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Pedro Cózar - One of the best experts on this subject based on the ideXlab platform.
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lower middle Visean transgressive carbonates in morocco palaeobiogeographic insights
Journal of African Earth Sciences, 2020Co-Authors: Pedro Cózar, Ian D. Somerville, Daniel Vachard, Alain Izart, Ismael Coronado, Ismael Said, Sergio Rodriguez, Mohamed El Houicha, Driss OuarhacheAbstract:Abstract Foraminifera have been used to revise the biostratigraphy of all known Mississippian outcrops in Morocco cited either as early Visean (or its equivalent V2a or V2a/b chronozones or the regional Cfm1 biozones), or mid Visean (or the foraminiferal zones V2b-V3a or Cfm 2-Cfm 3 biozones). This group of microfossils occur in shallow-water limestones within siliciclastic-dominant successions. Most of the previously determined lower Visean ages for the outcrops are now interpreted either as middle or even late Visean. Similarly, some outcrops originally assigned to the mid Visean are now considered as late Visean. Only two successions can be confirmed as belonging to the early Visean in the Western Meseta. The first succession, of uppermost lower Visean age (Cf4γ-δ subzones or MFZ11 zone), occurs in the lower part of the Sidi Sebaa Formation in the Mdakra Massif (south of the Sidi Bettache Basin). The second succession occurs in a small area in the lower part of the Khenifra Nappe (in the so-called Hvs1’ Formation), which is assigned to the base of the Visean (Cf4α2 subzone or MFZ9 zone). Middle Visean outcrops are more common, occurring in the western part of the Western Meseta (Mdakra and Khatouat massifs), north-central Western Meseta (Tilouine, Bouqachmir, El Goulib, Jbel Bouechchot), as well as in the South Western Meseta (Haouz-High Atlas of Marrakech) and the central High Atlas (Skoura). In contrast, the Visean succession in the Anti-Atlas domain is more continuous, from early to mid Visean. This scarcity of lower Visean outcrops suggests that the Moroccan Meseta was mostly an uplifted region at that time. The recognition of the early Visean in the Mdakra Massif suggests a marine connection from the west or northwest, linked with the Rheic Ocean, with an opposite orientation (from the southeast) for the main transgressions in the Meseta in the late Visean. Taking into consideration previous tectonic reconstructions of Morocco, the presence of early Visean marine rocks in the Khenifra region can only be explained by a southward connection with the Sahara across the Tinerhir and Tafilalt regions linking with the Palaeotethys Ocean, which later covered areas within the High Atlas during the mid Visean. This connection during the early Visean, suggests a relatively close position between the Moroccan Meseta and Gondwana, in spite of the disparity in the lithological successions; this is also recognized in the mid Visean. Thus, it appears that the Moroccan Meseta had not yet achieved its final emplacement completely juxtaposed to Gondwana.
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the lower middle Visean boundary interval in the palaeotethys refinements for the foraminiferal zonal schemes
Geological Magazine, 2020Co-Authors: Pedro Cózar, Ian D. Somerville, Daniel Vachard, Alain Izart, Ismael CoronadoAbstract:A new foraminiferal subzone (Cf5α or MFZ12α) in between the classical foraminiferal zonal biozones is characterized by the first occurrence of Archaediscus at concavus stage, primitive species of Pojarkovella, as well as the first Endothyranopsis s.s. This interval is represented in England, France and Morocco (in the western Palaeotethys) and in South China, and more widely in Iran (in the eastern Palaeotethys), where it is partly similar to the MFZ11B subzone defined by previous authors. The position of this new biozone within the Livian or Holkerian substages suggests that it has to be considered as part of the middle Visean substage. We therefore propose the abandonment of the notation MFZ11B, which includes lower Visean rocks, and the subdivision of the middle Visean zones MFZ12 and Cf5 into two subzones MFZ12α or Cf5α, and MFZ12β or Cf5β, with the latter subzone containing the classical Livian–Holkerian foraminiferal guides Pojarkovella nibelis and Koskinotextularia. Furthermore, the lower Visean MFZ11 zone can be subdivided in most Palaeotethyan basins into three subzones: a lower MFZ11α subzone (characterized by the first occurrence of Uralodiscus rotundus, as well as most species of Glomodiscus); a middle MFZ11β subzone (characterized by the first occurrence of Archaediscus at involutus stage and Conilidiscus); and an upper MFZ11γ subzone (characterized by the first occurrence of Nodosarchaediscus, Consobrinellopsis and Lituotubella).
