jeanflop/post_ocr_correction2 huggingface dataset:
de Toulouse, 1990, 267 p. G. BÉSSIERE, R. MIROUSE et M.-F. PERRET, Découverte de faunes de la limite Viséen-Namurien sous le « Culm » carbonifère du massif de Mouthoumet (Aude), C. R. Acad. Sci. Paris, 291, série II, 1980, p. 521-524. F. BIXEL, J. MULLER et P. ROGER, Carte géol. Pic du Midi d’Ossau et haut Bassin du Rio Gallego, et notice, Instit. Géodynam., Univ. de Bordeaux-III, 1985. K. T. BOERSMA, Devonian and Lower Carboniferous conodont biostratigraphy, Spanish central Pyrenees, Leidse Geol. Med., Leiden, D.49, 1973, p. 303-377. S. CRILAT, Recherches sur les gisements de P et de Mn liés aux jaspes du Carbonifère inférieur des Pyrénées et de la Montagne Noire, Mé. Sc. Terre, Univ. Pierre-et-Marie-Curie, Thèse Sc., Paris, 1981, 475 p. G. DELEPINE, A Contribution to the Study of the Fauna of the Dinantien in the Pyrenees, First Part : Goniatites and Crustacés, Bull. Soc. géol. Fr., 5e série, V, 1935, p. 65-75; b : 2e partie : the fauna of Mondette, p. 171-189. J.-J. DELVOLVE, Un bassin synorogénique varisque. Le Culm des Pyrénées centro-occidentales, Thèse Doct. Sc., Toulouse, 1987, 483 p. J.-J. DELVOLVÉ et M.-F. PERRET, Foraminifères, algues et conodontes bashkiriens du Culm des Pyrénées béarnaises, Geobios, Lyon, 20, 2, 1987, p. 193-213. J.-J. DELVOLVÉ, M.-F. PERRET et D. VACHARD, Découverte du Kachirien (Moscovien inférieur) à Fusulines et algues dans le massif des Cinco Villas, Geobios, Lyon, 20, 4, 1987, p. 541-548. J.-J. DELVOLVE et M.-F. PERRET, Variations de l’âge des sédiments calcaires et « Culm » carbonifère dans la chaîne varisque du Sud de la France : migration de l’orogène varisque, Geodin. Acta, Paris, 3, 2, 1989, p. 117-126. J.-J. DELVOLVÉ et P. SOUQUET, Un bassin d’avant-pays carbonifère dans les Pyrénées varisques, 14e RST, Toulouse, 1992, p. 51. W. ENGEL, Migration of Folding and Flysch Sedimentation on the Southern Flank of the Variscan Belt (Montagne Noire, Mouthoumet massif, Pyrénées), Z. dt. geol. Ges., Hannover, 135, 1984, p. 279-292. J. GANDL et J.-J. DELVOLVÉ, Une première faune de trilobites du Carbonifère supérieur des Pyrénées centrales françaises, Geobios, Lyon, 23, 5, 1990, p. 587-605. J. C. HARMS, J.
Lyon, 20, 2, 1987, p. 193-213. J.-J. DELVOLVÉ, M.-F. PERRET et D. VACHARD, Découverte du Kachirien (Moscovien inférieur) à Fusulines et algues dans le massif des Cinco Villas, Geobios, Lyon, 20, 4, 1987, p. 541-548. J.-J. DELVOLVE et M.-F. PERRET, Variations de l’âge des sédiments calcaires et « Culm » carbonifère dans la chaîne varisque du Sud de la France : migration de l’orogène varisque, Geodin. Acta, Paris, 3, 2, 1989, p. 117-126. J.-J. DELVOLVÉ et P. SOUQUET, Un bassin d’avant-pays carbonifère dans les Pyrénées varisques, 14e RST, Toulouse, 1992, p. 51. W. ENGEL, Migration of Folding and Flysch Sedimentation on the Southern Flank of the Variscan Belt (Montagne Noire, Mouthoumet massif, Pyrénées), Z. dt. geol. Ges., Hannover, 135, 1984, p. 279-292. J. GANDL et J.-J. DELVOLVÉ, Une première faune de trilobites du Carbonifère supérieur des Pyrénées centrales françaises, Geobios, Lyon, 23, 5, 1990, p. 587-605. J. C. HARMS, J. B. SOUTHARD, D. R. SPEARING et R. G. WALKER, Depositional environments as interpreted from primary sedimentary structures and stratification sequences, SEP M, Dallas, Short Course Notes, 2, 1975, 161 p. J. C. HARMS, J. B. SOUTHARD et R. G. WALKER, Structures and sequences in clastic rocks, SEPM, Short Course Notes, 9, 3, 1982, p. 28-32. J. KULLMANN et J.-J. DELVOLVÉ, Goniatites du Namurien des Pyrénées occidentales françaises. Implications stratigraphiques et paléogéographiques, Geobios, Lyon, 18, 1, 1985, p. 47-67. M. LEGRAND-BLAIN, J.-J. DELVOLVÉ et M.-F. PERRET, Les Brachiopodes carbonifères des Pyrénées centrales françaises, 1 : cadre stratigraphique et sédimentaire; étude des Strophomenida, Geobios, Lyon, 16, 3, 1983, p. 285-327. M. LEGRAND-BLAIN, J.-J. DELVOLVÉ et M.-F. PERRET, Les Brachiopodes carbonifères des Pyrénées centrales françaises, 2 : Étude des Orthida et des Spiriferida; biostratigraphie, paléoécologie, paléobiogéographie, Geobios, Lyon, 17, 3, 1984, p. 297-325. D. MASSA et D. VACHARD, Le Carbonifère de Libye occidentale : biostratigraphie et micropaléontologie. Position dans le domaine téthysien d’Afrique du Nord, Rev. Inst. Fr. du Pétrole, Paris, 34, 1, 1979, p. 3-64. R. MIROUSE, Recherches géologiques dans la partie occidentale de la Zone primaire axiale des Pyrénées, Thèse Sc., Toulouse, 1962, Mém. Serv. Carte géol. Fr., Paris, 1966, 456
