and measured porosity. Our interpretation of the fracture dataset and associated mineral deposits and alteration indicates a large unmapped fault zone (displacement around 10m) we infer to cross the quarry. This fracture zone comprises a core zone (>50 m thick), which is the most highly altered-fractured zone in the quarry. In the transition zone (20-25m thick), some E-W faults cross and displace the arkose/granite transition. The two major fracture sets (E-W and NNE-SSW strikes) are present in the damage zone (>100m thickness) and are typically randomly distributed, but sometimes are grouped in clusters (defined by high spacing coefficient of variation). The E-W fractures and faults are the result of local tectonic inheritance in relation to the Villé basin formation at the end of the Hercynian orogen. Based on rock alteration, these structures constitute good pathways for fluid, first of all for the meteoric fluid during the E-W fault zone creation associated to the Villé basin opening, and then for the hot brine, which clogged the system by quartz precipitation during the burial of the basin.
... Further east, the Africa-Eurasia-Anatolia convergence caused compression across the Alpine arc periphery [38]; tectonic inversion along the Mid-Hungarian line [39] [40]; subsidence of the south Caspian Sea [41]; and the uplift and emergence of Cyprus above the Mediterranean Sea Level since the late Miocene [42] [43]. This was accompanied by eastward migration of the Sinai-Arabia rotation pole and an increase in vertical subsidence along the Dead Sea Fault plate boundary [44]. ...
... The character of the postulated strike-slip regime has been subject of debate. Bergerat (1987) assumed that steeply dipping faults behaved during the Aquitanian as right-lateral strike-slip faults, whereas Meier and Eisbacher (1991) described a rotation of the extension direction from WNW-ESE during the Rupelian to NE-SW during the Aquitanian. This probably fits with the average NNW-strike direction of the normal faults that were active during the Late Chattian to Aquitanian or Burdigalian (Cerithium to Hydrobia Beds ;Schad 1964;Illies 1974;Manfred Lutz personal communication 2004). ...
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Abstract: A large-scale transfer zone subdivides the northern parts of the Upper Rhine Graben into a northern and a southern sub-basin. These sub-basins display the geometry of asymmetric half-grabens with opposing tilt directions. The transfer zone connects the western master fault of the northern half-graben with the eastern master fault of the southern half-graben. In the northern Upper Rhine Graben early syn-rift sedimentation (Late Priabonian to Late Rupelian) was controlled by the tectonically induced subsidence of these half-grabens (autogenetic), as well as by regional third-order sea level variations (allogenetic). Within the graben, lateral changes in subsidence rates (in dip and strike direction of fault blocks) controlled the development of accommodation space and thus, sediment thickness and facies. Furthermore, a low-displacement segment along the western border fault acted as a sediment entry point. Tectonics controlled the distribution of early syn-rift deposits and the palaeogeography of the northern Upper Rhine Graben. Keywords: Upper Rhine Graben, transfer zone, early syn-rift stage, tectonics, sedimentary cycles
... Further east, the Africa-Eurasia-Anatolia convergence caused compression across the Alpine arc periphery [38]; tectonic inversion along the Mid-Hungarian line [39] [40]; subsidence of the south Caspian Sea [41]; and the uplift and emergence of Cyprus above the Mediterranean Sea Level since the late Miocene [42] [43]. This was accompanied by eastward migration of the Sinai-Arabia rotation pole and an increase in vertical subsidence along the Dead Sea Fault plate boundary [44]. ...
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Subduction plays a fundamental role in plate tectonics and is a significant factor in modifying the structure and topography of the Earth. It is driven by convection forces that change over a >100 Myr time scale. However, when an oceanic plateau approaches, it plugs the subduction, and causes slab necking and tearing. This abrupt change may trigger a series of geodynamic (tectonic, volcanic) and sedimentary responses recorded across the convergence boundary and its surrounding regions by synchronous structural modifications. We suggest that a large enough triggering event may lead to a ripple tectonic effect that propagates outwards while speeding up the yielding of localized stress states that otherwise would not reach their threshold. The ripple effect facilitates tectonic, volcanic, and structural events worldwide that are seemingly unrelated. When the world’s largest oceanic plateau, Ontong Java Plateau (OJP), choked the Pacific-Australian convergence zone at ~6 Myr ago, it induced kinematic modifications throughout the Pacific region and along its plate margins. Other, seemingly unrelated, short-lived modifications were recorded worldwide during that time window. These modifications changed the rotation of the entire Pacific plate, which occupies ~20% of the Earth’s surface. In addition, the Scotia Sea spreading stopped, global volcanism increased, the Strait of Gibraltar closed, and the Mediterranean Sea dried up and induced the Messinian salinity crisis. In this paper, we attribute these and many other synchronous events to a new “ripple tectonics” mechanism. We suggest that the OJP incipient collision triggered the Miocene-Pliocene transition. Similarly, we suggest that innovative GPS-based studies conducted today may seek the connectivity between tectonic, seismic, and volcanic events worldwide.
... Elle aboutit à la collision pyrénéenne au sud (Choukroune et al., 1973). Elle entraine la formation d'un ensemble de plis et de chevauchements d'axes E/W et le rejeu en décrochement senestre d'accidents N/S à NE/SW pour partie héritée de la structuration hercynienne dans l'avant-pays nord pyrénéen et en Provence (Arthaud and Séguret, 1981;Bergerat, 1987 (Bergerat, 1982). La sédimentation dans la zone de Valence est caractérisée par des dépôts essentiellement d'âge 56 oligocène . ...
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Le bassin de Valence, un fossé d’effondrement appartenant au système ECRIS localisé le long du couloir Rhodanien, est l’objet d’études approfondies quant à son potentiel géothermique. Dû à l’histoire évolutive polyphasée du bassin, les réseaux de fractures du socle et de la base de la couverture sédimentaire ciblés pour l’exploitation géothermique présentent une organisation complexe. Cette étude vise donc à caractériser l’organisation du bassin de Valence et de ces réseaux de fractures. Elle s’appuie sur les données sismiques et de forages du bassin, ainsi que les cartes géologiques, le modèle numérique du terrain et des affleurements de la marge ardéchoise. Deux méthodes de caractérisation des orientations et des longueurs des fractures sont développées dans ce travail. Leur application a permis de déterminer les paramètres des modèles de réseaux de fractures, et a mis en évidence un fort héritage structural mais aussi un découplage du socle et de la couverture.