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Survival of early Viséan foraminifers in the Western Meseta of Morocco
Palaeoworld, 2020Co-Authors: Pedro Cózar, Daniel Vachard, Alain Izart, Ismael CoronadoAbstract:Abstract Typical early Visean foraminiferal assemblages documented in outcrops of the Western Meseta of Morocco led to the erroneous biostratigraphic dating of areas that later, after much effort, have been demonstrated to correspond to the mid and late Visean. These sections are analyzed to decipher if they are formed by reworked specimens or if this fauna really survived into younger rocks. Key sections are located in vast areas of the Western Meseta, in the north of the Azrou-Khenifra basin, Fourhal area, El Hammam Ridge, Oulmes area, Sidi Bettache basin (all on the north of the Western Meseta), and the Skoura region (on the southern border). The environmental settings as well as the taphonomical stage of preservation of the foraminifers suggest that most of the assemblages are composed of autochthonous or parautochthonous foraminifers and, thus, that the fauna really survived into the middle and even upper Visean carbonate platforms of the Western Meseta. In some sections, the early Visean foraminifers share the same levels with mid Visean foraminifers; in others, they share the same levels with mid and late Visean foraminifers, and in a third group, the early Visean foraminifers occur in the same stratigraphic sections with mid and late Visean assemblages, although never in exactly the same stratigraphic levels but alternating. These distributions exemplify the three patterns of interaction between the stratigraphic and biogeographic ranges of the assemblages. The absence of similar patterns is noteworthy in the surrounding regions of the Palaeotethys, and thus, this anomalous distribution can be discarded as a matter of dispersal from neighbouring regions. The absence of similar patterns in basins situated far from the Western Meseta allows abiotic factors to be discarded, such as tectonic/environmental setting, palaeolatitude or isolation. The most plausible hypothesis to explain the survival of these fauna is related to biotic factors, such as species interaction and competition, and they can be compared to some similar modern ecological patterns. However, the primary triggering factor allowing these biotic factors to interact is considered to be the late arrival of the mid Visean foraminifers to the Western Meseta, allowing them to occupy niches completely different from the rest of the Palaeotethys.
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Palaeobiogeographic context in the development of shallow-water late Viséan-early Bashkirian benthic foraminifers and calcareous algae in the Cantabrian Mountains (Spain)
Palaeogeography Palaeoclimatology Palaeoecology, 2018Co-Authors: Pedro Cózar, Ian D. Somerville, Silvia Blanco-ferrera, Javier Sanz-lópezAbstract:Abstract The late Visean to early Bashkirian shallow-water carbonate Valdediezma Platform in the Picos de Europa Province of the Cantabrian Zone, has been subdivided into eight microbiotic intervals by means of similarity clusters (using the Morisita coefficient). The most complete Visean-Bashkirian interval is represented in the Valdediezma Valley – Jitu l'Escarandi –road to Tresviso, where only the Steshevian to lower part of the Protvian (middle Serpukhovian) is missing. This interval is better represented in the Pompedrei Bridge to La Hermida composite section, and also in the deeper water section at Vegas de Sotres. These intervals contain a succession from the Mikhailovian (upper Visean) up to the Krasnopolyanian (lower Bashkirian). The assemblages of the Valdediezma Limestone show, comparatively, low similarity indices with the neighbouring basins in the collisional front in the western extremity of the Palaeotethys during the progression of the Variscan Orogeny. In this mobile belt, two domains are recognized; a western domain composed of outcrops in south-western Spain and in the Moroccan Meseta, and an eastern domain comprising basins located in southern France. Some basins, such as the Betic Cordillera, initially had more influence from the western domain, but later, during the late Serpukhovian, it is considered as being part of the eastern domain. The Valdediezma Platform foraminiferal and algal content is coincident with its location as an isolated platform, surrounded by deep-water seas, and with higher similarities with the eastern domain. Regional tectonic events are recognized from the late Visean onward, and they are mostly masked by the overprint of latest Pennsylvanian events. Facies changes are commonly observed, particularly at the base of the intervals, suggesting that facies control is the most important factor controlling the assemblages. It is considered that eustatic sea-level changes exerted a certain control on the assemblages.
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foraminifers in the latest tournaisian late Visean of southern france southern montagne noire and mouthoumet massif
Geobios, 2018Co-Authors: Daniel Vachard, Alain Izart, Ismael Coronado, Pedro CózarAbstract:Abstract In southern France, including the southern Montagne Noire and Mouthoumet Massif, foraminifers allow describing a biostratigraphical zonation for different formations included in those areas. Carbonate platforms are developed from the latest Tournaisian to the lower part of the late Visean. In between, up to six additional zones have been recognized. The foraminiferal study also includes the first formal description of early Visean foraminifers from the Vieussan area, a metamorphic area north of the main Mississippian stratigraphic sections of the Mont Peyroux nappe and ecailles de Cabrieres, as well as the dating of some preserved carbonates of the Mouthoumet Massif. Global foraminiferal guides are used for the definition of the zones, as well as other taxa considered as regional markers, but their detailed study might also be used for more continental to global level correlations. Lapparentidiscus irregularis nov. sp. and Ugurus intermedius nov. sp. are described.
Daniel Vachard - One of the best experts on this subject based on the ideXlab platform.
