31 results on '"Yans, J."'
Search Results
2. The Pliensbachian-Toarcian paleoclimate transition: New insights from organic geochemistry and C, H, N isotopes in a continental section from Central Asia
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Tramoy, R., Schnyder, J., Nguyen Tu, T.T., Yans, J., Jacob, J., Sebilo, M., Derenne, S., Philippe, M., Huguet, A., Pons, D., and Baudin, F.
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- 2016
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3. Detailed mineralogy and petrology of manganese oxyhydroxide deposits of the Imini district (Morocco)
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Dekoninck, A., Bernard, A., Barbarand, J., Saint-Bezar, B., Missenard, Y., Lepretre, R., Saddiqi, O., and Yans, J.
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- 2016
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4. Evidence for perturbation of the carbon cycle in the Middle Frasnian punctata Zone (late Devonian)
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Yans, J., Corfield, R.M., Racki, G., and Preat, A.
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Global warming -- Environmental aspects ,Carbon cycle (Biogeochemistry) -- Research ,Sea level -- Research ,Earth sciences - Abstract
New carbon isotopic data from the Devonian of Ardennes (Belgium) and partly from the Holy Cross Mountains (Poland) highlight an abrupt and high-amplitude negative excursion in the punctata conodont Zone. Published information from Moravia and China suggests that this Middle Frasnian negative excursion, jointly with the preceding large-scale positive shift, should be used as a global chemostratigraphic marker. Causation scenarios for this negative 'punctata Event' are correlated neither with major biota turnover nor major sea-level changes, but may be related to: (1) the Alamo Impact Event, that led to (2) the massive dissociation of methane hydrates and (3) the rapid onset of global warming. Keywords: punctata Event, Frasnian, carbon isotopes, Ardennes, Belgium.
- Published
- 2007
5. Palynology of the dinosaur-bearing Wealden facies in the natural pit of Bernissart (Belgium)
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Dejax, J., Pons, D., and Yans, J.
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- 2007
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6. Recognition and implication of tectonic loading-induced reheating in the northern Variscan front (Belgium and northern France), based on an illite Kübler index and oxygen isotope study
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Han, G., Yans, J., Goudalier, M., Lacquement, F., Corfield, R. M., Mansy, J. L., Boulvain, F., and Préat, A.
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- 2003
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7. Potential Discrimination of Belgian Black Marbles Using Petrography, Magnetic Susceptibility and Geochemistry.
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Boulvain, F., Poulain, G., Tourneur, F., and Yans, J.
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MAGNETIC susceptibility ,RARE earth metals ,PETROLOGY ,GEOCHEMISTRY ,MARBLE ,MARBLE sculpture ,BLACK cotton soil - Abstract
Five varieties of Belgian black marbles are investigated in order to discriminate them. Their age ranges from Frasnian (Golzinne) to Visean (Dinant, Theux, Basècle, Lives). Three methods were used: petrography, magnetic susceptibility and geochemistry of major elements and Rare Earth Elements (REE). The petrographic analyze reveals 16 microfacies reflecting very quiet environments, sporadically perturbed by more energetic phenomena like turbidites or storms. These microfacies are integrated in two depositional models: a quiet offshore setting, below or close to the storm wave base (Salet, Basècles) and a shallow but very restricted zone, protected from waves and currents (Lives and Golzinne). The magnetic susceptibility results show that all the black marbles are characterized by very low, even slightly negative values, except the Golzinne one which shows higher values. Geochemical data allow to discriminate between the Theux black marble (low SiO2 content), and the Basècles samples (low Al2O3, K2O and REE contents). These methods could be useful to determine/refine the origin of archaeological stones, even if all these analyses are destructive. Two archeologic samples were investigated in order to identify their possible origin. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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8. The Zemst borehole, first record of the EECO in the North Sea Basin and implications for Belgian Ypresian - Lutetian stratigraphy
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Steurbaut, E., King, C., Matthijs, J., Noiret, C., Yans, J., and Van Simaeys, S.
