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Emmanuel L.o. Martin - One of the best experts on this subject based on the ideXlab platform.
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age calibration of the lower ordovician fezouata lagerstatte morocco
Lethaia, 2018Co-Authors: Bertrand Lefebvre, Mustapha Akodad, Oliver Lehnert, Juan Carlos Gutierrezmarco, Khadija El Hariri, Emmanuel L.o. Martin, Hendrik Nowak, Thomas ServaisAbstract:The Fezouata Lagerstatte, discovered in the Lower Ordovician rocks of Morocco, is a Konservat-Lagerstatte of prime scientific importance. It provides access not only to the ‘shelly’ (skeletonized) part of its fossil assemblages, but also to non-biomineralized to lightly sclerotized organisms and to exceptionally preserved soft tissues of a complex ecosystem, mixing elements of both the ‘Cambrian Explosion’ and the ‘Great Ordovician Biodiversification Event’ (GOBE). The Fezouata Lagerstatte occurs at different intervals in the Fezouata Shale, a formation ranging from the lower Tremadocian to the upper Floian (Lower Ordovician). In spite of recent major advances in the detailed biostratigraphy of the Fezouata Shale, there is currently no consensus on the precise age of the fossiliferous levels yielding exceptionally preserved assemblages. Consequently, all available biostratigraphical evidence based on several fossil groups is here critically reviewed and discussed. It can be concluded that exceptional preservation is restricted to a few thin, discontinuous, lens-shaped horizons occurring in two distinct parts of the Fezouata Shale: a lower interval (260–330 m above the base of the formation) and an upper interval (570–620 m). Integrated biostratigraphical studies, essentially based on investigations of graptolites, acritarchs and conodonts, indicate that the lower interval can be correlated with the upper Tremadocian, whereas the upper interval corresponds to the middle Floian.
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biostratigraphic and palaeoenvironmental controls on the trilobite associations from the lower ordovician fezouata shale of the central anti atlas morocco
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Emmanuel L.o. Martin, Muriel Vidal, Daniel Vizcaino, Romain Vaucher, Bertrand Lefebvre, Pierre Sansjofre, J. DestombesAbstract:Abstract Trilobites are a major component of both biomineralized and soft-bodied assemblages of the Fezouata Biota, central Anti-Atlas, Morocco. Trilobite taxa of the Fezouata Shale (Tremadocian–Floian) in the Zagora area are typical of Lower Ordovician communities from shallow shelf environments, and show strong affinities with Early Ordovician assemblages from the Montagne Noire (southern France). Dramatic variations in both taxonomic composition and taphonomic attributes, together with the sedimentological facies changes, allow us to discriminate the palaeoenvironmental versus stratigraphic control on trilobite assemblages. Three communities are described along an onshore–offshore profile, namely the pilekiid-bavarillid, Agerina and raphiophorid biofacies. Additionally, three stratigraphic assemblages are identified: assemblage 1 is confined to the late Tremadocian, assemblage 2 ranges from late Tremadocian to middle Floian and assemblage 3 is restricted to the Floian. The higher diversity of some levels is explained by storm-induced inputs of debris from taxa living in adjacent environments. Additionally, control of relative seal level variation on some peculiarities of the trilobite fauna (specific endemicity, lack of some expected taxa) is evidenced in the Fezouata Shale. Finally, temporary dysoxic events are highlighted by preliminary geochemical analyses, probably allowing episodic exceptional preservation.
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biostratigraphy and palaeoecology of lower ordovician graptolites from the fezouata shale moroccan anti atlas
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Juan Carlos Gutierrezmarco, Emmanuel L.o. MartinAbstract:Abstract The Fezouata Shale (= Fezouata Formation) has produced the most complete Lower Ordovician graptolite succession known from the African continent, which was studied from 32 sections located along the western, central, and eastern Moroccan Anti-Atlas. A composite biostratigraphic and chronostratigraphic scheme is presented for the entire formation that, in ascending order, comprises the Anisograptus matanensis–Rhabdinopora flabelliformis anglica zones (uppermost lower Tremadocian), “Adelograptus” tenellus and Aorograptus victoriae zones (middle Tremadocian), Araneograptus murrayi and Hunnegraptus copiosus zones (upper Tremadocian), ?Cymatograptus protobalticus Zone (lower Floian), ?Baltograptus jacksoni Zone (middle Floian), and the Baltograptus minutus Zone plus an “Azygograptus interval” (upper Floian). Most of these zones or biozones are recorded for the first time in Africa, together with important graptolite species such as Ancoragraptus bulmani (Spjeldnaes), ?Cym. protobalticus (Monsen), ?B. jacksoni Rushton, Clonograptus multiplex (Nicholson), B. minutus (Tornquist) and Azygograptus eivionicus Elles. A correlation with the graptolite sucession from the Algerian Sahara is also suggested, reinforced by the common record of the minute anisograptid Choristograptus louhai Legrand, providing its second world occurrence in the Tremadocian of Morocco. The prior late Tremadocian dating of the Fezouata Lagerstatte is here extended to the middle Floian as revealed by the graptolite biochronology. The repeated record along the lower and middle parts of the Fezouata Formation of deep-water mesopelagic species of the genera Araneograptus — with mass occurrences of conical colonies, together with large horizontal rhabdosomes of Paratemnograptus, Paradelograptus, Clonograptus, “Tetragraptus” and Holograptus/Schizograptus do not fit the sedimentological interpretation of deposition of these strata in much shallower inshore to mid-shelf environments. This inconsistency has implications when inferring the living conditions of the Fezouata soft-bodied assemblages.