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lower middle Visean transgressive carbonates in morocco palaeobiogeographic insights
Journal of African Earth Sciences, 2020Co-Authors: Pedro Cózar, Ian D. Somerville, Daniel Vachard, Alain Izart, Ismael Coronado, Ismael Said, Sergio Rodriguez, Mohamed El Houicha, Driss OuarhacheAbstract:Abstract Foraminifera have been used to revise the biostratigraphy of all known Mississippian outcrops in Morocco cited either as early Visean (or its equivalent V2a or V2a/b chronozones or the regional Cfm1 biozones), or mid Visean (or the foraminiferal zones V2b-V3a or Cfm 2-Cfm 3 biozones). This group of microfossils occur in shallow-water limestones within siliciclastic-dominant successions. Most of the previously determined lower Visean ages for the outcrops are now interpreted either as middle or even late Visean. Similarly, some outcrops originally assigned to the mid Visean are now considered as late Visean. Only two successions can be confirmed as belonging to the early Visean in the Western Meseta. The first succession, of uppermost lower Visean age (Cf4γ-δ subzones or MFZ11 zone), occurs in the lower part of the Sidi Sebaa Formation in the Mdakra Massif (south of the Sidi Bettache Basin). The second succession occurs in a small area in the lower part of the Khenifra Nappe (in the so-called Hvs1’ Formation), which is assigned to the base of the Visean (Cf4α2 subzone or MFZ9 zone). Middle Visean outcrops are more common, occurring in the western part of the Western Meseta (Mdakra and Khatouat massifs), north-central Western Meseta (Tilouine, Bouqachmir, El Goulib, Jbel Bouechchot), as well as in the South Western Meseta (Haouz-High Atlas of Marrakech) and the central High Atlas (Skoura). In contrast, the Visean succession in the Anti-Atlas domain is more continuous, from early to mid Visean. This scarcity of lower Visean outcrops suggests that the Moroccan Meseta was mostly an uplifted region at that time. The recognition of the early Visean in the Mdakra Massif suggests a marine connection from the west or northwest, linked with the Rheic Ocean, with an opposite orientation (from the southeast) for the main transgressions in the Meseta in the late Visean. Taking into consideration previous tectonic reconstructions of Morocco, the presence of early Visean marine rocks in the Khenifra region can only be explained by a southward connection with the Sahara across the Tinerhir and Tafilalt regions linking with the Palaeotethys Ocean, which later covered areas within the High Atlas during the mid Visean. This connection during the early Visean, suggests a relatively close position between the Moroccan Meseta and Gondwana, in spite of the disparity in the lithological successions; this is also recognized in the mid Visean. Thus, it appears that the Moroccan Meseta had not yet achieved its final emplacement completely juxtaposed to Gondwana.
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the longest delay re emergence of coral reef ecosystems after the late devonian extinctions
Earth-Science Reviews, 2020Co-Authors: Le Yao, Xiangdong Wang, Jitao Chen, Daniel Vachard, Markus Aretz, Shuzhong Shen, Paul B WignallAbstract:Abstract Reefs are an excellent tool for tracking marine-ecosystem changes, especially through mass extinction transitions. Although metazoan reefs proliferated during the Phanerozoic, prolonged metazoan reef-recovery intervals often occurred after extinction events. Here, we document and review the reef-recovery interval following the Late Devonian Frasnian-Famennian (Kellwasser) and end-Famennian (Hangenberg) mass extinctions, which eliminated the largest area of metazoan (stromatoporoid-coral) reefs of the Phanerozoic. Previous reports of the late Visean coral bioconstructions from western Palaeotethys Ocean, may mark the first metazoan reef proliferation after the Hangenberg extinction. In this study, abundant coral reefs, coral frameworks and coral biostromes were described in detail for the first time from the late Visean strata on the South China Block (eastern Palaeotethys Ocean). The occurrence of these coral bioconstructions further suggests that the late Visean coral reef recovery may have been a widespread phenomenon. Based on the high-resolution reef database constructed in this study, three sub-intervals of the Mississippian metazoan reef recovery were distinguished, which are (1) metazoan “reef gap” phase (MRG) without metazoan reefs during the Tournaisian; (2) metazoan reef re-establishment phase (MRR) containing a few metazoan reefs from early Visean to early part of the late Visean; and (3) metazoan reef proliferation phase (MRP) with global coral reef flourishment during the middle part of the late Visean (late Asbian to early Brigantian substages). Hence, coral reef ecosystems proliferated and became dominant in marine ecosystems during the late Asbian to early Brigantian, indicating a prolonged metazoan reef recovery of about 12 Ma and 23 Ma until the MRR and MRP, respectively. Coral reef proliferation at this time shows that the Mississippian was not solely a period dominated by microbial reefs. Late Visean coral reef development coincided with increased nektonic and benthic diversity, showing that metazoan reef recovery closely tracked overall marine ecosystem evolution. Even compared with other slow reef-recovery intervals, such as the middle-late Cambrian and Early-Middle Triassic with the intervals until the MRR and MRP of 5 Ma and 2 Ma, and 15 Ma and 9 Ma respectively, the Mississippian metazoan reef recovery was the longest in reef history. Harsh climatic and oceanic conditions were present during the Mississippian, mainly including the widespread marine anoxia during the middle part of Tournaisian and the following recurrent glacial and interglacial climatic episodes with frequent changes in sea level, sedimentary facies and sea-water surface temperature, which may have stymied metazoan reef recovery during this time. During the late Visean, marine communities flourished during a phase of relative warm conditions and high sea level, and coincided with the long-delayed re-emergence of coral reef ecosystems after the Late Devonian extinctions.