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Integration of new data in sedimentology, micropalaeontology and organic carbon isotopeanalysis of upper Ypresian strata in central Belgium (Zemst hole) enables differentiationof a series of biotic events and carbon isotope trends, which are believed to be associated with the 1.5-million-year-long period of global warming, known as the Early Eocene Climatic Optimum (EECO). The relatively low values in δ13Corg(-26.5‰ to -27.1‰) in the interval from the Panisel Sand to the Merelbeke Clay Members (upper NP12-lower NP13) are shown to be coinciding with a fairly high frequency in Apectodinium (>3%, up to 14%) and a Discoaster-bloom (16%-50%, essentially D. kuepperi). This is quite analogous, although less prominent, to what has been observed during the Paleocene-Eocene Thermal Maximum (PETM: Apectodinium abundance of 75% at middle and high latitudes and Discoaster blooms in tropical areas). The abrupt positive shift of up to 1‰ in δ13Corg values at the base of the overlying Pittem Clay Member (mid-NP13, mid-chron C22r), which is coincident with the virtual disappearances of Apectodinium (Discoaster (Blackites inflatus), as adopted in the Gorrondatxe GSSP (Spain), cannot be applied in the North Sea Basin s.s. (excluding the Paris Basin) and that there is an urgent need for defining appropriate substitutes for this boundary at these latitudes.
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- 2015
9. Refined bio- (benthic foraminifera, dinoflagellate cysts) and chemostratigraphy (delta13Corg) of the earliest Eocene at Albas-Le Clot (Corbieres, France): implications for mammalian biochronology in Southern Europe
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Yans, J., Marandat, B, Masure, E, Serra-Kiel, J, Schnyder, J, Storme, J.-Y., Marivaux, L, Adnet, S, Vianey-Liaud, M, and Tabuce, R
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Mammalia [mammals] - Abstract
Utilizing bio- and chemostratigraphy, we propose an integrated dating of the upper part of the continental “Sparnacien des Corbières” and the overlying marine “lower-middle Ilerdian” succession of AlbasLe Clot (Corbières, France), in order to refine the position and age of the Le Clot mammalian locality. Our data show that this locality, which has yielded a mammal fauna early Ypresian in age (close to MP7, Mammal Paleo gene level), is located above the end of the carbon isotope excursion (CIE) the base of which defines the Paleocene–Eocene boundary. The Le Clot mammalian locality is therefore younger than the Paleocene–Eocene Thermal Maximum (PETM), and also younger than the Dormaal MP7 reference fauna in Belgium, which is correlated with the onset of the CIE (nannoplankton Zone NP9b). Moreover, we demonstrate that the Le Clot mammalian locality is older than the Eocene Thermal Maximum 2 (ETM2) event, located in the lower part of NP11 Zone. Associated with the ages of benthic foraminifera and dinocysts observed in the succession, our d13Corg chemostratigraphy suggests that the Le Clot locality is correlated to the upper NP10–lower NP11 Zones. The refined location of the CIE in the Albas-Le Clot section is discussed because two carbon isotope excursions are potentially recorded in the upper “Sparnacien des Corbières”, here recognized as mainly Thanetian in age.
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- 2014
10. Direct Orange 34 dye fixation by modified kaolin.
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CHARGUI, H., HAJJAJI, W., WOUTERS, J., YANS, J., and JAMOUSSI, F.
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- 2018
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11. Perturbation of a Tethyan coastal environment during the Paleocene–Eocene thermal maximum in Tunisia (Sidi Nasseur and Wadi Mezaz)
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Stassen, P., Dupuis, C., Steurbaut, E., Yans, J., and Speijer, R.P.
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Foraminifera [hole bearers] - Abstract
Despite the large number of studies on the Paleocene–Eocene thermal maximum (PETM), the knowledge of environmental and biotic responses in shallow marine environments remains quite poor. Benthic foraminiferal assemblages of the Sidi Nasseur and Wadi Mezaz sections in Tunisia were studied quantitatively and the paleoecologic interpretations provide new insights into the complex relationship between PETM global warming and perturbations of shallow marine settings. These sections expose upper Paleocene to lower Eocene shales and marls of the El Haria Formation up to the phosphate layers of the Chouabine Formation underlying the El Garia limestones. The Sidi Nasseur section contains a more complete and expanded Paleocene–Eocene boundary interval compared to Wadi Mezaz, although being truncated at the top. The Wadi Mezaz section contains a more complete post-PETM interval. The studied interval can be subdivided into a sequence of 4 biofacies, representing respectively a latest Paleocene biofacies, two PETM biofacies and one post-PETM Eocene biofacies.The latest Paleocene biofacies 1 consists of numerous calcareous benthic foraminifera (e.g. Anomalinoides midwayensis, Frondicularia aff. phosphatica and various Bulimina and Lenticulina species), abundant non-calcareous taxa (Haplophragmoides) and rare planktic foraminifera, indicating a slightly hypersaline eutrophic inner neritic to coastal environment, regularly interrupted by oxygen deficiency (moderate dysoxia). During the latest Paleocene, this highly productive environment shallowed as indicated by the increasing abundances of A. midwayensis. The variable dominance of non-calcareous agglutinated taxa in biofacies 1 indicates post-mortem dissolution effects. The TOC d13Corg record reveals a sharp negative excursion, marking the base of the Eocene. In general, the absence of lithologic changes, an increasing sedimentation rate and absence of reworking indicate that the initial part of the PETM is complete and expanded in the Sidi Nasseur section. A sharp faunal turnover coincides with this negative d13Corg excursion and is characterized by the disappearance or diminution of common Paleocene taxa in this area. During the PETM, benthic foraminifera are less abundant and consist of opportunistic non-calcareous taxa together with deeper dwelling (middle neritic) lagenids and buliminids (biofacies 2 and 3). Planktic foraminifera, dominated by flat-spired Acarinina (mainly A. multicamerata), become more abundant, as observed in many open marine sequences worldwide. All these faunal parameters suggest more stressed probably severe dysoxic sea floor conditions within a transgressive phase during the onset of the PETM. An estimation of the total duration of the Sidi Nasseur PETM interval is difficult to establish, yet the lack of recovery carbon isotope values suggests that the preserved PETM interval reflects only a part of the CIE “core”. The top of the PETM interval is truncated due to local (?) erosion during the early Eocene. The Eocene recovery fauna is mainly composed of Lenticulina and Stainforthia species (biofacies 4), indicating restricted coastal to hyposaline lagoonal eutrophic conditions, distinctly different from earlier environmental conditions.