... The absolute motion of (38) Africa (relative to the hotspots) modelled for the past 30 My (Pollitz, 1991) (Mazzoli & Helman, 1994) and a change in motion is observed at the same time in the Pacific and Atlantic (Schouten, Dick, & Klitgord, 1987), as well as a decrease in spreading rate in the South Atlantic (N€ urnberg & M€ uller, 1991). Since the end of the Miocene, a fan-shaped distribution of directions of compression has developed at the periphery of the Alpine arc (Bergerat, 1987). Since the Late Messinian time, a generally E-W to NW-SE shortening affected more or less extensively the Alpine foreland. ...
... Les premiers dépôts syn-rift sont datés du Lutétien et sont localisés dans de petits bassins peu profonds, l'extension E-W contrôle alors la subsidence dans la partie nord du bassin (fossé de Bresse) (Sissingh, 2001). Au sud, la compression pyrénéenne N-S réactive les failles NE-SW des Cévennes et de Nimes en décrochement sénestre et contrôle l'extension (Arthaud et Séguret, 1981 ;Bergerat, 1987 ; Mauffret et Gennesseaux, 1989). ...
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En France métropolitaine, les projets de géothermie haute température pour la production d’électricité sont principalement localisés dans le socle des fossés d’effondrement liés à la mise en place du Rift Ouest Européen. Le socle de ces fossés a été étudié sur deux analogues à l’affleurement sur les épaules du rift : les Vosges du Nord pour le fossé Rhénan et la bordure Est du Massif central pour la fosse de Valence. Cette étude a permis de montrer que le réseau de failles s’organise selon trois ordres de grandeurs de longueurs et d’espacements caractéristiques qui individualisent des blocs structuraux. Les orientations et l’espacement des failles formant ces blocs et la présence ou l’absence de certains ordres de grandeurs sont le résultat de l’héritage anté-rift du socle, ainsi que du mécanisme d’ouverture du bassin. Le potentiel réservoir des formations de socle et de la couverture surincombante a été analysé au regard de ces zones de failles et de l’altération supergène qui affecte le toit du socle. Ainsi, les lithologies potentiellement rencontrées en base des fossés ont pu être classées en fonction du potentiel de développement de porosité et de perméabilité matricielle dans les cœurs de failles, les zones endommagées et le réseau pervasif de fractures dans le protolithe. L’évolution de la fracturation dans les zones de failles a également pu être appréhendé, et une méthodologie de modélisation double milieu a été élaborée pour caractériser la porosité et la perméabilité de fractures et modéliser le fonctionnement d’un doublet géothermique dans une faille synthéthique équivalente aux cibles des projets géothermiques
... Though being poorly recognized in NW Europe, this event is locally well expressed in the Armorican massif with the extensional rejuvenation of major brittle structures, such as Kerforne-type faults, including CTFS. Lastly, the late N20 • -N60 • E extensional fault network was emplaced under a WNW-ESE s3 during a late or post-Oligocene extension phase, also recorded around the Anglo-Paris basin in the above-mentioned Sussex area, UK (Duperret et al., 2012;Vandycke, 2002), in Belgium (Vandycke, 2002), and in Rhine-Sâone grabens (Bergerat, 1987;Lacombe et al., 1993), where it is related to the west European rifting. In the study area, this extensional event is assumed to have caused the structural splitting of the inner shelf into a mosaic of blocks, encompassing the Le Guilvinec triangle-shaped graben along a reactivated network of N20 • -N60 • E and N150 • -N170 • E extensional faults. ...
... Though being poorly recognized in NW Europe, this event is locally well expressed in the Armorican massif with the extensional rejuvenation of major brittle structures, such as Kerforne-type faults, including CTFS. Lastly, the late N20 • -N60 • E extensional fault network was emplaced under a WNW-ESE s3 during a late or post-Oligocene extension phase, also recorded around the Anglo-Paris basin in the above-mentioned Sussex area, UK (Duperret et al., 2012;Vandycke, 2002), in Belgium (Vandycke, 2002), and in Rhine-Sâone grabens (Bergerat, 1987;Lacombe et al., 1993), where it is related to the west European rifting. In the study area, this extensional event is assumed to have caused the structural splitting of the inner shelf into a mosaic of blocks, encompassing the Le Guilvinec triangle-shaped graben along a reactivated network of N20 • -N60 • E and N150 • -N170 • E extensional faults. ...
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The Variscan crystalline basement exposed along the SW Brittany coast recorded extensive long-term planation processes during Mesozoic times. Detailed onshore-offshore mapping (600 km²) in the Penmarc'h-Concarneau granitic coastal area reveals a km-scale, deeply fractured submarine rocky shelf. High-resolution offshore imagery (bathymetry and seismic reflection dataset), combined to structural field investigations, on these surfaces allow us to identify a preserved network of both ductile and brittle structures. The inherited fault pattern is dominated by the N160°E-trending and long-lived Concarneau-Toulven fault zone (CTFS) that separates two distinct morphostructural blocks, and strongly influences the seaward limit of the Concarneau submarine rocky shelf, as well as the linear coastline of the Concarneau embayment. The structural imprint of the CTFS decreases progressively westwards with respect to a composite network of large-scale N50°E- and N140°E-oriented faults bounding the seaward edge of the Penmarc'h rocky shelf. The latter in turn splits into three large-scale blocks along N50°E- (La Torche Fault - LTF), N140°E- (Saint Guénolé Fault - SGF), and N160°E-trending normal faults. The morphostructural evolutionary model applied here to the Penmarc'h-Concarneau granitic coastal area resulted from the combined effects of structural Variscan inheritance and post-Variscan tectonics. Paleo-stress analysis of striated fault planes indicates three main Cenozoic tectonic events, inferred to have operated from Eocene to post -Oligocene times. The 3D-architecture of the Concarneau embayment, as a rocky shelf partially sealed with quaternary sediments, chiefly resulted from the reactivation of the CTFS during Eocene and Oligocene times. Further west, the surface of the Penmarc'h rocky shelf was tilted southeastward by the brittle reactivation of the LTF, and dissected by a horst-graben network post-Oligocene in age. The present-day morphology of the Penmarc'h and Concarneau domains depends on distinct driving processes: the Concarneau N160°E coastline is clearly controlled by tectonic processes via the CTFS, while the Penmarc'h headland land-sea contact appears to have been shaped by post-Cenozoic eustatism.