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the lower middle Visean boundary interval in the palaeotethys refinements for the foraminiferal zonal schemes
Geological Magazine, 2020Co-Authors: Pedro Cózar, Ian D. Somerville, Daniel Vachard, Alain Izart, Ismael CoronadoAbstract:A new foraminiferal subzone (Cf5α or MFZ12α) in between the classical foraminiferal zonal biozones is characterized by the first occurrence of Archaediscus at concavus stage, primitive species of Pojarkovella, as well as the first Endothyranopsis s.s. This interval is represented in England, France and Morocco (in the western Palaeotethys) and in South China, and more widely in Iran (in the eastern Palaeotethys), where it is partly similar to the MFZ11B subzone defined by previous authors. The position of this new biozone within the Livian or Holkerian substages suggests that it has to be considered as part of the middle Visean substage. We therefore propose the abandonment of the notation MFZ11B, which includes lower Visean rocks, and the subdivision of the middle Visean zones MFZ12 and Cf5 into two subzones MFZ12α or Cf5α, and MFZ12β or Cf5β, with the latter subzone containing the classical Livian–Holkerian foraminiferal guides Pojarkovella nibelis and Koskinotextularia. Furthermore, the lower Visean MFZ11 zone can be subdivided in most Palaeotethyan basins into three subzones: a lower MFZ11α subzone (characterized by the first occurrence of Uralodiscus rotundus, as well as most species of Glomodiscus); a middle MFZ11β subzone (characterized by the first occurrence of Archaediscus at involutus stage and Conilidiscus); and an upper MFZ11γ subzone (characterized by the first occurrence of Nodosarchaediscus, Consobrinellopsis and Lituotubella).
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Survival of early Viséan foraminifers in the Western Meseta of Morocco
Palaeoworld, 2020Co-Authors: Pedro Cózar, Daniel Vachard, Alain Izart, Ismael CoronadoAbstract:Abstract Typical early Visean foraminiferal assemblages documented in outcrops of the Western Meseta of Morocco led to the erroneous biostratigraphic dating of areas that later, after much effort, have been demonstrated to correspond to the mid and late Visean. These sections are analyzed to decipher if they are formed by reworked specimens or if this fauna really survived into younger rocks. Key sections are located in vast areas of the Western Meseta, in the north of the Azrou-Khenifra basin, Fourhal area, El Hammam Ridge, Oulmes area, Sidi Bettache basin (all on the north of the Western Meseta), and the Skoura region (on the southern border). The environmental settings as well as the taphonomical stage of preservation of the foraminifers suggest that most of the assemblages are composed of autochthonous or parautochthonous foraminifers and, thus, that the fauna really survived into the middle and even upper Visean carbonate platforms of the Western Meseta. In some sections, the early Visean foraminifers share the same levels with mid Visean foraminifers; in others, they share the same levels with mid and late Visean foraminifers, and in a third group, the early Visean foraminifers occur in the same stratigraphic sections with mid and late Visean assemblages, although never in exactly the same stratigraphic levels but alternating. These distributions exemplify the three patterns of interaction between the stratigraphic and biogeographic ranges of the assemblages. The absence of similar patterns is noteworthy in the surrounding regions of the Palaeotethys, and thus, this anomalous distribution can be discarded as a matter of dispersal from neighbouring regions. The absence of similar patterns in basins situated far from the Western Meseta allows abiotic factors to be discarded, such as tectonic/environmental setting, palaeolatitude or isolation. The most plausible hypothesis to explain the survival of these fauna is related to biotic factors, such as species interaction and competition, and they can be compared to some similar modern ecological patterns. However, the primary triggering factor allowing these biotic factors to interact is considered to be the late arrival of the mid Visean foraminifers to the Western Meseta, allowing them to occupy niches completely different from the rest of the Palaeotethys.
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foraminifers in the latest tournaisian late Visean of southern france southern montagne noire and mouthoumet massif
Geobios, 2018Co-Authors: Daniel Vachard, Alain Izart, Ismael Coronado, Pedro CózarAbstract:Abstract In southern France, including the southern Montagne Noire and Mouthoumet Massif, foraminifers allow describing a biostratigraphical zonation for different formations included in those areas. Carbonate platforms are developed from the latest Tournaisian to the lower part of the late Visean. In between, up to six additional zones have been recognized. The foraminiferal study also includes the first formal description of early Visean foraminifers from the Vieussan area, a metamorphic area north of the main Mississippian stratigraphic sections of the Mont Peyroux nappe and ecailles de Cabrieres, as well as the dating of some preserved carbonates of the Mouthoumet Massif. Global foraminiferal guides are used for the definition of the zones, as well as other taxa considered as regional markers, but their detailed study might also be used for more continental to global level correlations. Lapparentidiscus irregularis nov. sp. and Ugurus intermedius nov. sp. are described.
Ismael Coronado - One of the best experts on this subject based on the ideXlab platform.