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- 2012
12. Pierres et Tectonique en Hainaut (Belgique)
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Vandycke, S., Bergerat, Françoise, Baele, J.-M., Delaby, S., Delcourt, Jérémy, Deveseleer, J., Gaviglio, P., Hennebert, M., Licour, L., Papier, S., Quinif, Yves, Robaszinski, F., Rorive, A., Schroeder, C., Spagna, P., Yans, J., Dollin, Gitane, Institut des Sciences de la Terre de Paris (iSTeP), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)
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ComputingMilieux_MISCELLANEOUS ,[SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy ,[SDU.STU.MI] Sciences of the Universe [physics]/Earth Sciences/Mineralogy - Abstract
International audience
- Published
- 2011
13. Stratigraphie des sédiments à faciès Wealdien dans le Bassin de Mons (Belgique)
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Yans, J., Dejax, J., Schnyder, Johann, Spagna, P., Dupuis, C., Gerrienne, P., Queyroy, Marie José, Institut des Sciences de la Terre de Paris (iSTeP), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)
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[SDU.STU] Sciences of the Universe [physics]/Earth Sciences ,[SDU.STU]Sciences of the Universe [physics]/Earth Sciences - Published
- 2011
14. Reconstitution paléogéographique du massif ardennais : thermochronologie par traces de fission sur apatite
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Bour, I., Barbarand, J., Pagel, M., Gautheron, C., Yans, J., Quesnel, F., Delcambre, B., Interactions et dynamique des environnements de surface (IDES), and Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
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[SDU.STU]Sciences of the Universe [physics]/Earth Sciences - Published
- 2008
15. Palynological study of the dinosaurs-bearing wealden facies sediments of Bernissart (Belgium)
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Pons, D., Dejax, J., Yans, J., Paléobiodiversité et paléoenvironnements, Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), and Muséum national d'Histoire naturelle (MNHN)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)
- Published
- 2004
16. Removal of a knotted flow-directed catheter by a nonsurgical method.
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Kumar, Samuel P., Yans, Javad, Kwatra, Manmohanlal, Loesch, David M., Viturawong, Vichit, Kumar, S P, Yans, J, Kwatra, M, Loesch, D M, and Viturawong, V
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CATHETERS ,SURGERY ,PATIENT monitoring equipment ,CARDIAC catheterization ,FOREIGN bodies ,HEART - Abstract
Describes a case regarding the removal of a knotted flow-directed catheter by a nonsurgical method. Medical profile of the patient; Background on catheter knotting; Description of the nonsurgical technique performed during the surgery.
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- 1980
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17. Chapter 7 - Neoformed mineral parageneses in acid weathering systems: Sedimentary vs volcanic environments
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De Putter, Th., Bernard, A., Perruchot, A., Yans, J., Verbrugghe, Fr., and Dupuis, Ch.
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18. Upper Cretaceous feldspars in the Cenozoic Limagne Basin: A key argument in reconstructing the palaeocover of the Massif Central (France)
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Wattinne, A., Quesnel, F., Mélières, F., Guillou, H., Bourdillon, C., Barbarand, J., Baele, J.-M., and Yans, J.