... The absolute motion of (38) Africa (relative to the hotspots) modelled for the past 30 My (Pollitz, 1991) (Mazzoli & Helman, 1994) and a change in motion is observed at the same time in the Pacific and Atlantic (Schouten, Dick, & Klitgord, 1987), as well as a decrease in spreading rate in the South Atlantic (N€ urnberg & M€ uller, 1991). Since the end of the Miocene, a fan-shaped distribution of directions of compression has developed at the periphery of the Alpine arc (Bergerat, 1987). Since the Late Messinian time, a generally E-W to NW-SE shortening affected more or less extensively the Alpine foreland. ...
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A review of geological and geophysical observations points towards a worldwide kinematic change at around 6 Ma. The synchronicity of many manifestations (tectonics, magmatism, kinematics, ecological events, among others) at ~6 Ma, similar to those recognized from time to time on the geological timescale, argues for a global geodynamic event that has led to many regional consequences on Earth's surface. In particular, we propose that this global event was the main trigger for the three fold increase in sediment deposits in the world ocean over the last ~5 Ma, but also for the onset of the Messinian Salinity Crisis in the Mediterranean area, one of the most severe ecological crises in the Earth's history. We suggest this Messinian revolution to be the last occurrence of cyclic successions of global events.
... During the latest Eocene and Early Oligocene, the E-W extension in the West-European platform led to the formation of the West-European rift system [Bergerat, 1987;Hippolyte et al., 1991;Ziegler, 1994;Séranne, 1999]. During the Late Oligocene a second extensional phase was initiated as a result of the opening of the Liguro-Provençal back-arc basin [Rehault et al., 1984;Hippolyte et al., 1993;Mauffret and Gorini, 1996;Mauffret et al., 2004;Gattacceca et al., 2007;Jolivet et al., 2015]. ...
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The seaward extension of onshore formations and structures were previously almost unknown in Provence. The interpretation of 2D high-resolution marine seismic profiles together with the integration of sea-bottom rock samples provides new insights into the stratigraphic, structural and paleogeographic framework of pre-Messinian Salinity Crisis (MSC) deposits of the Provence continental shelf. Seven post-Jurassic seismic units have been identified on seismic profiles, mapped throughout the offshore Provence area and correlated with the onshore series. The studied marine surface and sub-surface database provided new insights into the mid and late Cretaceous paleogeography and structural framework as well as into the syn-and post-rift deformation in Provence. Thick (up to 2000 m) Aptian-Albian series whose deposition is controlled by E-W-trending faults are evidenced offshore. The occurrence and location of the Upper Cretaceous South-Provence basin is confirmed by the thick (up to 1500 m) basinal series downlaping the Aptian-Albian unit. This basin was fed in terrigenous sediments by a southern massif (" Massif Méridional ") whose present-day relict is the Paleozoic basement and its sedimentary cover from the Sicié imbricate. In the bay of Marseille, thick syn-rift (Rupelian to Aquitanian) deposition occurred (>1000 m). During the rifting phase, syn-sedimentary deformations consist of dominant N040 to N060 sub-vertical faults with a normal component and N050 drag-synclines and anticlines. The syn-rift and early post-rift units (Rupelian to early Burdigalian) are deformed and form a set of E-W-trending en echelon folds that may result from sinistral strike-slip reactivation of N040 to N060 normal faults during a N-S com-pressive phase of early-to-mid Burdigalian age (18-20 Ma). Finally, minor fault reactivation and local folding affect post-rift deposits within a N160-trending corridor localized south of La Couronne, and could result from a later, post-Burdigalian and pre-Pliocene compressive phase. Cadre tectonostratigraphique des formations anté-pliocènes du plateau continental de Provence (golfe du Lion oriental, SE France) Mots-clés. – Géologie marine, Tectonostratigraphie, Stratigraphie sismique, Paléogéographie crétacée, Rifting oligo-miocène, Compression post-rift Résumé. – Le prolongement en mer des formations et des structures provençales était jusqu'alors largement inconnu. L'interprétation de profils de sismique-réflexion marine 2D et l'intégration de dragages et carottages du fond-marin ont permis d'apporter des éléments nouveaux concernant le cadre stratigraphique, structural et paléogéographique des dé-pôts anté-Messiniens du plateau continental de Provence. Sept unités sismiques post-jurassiques ont été identifiées sur les profils sismiques, cartographiées à travers le plateau continental et corrélées avec les séries affleurant à terre. Une épaisse unité apto-albienne (jusqu'à 2000 m) dont le dépôt est contrôlé par des failles E-W a été mise en évidence en mer. L'existence d'un bassin subsident au Crétacé supérieur sur le plateau continental de Provence a été confirmée par le développement d'une épaisse série de bassin (jusqu'à 1500 m) reposant en downlap sur l'Apto-Albien. Le socle mé-tamorphique de l'écaille de Sicié et sa couverture sédimentaire peut être considéré comme une relique allochtone du « Massif Méridional » ayant alimenté le Bassin sud-provençal en éléments terrigènes au Crétacé supérieur. Dans la rade de Marseille, une épaisse unité syn-rift (Rupélien à Aquitanien) a été mise en évidence (>1000 m), structurée en une série de synformes en échelon d'axe E-W et affectée par des failles d'orientation dominante N040 à N060. Sur le flanc sud des synformes, la formation de plis d'axe N050 est associée à une déformation syn-sédimentaire. La formation des synformes en échelon d'axe E-W résulterait d'une réactivation en décrochement des failles N040 à N060 pendant une phase de compression N-S dont l'âge est compris entre le Burdigalien inférieur et moyen (18-20 Ma). Enfin, les dépôts post-rift sont affectés par des déformations mineures (réactivation de failles et plis associés), le long d'un couloir d'orientation N160 à l'ouest de la baie de Marseille, attribuables à une phase de compression post-burdigalienne et anté-pliocène.