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Biostratigraphy and palaeoecology of Lower Ordovician graptolites from the Fezouata Shale (Moroccan Anti-Atlas)
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Juan Carlos Gutierrez-marco, Emmanuel L.o. MartinAbstract:The Fezouata Shale (=Fezouata Formation) has produced the most complete Lower Ordovician graptolite succession known from the African continent, which was studied from 32 sections located along the western, central, and eastern Moroccan Anti-Atlas. A composite biostratigraphic and chronostratigraphic scheme is presented for the entire formation that, in ascending order, comprises the Anisograptus matanensis-Rhabdinopora flabelliformis anglica zones (uppermost lower Tremadocian), \textquotedblleftAdelograptus\textquotedblright tenellus and Aorograptus victoriae zones (middle Tremadocian), Araneograptus murrayi and Hunnegraptus copiosus zones (upper Tremadocian), ?Cymatograptus protobalticus Zone (lower Floian), ?Baltograptus jacksoni Zone (middle Floian), and the Baltograptus minutus Zone plus an \textquotedblleftAzygograptus interval\textquotedblright (upper Floian). Most of these zones or biozones are recorded for the first time in Africa, together with important graptolite species such as Ancoragraptus bulmani (Spjeldnaes), ?Cym. protobalticus (Monsen), ?B. jacksoni Rushton, Clonograptus multiplex (Nicholson), B. minutus (Tornquist) and Azygograptus eivionicus Elles. A correlation with the graptolite sucession from the Algerian Sahara is also suggested, reinforced by the common record of the minute anisograptid Choristograptus louhai Legrand, providing its second world occurrence in the Tremadocian of Morocco. The prior late Tremadocian dating of the Fezouata Lagerstatte is here extended to the middle Floian as revealed by the graptolite biochronology. The repeated record along the lower and middle parts of the Fezouata Formation of deep water mesopelagic species of the genera Araneograptus with mass occurrences of conical colonies, together with large horizontal rhabdosomes of Paratemnograptus, Paradelograptus, Clonograptus, \textquotedblleftTetragraptus\textquotedblright and Holograptus/Schizograptus do not fit the sedimentological interpretation of deposition of these strata in much shallower inshore to mid-shelf environments. This inconsistency has implications when inferring the living conditions of the Fezouata soft-bodied assemblages. (C) 2016 Elsevier B.V. All rights reserved.
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Biostratigraphic and palaeoenvironmental controls on the trilobite associations from the Lower Ordovician Fezouata Shale of the central Anti-Atlas, Morocco
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Emmanuel L.o. Martin, Muriel Vidal, Daniel Vizcaino, Romain Vaucher, J. Destombes, Pierre Sansjofre, Bertrand LefebvreAbstract:Trilobites are a major component of both biomineralized and soft-bodied assemblages of the Fezouata Biota, central Anti-Atlas, Morocco. Trilobite taxa of the Fezouata Shale (Tremadocian-Floian) in the Zagora area are typical of Lower Ordovician communities from shallow shelf environments, and show strong affinities with Early Ordovician assemblages from the Montagne Noire (southern France). Dramatic variations in both taxonomic composition and taphonomic attributes, together with the sedimentological facies changes, allow us to discriminate the palaeoenvironmental versus stratigraphic control on trilobite assemblages. Three communities are described along an onshore-offshore profile, namely the pilekiid-bavarillid, Agerina and raphiophorid biofacies. Additionally, three stratigraphic assemblages are identified: assemblage 1 is confined to the late Tremadocian, assemblage 2 ranges from late Tremadocian to middle Floian and assemblage 3 is restricted to the Floian. The higher diversity of some levels is explained by storm-induced inputs of debris from taxa living in adjacent environments. Additionally, control of relative seal level variation on some peculiarities of the trilobite fauna (specific endemicity, lack of some expected taxa) is evidenced in the Fezouata Shale. Finally, temporary dysoxic events are highlighted by preliminary geochemical analyses, probably allowing episodic exceptional preservation. (C) 2016 Elsevier B.V. All rights reserved.
Bertrand Lefebvre - One of the best experts on this subject based on the ideXlab platform.