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CRETACEOUS paleoclimatology , *FELDSPAR , *CENOZOIC paleoecology , *GEOLOGICAL basins , *GRABENS (Geology) , *OLIGOCENE paleoclimatology , *MIOCENE paleoecology - Abstract
Abstract: The northern part of the N–S-trending basin of the Limagne graben, located in the northern part of the Massif Central (France), contains Oligocene and Miocene calcareous lacustrine deposits. The area is known for its stromatolite reefs surrounded by marl, clay and uncemented carbonate sand with oncolites. Because the origin of the carbonate accumulated by cyanobacteria has long been debated, the clayey deposits associated with the stromatolites were analysed using XRD, SEM and K–Ar dating methods. The results show a monotonous assemblage of carbonates, dioctahedral smectite, illite–smectite (Reichweite) R=0, glauconitic illite and abundant orthoclase. Detrital minerals such as quartz and detrital illite are found near the basin''s borders but are very scarce in its central part, indicating a lack of detrital input from the regional basement. Hence, the abundant orthoclase found in all the clayey deposits of the Limagne Basin cannot be linked to erosion of the surrounding Hercynian basement. The SEM analysis showed the orthoclase crystals to have a tabular morphology with sharp boundaries and to be embedded within a clay matrix, whilst the K–Ar dating of the orthoclase and glauconitic illite yielded ages ranging from 90 to 66±2Ma, i.e. Turonian to Maastrichtian. These two results clearly indicate that the fill of the Limagne Basin, composed mainly of carbonate, clay and orthoclase, must have been partly due to the erosion of an Upper Cretaceous sedimentary blanket once covering the Massif Central basement. This cover was probably constituted of chalk, dioctahedral smectite, I/S and glauconitic illite, associated with authigenic orthoclase and flint. Flints are found reworked in the alluvial formations of the Late Pliocene Lower Bourbonnais sands and clays (‘Sables et argiles du Bourbonnais’) and in the Pleistocene terraces. Moreover, relicts of the Upper Cretaceous cover were preserved during the sedimentary filling of the Cenozoic Limagne Basin. Authigenic orthoclase of similar shape has been described in the Chalk Group of the Paris Basin and from localities in northern France and Belgium. The mineral is rare in the Turonian chalk but increases rapidly at the base of the Coniacian to Campanian chalk; it has also been noted that the number of orthoclase crystals increases as the quantity of clastic components decreases. Similar orthoclase crystals were found associated with dioctahedral smectite in the decarbonated residues of the Coniacian to Santonian chalk from Fécamp and Etretat (northern France). Moreover, our results are consistent with other data from within and around the Paris Basin, such as the palaeogeography and facies distribution of the Chalk formations, the residual flints in the clay-with-flints of the southern Paris Basin and around the Morvan, and apatite fission-track thermochronology data from the Hercynian basement of the Massif Central and the Morvan. All these data indicate a major connection between the Paris Basin and the Tethys, and an extensive palaeocover on the Massif Central and Morvan basement. [Copyright &y& Elsevier]
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- 2010
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19. A new primate community from the earliest Oligocene of the Atlantic margin of Northwest Africa: Systematic, paleobiogeographic, and paleoenvironmental implications.
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Marivaux L, Benammi M, Baidder L, Saddiqi O, Adnet S, Charruault AL, Tabuce R, Yans J, and Benammi M
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- Animals, Paleontology, Environment, Tooth anatomy & histology, Fossils anatomy & histology, Primates anatomy & histology
- Abstract
We report a new Paleogene primate community discovered in the uppermost part of the Samlat Formation outcropping on the continental shore of the Rio de Oro, east of the Dakhla peninsula (in the south of Morocco, near the northern border of Mauritania). Fossils consist of isolated teeth, which were extracted by wet screening of estuarine sediments (DAK C
2 ) dating from the earliest Oligocene (ca. 33.5 Ma). These dental remains testify to the presence of at least eight primate species, documenting distinct families, four of which are among the Anthropoidea (Oligopithecidae [Catopithecus aff. browni], Propliopithecidae [?Propliopithecus sp.], Parapithecidae [Abuqatrania cf. basiodontos], and Afrotarsiidae [Afrotarsius sp.]) and four in the Strepsirrhini (a Djebelemuridae [cf. 'Anchomomys' milleri], a Galagidae [Wadilemur cf. elegans], a possible lorisiform [Orogalago saintexuperyi gen. et sp. nov.], and a strepsirrhine of indeterminate affinities [Orolemur mermozi gen. et sp. nov.]). This record of various primates at Dakhla represents the first Oligocene primate community from Northwest Africa, especially from the Atlantic margin of that landmass. Considering primates plus rodents (especially hystricognaths), the taxonomic proximity at the generic (even specific) level between DAK C2 (Dakhla) and the famous Egyptian fossil-bearing localities of the Jebel Qatrani Formation (Fayum Depression), either dating from the latest Eocene (L-41) or from the early Oligocene, suggests the existence of an east-west 'trans-North African' environmental continuum during the latest Eocene-earliest Oligocene time interval. The particularly diverse mammal fauna from DAK C2 , recorded within the time window of global climate deterioration characterizing the Eocene/Oligocene transition, suggests that this tropical region of northwest Africa was seemingly less affected, if at all, by the cooling and associated paleoenvironmental and biotic changes documented at that time or at least that the effects were delayed. The expected densely forested paleoenvironment bordering the western margin of North Africa at the beginning of the early Oligocene probably offered better tropical refugia than higher latitudes or more inland areas during the cooling episode., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)- Published
- 2024
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20. Unsupervised topological analysis of polarized light microscopy: application to quantitative birefringence imaging.