... À l'ouest, le bassin est limité par le faisceau de failles NE-SW des Cévennes. L'extension mésozoïque a été suivie par un jeu décrochant senestre [Bergerat, 1965[Bergerat, , 1987Macquar, 1973] pendant les chevauchements à vergence nord de l'Éocène résultant d'une compression orientée N015E [Arthaud et Laurent, 1995]. Dans le golfe du Lion et dans les Corbières, le prolongement de ces accidents de direction cévenole s'infléchit vers le sud. ...
Article
Eocene "syntectonic" remagnetization has been documented throughout the Corbieres orocline, from the Fenouilledes area to the Saint-Chinian arc. Analysis of the Saint-Paul de Fenouillet synclinorium shows that, although the main part of this area retained its initial E-W orientation, its eastern end was affected by a strong anti-clockwise rotation. The N-S part of the orocline is composed of blocks that are several kilometres in size, which display homogeneous anti-clockwise rotations that differ from one block to another. Paleomagnetism brought out the importance of the Vingrau structure that trends NE-SW like the fault network of the Cevennes, and which itself separates blocks affected by differing amounts of rotation. Moreover, it has been shown that the basement has also been affected by the same rotation as the overlying Corbieres thrust sheet. Comparison between the paleomagnetic data and the remagnetization obtained in the Cevennes area (which dated the MVT ore deposit to the Eocene), shows that similar remagnetization also affects the Pyrenean foreland.
... Au cours du Miocène la plate-forme ouest européenne est à nouveau soumise aux effets de l'orogenèse alpine (phase alpine s.s.) et à une compression orientée globalement NW-SE (Bergerat, 1987 ;Suzzoni, 1988). C'est donc au Mio-Pliocène qu'il convient de rapporter les derniers rejeux compressifs, postérieurs aux argiles à silex, des failles affectant la couverture mésozoïque de la feuille. ...
... À l'ouest, le bassin est limité par le faisceau de failles NE-SW des Cévennes. L'extension mésozoïque a été suivie par un jeu décrochant senestre [Bergerat, 1965[Bergerat, , 1987Macquar, 1973] pendant les chevauchements à vergence nord de l'Éocène résultant d'une compression orientée N015E [Arthaud et Laurent, 1995]. Dans le golfe du Lion et dans les Corbières, le prolongement de ces accidents de direction cévenole s'infléchit vers le sud. ...
Article
Une réaimantation “syntectonique” éocène a été mise en évidence dans toute la virgation des Corbières, des Fenouillèdes à l’arc de Saint-Chinian. Son analyse montre que le synclinorium de Saint-Paul de Fenouillet a conservé son orientation E-W originelle, alors que son extrémité orientale a subi une torsion anti-horaire importante à l’amorce de la virgation. La branche méridienne de la virgation est composée de blocs plurikilométriques qui présentent une rotation senestre homogène sur toute leur surface, mais différente d’un bloc à l’autre. Le paléomagnétisme a permis de mettre l’accent sur le caractère majeur de l’accident de Vingrau, orienté NE-SW comme le réseau de failles des Cévennes, qui limite des blocs ayant subi, de part et d’autre, des rotations de valeurs différentes. En outre, il a été démontré que localement le socle avait subi la même rotation au même titre que la nappe des Corbières qui le surmonte. La comparaison des données paléomagnétiques avec la réaimantation, déterminée dans les Cévennes et ayant permis de dater de l’Eocène les minéralisations sulfurées liées aux strates (MVT), montre que la même réaimantation est présente dans l’avant-pays pyrénéen.
... À l'ouest, le bassin est limité par le faisceau de failles NE-SW des Cévennes. L'extension mésozoïque a été suivie par un jeu décrochant senestre [Bergerat, 1965 [Bergerat, , 1987 Macquar, 1973] pendant les chevauchements à vergence nord de l'Éocène résultant d'une compression orientée N015E [Arthaud et Laurent, 1995] . Dans le golfe du Lion et dans les Corbières , le prolongement de ces accidents de direction cévenole s'infléchit vers le sud. ...
Article
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Résumé. – Une réaimantation "syntectonique" éocène a été mise en évidence dans toute la virgation des Corbières, des Fenouillèdes à l'arc de Saint-Chinian. Son analyse montre que le synclinorium de Saint-Paul de Fenouillet a conservé son orientation E-W originelle, alors que son extrémité orientale a subi une torsion anti-horaire importante à l'amorce de la virgation. La branche méridienne de la virgation est composée de blocs plurikilométriques qui présentent une rota-tion senestre homogène sur toute leur surface, mais différente d'un bloc à l'autre. Le paléomagnétisme a permis de mettre l'accent sur le caractère majeur de l'accident de Vingrau, orienté NE-SW comme le réseau de failles des Céven-nes, qui limite des blocs ayant subi, de part et d'autre, des rotations de valeurs différentes. En outre, il a été démontré que localement le socle avait subi la même rotation au même titre que la nappe des Corbières qui le surmonte. La com-paraison des données paléomagnétiques avec la réaimantation, déterminée dans les Cévennes et ayant permis de dater de l'Eocène les minéralisations sulfurées liées aux strates (MVT), montre que la même réaimantation est présente dans l'avant-pays pyrénéen. Abstract. – Eocene "syntectonic" remagnetization has been documented throughout the Corbières orocline, from the Fenouillèdes area to the Saint-Chinian arc. Analysis of the Saint-Paul de Fenouillet synclinorium shows that, although the main part of this area retained its initial E-W orientation, its eastern end was affected by a strong anti-clockwise ro-tation. The N-S part of the orocline is composed of blocks that are several kilometres in size, which display homoge-neous anti-clockwise rotations that differ from one block to another. Paleomagnetism brought out the importance of the Vingrau structure that trends NE-SW like the fault network of the Cévennes, and which itself separates blocks affected by differing amounts of rotation. Moreover, it has been shown that the basement has also been affected by the same rota-tion as the overlying Corbières thrust sheet. Comparison between the paleomagnetic data and the remagnetization ob-tained in the Cévennes area (which dated the MVT ore deposit to the Eocene), shows that similar remagnetization also affects the Pyrenean foreland.