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age calibration of the lower ordovician fezouata lagerstatte morocco
Lethaia, 2018Co-Authors: Bertrand Lefebvre, Mustapha Akodad, Oliver Lehnert, Juan Carlos Gutierrezmarco, Khadija El Hariri, Emmanuel L.o. Martin, Hendrik Nowak, Thomas ServaisAbstract:The Fezouata Lagerstatte, discovered in the Lower Ordovician rocks of Morocco, is a Konservat-Lagerstatte of prime scientific importance. It provides access not only to the ‘shelly’ (skeletonized) part of its fossil assemblages, but also to non-biomineralized to lightly sclerotized organisms and to exceptionally preserved soft tissues of a complex ecosystem, mixing elements of both the ‘Cambrian Explosion’ and the ‘Great Ordovician Biodiversification Event’ (GOBE). The Fezouata Lagerstatte occurs at different intervals in the Fezouata Shale, a formation ranging from the lower Tremadocian to the upper Floian (Lower Ordovician). In spite of recent major advances in the detailed biostratigraphy of the Fezouata Shale, there is currently no consensus on the precise age of the fossiliferous levels yielding exceptionally preserved assemblages. Consequently, all available biostratigraphical evidence based on several fossil groups is here critically reviewed and discussed. It can be concluded that exceptional preservation is restricted to a few thin, discontinuous, lens-shaped horizons occurring in two distinct parts of the Fezouata Shale: a lower interval (260–330 m above the base of the formation) and an upper interval (570–620 m). Integrated biostratigraphical studies, essentially based on investigations of graptolites, acritarchs and conodonts, indicate that the lower interval can be correlated with the upper Tremadocian, whereas the upper interval corresponds to the middle Floian.
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biostratigraphic and palaeoenvironmental controls on the trilobite associations from the lower ordovician fezouata shale of the central anti atlas morocco
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Emmanuel L.o. Martin, Muriel Vidal, Daniel Vizcaino, Romain Vaucher, Bertrand Lefebvre, Pierre Sansjofre, J. DestombesAbstract:Abstract Trilobites are a major component of both biomineralized and soft-bodied assemblages of the Fezouata Biota, central Anti-Atlas, Morocco. Trilobite taxa of the Fezouata Shale (Tremadocian–Floian) in the Zagora area are typical of Lower Ordovician communities from shallow shelf environments, and show strong affinities with Early Ordovician assemblages from the Montagne Noire (southern France). Dramatic variations in both taxonomic composition and taphonomic attributes, together with the sedimentological facies changes, allow us to discriminate the palaeoenvironmental versus stratigraphic control on trilobite assemblages. Three communities are described along an onshore–offshore profile, namely the pilekiid-bavarillid, Agerina and raphiophorid biofacies. Additionally, three stratigraphic assemblages are identified: assemblage 1 is confined to the late Tremadocian, assemblage 2 ranges from late Tremadocian to middle Floian and assemblage 3 is restricted to the Floian. The higher diversity of some levels is explained by storm-induced inputs of debris from taxa living in adjacent environments. Additionally, control of relative seal level variation on some peculiarities of the trilobite fauna (specific endemicity, lack of some expected taxa) is evidenced in the Fezouata Shale. Finally, temporary dysoxic events are highlighted by preliminary geochemical analyses, probably allowing episodic exceptional preservation.
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Biostratigraphic and palaeoenvironmental controls on the trilobite associations from the Lower Ordovician Fezouata Shale of the central Anti-Atlas, Morocco
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Emmanuel L.o. Martin, Muriel Vidal, Daniel Vizcaino, Romain Vaucher, J. Destombes, Pierre Sansjofre, Bertrand LefebvreAbstract:Trilobites are a major component of both biomineralized and soft-bodied assemblages of the Fezouata Biota, central Anti-Atlas, Morocco. Trilobite taxa of the Fezouata Shale (Tremadocian-Floian) in the Zagora area are typical of Lower Ordovician communities from shallow shelf environments, and show strong affinities with Early Ordovician assemblages from the Montagne Noire (southern France). Dramatic variations in both taxonomic composition and taphonomic attributes, together with the sedimentological facies changes, allow us to discriminate the palaeoenvironmental versus stratigraphic control on trilobite assemblages. Three communities are described along an onshore-offshore profile, namely the pilekiid-bavarillid, Agerina and raphiophorid biofacies. Additionally, three stratigraphic assemblages are identified: assemblage 1 is confined to the late Tremadocian, assemblage 2 ranges from late Tremadocian to middle Floian and assemblage 3 is restricted to the Floian. The higher diversity of some levels is explained by storm-induced inputs of debris from taxa living in adjacent environments. Additionally, control of relative seal level variation on some peculiarities of the trilobite fauna (specific endemicity, lack of some expected taxa) is evidenced in the Fezouata Shale. Finally, temporary dysoxic events are highlighted by preliminary geochemical analyses, probably allowing episodic exceptional preservation. (C) 2016 Elsevier B.V. All rights reserved.