9, 3, 1982, p. 28-32. J. KULLMANN et J.-J. DELVOLVÉ, Goniatites du Namurien des Pyrénées occidentales françaises. Implications stratigraphiques et paléogéographiques, Geobios, Lyon, 18, 1, 1985, p. 47-67. M. LEGRAND-BLAIN, J.-J. DELVOLVÉ et M.-F. PERRET, Les Brachiopodes carbonifères des Pyrénées centrales françaises, 1 : cadre stratigraphique et sédimentaire; étude des Strophomenida, Geobios, Lyon, 16, 3, 1983, p. 285-327. M. LEGRAND-BLAIN, J.-J. DELVOLVÉ et M.-F. PERRET, Les Brachiopodes carbonifères des Pyrénées centrales françaises, 2 : Étude des Orthida et des Spiriferida; biostratigraphie, paléoécologie, paléobiogéographie, Geobios, Lyon, 17, 3, 1984, p. 297-325. D. MASSA et D. VACHARD, Le Carbonifère de Libye occidentale : biostratigraphie et micropaléontologie. Position dans le domaine téthysien d’Afrique du Nord, Rev. Inst. Fr. du Pétrole, Paris, 34, 1, 1979, p. 3-64. R. MIROUSE, Recherches géologiques dans la partie occidentale de la Zone primaire axiale des Pyrénées, Thèse Sc., Toulouse, 1962, Mém. Serv. Carte géol. Fr., Paris, 1966, 456 p. R. MIROUSE, G. BARROUQUÈRE, G. BESSIÈRE, J. J. DELVOLVÉ et M.-F. PERRET, Amorce de la sédimentation synorogénique dans les Pyrénées varisques. Données chronologiques; implications paléogéographiques, Geol. Rundsch., Stuttgart, 72, 1, 1983, p. 253-281. E. MUTTI et F. RICCI LUCCHI, Le torbiditi dell'Appennino settentrionale; introduzione all'analisi di facies, Mem. Soc. Geol. It., Rome, 11, 1972, p. 161-199. M.-F. PERRET, Recherches micropaléontologiques et biostratigraphiques (Conodontes-Foraminifères) dans le Carbonifère pyrénéen, Thèse Doct. Sc., Toulouse, 1989, 597 p. D. VACHARD, Contribution à l'étude stratigraphique et micropaléontologique (Algues et Foraminifères) du Dévonien-Carbonifère inférieur de la partie orientale du versant méridional de la Montagne Noire (Hérault, France), Thèse Doct. 3e Cycle, Paris, 1974, 408 p. D. VACHARD, M.-F. PERRET et J.-J. DELVOLVÉ, Algues, pseudo-algues et foraminifères des niveaux bashkirien dans les secteurs d’Escarra et Aragon Subordano, Geobios, Lyon, 22, 6, 1989, p. 697-723. D. VACHARD, J.-J. DELVOLVÉ et M. HANSOTTE, Foraminifères, algues et pseudo-algues du Serpukhovien du massif de l’Arizón (Carbonifère inférieur des Pyrénées). Geobios, Lyon, 24, 3, 1991, p. 251-256. H. WENSINK, Paleozoic of the Gallego and Ara valleys, Huesca Province, Spanish Pyrenees, Est. Geol., Madrid, XVIII, 1/2, 1961, p. 1-74. J.-J. D. et P. S. : Laboratoire de Géologie Sédimentaire et Paléontologie, et
Geol. It., Rome, 11, 1972, p. 161-199. M.-F. PERRET, Recherches micropaléontologiques et biostratigraphiques (Conodontes-Foraminifères) dans le Carbonifère pyrénéen, Thèse Doct. Sc., Toulouse, 1989, 597 p. D. VACHARD, Contribution à l'étude stratigraphique et micropaléontologique (Algues et Foraminifères) du Dévonien-Carbonifère inférieur de la partie orientale du versant méridional de la Montagne Noire (Hérault, France), Thèse Doct. 3e Cycle, Paris, 1974, 408 p. D. VACHARD, M.-F. PERRET et J.-J. DELVOLVÉ, Algues, pseudo-algues et foraminifères des niveaux bashkirien dans les secteurs d’Escarra et Aragon Subordano, Geobios, Lyon, 22, 6, 1989, p. 697-723. D. VACHARD, J.-J. DELVOLVÉ et M. HANSOTTE, Foraminifères, algues et pseudo-algues du Serpukhovien du massif de l’Arizón (Carbonifère inférieur des Pyrénées). Geobios, Lyon, 24, 3, 1991, p. 251-256. H. WENSINK, Paleozoic of the Gallego and Ara valleys, Huesca Province, Spanish Pyrenees, Est. Geol., Madrid, XVIII, 1/2, 1961, p. 1-74. J.