... Fault-slip data from Lacombe et al. [1992] indicate a N-S compression during the Late Cretaceous-Eocene along the Sainte-Victoire range and the Arc basin. Other data from Bergerat [1987], show that this shortening direction was the same in the whole European platform during this same period. However we present here structural data that suggest a N145 o to N155 o shortening along the La Nerthe range. ...
Article
The Eocene shortening directions along the Southern Provence fold-and-thrust belt are commonly assumed to be N-S. We present here new observations and data that allow reinterpreting the structure of the La Nerthe range as a right-lateral transpressive flower structure. Structural data collected along the range argue for an Eocene N145o shortening event. The age of this shortening event is constrained by the fact that faulting and folding affect the Late Cretaceous-Paleocene continental deposits along the northern flank of the La Nerthe range and is sealed by the Miocene marine deposits. Moreover striated fault planes display both horizontal and vertical striae suggesting that they were reactivated during the Oligocene extensional event. We question here the shortening directions along the Southern Provence thrust belt. Structural data suggest both N-S and NNW-SSE shortening directions during the Eocene. During the Eocene the Provence area was in the foreland of a complex orogenic belt that extended from the Betic Cordillera to the Corsica-Sardinia block. This orogenic belt developed along the subduction linked to the convergence between Africa and Eurasia. Although the convergence vector was nearly N-S the NE-SW orientation of the trench may have led to a complex deformation pattern along the orogenic belt with NW-SE and N-S shortening directions that reflected both the along-trench compression and the regional convergence.
... This generalised E-W extension, while Africa and Europe were still undergoing N-S convergence, can be explained by a slower rate of expansion of the North Atlantic in relation to the Central Atlantic during this period. This in turn led to sinistral displacement in the African-Arabian block in relation to Europe (Bergerat, 1987;Ziegler, 1988), with this strike-slip component dominating the N-S convergence component. In the Paris Basin, the accommodation curves show a resumption of subsidence. ...
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This article presents the preliminary results of a study concerning the relationships between weathering and instances of vertical deformation of the west European lithosphere in France during the post-Paleozoic period.
... À l'ouest, le bassin est limité par le faisceau de failles NE-SW des Cévennes. L'extension mésozoïque a été suivie par un jeu décrochant senestre [Bergerat, 1965[Bergerat, , 1987Macquar, 1973] pendant les chevauchements à vergence nord de l'Éo- cène résultant d'une compression orientée N015E [Arthaud et Laurent, 1995]. Dans le golfe du Lion et dans les Corbiè- res, le prolongement de ces accidents de direction cévenole s'infléchit vers le sud. ...
Conference Paper
This study was carried out in the eastern part of the French Pyrénées where the tectonic structures, E-W oriented, bend northward at the Corbières virgation. This change affects the North-Pyrenean zone that overlains the foreland at the North Pyrenean thrust and its eastern extension, the Corbières thrust sheet. In this area, the Corbières thrust sheet is formed by the Mesozoic cover overlying down flat the Cenozoic formations of the Aude basin. The studied sites belongs to the North Pyrenean zone and to the Corbières thrust sheet and correspond to ages from Lias to Lower Cretaceous. Rock-magnetism analyses indicate that magnetite is the main magnetization carrier. Natural Remanent Magnetization mostly corresponds to a viscous component A and a component B determined during treatments from 300 to 400-500°C. Some samples also present a higher temperature component C, which cannot be isolated because of strong mineralogical alteration during thermal demagnetization at these temperatures or of too weak magnetization intensity. Dip variation in neighboring sites allows fold tests indicating synfolding remagnetization (i.e. acquired between or during different tectonic phases) for the component B. Direction of the latter has been then determined using small circles method for groups of neighboring sites. Previous study presented last year and made in the large Saint-Paul de Fenouillet syncline showed that western E-W part of the syncline is only locally affected by weak rotations while a large counterclockwise rotation affected all the eastern part of the syncline at the Corbières virgation during the Tertiary tectonic phase. New data have been acquired in numerous sites from the Corbières thrust sheet south from the Aude River. They point out that the different units of the Corbières thrust sheet also show large counterclockwise rotation. The emplacement of the the Corbières thrust sheet then appears as the result of a large movement of rotation of the North Pyrenean cover rather than a simple northeastward translation of a cover. Use of small circles method also yields the reconstruction of folds at the intermediate stage of folding. Main folding periods were the Upper Cretaceous and the Eocene. In the western part of the Saint-Paul de Fenouillet syncline, the main folding is of Tertiary age, but the relative importance of the two phases of folding is much more variable in the eastern part of the syncline and in the Corbières thrust sheet of more southern origin.
... The Eocene compressional phase was followed by a significant extensional episode in the European plate with the formation of the Oligocene-Early Miocene grabens (graben of the Rhine, Bresse and Limagnes, Gulf of Lion) (Bergerat, 1987;Olivet, 1996). This extension is a result of the subduction of the African plate below the European plate (35 to 19 My). ...
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We present a lithospheric section of the northern Tyrrhenian basin based on principal observations along a transect from Corsica Island to Tuscany margin. Offshore, crustal structure observations come from the LISA deep seismic cruise, composed by Multi-Channel Seismic profiles and wide angle reflection/refraction seismic data. Other parts of the section are constrained by published data, from different geophysical sources. A great detachment between Alpine Corsica and Hercynian Corsica constitutes the base of the Corsica basin. The end of this detachment is probably located below the Elba Island in the ductile lower crust where we observed an east dipping reflector interpreted as ductile shear zone. Similar detachments have been observed beneath the Punta-Ala basin on the Tuscany margin. Our section shows a thin crust below Corsican Basin (15 km thick) and a thicker crust below the Pianosa ridge (25 km). Between Elba Island and the Tuscany coast the Moho reflections shallow to (23 km/depth) as identified on the MCS profiles and from the modelling of the wide-angle reflection/refraction seismic date. An asthenospheric mantle uplift produces a significant heat flow below the Tuscany margin. The base of the lithosphere is located at 75 km depth below the Corsica margin, at 50 km below the Corsica basin and as shallow as 30 km below the Tuscany margin. The shift observed between the Corsica Basin and the Tuscany coast suggests an asymmetric lithospheric thinning which involves a detachment fault located at the base of the Corsican basin.