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lower middle Visean transgressive carbonates in morocco palaeobiogeographic insights
Journal of African Earth Sciences, 2020Co-Authors: Pedro Cózar, Ian D. Somerville, Daniel Vachard, Alain Izart, Ismael Coronado, Ismael Said, Sergio Rodriguez, Mohamed El Houicha, Driss OuarhacheAbstract:Abstract Foraminifera have been used to revise the biostratigraphy of all known Mississippian outcrops in Morocco cited either as early Visean (or its equivalent V2a or V2a/b chronozones or the regional Cfm1 biozones), or mid Visean (or the foraminiferal zones V2b-V3a or Cfm 2-Cfm 3 biozones). This group of microfossils occur in shallow-water limestones within siliciclastic-dominant successions. Most of the previously determined lower Visean ages for the outcrops are now interpreted either as middle or even late Visean. Similarly, some outcrops originally assigned to the mid Visean are now considered as late Visean. Only two successions can be confirmed as belonging to the early Visean in the Western Meseta. The first succession, of uppermost lower Visean age (Cf4γ-δ subzones or MFZ11 zone), occurs in the lower part of the Sidi Sebaa Formation in the Mdakra Massif (south of the Sidi Bettache Basin). The second succession occurs in a small area in the lower part of the Khenifra Nappe (in the so-called Hvs1’ Formation), which is assigned to the base of the Visean (Cf4α2 subzone or MFZ9 zone). Middle Visean outcrops are more common, occurring in the western part of the Western Meseta (Mdakra and Khatouat massifs), north-central Western Meseta (Tilouine, Bouqachmir, El Goulib, Jbel Bouechchot), as well as in the South Western Meseta (Haouz-High Atlas of Marrakech) and the central High Atlas (Skoura). In contrast, the Visean succession in the Anti-Atlas domain is more continuous, from early to mid Visean. This scarcity of lower Visean outcrops suggests that the Moroccan Meseta was mostly an uplifted region at that time. The recognition of the early Visean in the Mdakra Massif suggests a marine connection from the west or northwest, linked with the Rheic Ocean, with an opposite orientation (from the southeast) for the main transgressions in the Meseta in the late Visean. Taking into consideration previous tectonic reconstructions of Morocco, the presence of early Visean marine rocks in the Khenifra region can only be explained by a southward connection with the Sahara across the Tinerhir and Tafilalt regions linking with the Palaeotethys Ocean, which later covered areas within the High Atlas during the mid Visean. This connection during the early Visean, suggests a relatively close position between the Moroccan Meseta and Gondwana, in spite of the disparity in the lithological successions; this is also recognized in the mid Visean. Thus, it appears that the Moroccan Meseta had not yet achieved its final emplacement completely juxtaposed to Gondwana.
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the lower middle Visean boundary interval in the palaeotethys refinements for the foraminiferal zonal schemes
Geological Magazine, 2020Co-Authors: Pedro Cózar, Ian D. Somerville, Daniel Vachard, Alain Izart, Ismael CoronadoAbstract:A new foraminiferal subzone (Cf5α or MFZ12α) in between the classical foraminiferal zonal biozones is characterized by the first occurrence of Archaediscus at concavus stage, primitive species of Pojarkovella, as well as the first Endothyranopsis s.s. This interval is represented in England, France and Morocco (in the western Palaeotethys) and in South China, and more widely in Iran (in the eastern Palaeotethys), where it is partly similar to the MFZ11B subzone defined by previous authors. The position of this new biozone within the Livian or Holkerian substages suggests that it has to be considered as part of the middle Visean substage. We therefore propose the abandonment of the notation MFZ11B, which includes lower Visean rocks, and the subdivision of the middle Visean zones MFZ12 and Cf5 into two subzones MFZ12α or Cf5α, and MFZ12β or Cf5β, with the latter subzone containing the classical Livian–Holkerian foraminiferal guides Pojarkovella nibelis and Koskinotextularia. Furthermore, the lower Visean MFZ11 zone can be subdivided in most Palaeotethyan basins into three subzones: a lower MFZ11α subzone (characterized by the first occurrence of Uralodiscus rotundus, as well as most species of Glomodiscus); a middle MFZ11β subzone (characterized by the first occurrence of Archaediscus at involutus stage and Conilidiscus); and an upper MFZ11γ subzone (characterized by the first occurrence of Nodosarchaediscus, Consobrinellopsis and Lituotubella).