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Palaeoecological aspects of the diversification of echinoderms in the Lower Ordovician of central Anti-Atlas, Morocco
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Bertrand Lefebvre, Bernard Pittet, Emmanuel L.o. Martin, Ninon Allaire, Thomas E. Guensburg, Aaron W. Hunter, Khaoula Kouraiss, Elise Nardin, Fleur Noailles, Colin D. SumrallAbstract:Echinoderms are one of the major components of benthic faunas in the Lower Ordovician sequence near Zagora, central Anti-Atlas, Morocco. The Fezouata Shale (Tremadocian-late Floian) has yielded numerous, exquisitely preserved echinoderm assemblages, ranging through several stratigraphic levels and palaeoenvironmental conditions. These associations offer a unique opportunity to document both evolutionary and palaeoecological aspects of echinoderm diversification in high-latitude, siliciclastic-dominated western Gondwana sediments, where rapid in situ burials facilitated excellent faunal census conditions. Lower shoreface deposits of the Fezouata Shale provide the most complete record of successive echinoderm faunas. In late Tremadocian times, these relatively shallow shelf deposits show the progressive replacement of low-diversity, opportunistic, Cambrian like, dwarfed communities dominated by cornute stylophorans, in unhospitable, dysoxic environmental conditions by higher diversity benthic assemblages, more typical of the Great Ordovician Biodiversification Event and dominated by blastozoans, on well-oxygenated sea-floors. The turnover of the Ordovician radiation was apparently slightly delayed in more proximal settings. Eocrinoid meadows persisted in shallower environmental conditions up to the middle Floian. In the late Floian, they were replaced by diploporite-dominated communities, typical of later Ordovician high-latitude peri-Gondwanan faunas. From a palaeobiogeographic point of view, low-diversity assemblages display relatively strong affinities with cosmopolitan late Cambrian echinoderm faunas, whereas high-diversity communities are dominated by peri-Gondwanan taxa. (C) 2016 Elsevier B.V. All rights reserved.
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The Fezouata Shale (Lower Ordovician, Anti-Atlas, Morocco): A historical review
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Ihadija El Hariri, Peter Van Roy, Thomas Servais, Rudy Lerosey-aubril, Bertrand LefebvreAbstract:Exceptionally preserved fossils yield crucial information about the evolution of Life on Earth. The Fezouata Biota from the Lower Ordovician of Morocco is a Konservat-Lagerstatte of major importance, and it is today considered as an `Ordovician Burgess Shale.' This biota was discovered only some 15 years ago, but geological studies of the area date back to the beginning of the 20th century. Pioneering geological investigations lead to the discovery of Ordovician strata in the Anti-Atlas (1929) and ultimately resulted in their formal subdivision into four main stratigraphic units (1942). In the Agdz area, the presence of fossiliferous Tremadocian (Lower Ordovician) strata was suspected as early as 1939, but only definitively confirmed in 1955. In the 1960s-1990s, Jacques Destombes provided the first detailed biostratigraphic framework for the Lower Ordovician of the Anti-Atlas, and collected thousands of fossils that were subsequently described in a series of monographs. In the early 2000s, exceptionally preserved fossils were discovered in the Fezouata Shale (Tremadocian-late Floian) in the central Anti-Atlas by Mohamed `Ou Said' Ben Moula. This biota, now known as the Fezouata Biota, is of utmost importance, for it demonstrates the extent in the fossil record of non-biomineralising animals typical of the `Cambrian Explosion' into the Ordovician, during the `Great Ordovician Biodiversification.' Although most components are still in need of formal descriptions, a fairly good picture of the composition and organisation of this biota, and how it contributes to our understanding of the early evolution of metazoan communities, can now be depicted. Moreover, recent studies have substantially clarified the biostratigraphical and palaeoenvironmental context of the Fezouata Shale, and are now being followed up by detailed investigations of the taphonomy, geochemistry and micropalaeontology of this unique Konservat-Lagerstatte. These efforts will soon greatly benefit from the recovery of fresh, unweathered samples from drill cores. (C) 2015 Elsevier B.V. All rights reserved.
Thomas Servais - One of the best experts on this subject based on the ideXlab platform.
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age calibration of the lower ordovician fezouata lagerstatte morocco
Lethaia, 2018Co-Authors: Bertrand Lefebvre, Mustapha Akodad, Oliver Lehnert, Juan Carlos Gutierrezmarco, Khadija El Hariri, Emmanuel L.o. Martin, Hendrik Nowak, Thomas ServaisAbstract:The Fezouata Lagerstatte, discovered in the Lower Ordovician rocks of Morocco, is a Konservat-Lagerstatte of prime scientific importance. It provides access not only to the ‘shelly’ (skeletonized) part of its fossil assemblages, but also to non-biomineralized to lightly sclerotized organisms and to exceptionally preserved soft tissues of a complex ecosystem, mixing elements of both the ‘Cambrian Explosion’ and the ‘Great Ordovician Biodiversification Event’ (GOBE). The Fezouata Lagerstatte occurs at different intervals in the Fezouata Shale, a formation ranging from the lower Tremadocian to the upper Floian (Lower Ordovician). In spite of recent major advances in the detailed biostratigraphy of the Fezouata Shale, there is currently no consensus on the precise age of the fossiliferous levels yielding exceptionally preserved assemblages. Consequently, all available biostratigraphical evidence based on several fossil groups is here critically reviewed and discussed. It can be concluded that exceptional preservation is restricted to a few thin, discontinuous, lens-shaped horizons occurring in two distinct parts of the Fezouata Shale: a lower interval (260–330 m above the base of the formation) and an upper interval (570–620 m). Integrated biostratigraphical studies, essentially based on investigations of graptolites, acritarchs and conodonts, indicate that the lower interval can be correlated with the upper Tremadocian, whereas the upper interval corresponds to the middle Floian.