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We present a compilation of over 1700 focal mechanisms for nearly 1300 earthquakes in metropolitan France and conterminous Western Europe. It is based on both published and unpublished sources (articles, reports, observatory websites) for which the focal mechanism solutions have been verified for internal consistency, corrected in cases of minor errors and rejected in cases of major inconsistencies between the parameters. The database, labeled FMHex20, is a first version and should be regularly updated in the future as part of an ongoing effort within the Seismicity Transverse Action of the French RESIF research infrastructure. We also present first-order seismotectonic analyses for the whole metropolitan France and for a couple of example regions (Western France and Northern Alps-Jura-Vosges) to illustrate how the FMHex20 database can serve as a basis for geodynamic or seismic hazard zonation studies. Combined with complementary datasets, it can improve our understanding of the kinematics of potentially active faults, including in very-low-strain-rate regions as is the case for most of metropolitan France.
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Numerous recent studies indicate that crustal-scale fault zones represent efficient conduits for meteoric fluids to flow down to mid-crustal depths (Haines et al., 2016). The present study aims to understand the potential of a new and novel type of geothermal system for high temperature and electricity production: Crustal Fault Zones (CFZ). One such example is the Pontgibaud fault zone (French Massif Central), a 30 km-long and 3 km-wide mineralized fault zone. The Pontgibaud fault zone is also characterized by numerous CO 2-rich-thermo-mineral springs. Moreover, this area is also defined by local and regional surface heat flow values of 110 mW/m 2 (International Heat Flow Commission database) involving temperature gradients between 37 and 41 °C/km. The Pontgibaud fault zone has been well studied in the last few years (Bellanger et al., 2017), electrical conductivity anomalies have been identified (Ars et al., 2019) and the temperature anomaly has been estimated (Duwiquet et al., 2019). Estimation of the geothermal resource have been established by 2D geological numerical modelling, with Thermal-Hydraulic (TH) coupling. Here we propose to integrate structural field observation into 3D geological numerical modelling with Thermal-Hydraulic-(Mechanical) (TH(M)) coupling. We then evaluate the various applications for high-temperature geothermal exploitation.
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The Limagne Basin (French Massif Central) is an extensive continental lacustrine system accommodating microbial and metazoan buildups from Chattian to Aquitanian age. A description of these buildups and their associated biotic components in Grand Gandaillat and Crechy quarries provides insights into their spatio-temporal distribution patterns. Flats, cauliflowers, domes, cones and coalescent columnar morphologies have been identified with a main laminated mesofabric and laminated, columnar, filamentous and caddisfly-coated microfabrics. Two low-gradient margin models emerged based on the changes in the distribution, morphology and size of the microbial and metazoan-rich deposits through time: the first model applies to the Chattian deposits in the Grand Gandaillat quarry and the second to the Aquitanian deposits in the Crechy quarry. This study emphasizes the heterogeneity of marginal lacustrine carbonate-siliciclastic cycles. The lacustrine/palustrine cycles of the Limagne Basin record (i) lacustrine deposits composed of microbial and metazoan buildups and organic matter-rich marls indicating periods of high accommodation, and (ii) palustrine deposits composed of mudstone and clayey paleosoils, indicative of periods of low accommodation. The cycles differ with thin and symmetrical deposits that dominate the Chattian cycles whereas thicker and asymmetrical deposits mark the Aquitanian cycles. In addition, the Chattian buildups are exclusively microbial and only a few centimeters thick whereas the Aquitanian ones are multiple meters in height and are composed of both microbes and metazoans. Climatic, tectonism, volcanic and local parameters are involved in the deposition of buildups and their organization in each different cycle. Climate may control the long-term arid/humid sedimentary succession, tectonic may explain the difference in the deposit thickness between two cycles of different ages and localizations as well as the specific distribution of the buildups throughout the basin, volcanism may control the chemical lacustrine conditions and local physiography may impact the soil removal ability of the lake margin.
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Les reliefs culminants des Monts du Vivarais font figure de reliefs résiduels s'enlevant au-dessus des vestiges d'une haute surface d'érosion, la surface éotertiaire S1, dans laquelle les auteurs voient — comme en Limousin — une paléoforme dérivée acycliquement de la pédiplaine permo-triasique So. Les vestiges de S1 dominent à leur tour, par des talus francs, une basse surface d'érosion, la surface mésotertiaire S2. Le façonnement de S2 est mis au compte d'une pédiplanation mésonummulitique (Eocène supérieur - Oligocène inférieur). Ce sont les produits de cette pédiplanation qui ont alimenté les séries corrélatives piégées dans les bassins du Velay, du Forez et du Bas-Dauphiné. La reprise d'érosion cyclique responsable de l'étagement S1 - S 2 est imputée à un ploiement en dôme de S1, en contrecoup de la phase pyrénéenne de l'orogénie alpine. Il ne semble pas que les implications géomorphologiques directes du rifting oligocène aient été à la mesure de l'intérêt tectonique du phénomène. Tout se passe en effet comme si, réserve faite des abords immédiats du rift, les équilibres géomorphologiques hérités du Mésonummulitique s'étaient réaménagés acycliquement jusqu'à la fin de l'Oligocène. Ce n'est qu'à l'époque suivante, et en liaison avec le jeu d'une puissante flexure méridienne, que le Piedmont rhodanien s'individualisera vis-à-vis de la Montagne vivaraise.