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Survival of early Viséan foraminifers in the Western Meseta of Morocco
Palaeoworld, 2020Co-Authors: Pedro Cózar, Daniel Vachard, Alain Izart, Ismael CoronadoAbstract:Abstract Typical early Visean foraminiferal assemblages documented in outcrops of the Western Meseta of Morocco led to the erroneous biostratigraphic dating of areas that later, after much effort, have been demonstrated to correspond to the mid and late Visean. These sections are analyzed to decipher if they are formed by reworked specimens or if this fauna really survived into younger rocks. Key sections are located in vast areas of the Western Meseta, in the north of the Azrou-Khenifra basin, Fourhal area, El Hammam Ridge, Oulmes area, Sidi Bettache basin (all on the north of the Western Meseta), and the Skoura region (on the southern border). The environmental settings as well as the taphonomical stage of preservation of the foraminifers suggest that most of the assemblages are composed of autochthonous or parautochthonous foraminifers and, thus, that the fauna really survived into the middle and even upper Visean carbonate platforms of the Western Meseta. In some sections, the early Visean foraminifers share the same levels with mid Visean foraminifers; in others, they share the same levels with mid and late Visean foraminifers, and in a third group, the early Visean foraminifers occur in the same stratigraphic sections with mid and late Visean assemblages, although never in exactly the same stratigraphic levels but alternating. These distributions exemplify the three patterns of interaction between the stratigraphic and biogeographic ranges of the assemblages. The absence of similar patterns is noteworthy in the surrounding regions of the Palaeotethys, and thus, this anomalous distribution can be discarded as a matter of dispersal from neighbouring regions. The absence of similar patterns in basins situated far from the Western Meseta allows abiotic factors to be discarded, such as tectonic/environmental setting, palaeolatitude or isolation. The most plausible hypothesis to explain the survival of these fauna is related to biotic factors, such as species interaction and competition, and they can be compared to some similar modern ecological patterns. However, the primary triggering factor allowing these biotic factors to interact is considered to be the late arrival of the mid Visean foraminifers to the Western Meseta, allowing them to occupy niches completely different from the rest of the Palaeotethys.
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foraminifers in the latest tournaisian late Visean of southern france southern montagne noire and mouthoumet massif
Geobios, 2018Co-Authors: Daniel Vachard, Alain Izart, Ismael Coronado, Pedro CózarAbstract:Abstract In southern France, including the southern Montagne Noire and Mouthoumet Massif, foraminifers allow describing a biostratigraphical zonation for different formations included in those areas. Carbonate platforms are developed from the latest Tournaisian to the lower part of the late Visean. In between, up to six additional zones have been recognized. The foraminiferal study also includes the first formal description of early Visean foraminifers from the Vieussan area, a metamorphic area north of the main Mississippian stratigraphic sections of the Mont Peyroux nappe and ecailles de Cabrieres, as well as the dating of some preserved carbonates of the Mouthoumet Massif. Global foraminiferal guides are used for the definition of the zones, as well as other taxa considered as regional markers, but their detailed study might also be used for more continental to global level correlations. Lapparentidiscus irregularis nov. sp. and Ugurus intermedius nov. sp. are described.
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a mid tournaisian late Visean carbonate ramp reconstructed from nappes and olistolites in the southern montagne noire france
Sedimentary Geology, 2017Co-Authors: Pedro Cózar, Daniel Vachard, Alain Izart, Ismael CoronadoAbstract:Abstract The mainly calcareous succession from the mid Tournaisian to the lower part of the upper Visean in the Southern Montagne Noire Mont Peyroux nappes and Cabrieres slices is sedimentologically revised. From the late Visean, the Variscan orogeny affected the area, and the studied Mississippian part of the succession was considered as part (together with the Devonian) of a period of tectonic quiescence, later included as nappes and olistolites in a wildflysch. This study presents the facies from pelagic limestones, calciturbidites, bioclastic limestones and microbial limestones, and the relationship between platform and calciturbidites in the pre-orogenic context of the Montagne Noire basin during the Mississippian. The differences in the lithostratigraphy is analyzed by means of four tectonostratigraphical units (Mont Peyroux nappe, Roquessels band, Cabrieres area and La Serre band) previously defined by other authors, that together with the deep-water Vieussan-Caragnas unit (not studied here due to the poverty in chronostratigraphical data) allow reconstructing the original carbonate platform. The latter seems to correspond to a ramp for the latest Tournaisian to early Visean, and a distally-steppened ramp from the middle Visean to the early late Visean, including basin plain to slope as the deepest water environments, and middle ramp as the shallowest, except for the uppermost part of the succession, where the inner ramp is recognized. During this period, the shallowing tendency in the tectonostratigraphic units is well marked: Mont Peyroux nappe – Roquessels band – Cabrieres area – La Serre band (from deeper to shallower), which differs from the shallowing trend defined by previous authors during the Devonian. Strong similarities are observed with the preserved Mississippian carbonates in the Mouthoumet Massif to the south, which might represent the shallowest water deposits of the ramp, not preversed in the Cabrieres-La Serre areas.