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Bouhy J, Roy N, Dekoninck A, Poot J, Yans J, and Deparis O
- Abstract
The determination of birefringence (magnitude and axis orientation) of optical materials is of significant interest in various fields. In the case of composite samples, this task becomes complicated and time-consuming; therefore, a partially automated procedure for reconstructing birefringence spatial distribution becomes valuable. Herein, we propose a procedure to reconstruct the spatial distributions of the retardance and optical axis orientation in a geological thin section from sparse quantitative birefringence measurements, using automatic boundary detection on cross-polarized light microscopy images. We examine two particular areas on the selected geological thin section: one that presents a uniaxial crystal with a circular cross-section of its refractive index ellipsoid and the other with grains of varying orientations. The measurement gives the orientation of the grain's optical axis both in and out of the plane of the thin section, which explains the qualitative observations with the cross-polarized light microscope. Future work will connect the measured orientation of the rock thin section with its 3D geological orientation in the field.
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- 2024
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21. Ni-rich mineral nepouite explains the exceptional green color of speleothems.
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Vlieghe M, Rochez G, Pire-Stevenne S, Storme JY, Dekoninck A, Vanbrabant Y, Namur O, Zhang Y, Van Ham-Meert A, Donnadieu JP, Berbigé M, Hasbroucq JL, and Yans J
- Abstract
Speleothems are secondary mineral structures typically found in karstic caves and usually composed of calcite or aragonite. Despite being naturally white, some might exhibit unusual colors, such as blue, black, red, yellow or green. The causes of these exceptional colorations are poorly understood, especially for green speleothems, which are barely reported. Here we describe the occurrence of the green Ni-bearing serpentine nepouite in green aragonite and calcite speleothems, in the Aven du Marcou (Hérault, France). Nepouite is mainly found as flat lamellar crystals in the outer rim of green speleothems and crystallized alongside radially grown aragonite crystals. This supports nepouite beginning to crystallize recently, due to a change in the chemical composition of the water. Nepouite also exhibits extensive substitution between Ni, Mg and Zn. The various elements responsible for nepouite precipitation are thought to come from the weathering of pyrite crystals in the overlying rocks, which is consistent with the pH conditions of the cave and the Al-free composition of nepouite. This study explains the crystallization mechanisms and stability conditions of silicate minerals in colored caves., (© 2023. Springer Nature Limited.)
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- 2023
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22. Pterosaur melanosomes support signalling functions for early feathers.
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Cincotta A, Nicolaï M, Campos HBN, McNamara M, D'Alba L, Shawkey MD, Kischlat EE, Yans J, Carleer R, Escuillié F, and Godefroit P
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- Animals, Pigmentation, Biological Evolution, Dinosaurs anatomy & histology, Feathers, Fossils, Melanosomes
- Abstract
Remarkably well-preserved soft tissues in Mesozoic fossils have yielded substantial insights into the evolution of feathers
1 . New evidence of branched feathers in pterosaurs suggests that feathers originated in the avemetatarsalian ancestor of pterosaurs and dinosaurs in the Early Triassic2 , but the homology of these pterosaur structures with feathers is controversial3,4 . Reports of pterosaur feathers with homogeneous ovoid melanosome geometries2,5 suggest that they exhibited limited variation in colour, supporting hypotheses that early feathers functioned primarily in thermoregulation6 . Here we report the presence of diverse melanosome geometries in the skin and simple and branched feathers of a tapejarid pterosaur from the Early Cretaceous found in Brazil. The melanosomes form distinct populations in different feather types and the skin, a feature previously known only in theropod dinosaurs, including birds. These tissue-specific melanosome geometries in pterosaurs indicate that manipulation of feather colour-and thus functions of feathers in visual communication-has deep evolutionary origins. These features show that genetic regulation of melanosome chemistry and shape7-9 was active early in feather evolution., (© 2022. The Author(s).)- Published
- 2022
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23. The rise of feathered dinosaurs: Kulindadromeus zabaikalicus , the oldest dinosaur with 'feather-like' structures.
