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Lina Maria Ospina-ostios - One of the best experts on this subject based on the ideXlab platform.
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Revision of the planktonic foraminiferal biostratigraphy of the Voirons Flysch (Chablais Prealps, Haute-Savoie, France)
Swiss Journal of Geosciences, 2018Co-Authors: Jérémy Ragusa, Lina Maria Ospina-ostios, Silvia Spezzaferri, Pascal KindlerAbstract:The ages obtained from planktonic foraminiferal assemblages retrieved from two exposures in the Gurnigel Flysch and from the re-examination of similar material gathered by previous researchers from the Voirons Flysch reveal only minor discrepancies with previous studies based on nannofossil biostratigraphy. In contrast, major divergences between this work and previous studies on the Voirons Flysch also based on planktonic foraminifera have been identified. They are generally related to distinct approaches in species classification and the use of different zonal schemes. Based on our data, the age of the Voirons Flysch extends from the Early Eocene (planktonic foraminiferal zone P7) to the Middle Eocene (planktonic foraminiferal zone P12). Contrasting with claims made in earlier studies, no specimen of Late Eocene or Early Oligocene age has been observed in the revised material. However, we cannot exclude a younger age (possibly Late Eocene) for the upper portion of this Flysch from which we did not revise any sample. Thus, more research and sampling are needed to resolve this question. The palaeogeographic origin of the Voirons-Wägital complex as well as the sedimentation history of these Flyschs need now to be re-evaluated in light of this revised biostratigraphic data.
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Provenance analysis of the Voirons Flysch (Gurnigel nappe, Haute-Savoie, France): stratigraphic and palaeogeographic implications
International Journal of Earth Sciences, 2017Co-Authors: Jérémy Ragusa, Pascal Kindler, Branimir Segvic, Lina Maria Ospina-ostiosAbstract:The Chablais Prealps (Haute-Savoie, France) represent a well-preserved accretionary wedge of the Western Alpine Tethys. They comprise a stack of sedimentary nappes related to palaeogeographic realms ranging from the Ultrahelvetic to the Southern Penninic. The provenance analysis is based on the Gazzi-Dickinson method and on QEMSCAN^® for heavy-minerals. The Quartzose petrofacies is the most important of the two sources, and supplied three of the four formations of the Voirons Flysch. It is similar to the sources that fed the other Flyschs from the Gurnigel nappe. It is characterised by a mature, quartz-rich assemblage and a heavy-mineral population dominated by apatite and the zircon–tourmaline–rutile mineral group. These observations suggest a Clastic wedge provenance. The Feldspathic petrofacies is derived from a feldspar-rich source associated with metamorphic clasts and a heavy-mineral population dominated by garnet. This provenance characterises only one formation of the Voirons Flysch, and is related to the axial belt provenance. This provenance analysis shows that the Middle Eocene to Early Oligocene Voirons Flysch was fed by two sources, in contrast to the other Flyschs of the Gurnigel nappe, and further suggests that this Flysch was not deposited in the Piemont Ocean but in the Valais domain. Based on the results and comparative provenance analysis with the other Flyschs of the Gurnigel nappe, we propose a generic feeding model which involves the Sesia–Dent Blanche nappe, the sedimentary nappes incorporated in the accretionary prism, and probably the Briançonnais basement.
Jérémy Ragusa - One of the best experts on this subject based on the ideXlab platform.
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Revision of the planktonic foraminiferal biostratigraphy of the Voirons Flysch (Chablais Prealps, Haute-Savoie, France)
Swiss Journal of Geosciences, 2018Co-Authors: Jérémy Ragusa, Lina Maria Ospina-ostios, Silvia Spezzaferri, Pascal KindlerAbstract:The ages obtained from planktonic foraminiferal assemblages retrieved from two exposures in the Gurnigel Flysch and from the re-examination of similar material gathered by previous researchers from the Voirons Flysch reveal only minor discrepancies with previous studies based on nannofossil biostratigraphy. In contrast, major divergences between this work and previous studies on the Voirons Flysch also based on planktonic foraminifera have been identified. They are generally related to distinct approaches in species classification and the use of different zonal schemes. Based on our data, the age of the Voirons Flysch extends from the Early Eocene (planktonic foraminiferal zone P7) to the Middle Eocene (planktonic foraminiferal zone P12). Contrasting with claims made in earlier studies, no specimen of Late Eocene or Early Oligocene age has been observed in the revised material. However, we cannot exclude a younger age (possibly Late Eocene) for the upper portion of this Flysch from which we did not revise any sample. Thus, more research and sampling are needed to resolve this question. The palaeogeographic origin of the Voirons-Wägital complex as well as the sedimentation history of these Flyschs need now to be re-evaluated in light of this revised biostratigraphic data.