-J. D. et P. S. : Laboratoire de Géologie Sédimentaire et Paléontologie, et URA-CNRS n° 1405 : Stratigraphie séquentielle et Micropaléontologie, Université Paul-Sabatier, Toulouse-III, 39, allée Jules-Guesde, 31062 Toulouse Cedex, France; D. V. : Laboratoire de Paléobotanique et URA-CNRS n° 1365 : Paléontologie et Paléogéographie du Paléozoïque, Université des Sciences et Technologies de Lille, 59655 Villeneuve d’Ascq Cedex, France; M.-F. P. et P. A. : Laboratoire de Géologie Structurale et Tectonophysique, Université Paul-Sabatier, Toulouse-III, 38, rue des Trente-Six-Ponts, 31400 Toulouse, France. Tectonique/Tectonics Sur la succession des épisodes extensifs au cours du désépaississement carbonifère du Massif Central français Michel FAURE et Jean-François BECQ-GIRAUDON Résumé — Dans la chaîne varisque du Massif Central français, les deux directions d’allongement maximum NW-SE et NE-SW dues au désépaississement post-collisionnel carbonifère ne sont pas contemporaines, mais successives. Au Namuro-Westphalien, l’extension se caractérise par une déformation ductile SE-NW, associée à une rétromorphose syntectonique et à la mise en place de granitoïdes. Au Stéphano-Autunien, l’extension devient NE-SW. Elle produit des dômes migmatitiques et contrôle la localisation des bassins houillers. Le passage entre les deux types d’extension est discuté en termes de rotation ou d’inversion des contraintes principales a2 et CT3. On the succession of extensional episodes during the carboniferous crustal unthickening of the French Massif Central Abstract In the Variscan belt
A. : Laboratoire de Géologie Structurale et Tectonophysique, Université Paul-Sabatier, Toulouse-III, 38, rue des Trente-Six-Ponts, 31400 Toulouse, France. Tectonique/Tectonics Sur la succession des épisodes extensifs au cours du désépaississement carbonifère du Massif Central français Michel FAURE et Jean-François BECQ-GIRAUDON Résumé — Dans la chaîne varisque du Massif Central français, les deux directions d’allongement maximum NW-SE et NE-SW dues au désépaississement post-collisionnel carbonifère ne sont pas contemporaines, mais successives. Au Namuro-Westphalien, l’extension se caractérise par une déformation ductile SE-NW, associée à une rétromorphose syntectonique et à la mise en place de granitoïdes. Au Stéphano-Autunien, l’extension devient NE-SW. Elle produit des dômes migmatitiques et contrôle la localisation des bassins houillers. Le passage entre les deux types d’extension est discuté en termes de rotation ou d’inversion des contraintes principales a2 et CT3. On the succession of extensional episodes during the carboniferous crustal unthickening of the French Massif Central Abstract In the Variscan belt of the French Massif Central, the two directions of maximum stretching NE-SW and NW-SE which are related to Carboniferous post-collisional thinning, are not coeval but successive. In Namurian-Westphalian, extension is characterized by a NW-SE ductile deformation during widespread retrogression and emplacement of granitoids. In Stephanian-Autunian, extension becomes NE-SW. It produces migmatitic domes and controls the onset of coal basins. The transition from one to the other type of extension is discussed in terms of principal stress rotation or inversion. Abridged English Version — In the Variscan collision belt of the French Massif Central, Devonian-early Carboniferous crustal thickening (Matte 1986; Ledru et al. 1989) is followed by unthickening-related phenomena such as ductile and brittle deformations, coal basin formation and granite emplacement (Menard and Molnar, 1988; Faure, 1989; Van den Driesche and Brun, 1989; Malavieille et al., 1990; Echtler and Malavieille, 1990; Faure et al., 1990). As already noticed (Burg et al., 1990) extension occurred along two perpendicular directions of maximum stretching, namely a NW-SE one predominantly found to the West and a NE-SW one found to the East. The Sillon Houiller fault is assumed to be a transfer fault between these two areas (Burg et al., 1990). However, our observations lead