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first appearance datums fads of selected acritarch taxa and correlation between lower and middle ordovician stages
Lethaia, 2018Co-Authors: Thomas Servais, Hendrik Nowak, Claudia V Rubinstein, Marco Vecoli, Stewart G. Molyneux, Wenhui WangAbstract:First Appearance Datums (FADs) of selected, easily recognizable acritarch morphotypes are assessed to determine their potential contribution to correlation between Lower and Middle Ordovician stages and substage divisions along the Gondwanan margin (Perigondwana) and between Perigondwana and other palaeocontinents. The FADs for 19 genera, species and species groups are recorded throughout their biogeographical ranges. The taxa investigated fall into three groups. Some have FADs at about the same level throughout their biogeographical ranges and are useful for long-distance and intercontinental correlation. Among these are Coryphidium, Dactylofusa velifera, Peteinosphaeridium and Rhopaliophora in the upper Tremadocian Stage; Arbusculidium filamentosum, Aureotesta clathrata simplex and Coryphidium bohemicum in the lower–middle Floian Stage; Dicrodiacrodium in the upper Floian Stage; Frankea in the Dapingian–lower Darriwilian stages; and Orthosphaeridium spp., with FADs in the Dapingian–lower Darriwilian stages of Perigondwanan regions and at about the same level in Baltica. Other taxa, however, have diachronous (or apparently diachronous) FADs, and this needs to be taken into account when using them for correlation. A second group of genera and species, comprising Striatotheca, the Veryhachium lairdii group and the V. trispinosum group, have a recurring pattern of FADs in the Tremadocian Stage on Avalonia and in South Gondwana and West Gondwana, but in the Floian Stage of South China and East Gondwana. The third group, consisting of Arkonia, Ampullula, Barakella, Dasydorus, Liliosphaeridium and Sacculidium, have FADs that are markedly diachronous throughout their biogeographical ranges, although the global FADs of Arkonia, Ampullula, Liliosphaeridium and Sacculidium are apparently in South China and/or East Gondwana. It is possible that diachronous FADs are only apparent and an artefact of sampling. Nevertheless, an alternative interpretation, suggested by recurring patterns, is that some as yet undetermined factor controlled a slower biogeographical spread over time, resulting in diachroneity.
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Tremadocian early ordovician chitinozoan biostratigraphy of south china an update
Review of Palaeobotany and Palynology, 2017Co-Authors: Thomas Servais, Yan Liang, Peng Tang, Jianbo Liu, Wenhui WangAbstract:Abstract The lowest Ordovician (Tremadocian) chitinozoan biostratigraphy of the South China Palaeoplate has been reviewed and updated, based on new investigation from the Upper Yangtze area. The systematic paleontology of Lagenochitina pestovoensis Obut 1973 and Lagenochitina destombesi Elaouad-Debbaj 1988, has been revised. Previous identifications of L. destombesi from South China are considered questionable, and the L . destombesi Biozone, recognized from Baltica, northern Gondwana and peri-Gondwana, is therefore no longer used for the middle-upper part of the Tremadocian in South China. Two chitinozoan biozones are recognized, including the Lagenochitina pestovoensis Biozone (lower) and the Euconochitina symmetrica Biozone (upper) for the middle and upper part of the South Chinese Tremadocian. International correlation of the E. symmetrica Biozone indicates that the base of this biozone in South China is lower than the records in North America and northern Gondwana, and that the biozone is confined within the upper Tremadocian in South China.
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palynomorphs of the fezouata shale lower ordovician morocco age and environmental constraints of the fezouata biota
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Hendrik Nowak, Mustapha Akodad, Romain Vaucher, Thijs R.a. Vandenbroucke, Robert R Gaines, Bernard Pittet, Thomas ServaisAbstract:Abstract The present study documents new palynological investigations of the Fezouata Shale from the Anti-Atlas (Morocco). Palynomorphs were extracted from samples collected from both outcrops and drill cuttings. Outcrop samples were taken near Zagora, and include some that were collected during excavation of stratigraphic horizons where exceptionally well-preserved fossils of the Fezouata Lagerstatte occur. Subsurface samples were taken from the AZ-1 (Adrar Zouggar Mountain) borehole, which was extracted some 300 km to the southwest of Zagora. The palynological samples yielded acritarchs, chitinozoans, scolecodonts, conodonts and fragments of graptolites. The abundance and quality of preservation of palynomorphs varies greatly, but rich and diverse assemblages were recovered from several samples. The diversity and composition of the assemblages points to an open shelf environment. Generally mixed preservation states suggest resedimentation or differential transport histories. The acritarchs can be assigned to the diagnostic messaoudensis-trifidum acritarch assemblage, which is typical of the Tremadocian/Floian boundary interval of the Gondwanan margin in high southern palaeolatitudes. The acritarch taxa present in some of the lower parts of the Fezouata Shale including levels of exceptional preservation can be attributed to sub-assemblages 1–2 of the messaoudensis-trifidum assemblage and thus point to a late Tremadocian age of the Fezouata Lagerstatte, confirming biostratigraphic data provided by graptolites of the Araneograptus murrayi graptolite biozone. Chitinozoans from the Fezouata Shale are from the E. symmetrica and E. brevis biozones and include various species that are well-known from several localities on the Gondwanan margin and from other palaeocontinents (Baltica, Laurentia, and South China), demarcating broad links between those regions. The coincidence between index fossils of these three groups, hitherto not all found in the same level, suggests that the age assignments of chitinozoan biozones may be in need of revision.