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Cincotta A, Pestchevitskaya EB, Sinitsa SM, Markevich VS, Debaille V, Reshetova SA, Mashchuk IM, Frolov AO, Gerdes A, Yans J, and Godefroit P
- Abstract
Diverse epidermal appendages including grouped filaments closely resembling primitive feathers in non-avian theropods, are associated with skeletal elements in the primitive ornithischian dinosaur Kulindadromeus zabaikalicus from the Kulinda locality in south-eastern Siberia. This discovery suggests that "feather-like" structures did not evolve exclusively in theropod dinosaurs, but were instead potentially widespread in the whole dinosaur clade. The dating of the Kulinda locality is therefore particularly important for reconstructing the evolution of "feather-like" structures in dinosaurs within a chronostratigraphic framework. Here we present the first dating of the Kulinda locality, combining U-Pb analyses (LA-ICP-MS) on detrital zircons and monazites from sedimentary rocks of volcaniclastic origin and palynological observations. Concordia ages constrain the maximum age of the volcaniclastic deposits at 172.8 ± 1.6 Ma, corresponding to the Aalenian (Middle Jurassic). The palynological assemblage includes taxa that are correlated to Bathonian palynozones from western Siberia, and therefore constrains the minimum age of the deposits. The new U-Pb ages, together with the palynological data, provide evidence of a Bathonian age-between 168.3 ± 1.3 Ma and 166.1 ± 1.2 Ma-for Kulindadromeus . This is older than the previous Late Jurassic to Early Cretaceous ages tentatively based on local stratigraphic correlations. A Bathonian age is highly consistent with the phylogenetic position of Kulindadromeus at the base of the neornithischian clade and suggests that cerapodan dinosaurs originated in Asia during the Middle Jurassic, from a common ancestor that closely looked like Kulindadromeus . Our results consequently show that Kulindadromeus is the oldest known dinosaur with "feather-like" structures discovered so far., Competing Interests: The authors declare there are no competing interests.
- Published
- 2019
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24. Molecular composition and ultrastructure of Jurassic paravian feathers.
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Lindgren J, Sjövall P, Carney RM, Cincotta A, Uvdal P, Hutcheson SW, Gustafsson O, Lefèvre U, Escuillié F, Heimdal J, Engdahl A, Gren JA, Kear BP, Wakamatsu K, Yans J, and Godefroit P
- Subjects
- Animals, Durapatite chemistry, Epidermis ultrastructure, Fossils, Melanins, Microbodies ultrastructure, Microscopy, Electron, Spectrometry, Mass, Secondary Ion, Spectrometry, X-Ray Emission, Spectrophotometry, Infrared, Time Factors, Birds anatomy & histology, Dinosaurs anatomy & histology, Feathers ultrastructure
- Abstract
Feathers are amongst the most complex epidermal structures known, and they have a well-documented evolutionary trajectory across non-avian dinosaurs and basal birds. Moreover, melanosome-like microbodies preserved in association with fossil plumage have been used to reconstruct original colour, behaviour and physiology. However, these putative ancient melanosomes might alternatively represent microorganismal residues, a conflicting interpretation compounded by a lack of unambiguous chemical data. We therefore used sensitive molecular imaging, supported by multiple independent analytical tests, to demonstrate that the filamentous epidermal appendages in a new specimen of the Jurassic paravian Anchiornis comprise remnant eumelanosomes and fibril-like microstructures, preserved as endogenous eumelanin and authigenic calcium phosphate. These results provide novel insights into the early evolution of feathers at the sub-cellular level, and unequivocally determine that melanosomes can be preserved in fossil feathers.
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- 2015
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25. Integrated Paleoenvironmental Reconstruction and Taphonomy of a Unique Upper Cretaceous Vertebrate-Bearing Locality (Velaux, Southeastern France).