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the longest delay re emergence of coral reef ecosystems after the late devonian extinctions
Earth-Science Reviews, 2020Co-Authors: Le Yao, Xiangdong Wang, Jitao Chen, Daniel Vachard, Markus Aretz, Shuzhong Shen, Paul B WignallAbstract:Abstract Reefs are an excellent tool for tracking marine-ecosystem changes, especially through mass extinction transitions. Although metazoan reefs proliferated during the Phanerozoic, prolonged metazoan reef-recovery intervals often occurred after extinction events. Here, we document and review the reef-recovery interval following the Late Devonian Frasnian-Famennian (Kellwasser) and end-Famennian (Hangenberg) mass extinctions, which eliminated the largest area of metazoan (stromatoporoid-coral) reefs of the Phanerozoic. Previous reports of the late Visean coral bioconstructions from western Palaeotethys Ocean, may mark the first metazoan reef proliferation after the Hangenberg extinction. In this study, abundant coral reefs, coral frameworks and coral biostromes were described in detail for the first time from the late Visean strata on the South China Block (eastern Palaeotethys Ocean). The occurrence of these coral bioconstructions further suggests that the late Visean coral reef recovery may have been a widespread phenomenon. Based on the high-resolution reef database constructed in this study, three sub-intervals of the Mississippian metazoan reef recovery were distinguished, which are (1) metazoan “reef gap” phase (MRG) without metazoan reefs during the Tournaisian; (2) metazoan reef re-establishment phase (MRR) containing a few metazoan reefs from early Visean to early part of the late Visean; and (3) metazoan reef proliferation phase (MRP) with global coral reef flourishment during the middle part of the late Visean (late Asbian to early Brigantian substages). Hence, coral reef ecosystems proliferated and became dominant in marine ecosystems during the late Asbian to early Brigantian, indicating a prolonged metazoan reef recovery of about 12 Ma and 23 Ma until the MRR and MRP, respectively. Coral reef proliferation at this time shows that the Mississippian was not solely a period dominated by microbial reefs. Late Visean coral reef development coincided with increased nektonic and benthic diversity, showing that metazoan reef recovery closely tracked overall marine ecosystem evolution. Even compared with other slow reef-recovery intervals, such as the middle-late Cambrian and Early-Middle Triassic with the intervals until the MRR and MRP of 5 Ma and 2 Ma, and 15 Ma and 9 Ma respectively, the Mississippian metazoan reef recovery was the longest in reef history. Harsh climatic and oceanic conditions were present during the Mississippian, mainly including the widespread marine anoxia during the middle part of Tournaisian and the following recurrent glacial and interglacial climatic episodes with frequent changes in sea level, sedimentary facies and sea-water surface temperature, which may have stymied metazoan reef recovery during this time. During the late Visean, marine communities flourished during a phase of relative warm conditions and high sea level, and coincided with the long-delayed re-emergence of coral reef ecosystems after the Late Devonian extinctions.
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coupled sedimentary and δ13c records of late mississippian platform to slope successions from south china insight into δ13c chemostratigraphy
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Xiangdong Wang, Jitao Chen, Isabel P Montanez, Yuping Qi, Qiulai WangAbstract:Abstract Variability in stratigraphic accumulation rates and distribution of stratal hiatuses along with strong endemism of index fossils hinder regional to global stratigraphic correlation of the Visean–Serpukhovian (V–S) boundary interval (late Mississippian) and thus geological inferences regarding the onset of the late Paleozoic ice age. Here we integrate high-resolution δ13C time series with detailed sedimentary facies analysis of late Visean–early Serpukhovian (V–S) carbonate platform-to-slope successions from South China to evaluate the influences of local depositional and diagenetic processes on δ13Ccarb and to address the correlation issue. Analysis of 11 sedimentary facies from 5 outcrop sections indicates a restricted platform setting (Yashui section) dominated by bioclastic wacke-packstone to lime mudstone in which paleokarst developed, and contemporaneous carbonate slope settings dominated by thin-bedded lime mudstones intercalated with slumps and calciturbidites. Based on vertical facies assemblages, three depositional units are recognized, recording a significant sea-level drawdown across the V–S boundary. Multiple negative δ13C excursions (> 1‰) can be correlated across the V–S boundary interval in several slope sections (Naqing, Luokun, and Narao sections). Variability in the V–S boundary δ13C record in some sections is interpreted to record truncation physically by submarine erosion by slumps or chemically during karstification. A long-term decrease in δ13C values through the Serpukhovian of the Yashui section likely records local influences on carbon cycling in the restricted platform setting. This negative δ13C trend and associated depositional facies at the Yashui section can be correlated to the Arrow Canyon section, USA, which, together with other coeval global sedimentary and geochemical records, indicate a widespread eustatic drawdown in the late Visean with initial buildup of Gondwanan ice sheets. We conclude that integrated sedimentary facies analysis and δ13C chemostratigraphy can be used for stratigraphic correlation when interpreted within a well-constrained sedimentary and carbon-isotope regional framework.