migmatitic domes and controls the onset of coal basins. The transition from one to the other type of extension is discussed in terms of principal stress rotation or inversion. Abridged English Version — In the Variscan collision belt of the French Massif Central, Devonian-early Carboniferous crustal thickening (Matte 1986; Ledru et al. 1989) is followed by unthickening-related phenomena such as ductile and brittle deformations, coal basin formation and granite emplacement (Menard and Molnar, 1988; Faure, 1989; Van den Driesche and Brun, 1989; Malavieille et al., 1990; Echtler and Malavieille, 1990; Faure et al., 1990). As already noticed (Burg et al., 1990) extension occurred along two perpendicular directions of maximum stretching, namely a NW-SE one predominantly found to the West and a NE-SW one found to the East. The Sillon Houiller fault is assumed to be a transfer fault between these two areas (Burg et al., 1990). However, our observations lead us to modify this interpretation: the two stretching directions are not coeval. The NW-SE extension occurred in Namurian-Westphalian whereas the NE-SW one occurred in Stephanian-Autunian. NW-SE NAMURIAN-WESTPHALIAN EXTENSION. — NW-SE stretching lineations are widespread in the Western part of the Massif Central, or Limousin area (Guillot, 1981; Floc’h, 1983). They have been variously interpreted. For some authors (Brun and Burg, 1982; Burg et al., 1987) it is the last stage of a progressive anticlockwise stress field rotation during the Variscan compression. For Bouchez and Jover (1986), the lineation shows a top-to-the WestNW shear related to Himalayan type nappes. More recently, the lineation has been interpreted as the maximum stretching direction related to extensional deformation of Namurian-Westphalian age (Faure, 1989; Faure et al., 1990; Dumas et al., 1990; Faure and Pons, 1991). This interpretation is based on normal fault geometry of the shear surfaces and syntectonic retrogression of the metamorphic series. During extension, many granitic plutons emplace synkinematically. The most spectacular effect of extension is the southeastward collapse of the Gueret Extensional Allochthon which behaved as a rigid block. Note présentée par Jean AUBOUIN. 0764-4450/93/03160967 $ 2.00 (é) Académie des Sciences The top-to-the southeast shear sense is not systematic in Limousin,
have been variously interpreted. For some authors (Brun and Burg, 1982; Burg et al., 1987) it is the last stage of a progressive anticlockwise stress field rotation during the Variscan compression. For Bouchez and Jover (1986), the lineation shows a top-to-the WestNW shear related to Himalayan type nappes. More recently, the lineation has been interpreted as the maximum stretching direction related to extensional deformation of Namurian-Westphalian age (Faure, 1989; Faure et al., 1990; Dumas et al., 1990; Faure and Pons, 1991). This interpretation is based on normal fault geometry of the shear surfaces and syntectonic retrogression of the metamorphic series. During extension, many granitic plutons emplace synkinematically. The most spectacular effect of extension is the southeastward collapse of the Gueret Extensional Allochthon which behaved as a rigid block. Note présentée par Jean AUBOUIN. 0764-4450/93/03160967 $ 2.00 (é) Académie des Sciences The top-to-the southeast shear sense is not systematic in Limousin, top-to-the northwest shear has been observed along the Nantiat fault, Sussac antiform and south Limousin area; however, extension is proved only in the first case. The Gueret allochthon and its relative autochthon (Chavanon series) are suddenly interrupted by the Sillon Houiller. Taking into account the Stephanian 60 km left-lateral offset along this fault (Grolier and Letourneur, 1968), a similar structure is found in the Treban and Sioule areas. Our microtectonic study of the Sioule series indicates a synretrogression top-to-the southeast ductile shear coeval to the southeastward extravasion of Namurian-Westphalian magmatic bodies of Echassières and Pouzol-Servant. Northwest-southeast