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Palynomorphs of the Fezouata Shale (Lower Ordovician, Morocco): Age and environmental constraints of the Fezouata Biota
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Hendrik Nowak, Mustapha Akodad, Romain Vaucher, Robert R Gaines, Bernard Pittet, Thomas Servais, Thijs R.a. VandenbrouckeAbstract:The present study documents new palynological investigations of the Fezouata Shale from the Anti-Atlas (Morocco). Palynomorphs were extracted from samples collected from both outcrops and drill cuttings. Outcrop samples were taken near Zagora, and include some that were collected during excavation of stratigraphic horizons where exceptionally well-preserved fossils of the Fezouata Lagerstatte occur. Subsurface samples were taken from the AZ-1 (Adrar Zouggar Mountain) borehole, which was extracted some 300 km to the southwest of Zagora. The palynological samples yielded acritarchs, chitinozoans, scolecodonts, conodonts and fragments of graptolites. The abundance and quality of preservation of palynomorphs varies greatly, but rich and diverse assemblages were recovered from several samples. The diversity and composition of the assemblages points to an open shelf environment. Generally mixed preservation states suggest resedimentation or differential transport histories. The acritarchs can be assigned to the diagnostic messaoudensis-trifidum acritarch assemblage, which is typical of the Tremadocian/Floian boundary interval of the Gondwanan margin in high southern palaeolatitudes. The acritarch taxa present in some of the lower parts of the Fezouata Shale including levels of exceptional preservation can be attributed to sub-assemblages 1-2 of the messaoudensis-trifidum assemblage and thus point to a late Tremadocian age of the Fezouata Lagerstatte, confirming biostratigraphic data provided by graptolites of the Araneograptus murrayi graptolite biozone. Chitinozoans from the Fezouata Shale are from the E. symmetrica and E. brevis biozones and include various species that are well-known from several localities on the Gondwanan margin and from other palaeocontinents (Baltica, Laurentia, and South China), demarcating broad links between those regions. The coincidence between index fossils of these three groups, hitherto not all found in the same level, suggests that the age assignments of chitinozoan biozones may be in need of revision. (C) 2016 Elsevier B.V. All rights reserved.
Thijs R.a. Vandenbroucke - One of the best experts on this subject based on the ideXlab platform.
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palynomorphs of the fezouata shale lower ordovician morocco age and environmental constraints of the fezouata biota
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Hendrik Nowak, Mustapha Akodad, Romain Vaucher, Thijs R.a. Vandenbroucke, Robert R Gaines, Bernard Pittet, Thomas ServaisAbstract:Abstract The present study documents new palynological investigations of the Fezouata Shale from the Anti-Atlas (Morocco). Palynomorphs were extracted from samples collected from both outcrops and drill cuttings. Outcrop samples were taken near Zagora, and include some that were collected during excavation of stratigraphic horizons where exceptionally well-preserved fossils of the Fezouata Lagerstatte occur. Subsurface samples were taken from the AZ-1 (Adrar Zouggar Mountain) borehole, which was extracted some 300 km to the southwest of Zagora. The palynological samples yielded acritarchs, chitinozoans, scolecodonts, conodonts and fragments of graptolites. The abundance and quality of preservation of palynomorphs varies greatly, but rich and diverse assemblages were recovered from several samples. The diversity and composition of the assemblages points to an open shelf environment. Generally mixed preservation states suggest resedimentation or differential transport histories. The acritarchs can be assigned to the diagnostic messaoudensis-trifidum acritarch assemblage, which is typical of the Tremadocian/Floian boundary interval of the Gondwanan margin in high southern palaeolatitudes. The acritarch taxa present in some of the lower parts of the Fezouata Shale including levels of exceptional preservation can be attributed to sub-assemblages 1–2 of the messaoudensis-trifidum assemblage and thus point to a late Tremadocian age of the Fezouata Lagerstatte, confirming biostratigraphic data provided by graptolites of the Araneograptus murrayi graptolite biozone. Chitinozoans from the Fezouata Shale are from the E. symmetrica and E. brevis biozones and include various species that are well-known from several localities on the Gondwanan margin and from other palaeocontinents (Baltica, Laurentia, and South China), demarcating broad links between those regions. The coincidence between index fossils of these three groups, hitherto not all found in the same level, suggests that the age assignments of chitinozoan biozones may be in need of revision.