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Cincotta A, Yans J, Godefroit P, Garcia G, Dejax J, Benammi M, Amico S, and Valentin X
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- Alligators and Crocodiles anatomy & histology, Animals, Biological Evolution, Dinosaurs anatomy & histology, Environment, Fishes anatomy & histology, Paleontology methods, Skull anatomy & histology, Tooth anatomy & histology, Bone and Bones anatomy & histology, Fossils anatomy & histology, Vertebrates anatomy & histology
- Abstract
The Velaux-La Bastide Neuve fossil-bearing site (Bouches-du-Rhône, France) has yielded a diverse vertebrate assemblage dominated by dinosaurs, including the titanosaur Atsinganosaurus velauciensis. We here provide a complete inventory of vertebrate fossils collected during two large-scale field campaigns. Numerous crocodilian teeth occur together with complete skulls. Pterosaur, hybodont shark and fish elements are also represented but uncommon. Magnetostratigraphic analyses associated with biostratigraphic data from dinosaur eggshell and charophytes suggest a Late Campanian age for the locality. Lithologic and taphonomic studies, associated with microfacies and palynofacies analyses, indicate a fluvial setting of moderate energy with broad floodplain. Palynomorphs are quite rare; only three taxa of pollen grains occur: a bisaccate taxon, a second form probably belonging to the Normapolles complex, and another tricolporate taxon. Despite the good state of preservation, these taxa are generally difficult to identify, since they are scarce and have a very minute size. Most of the vertebrate remains are well preserved and suggest transport of the carcasses over short distances before accumulation in channel and overbank facies, together with reworked Aptian grains of glauconite, followed by a rapid burial. The bones accumulated in three thin layers that differ by their depositional modes and their taphonomic histories. Numerous calcareous and iron oxides-rich paleosols developed on the floodplain, suggesting an alternating dry and humid climate in the region during the Late Campanian.
- Published
- 2015
- Full Text
- View/download PDF
26. A morphological intermediate between eosimiiform and simiiform primates from the late middle Eocene of Tunisia: Macroevolutionary and paleobiogeographic implications of early anthropoids.
- Author
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Marivaux L, Essid el M, Marzougui W, Khayati Ammar H, Adnet S, Marandat B, Merzeraud G, Ramdarshan A, Tabuce R, Vianey-Liaud M, and Yans J
- Subjects
- Animals, Anthropology, Physical, Molar anatomy & histology, Tunisia, Biological Evolution, Fossils, Haplorhini anatomy & histology, Haplorhini classification
- Abstract
Although advanced anthropoid primates (i.e., Simiiformes) are recorded at the end of the Eocene in North Africa (Proteopithecidae, Parapithecidae, and Oligopithecidae), the origin and emergence of this group has so far remained undocumented. The question as to whether these primates are the result of a monophyletic radiation of endemic anthropoids in Africa, or several Asian clades colonizing Africa, is a current focus of paleoprimatology. In this article, we report the discovery of a new anthropoid from Djebel el Kébar in central Tunisia, dating from the late middle Eocene (Bartonian). This taxon, Amamria tunisiensis, new genus and species, currently known by only one isolated upper molar, is among the most ancient anthropoids to be recorded in Africa thus far. Amamria displays a suite of dental features that are primarily observed in Eosimiiformes (stem Anthropoidea). However, it is not allocated to any known family of that group (i.e., Asian Eosimiidae and Afro-Asian Afrotarsiidae) inasmuch as it develops some dental traits that are unknown among eosimiiforms, but can be found in African simiiform anthropoids such as proteopithecids and oligopithecids. With such a mosaic of dental traits, Amamria appears to be a structural intermediate, and as such it could occupy a key position, close to the root of the African simiiforms. Given its antiquity and its apparent pivotal position, the possibility exists that Amamria could have evolved in Africa from Asian eosimiiform or Asian "proto"-simiiform ancestors, which would have entered Africa sometime during the middle Eocene. Amamria could then represent one of the earliest offshoots of the African simiiform radiation. This view would then be rather in favor of the hypothesis of a monophyletic radiation of endemic simiiform anthropoids in Africa. Finally, these new data suggest that there must have been at least two Asian anthropoid colonizers of Africa: the afrotarsiids and the ancestor of Amamria., (© 2014 Wiley Periodicals, Inc.)
- Published
- 2014
- Full Text
- View/download PDF
27. First Clarkforkian equivalent Land Mammal Age in the latest Paleocene basal Sparnacian facies of Europe: fauna, flora, paleoenvironment and (bio)stratigraphy.