trending lineations are widespread in the metamorphic series of Eastern Massif Central (Brun and Burg, 1982; Burg et al., 1987). In the Livradois area, retrogression (Forestier, 1963) is coeval to a top-to-the south-southeast ductile shearing (Mouktar, 1985). In the Truyère area, the northwest-southeast trending lineations which are found in the contact aureole of the Margeride granite (Burg and Matte, 1978) are related to its extensional emplacement. Lastly, in the Cévennes area, the micaschist series is intruded by porphyroid granodiorite plutons of Mont-Loire and Aigoual-St-Guiral-Liron characterized by an east-west to northeast-southwest stretching lineation. Shape reconstruction of the plutons and kinematic studies of the host rocks
along this fault (Grolier and Letourneur, 1968), a similar structure is found in the Treban and Sioule areas. Our microtectonic study of the Sioule series indicates a synretrogression top-to-the southeast ductile shear coeval to the southeastward extravasion of Namurian-Westphalian magmatic bodies of Echassières and Pouzol-Servant. Northwest-southeast trending lineations are widespread in the metamorphic series of Eastern Massif Central (Brun and Burg, 1982; Burg et al., 1987). In the Livradois area, retrogression (Forestier, 1963) is coeval to a top-to-the south-southeast ductile shearing (Mouktar, 1985). In the Truyère area, the northwest-southeast trending lineations which are found in the contact aureole of the Margeride granite (Burg and Matte, 1978) are related to its extensional emplacement. Lastly, in the Cévennes area, the micaschist series is intruded by porphyroid granodiorite plutons of Mont-Loire and Aigoual-St-Guiral-Liron characterized by an east-west to northeast-southwest stretching lineation. Shape reconstruction of the plutons and kinematic studies of the host rocks suggest that the bodies are rooted to the west-northwest and extruded to the east-southeast (Faure et al., 1992; Lucas, 1992). Therefore, the Sillon Houiller is not a clear boundary for the northwest-southeast trending Namurian-Westphalian extension which is found on both sides of the fault. Although Namurian-Westphalian sediments are lacking in the Massif Central, the extensional brittle behaviour of the upper crust can be inferred from the northeast-southwest trending microgranitic dykes crossing the Gueret allochthon. These dykes are interpreted to infill tension gashes opened during the northwest-southeast extension. NE-SW STEPHANIAN-AUTUNIAN EXTENSION. — Crustal unthickening leads to the formation of metamorphic core complexes such as the Montagne Noire and Velay (Van den Driesche and Brun, 1989; Malavieille et al., 1990; Echtler and Malavieille, 1990). These domes formed with a north-northeast-south-southwest stretching are bounded by detachment faults which control the opening of troughs where Late Paleozoic deposits were trapped. The unconformities locally observed between Stephanian and Permian rocks (Grolier, 1971; Paquette, 1980) are due to layer tilt during basin opening. The structural control of the limnic coal basins has been known for a long time (Bertrand, 1888; Vetter, 1971; Arthaud and Matte, 1975; Gelard et al., 1986; Bles et al., 1989). The basins
the Massif Central, the extensional brittle behaviour of the upper crust can be inferred from the northeast-southwest trending microgranitic dykes crossing the Gueret allochthon. These dykes are interpreted to infill tension gashes opened during the northwest-southeast extension. NE-SW STEPHANIAN-AUTUNIAN EXTENSION. — Crustal unthickening leads to the formation of metamorphic core complexes such as the Montagne Noire and Velay (Van den Driesche and Brun, 1989; Malavieille et al., 1990; Echtler and Malavieille, 1990). These domes formed with a north-northeast-south-southwest stretching are bounded by detachment faults which control the opening of troughs where Late Paleozoic deposits were trapped. The unconformities locally observed between Stephanian and Permian rocks (Grolier, 1971; Paquette, 1980) are due to layer tilt during basin opening. The structural control of the limnic coal basins has been known for a long time (Bertrand, 1888; Vetter, 1971; Arthaud and Matte, 1975; Gelard et al., 1986; Bles et al., 1989). The basins are grouped into several types (fig. 1): 1. The basins located along north-south strike-slip faults (Sillon Houiller, Argentat fault) are left-lateral pull-aparts (Bles et al., 1989; Becq-Giraudon, 1985; Marest, 1985; Robert, 1985). 