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This review paper deals with the geology of the NW Indian Himalaya situated in the states of Jammu and Kashmir, Himachal Pradesh and Garhwal. The models and mechanisms discussed, concerning the tectonic and metamorphic history of the Himalayan range, are based on a new compilation of a geological map and cross sections, as well as on paleomagnetic, stratigraphic, petrologic, structural, metamorphic, thermobarometric and radiometric data. The protolith of the Himalayan range, the North Indian flexural passive margin of the Neo-Tethys ocean, consists of a Lower Proterozoic basement, intruded by 1.8-1.9 Ga bimodal magmatites, overlain by a horizontally stratified sequence of Upper Proterozoic to Paleocene sediments, intruded by 470-500 Ma old Ordovician mainly peraluminous s-type granites, Carboniferous tholeiitic to alkaline basalts and intruded and overlain by Permian tholeiitic continental flood basalts. No elements of the Archaen crystalline basement of the South Indian shield have been identified in the Himalayan range. Deformation of the Himalayan accretionary wedge resulted from the continental collision of India and Asia beginning some 65-55 Ma ago, after the NE-directed underthrusting of the Neo-Tethys oceanic crust below Asia and the formation of the Andean-type 103-50 (-41) Ma old Ladakh batholith to the north of the Indus Suture. Cylindrical in geometry, the Himalayan range consists, from NE to SW, from older to younger tectonic elements, of the following zones: 1) The 25 km wide Ladakh batholith and the Asian mantle wedge form the backstop of the growing Himalayan accretionary wedge. 2) The Indus Suture zone is composed of obducted slices of the oceanic crust, island arcs, like the Dras arc, overlain by Late Cretaceous fore arc basin sediments and the mainly Paleocene to Early Eocene and Miocene epi-sutural intra-continental Indus molasse. 3) The Late Paleocene to Eocene North Himalayan nappe stack, up to 40 km thick prior to erosion, consists of Upper Proterozoic to Paleocene rocks, with the eclogitic and coesite bearing T'so Morari gneiss nappe at its base. It includes a branch of the Central Himalayan detachment, the 22-18 Ma old Zanskar Shear zone that is intruded and dated by the 22 Ma Gumburanjun leucogranite: it reactivates the frontal thrusts of the SW-verging North Himalayan nappes. 4) The late Eocene-Miocene SW-directed High Himalayan or "Crystalline" nappe comprises Upper Proterozoic to Mesozoic sediments and Ordovician granites, identical to those of the North Himalayan nappes. The Main Central thrust at its base was created in a zone of Eocene to Early Oligocene anatexis by ductile detachment of the subducted Indian crust, below the pre-existing 25-35 km thick NE-directed Shikar Beh and SW-directed North Himalayan nappe stacks. 5) The late Miocene Lesser Himalayan thrust with the Main Boundary Thrust at its base consists of early Proterozoic to Cambrian rocks intruded by 1.8-1.9 Ga bimodal magmatites. The Subhimalaya is a thrust wedge of Himalayan fore deep basin sediments, composed of the Early Eocene marine Subathu marls and sandstones as well as the up to 8'000 m-thick Miocene to recent Ganga molasse, a coarsening upwards sequence of shales, sandstones and conglomerates. The active frontal thrust is covered by the sediments of the Indus-Ganga plains.
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Geomorphological studies led in the natural region ot Ried nord allowed to comprehend its hydrological mechanisms and evolutions from the Bronze Age to the Antiquity/Early Middle Age. Livelihood in this area has also been assessed. During the Bronze Age (2859-2757 cal. BP; 3441-3264 cal. BP), the site is occupied by an active meander of the Rhine. The surrounding landscape is covered by an alluvial forest. Clearing evidences are observed, probably located on the terrace of Haguenau. Then, step by step, the channel is filled. During Hallstatt-Early Tene period (2759-2378 cal. BP), the area evolves towards a paludal environment and clearing activities are identified in the surroundings; first evidence of anthropisation and farming are recorded. After this paludal episode, the "Ried nord" shows hydrological activity taking back and alluvial forests cover again the landscape. However on-going farming evidences are recorded. Around 2 296-1999 cal. BP, the channel is active again and the stream flow raises regularly. Over this period, pollen grains are not preserved. Progressively, the size of the channel seems to decrease until its permanent closure at the beginning of the Antiquity. In the Early Middle Ages the ground is stable enough to allow the settlement implementation.
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Geological and geomorphological studies performed during an operation of preventive archaeology (Parc d'Activités Economiques Intercommunal du Giessen, Scherwiller, Bas-Rhin, 2008), on paleochannels of a vosgian river, the Giessen, provide new insight on the formation, the evolution and the interactions between man and environment in this area during the Holocene. The approach was based on the field observation and data from sedimentology, chronostratigraphy and palynology. During the early and middle Holocene, the studied zone was crossed by three channels: they are respectively dated from the Boreal (10200-8900 cal. BP)/early Atlantic (8900-6800 cal. BP), recent Atlantic (6800-5700 cal. BP) and Subboréal (5700-2600 cal. BP). They migrated step by step to the northward to the course of the present river. The presence of an artificial antic pool, around which Gallo-Roman farm activity was developed, has allowed the recording and analysis of the recent Holocene sequences. No deposit by the Giessen in the IIIth century is recorded. The alluvial plain alternated between wet and drier zones. From the IVth century, Gallo-Roman occupation and the Giessen River seem to have migrated away from the pool, and the depression was filled by the deposition of suspended overflow material. From the VIIIth century until the contemporary period, the area was covered by deposits of Giessen overflow. The diversity of sedimentary facies underlines the large potential of the Giessen divagations. This increase of the deposits is associated with a constant land-clearing.