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Provenance analysis of the Voirons Flysch (Gurnigel nappe, Haute-Savoie, France): stratigraphic and palaeogeographic implications
International Journal of Earth Sciences, 2017Co-Authors: Jérémy Ragusa, Pascal Kindler, Branimir Segvic, Lina Maria Ospina-ostiosAbstract:The Chablais Prealps (Haute-Savoie, France) represent a well-preserved accretionary wedge of the Western Alpine Tethys. They comprise a stack of sedimentary nappes related to palaeogeographic realms ranging from the Ultrahelvetic to the Southern Penninic. The provenance analysis is based on the Gazzi-Dickinson method and on QEMSCAN^® for heavy-minerals. The Quartzose petrofacies is the most important of the two sources, and supplied three of the four formations of the Voirons Flysch. It is similar to the sources that fed the other Flyschs from the Gurnigel nappe. It is characterised by a mature, quartz-rich assemblage and a heavy-mineral population dominated by apatite and the zircon–tourmaline–rutile mineral group. These observations suggest a Clastic wedge provenance. The Feldspathic petrofacies is derived from a feldspar-rich source associated with metamorphic clasts and a heavy-mineral population dominated by garnet. This provenance characterises only one formation of the Voirons Flysch, and is related to the axial belt provenance. This provenance analysis shows that the Middle Eocene to Early Oligocene Voirons Flysch was fed by two sources, in contrast to the other Flyschs of the Gurnigel nappe, and further suggests that this Flysch was not deposited in the Piemont Ocean but in the Valais domain. Based on the results and comparative provenance analysis with the other Flyschs of the Gurnigel nappe, we propose a generic feeding model which involves the Sesia–Dent Blanche nappe, the sedimentary nappes incorporated in the accretionary prism, and probably the Briançonnais basement.
Mario Tramontana - One of the best experts on this subject based on the ideXlab platform.
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tectono sedimentary evolution of the southern branch of the western tethys maghrebian Flysch basin and lucanian ocean consequences for western mediterranean geodynamics
Terra Nova, 2005Co-Authors: Francesco Guerrera, Manuel Martinmartin, Vincenzo Perrone, Mario TramontanaAbstract:The evolution of the oceanic Maghrebian Flysch Basin and its continuation in the Southern Apennines was studied by reconstructing mainly representative stratigraphic successions. In all sectors a common evolution has been identified. Rifting and drifting phases are indicated by remnants of oceanic crust, Jurassic limestones, Cretaceous–Palaeogene turbiditic and pelagic deposits. The pre-orogenic sedimentation was mainly controlled by extensional tectonics and sea-level changes. The occurrence of a generalized foredeep stage since the Early Miocene is testified by thick siliciclastic and volcaniclastic syn-orogenic Flysch successions. The deformation of the oceanic areas began in the Burdigalian and the resulting nappes were stacked in the growing chains. During the Middle Miocene, piggy-back basins developed and the building of the chains was accomplished in the Late Tortonian. Areal distribution and ages of Flysch deposits represent an important tool for the study of the diachronous growth of the accretionary wedges.
Pavel Cizek - One of the best experts on this subject based on the ideXlab platform.