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Palynomorphs of the Fezouata Shale (Lower Ordovician, Morocco): Age and environmental constraints of the Fezouata Biota
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Hendrik Nowak, Mustapha Akodad, Romain Vaucher, Robert R Gaines, Bernard Pittet, Thomas Servais, Thijs R.a. VandenbrouckeAbstract:The present study documents new palynological investigations of the Fezouata Shale from the Anti-Atlas (Morocco). Palynomorphs were extracted from samples collected from both outcrops and drill cuttings. Outcrop samples were taken near Zagora, and include some that were collected during excavation of stratigraphic horizons where exceptionally well-preserved fossils of the Fezouata Lagerstatte occur. Subsurface samples were taken from the AZ-1 (Adrar Zouggar Mountain) borehole, which was extracted some 300 km to the southwest of Zagora. The palynological samples yielded acritarchs, chitinozoans, scolecodonts, conodonts and fragments of graptolites. The abundance and quality of preservation of palynomorphs varies greatly, but rich and diverse assemblages were recovered from several samples. The diversity and composition of the assemblages points to an open shelf environment. Generally mixed preservation states suggest resedimentation or differential transport histories. The acritarchs can be assigned to the diagnostic messaoudensis-trifidum acritarch assemblage, which is typical of the Tremadocian/Floian boundary interval of the Gondwanan margin in high southern palaeolatitudes. The acritarch taxa present in some of the lower parts of the Fezouata Shale including levels of exceptional preservation can be attributed to sub-assemblages 1-2 of the messaoudensis-trifidum assemblage and thus point to a late Tremadocian age of the Fezouata Lagerstatte, confirming biostratigraphic data provided by graptolites of the Araneograptus murrayi graptolite biozone. Chitinozoans from the Fezouata Shale are from the E. symmetrica and E. brevis biozones and include various species that are well-known from several localities on the Gondwanan margin and from other palaeocontinents (Baltica, Laurentia, and South China), demarcating broad links between those regions. The coincidence between index fossils of these three groups, hitherto not all found in the same level, suggests that the age assignments of chitinozoan biozones may be in need of revision. (C) 2016 Elsevier B.V. All rights reserved.
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chitinozoans from the Tremadocian graptolite shales of the jiangnan slope in south china
Review of Palaeobotany and Palynology, 2013Co-Authors: Thijs R.a. Vandenbroucke, Wenhui Wang, Hongzhen Feng, Jacques VerniersAbstract:In the Nanba section of the Yiyang area in the Hunan Province (South China terrane), chitinozoans were recovered from three Tremadocian graptolite biozones (the Adelograptus tenellus, Aorograptus victoriae and Araneograptus murrayi biozones). Three genera and 12 species are identified from 16 different stratigraphical levels. Three chitinozoan biozones are distinguished, based on the Early Ordovician index species Lagenochitina destombesi Elaouad-Debbaj, 1988, Lagenochitina esthonica Eisenack, 1955 and Euconochitina symmetrica (Taugourdeau and de Jekhowsky, 1960). Together with coexisting graptolites, these chitinozoans are used for precise correlation at both regional and global scales. The fossiliferous strata of the Yiyang area allow us to calibrate the earliest chitinozoan biozones versus the reference graptolite biozones. The presence of the earliest specimen of L. destombesi in the lowest sample is doubtful, but an unidentified specimen of ?Conochitina, is found at the same level, and this taxon could potentially represent the oldest chitinozoans, if it can be proven to appear below L. destombesi.
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palynomorphs of the fezouata shale lower ordovician morocco age and environmental constraints of the fezouata biota
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Hendrik Nowak, Mustapha Akodad, Romain Vaucher, Thijs R.a. Vandenbroucke, Robert R Gaines, Bernard Pittet, Thomas ServaisAbstract:Abstract The present study documents new palynological investigations of the Fezouata Shale from the Anti-Atlas (Morocco). Palynomorphs were extracted from samples collected from both outcrops and drill cuttings. Outcrop samples were taken near Zagora, and include some that were collected during excavation of stratigraphic horizons where exceptionally well-preserved fossils of the Fezouata Lagerstatte occur. Subsurface samples were taken from the AZ-1 (Adrar Zouggar Mountain) borehole, which was extracted some 300 km to the southwest of Zagora. The palynological samples yielded acritarchs, chitinozoans, scolecodonts, conodonts and fragments of graptolites. The abundance and quality of preservation of palynomorphs varies greatly, but rich and diverse assemblages were recovered from several samples. The diversity and composition of the assemblages points to an open shelf environment. Generally mixed preservation states suggest resedimentation or differential transport histories. The acritarchs can be assigned to the diagnostic messaoudensis-trifidum acritarch assemblage, which is typical of the Tremadocian/Floian boundary interval of the Gondwanan margin in high southern palaeolatitudes. The acritarch taxa present in some of the lower parts of the Fezouata Shale including levels of exceptional preservation can be attributed to sub-assemblages 1–2 of the messaoudensis-trifidum assemblage and thus point to a late Tremadocian age of the Fezouata Lagerstatte, confirming biostratigraphic data provided by graptolites of the Araneograptus murrayi graptolite biozone. Chitinozoans from the Fezouata Shale are from the E. symmetrica and E. brevis biozones and include various species that are well-known from several localities on the Gondwanan margin and from other palaeocontinents (Baltica, Laurentia, and South China), demarcating broad links between those regions. The coincidence between index fossils of these three groups, hitherto not all found in the same level, suggests that the age assignments of chitinozoan biozones may be in need of revision.