Article
Geological and geomorphological studies performed during an operation of preventive archaeology (Parc d’Activités Economiques Intercommunal du Giessen, Scherwiller, Bas-Rhin, 2008), on paleochannels of a vosgian river, the Giessen, provide new insight on the formation, the evolution and the interactions between man and environment in this area during the Holocene. The approach was based on the field observation and data from sedimentology, chronostratigraphy and palynology. During the early and middle Holocene, the studied zone was crossed by three channels: they are respectively dated from the Boreal (10200-8900 cal. BP) / early Atlantic (8900-6800 cal. BP), recent Atlantic (6800 - 5700 cal. BP) and Subboréal (5700-2600 cal. BP). They migrated step by step to the northward to the course of the present river. The presence of an artificial antic pool, around which Gallo-Roman farm activity was developed, has allowed the recording and analysis of the recent Holocene sequences. No deposit by the Giessen in the IIIth century is recorded. The alluvial plain alternated between wet and drier zones. From the IVth century, Gallo-Roman occupation and the Giessen River seem to have migrated away from the pool, and the depression was filled by the deposition of suspended overflow material. From the VIIIth century until the contemporary period, the area was covered by deposits of Giessen overflow. The diversity of sedimentary facies underlines the large potential of the Giessen divagations. This increase of the deposits is associated with a constant land-clearing.
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The southern Black Forest inspired Walther Penck to develop his theory on the relations between Piedmont benchlands and tectonics. The explanation proposed by Penck has to be rejected, but the results of field investigation provide evidence for the existence of culminating step-like landforms. Flat ridge summits are arranged in steps with distinct 'cyclic' scarps in between. Three true erosion surfaces, S1, S2 and S3, are identified in the Feldberg and Belchen areas. S1 is presumed to derive from the Permo-Triassic pediplain through an acyclic evolution, whereas S2 and S3 are correlated with updoming under compressive phases of the alpine orogeny in the mid-Tertiary and the Miocene respectively. The morphology and formation of scarps suggest pedimentation processes as responsible for their formation. Lower terraces have been carved by linear incision as a result of uplift during the Plio-Pleistocene. The carving of cirques during the Pleistocene was locally facilitated by the occurrence of cyclic scarps.
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In the La Serre horst of the Alpine foreland, the pre-Triassic La Serre median fault zone separates a Late Devonian-Early Carboniferous granite from an ignimbrite of unknown age and from Permian deposits. Motion along this fault zone took place first in ductile conditions and then evolved in brittle conditions. Both ductile and brittle shear criteria indicate a top-NE normal-dextral displacement. Similar motions are reported along faults bounding Late Palaeozoic intramontane coal basins located in the Massif Central and correspond to a widespread NE-SW Late to Post-Orogenic extension that affected the Variscan basement during Late Carboniferous to Early Permian times. To cite this article: G. Coromina, O. Fabbri, C. R. Geoscience 336 (2004).
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Fault plane solutions for 128 earthquakes which occurred in France and neighbouring areas have been determined. Stress field information given by these data are discussed in relation to previous tectonic knowledge.The Western Alps are characterized by a compressional regime with a fan-shaped distribution of P axes, which might be related to the interaction mechanism between Europe and the Adriatic plate.The Pyrenean region is mainly submitted to a south-north compression. Tectonic activity in this area seems to be determined by the presence of two subduction zones with reverse dips, in the South Bay of Biscay and in the Central Pyrenees.The transition zone between these two active belts is characterized by significant seismicity with a transpression regime.
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Recent tectonics in the southern Alps is studied by means of a brittle microtectonics analysis. The results enable reconstruction of the stress field evolution since late Oligocène. We show that this evolution depends on the boundary conditions for each domain. The quick variation of stress directions in the Digne and Nice nappes are due to the free boundary conditions which exist in their fronts (Valensole and Var basins respectively). They have favoured gravitationnal phenomena in the uplifted inner parts of the nappes. The Castellane nappe, which is locked in its front against the Maures massif, displays a more stable stress field. The reconstruction of the quaternary stress field allows us to determine focal mechanisms of possibly active major faults. These results are compared with historical seismicity and earthquake focal mechanisms. A geodynamical model is proposed in conclusion.
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This paper is included in the Special Publication entitled 'Cenozoic foreland basins of Western Europe' edited by A. Mascle, C. Puigdefabregas, H.P. Luterbacher and M. Fernandez. The tectonic evolution of the NW alpine front and foreland basin is reviewed in the light of new structural and chrono-stratigraphical data. Seismic-reflection profiles from the Jura fold thrust belt and Molasse basin, surface-geology and thrust-system considerations lead to a complete cross-section of the NW Alpine front including the Helvetic domain. Restoration of this section places individual Cenozoic formations in their approximate palaeogeographic position. 'Geohistory' plots are constructed for five profiles along a SE-NW transect. Thrust front, onlap and forebulge advanced at high rates of 10-20 km/Ma -1 at the onset of foreland basin formation in the late Eocene/early Oligocene (40-30 Ma). In these early stages, the foreland basin is an underfilled flexural trough with about 100 km width, less than 600 m water depth at the deepest point and less than 200 m of total accumulated sediments. From 30 to 22 Ma, thrust front and 'pinch-out' migrate at a decreased rate of about 5 km/Ma -1 northwestward. The basin width remains constant at around 100 km; an increased total subsidence (c. 2.7 km) is compensated by sedimentation. At around 22 Ma, the thrust front seems to come to a halt southeast of Lausanne, whereas a strong subsidence trend prevails. After the Serravallian (c. 12 Ma) the Alpine thrust front jumps by about 100 km northwestward from a position southeast of Lausanne to the external Jura leading to thrust related uplift, deformation and concommitant erosion of the entire basin fill. No new flexural foreland basin in response to the modified thrust- and load-geometry has yet been developed. The present-day Molasse basin is only a small remnant of a much larger foreland basin in a very advanced stage of its evolution.
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Detailed studies of fracture patterns and palaeostress reconstruction based on fault slip data analysis allow identification of five main palaeostress fields in the Cretaceous formations of the Boulonnais and Kent areas. These stress patterns correspond to six successive tectonic events: (1) a N-S compression/E-W extension of early Cenomanian age, (2) an E-W extension of late Cenomanian age, and (3) four post-Santonian events with N-S, E-W, NW-SE and NE-SW extensions, respectively. The first event, interpreted from conjugate strike-slip faults is related to the beginning of the Sub-Hercynian phase and linked to a right-lateral motion of the Nord-Artois Shear Zone. The first E-W extensional event and the N-S extensional event could be related to the last rifting episodes of the North Sea graben and English Channel (Wessex basin). The others post-Santonian extensional events are related to Late Cretaceous, Tertiary and Recent tectonic episodes.
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