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Middle Viséan (Mississippian) coral biostrome in central Guizhou, southwestern China and its palaeoclimatological implications
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Le Yao, Xiangdong Wang, Steve Kershaw, Wei Lin, Wenkun QieAbstract:Abstract A middle Visean (Mississippian) coral biostrome is reported for the first time from the Shangsi Formation in Yashui area, central Guizhou Province, southwestern China (palaeogeographically located in eastern Palaeotethys). The biostrome, which is about 500 m across and 2.5–3.9 m thick, is laterally variable and composed of rugose and tabulate corals with low taxonomic diversity comprising 4 rugose and 1 tabulate coral species belonging to 5 genera. Three growth stages of the biostrome are distinguished, based on different compositions of coral taxa. Average coral contents of the biostrome increase from 38.7% to 72.0% upward and the main builders are Siphonodendron pentalaxoidea, Syringopora sp. and Kueichouphyllum sinense. Associated fossils include abundant brachiopods, crinoids and common foraminifers together with rare calcareous algae, bryozoans, gastropods and ostracods. Relative sea-level changes are interpreted to have controlled growth and demise of the biostrome, which grew continuously during sea-level rise and decreasing water energy, as evident from the gradually increasing of micrite content and in situ coral colonies. However, the biostrome declined and died as the sea level fell and hydrodynamic energy strengthened, indicated by an increase of bioclasts and sparry calcite cement (indicating lack of micritic matrix due to higher energy) overlying the biostrome. This coral biostrome has similar biotic composition to middle to late Visean coral biostromes in Europe and North Africa (western Palaeotethys). The approximately coeval occurrence of coral biostromes in both eastern and western Palaeotethys suggests that a relatively global warm episode existed during the Visean Stage.
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late Visean early serpukhovian conodont succession at the naqing nashui section in guizhou south china
Geological Magazine, 2014Co-Authors: Tamara I Nemyrovska, Barry C. Richards, Xiangdong Wang, Jitao Chen, Zhihao Wang, Richard H Lane, Qiulai WangAbstract:This study reports the conodont succession across the Visean–Serpukhovian (V/S) boundary interval at the Naqing section, South China. Continuous centimetre-scale sampling of the relatively deep-water section in recent years has provided new data for a more detailed biostratigraphy of conodonts across the Visean–Serpukhovian boundary. Three conodont zones were described in ascending order: the Gnathodus bilineatus , Lochriea nodosa and Lochriea ziegleri zones. The first appearance datum (FAD) of L. ziegleri has been moved down to 60.1 m above the base of the Naqing section. The correlation of the conodont succession across the Visean–Serpukhovian boundary in the Naqing section with other sections in Eurasia is discussed.
Qiulai Wang - One of the best experts on this subject based on the ideXlab platform.
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coupled sedimentary and δ13c records of late mississippian platform to slope successions from south china insight into δ13c chemostratigraphy
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Xiangdong Wang, Jitao Chen, Isabel P Montanez, Yuping Qi, Qiulai WangAbstract:Abstract Variability in stratigraphic accumulation rates and distribution of stratal hiatuses along with strong endemism of index fossils hinder regional to global stratigraphic correlation of the Visean–Serpukhovian (V–S) boundary interval (late Mississippian) and thus geological inferences regarding the onset of the late Paleozoic ice age. Here we integrate high-resolution δ13C time series with detailed sedimentary facies analysis of late Visean–early Serpukhovian (V–S) carbonate platform-to-slope successions from South China to evaluate the influences of local depositional and diagenetic processes on δ13Ccarb and to address the correlation issue. Analysis of 11 sedimentary facies from 5 outcrop sections indicates a restricted platform setting (Yashui section) dominated by bioclastic wacke-packstone to lime mudstone in which paleokarst developed, and contemporaneous carbonate slope settings dominated by thin-bedded lime mudstones intercalated with slumps and calciturbidites. Based on vertical facies assemblages, three depositional units are recognized, recording a significant sea-level drawdown across the V–S boundary. Multiple negative δ13C excursions (> 1‰) can be correlated across the V–S boundary interval in several slope sections (Naqing, Luokun, and Narao sections). Variability in the V–S boundary δ13C record in some sections is interpreted to record truncation physically by submarine erosion by slumps or chemically during karstification. A long-term decrease in δ13C values through the Serpukhovian of the Yashui section likely records local influences on carbon cycling in the restricted platform setting. This negative δ13C trend and associated depositional facies at the Yashui section can be correlated to the Arrow Canyon section, USA, which, together with other coeval global sedimentary and geochemical records, indicate a widespread eustatic drawdown in the late Visean with initial buildup of Gondwanan ice sheets. We conclude that integrated sedimentary facies analysis and δ13C chemostratigraphy can be used for stratigraphic correlation when interpreted within a well-constrained sedimentary and carbon-isotope regional framework.
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late Visean early serpukhovian conodont succession at the naqing nashui section in guizhou south china
Geological Magazine, 2014Co-Authors: Tamara I Nemyrovska, Barry C. Richards, Xiangdong Wang, Jitao Chen, Zhihao Wang, Richard H Lane, Qiulai WangAbstract:This study reports the conodont succession across the Visean–Serpukhovian (V/S) boundary interval at the Naqing section, South China. Continuous centimetre-scale sampling of the relatively deep-water section in recent years has provided new data for a more detailed biostratigraphy of conodonts across the Visean–Serpukhovian boundary. Three conodont zones were described in ascending order: the Gnathodus bilineatus , Lochriea nodosa and Lochriea ziegleri zones. The first appearance datum (FAD) of L. ziegleri has been moved down to 60.1 m above the base of the Naqing section. The correlation of the conodont succession across the Visean–Serpukhovian boundary in the Naqing section with other sections in Eurasia is discussed.