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large scale thin skinned tectonics in the eastern boundary of the bohemian massif
Tectonics, 1991Co-Authors: Pavel Cizek, Cestmir TomekAbstract:Two new seismic reflection profiles and a deep borehole reveal thin-skinned thrusting on the easternmost part of the Rheno-Hercynian zone of the Variscan belt of Europe. Above Precambrian Brunnia basement the profiles show three different seismic zones within the compressed Palaeozoic sedimentary section. The borehole data suggest that the lower zone is a deformed “paraautochthonous” Brunnia basement covered by Upper Devonian and Lower Carboniferous shelf carbonates with numerous local overthrusts. This zone is overthrust by the uppermost seismic zone of Lower Carboniferous Culm Flysch wedge and in the west by the eastward dipping zone. This intervening seismic zone on the east end of the profiles is a foreland dipping thrust sheet of another Culm Flysch complex (mainly Horni Benesov Formation), or seismic crocodiles in the sense of Meissner (1989). Inverted metamorphism between the Culm Flysch and the Brunnia shelf sequences encountered in the well Potstat-1, and strong slaty cleavage in the intervening zone, suggests that the upper zone is allochthonous, heaving been thrust from deeper levels tens of kilometres eastward over carbonates. Imbrication of the carbonates as part of the footwall suggest relatively strong coupling between the Palaeozoic sediments and underlying basement at the time of thrusting.
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Large‐scale thin‐skinned tectonics in the eastern boundary of the Bohemian Massif
Tectonics, 1991Co-Authors: Pavel Cizek, Čestmír TomekAbstract:Two new seismic reflection profiles and a deep borehole reveal thin-skinned thrusting on the easternmost part of the Rheno-Hercynian zone of the Variscan belt of Europe. Above Precambrian Brunnia basement the profiles show three different seismic zones within the compressed Palaeozoic sedimentary section. The borehole data suggest that the lower zone is a deformed “paraautochthonous” Brunnia basement covered by Upper Devonian and Lower Carboniferous shelf carbonates with numerous local overthrusts. This zone is overthrust by the uppermost seismic zone of Lower Carboniferous Culm Flysch wedge and in the west by the eastward dipping zone. This intervening seismic zone on the east end of the profiles is a foreland dipping thrust sheet of another Culm Flysch complex (mainly Horni Benesov Formation), or seismic crocodiles in the sense of Meissner (1989). Inverted metamorphism between the Culm Flysch and the Brunnia shelf sequences encountered in the well Potstat-1, and strong slaty cleavage in the intervening zone, suggests that the upper zone is allochthonous, heaving been thrust from deeper levels tens of kilometres eastward over carbonates. Imbrication of the carbonates as part of the footwall suggest relatively strong coupling between the Palaeozoic sediments and underlying basement at the time of thrusting.
Paul Angrand - One of the best experts on this subject based on the ideXlab platform.
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Tectono‐Stratigraphic and Thermal Evolution of the Western Betic Flysch: Implications for the Geodynamics of South Iberian Margin and Alboran Domain
Tectonics, 2020Co-Authors: Maxime Daudet, Frédéric Mouthereau, Stéphanie Brichau, Ana Crespo‐blanc, Cécile Gautheron, Paul AngrandAbstract:The Betic-Rif orogen is a key region to understand the evolution of the plate boundary between Africa and Iberia/Europe. This study focuses on the Flysch Complex, which is considered the sedimentary cover of a domain originally positioned between the Iberian and Alboran margins. Based on stratigraphic and depositional evolution constraints, evidence for salt tectonics, combined with new apatite fission-tracks (AFT) and (U-Th-Sm)/He ages from the Flysch Complex and the Subbetic Zone, we propose a geodynamic interpretation for the formation of the Betic Cordillera, accounting for moderate N-directed transport of the Flysch Complex and synchronous exhumation between External and Internal Zones of the Betic. Early contraction between Africa and Iberia/Europe is reflected in the Cretaceous Flysch basin by a prolonged period of residence in the partial annealing zone for AFT and onset of foreland subsidence at 50 Ma. This stage lasted until the Early to Middle Miocene (20-15 Ma), marked by the rapid succession, in less than 5 Ma, of the deposition of Cenozoic Flysch and their rapid exhumation. This event is interpreted to reflect the W-directed retreating mantle delamination between Africa and Iberia margins at the origin of the collapse of the proto-Betic orogenic domain and formation of the Alboran domain.