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biostratigraphic and palaeoenvironmental controls on the trilobite associations from the lower ordovician fezouata shale of the central anti atlas morocco
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Emmanuel L.o. Martin, Muriel Vidal, Daniel Vizcaino, Romain Vaucher, Bertrand Lefebvre, Pierre Sansjofre, J. DestombesAbstract:Abstract Trilobites are a major component of both biomineralized and soft-bodied assemblages of the Fezouata Biota, central Anti-Atlas, Morocco. Trilobite taxa of the Fezouata Shale (Tremadocian–Floian) in the Zagora area are typical of Lower Ordovician communities from shallow shelf environments, and show strong affinities with Early Ordovician assemblages from the Montagne Noire (southern France). Dramatic variations in both taxonomic composition and taphonomic attributes, together with the sedimentological facies changes, allow us to discriminate the palaeoenvironmental versus stratigraphic control on trilobite assemblages. Three communities are described along an onshore–offshore profile, namely the pilekiid-bavarillid, Agerina and raphiophorid biofacies. Additionally, three stratigraphic assemblages are identified: assemblage 1 is confined to the late Tremadocian, assemblage 2 ranges from late Tremadocian to middle Floian and assemblage 3 is restricted to the Floian. The higher diversity of some levels is explained by storm-induced inputs of debris from taxa living in adjacent environments. Additionally, control of relative seal level variation on some peculiarities of the trilobite fauna (specific endemicity, lack of some expected taxa) is evidenced in the Fezouata Shale. Finally, temporary dysoxic events are highlighted by preliminary geochemical analyses, probably allowing episodic exceptional preservation.
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Biostratigraphic and palaeoenvironmental controls on the trilobite associations from the Lower Ordovician Fezouata Shale of the central Anti-Atlas, Morocco
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Emmanuel L.o. Martin, Muriel Vidal, Daniel Vizcaino, Romain Vaucher, J. Destombes, Pierre Sansjofre, Bertrand LefebvreAbstract:Trilobites are a major component of both biomineralized and soft-bodied assemblages of the Fezouata Biota, central Anti-Atlas, Morocco. Trilobite taxa of the Fezouata Shale (Tremadocian-Floian) in the Zagora area are typical of Lower Ordovician communities from shallow shelf environments, and show strong affinities with Early Ordovician assemblages from the Montagne Noire (southern France). Dramatic variations in both taxonomic composition and taphonomic attributes, together with the sedimentological facies changes, allow us to discriminate the palaeoenvironmental versus stratigraphic control on trilobite assemblages. Three communities are described along an onshore-offshore profile, namely the pilekiid-bavarillid, Agerina and raphiophorid biofacies. Additionally, three stratigraphic assemblages are identified: assemblage 1 is confined to the late Tremadocian, assemblage 2 ranges from late Tremadocian to middle Floian and assemblage 3 is restricted to the Floian. The higher diversity of some levels is explained by storm-induced inputs of debris from taxa living in adjacent environments. Additionally, control of relative seal level variation on some peculiarities of the trilobite fauna (specific endemicity, lack of some expected taxa) is evidenced in the Fezouata Shale. Finally, temporary dysoxic events are highlighted by preliminary geochemical analyses, probably allowing episodic exceptional preservation. (C) 2016 Elsevier B.V. All rights reserved.
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Palynomorphs of the Fezouata Shale (Lower Ordovician, Morocco): Age and environmental constraints of the Fezouata Biota
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Hendrik Nowak, Mustapha Akodad, Romain Vaucher, Robert R Gaines, Bernard Pittet, Thomas Servais, Thijs R.a. VandenbrouckeAbstract:The present study documents new palynological investigations of the Fezouata Shale from the Anti-Atlas (Morocco). Palynomorphs were extracted from samples collected from both outcrops and drill cuttings. Outcrop samples were taken near Zagora, and include some that were collected during excavation of stratigraphic horizons where exceptionally well-preserved fossils of the Fezouata Lagerstatte occur. Subsurface samples were taken from the AZ-1 (Adrar Zouggar Mountain) borehole, which was extracted some 300 km to the southwest of Zagora. The palynological samples yielded acritarchs, chitinozoans, scolecodonts, conodonts and fragments of graptolites. The abundance and quality of preservation of palynomorphs varies greatly, but rich and diverse assemblages were recovered from several samples. The diversity and composition of the assemblages points to an open shelf environment. Generally mixed preservation states suggest resedimentation or differential transport histories. The acritarchs can be assigned to the diagnostic messaoudensis-trifidum acritarch assemblage, which is typical of the Tremadocian/Floian boundary interval of the Gondwanan margin in high southern palaeolatitudes. The acritarch taxa present in some of the lower parts of the Fezouata Shale including levels of exceptional preservation can be attributed to sub-assemblages 1-2 of the messaoudensis-trifidum assemblage and thus point to a late Tremadocian age of the Fezouata Lagerstatte, confirming biostratigraphic data provided by graptolites of the Araneograptus murrayi graptolite biozone. Chitinozoans from the Fezouata Shale are from the E. symmetrica and E. brevis biozones and include various species that are well-known from several localities on the Gondwanan margin and from other palaeocontinents (Baltica, Laurentia, and South China), demarcating broad links between those regions. The coincidence between index fossils of these three groups, hitherto not all found in the same level, suggests that the age assignments of chitinozoan biozones may be in need of revision. (C) 2016 Elsevier B.V. All rights reserved.