2. East-west to northeast-southwest normal-right-lateral faults control basins such as St-Etienne (Malavieille et al., 1990; Becq-Giraudon and Jacquemin, 1992), Blanzy (Valle et al., 1988), Graissessac (Becq-Giraudon, 1973; Echtler and Malavieille, 1990) or Rodez (Becq-Giraudon, 1986). 3. Several basins, e.g. Ahun, Commentry, Montvicq, are bounded by northwest-southeast normal faults (Fayol, 1888; Freytet, 1960). 4. The Decazeville basin is formed at the junction between northeast-southwest and northwest-southeast normal faults (Vetter, 1971). 5. The Gard basin, bounded by the Villefort and Cévennes faults, opened along the northeast-southwest trend (Gras, 1970; Frère, 1984; Delenin, 1990). Most of the coal basins opened in the northeast-southwest direction. This result does not imply that they were formed in a compressive stress field but simply suggests that the maximum and minimum principal horizontal stresses (a" and σ3) were close to the northwest-southeast and northeast-southwest trends respectively. The real σ3 could be vertical and a" is in fact σ2. Other evidence for a Stephanian northeast-southwest stretching is found in several places in the basement (Arthaud and Matte,
1992), Blanzy (Valle et al., 1988), Graissessac (Becq-Giraudon, 1973; Echtler and Malavieille, 1990) or Rodez (Becq-Giraudon, 1986). 3. Several basins, e.g. Ahun, Commentry, Montvicq, are bounded by northwest-southeast normal faults (Fayol, 1888; Freytet, 1960). 4. The Decazeville basin is formed at the junction between northeast-southwest and northwest-southeast normal faults (Vetter, 1971). 5. The Gard basin, bounded by the Villefort and Cévennes faults, opened along the northeast-southwest trend (Gras, 1970; Frère, 1984; Delenin, 1990). Most of the coal basins opened in the northeast-southwest direction. This result does not imply that they were formed in a compressive stress field but simply suggests that the maximum and minimum principal horizontal stresses (a" and σ3) were close to the northwest-southeast and northeast-southwest trends respectively. The real σ3 could be vertical and a" is in fact σ2. Other evidence for a Stephanian northeast-southwest stretching is found in several places in the basement (Arthaud and Matte, 1975; Deroin and Benoit, 1992; Bles et al., 1982; Vergely and Blanc, 1981; Dutartre, 1982). THE TRANSITION BETWEEN THE TWO EXTENSIONAL STRESS FIELDS. In the Upper Paleozoic of the Massif Central, several biostratigraphic problems arise due to the evolution of paleoflora and paleoenvironmental conditions (Broutin et al., 1990; Doubinger et al., 1992). Moreover, the radiometric measurement accuracy does not allow an exact correlation between deformations observed in the basins and the basement. Westphalian-Lower Stephanian deposits are located either in restricted areas (Decazeville, St-Etienne) or at the periphery of the Massif Central (Gard, Carmaux). Although their structural control is not constrained yet, age consideration suggests a relation with the northwest-southeast extension. The opening of coal basins with the northeast-southwest trend becomes general in Upper Stephanian in the whole Massif Central. Brittle and ductile tectonics clearly show that the two extensional stress fields are not coeval and that the Sillon Houiller is not a transfer fault since they are found on both sides of the fault. The transition between the two stress fields can be explained in two ways, either by a rotation of the stress ellipse around a vertical axis or by an exchange in modulus between σ2 and σ3. INTRODUCTION.