- Author
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Smith T, Quesnel F, De Plöeg G, De Franceschi D, Métais G, De Bast E, Solé F, Folie A, Boura A, Claude J, Dupuis C, Gagnaison C, Iakovleva A, Martin J, Maubert F, Prieur J, Roche E, Storme JY, Thomas R, Tong H, Yans J, and Buffetaut E
- Subjects
- Amphibians anatomy & histology, Amphibians classification, Animals, Birds anatomy & histology, Birds classification, Carbon Isotopes, Europe, Fishes anatomy & histology, Fishes classification, Geologic Sediments, Mammals classification, Paleontology, Plants anatomy & histology, Plants classification, Reptiles anatomy & histology, Reptiles classification, Biological Evolution, Fossils, Mammals anatomy & histology, Phylogeny
- Abstract
The Paleocene-Eocene Thermal Maximum (PETM) is correlated with the first occurrences of earliest modern mammals in the Northern Hemisphere. The latest Paleocene Clarkforkian North American Land Mammal Age, that has yielded rodents and carnivorans, is the only exception to this rule. However, until now no pre-PETM localities have yielded modern mammals in Europe or Asia. We report the first Clarkforkian equivalent Land Mammal Age in the latest Paleocene deposits of the basal Sparnacian facies at Rivecourt, in the north-central part of the Paris Basin. The new terrestrial vertebrate and macroflora assemblages are analyzed through a multidisciplinary study including sedimentologic, stratigraphic, isotopic, and palynological aspects in order to reconstruct the paleoenvironment and to evaluate biochronologic and paleogeographic implications. The mammals are moderately diverse and not abundant, contrary to turtles and champsosaurs. The macroflora is exceptional in preservation and diversity with numerous angiosperms represented by flowers, fruits, seeds and wood preserved as lignite material, revealing an abundance of Arecaceae, Betulaceae, Icacinaceae, Menispermaceae, Vitaceae and probably Cornaceae. Results indicate a Late Paleocene age based on carbon isotope data, palynology and vertebrate occurrences such as the choristoderan Champsosaurus, the arctocyonid Arctocyon, and the plesiadapid Plesiadapis tricuspidens. However, several mammal species compare better with the earliest Eocene. Among these, the particular louisinid Teilhardimys musculus, also recorded from the latest Paleocene of the Spanish Pyrenees, suggests a younger age than the typical MP6 reference level. Nevertheless, the most important aspect of the Rivecourt fauna is the presence of dental remains of a rodent and a "miacid" carnivoran, attesting to the presence of two modern mammalian orders in the latest Paleocene of Europe. Interestingly, these two groups are also the only modern groups recorded from the latest Paleocene of North America, making Rivecourt the first direct equivalent to the Clarkforkian Land Mammal Age outside of North America.
- Published
- 2014
- Full Text
- View/download PDF
28. Anomalous origin of the right coronary artery above the left sinus of Valsalva.
- Author
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Yans J, Kumar SP, and Kwatra M
- Subjects
- Aged, Coronary Angiography, Coronary Vessel Anomalies physiopathology, Electrocardiography, Humans, Male, Coronary Vessel Anomalies diagnostic imaging, Sinus of Valsalva
- Abstract
Various anomalies of coronary arterial origin have been described. These anatomical variations are discovered either by coronary angiography or at autopsy. We are reporting a case of anomalous origin of the right coronary artery above the left sinus of Valsalva. To our knowledge, this anomaly has not been described before. A technique for selectively catheterizing such an aberrant coronary artery is described.
- Published
- 1978
- Full Text
- View/download PDF
29. Unusual artifacts in electrocardiographic monitoring.
- Author
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Kumar SP, Yans J, and Kwatra M
- Subjects
- Adult, Aged, Angina Pectoris physiopathology, Cardiac Complexes, Premature physiopathology, Cardiac Pacing, Artificial, Coronary Disease physiopathology, Heart physiology, Humans, Male, Middle Aged, Monitoring, Physiologic, Telemetry, Electrocardiography methods
- Abstract
Three unusual artifacts noted during Holter and telemetry monitoring, not previously described, are presented. Recognition of the artifacts prevented misinterpretation and wrong treatment. The clues to the identification of the artifacts and the need for avoiding wrong interpretation and inappropriate treatment are discussed. The cause of the telemetry artifact is discussed.
- Published
- 1979
- Full Text
- View/download PDF
30. Carotid sinus syncope. Report of two cases.
- Author
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Chughtai AL, Yans J, and Kwatra M
- Subjects
- Aged, Heart Arrest etiology, Heart Arrest therapy, Humans, Male, Massage adverse effects, Pacemaker, Artificial, Recurrence, Carotid Sinus, Syncope therapy
- Abstract
In two cases of hyperactive carotid sinus with syncope, both patients had a history of syncopal attacks. Carotid sinus massage produced asystole lasting for four seconds with recurrent symptoms. Permanent demand pacemakers were implanted in both patients, causing a relief of symptoms.
- Published
- 1977
31. Pacemaker induced diaphragmatic contractions.
- Author
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Chughtai AL, Yans J, and Kwatra M
- Subjects
- Aged, Electrocardiography, Humans, Male, Cardiac Pacing, Artificial adverse effects, Diaphragm physiology, Muscle Contraction
- Published
- 1979
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