175 research outputs found

    The Early to Middle Ordovician graptolite faunal succession of the Trail Creek region, central Idaho, U.S.A

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    The Middle Ordovician graptolite biostratigraphy of the Trail Creek region of Idaho is reviewed and revised. The oldest known fauna belongs to the Didymograptellus bifidus Biozone. The Isograptus victoriae lunatus, I. victoriae maximodivergens, Oncograptus, Undulograptus austrodentatus and Holmograptus lentus Biozones can be differentiated. Pseudophyllograptus archaios (Braithwaite) is found for the first time in the Trail Creek region. This species represents a conspicuous North American mid-continent faunal element and enables the correlation of the endemic P. archaios-C. flexilis Biozone of Utah with the D. bifidus Biozone of the Pacific faunal realm, thus, providing an important tool for the correlation of endemic mid-continent faunas with the pandemic deep water graptolite faunas

    Lower Llanvirn (Ordovician) Graptolites and Acritarchs from the "Assise de Huy", bande de Sambre-et-Meuse, Belgium

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    The Huy formation («assise de Huy») is the oldest unit present in outcrops in the Belgian «Bande de Sambre-et-Meuse». Graptolites and acritarchs show that the beds are of early Llanvirn Didymograptus artus Biozone age. The localities of Huy and of Sart-Bernard and the Wépion borehole are reinvestigated and the collection of Maillieux, 1939 is restudied

    Ordovician sponge spicules from Spitsbergen, Nevada and Newfoundland: new evidence for the Hexactinellida early differentiation

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    Division of Hexactinellida into the subclasses Amphidiscophora and Hexasterophora is now generally accepted due to their very distinct types of microscleres, namely amphidiscs and hexasters, respectively. Microscleres of this type have been recognized in the Lower Paleozoic. We examined exceptionally well preserved spicule assemblages from three particular Lower to Middle Ordovician localities: Spitsb ergen (Floian-Dapingian), Nevada (Vinini Formation, Dapingian) and Newfoundland (Cow Head Formation, Tremadocian and Table Head Group, Darriwilian). The presence of hexaster-type spicules, hemidiscs and amphidiscs is reported here. The hexasters are certainly documented from the Lower Ordovician and possibly from the Cambrian. Although hemidiscs were reported from the Lower Ordovician, oldest true amphidiscs were reported from the Silurian. The occurrence of amphidiscs in these localities implies that the Amphidiscophora can be certainly traced back to the Lower Ordovician. The occurrence of five different types of scopules (typical microscleres of the Sceptrulophora) significantly increases the diversity of this group in the Ordovician. The collection also includes important and variable types of hexactinellid spicules (pinular hexactines and pentactines, equinate hexactines, tauactins and inflated pentactines, and different types of uncinate monactins), calcareous heteractines, and different types of demosponge spicules (oxiasters, C-shaped sigmata, trianes and dendroclones).Sesiones libresFacultad de Ciencias Naturales y Muse

    Beyond Idealism: Democracy and Ethics Reform

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    The effort to oppose corruption has brought in recent decades a heightened emphasis on ethics, the establishment of official ethics codes, the creation of the first government agencies explicitly authorized to enforce ethics, and even the creation of ethics committees in Congress. Dennis Thompson has taken the lead in advocating and analyzing the increased attention to ethics, and yet one of his more recent studies draws attention to some “paradoxes” inherent in the pursuit of ethics in government. We take issue with Thompson’s argument that ethics is in some sense the most important of all policies. The hope for “ethics in government” may only be satisfied at a very modest level through the work of the current ethics agencies, the enforcement of ethics in government can impose important costs on the ethics project itself, and the democratic processes of government may limit what we should do to constrain the power of self-interest.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

    New insights for the paleobiogeographic analysis of the Early Ordovician graptolite fauna of northwestern Argentina

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    Trichograptus dilaceratus (Herrmann), Acrograptus gracilis (Törnquist), Expansograptus urbanus (Monsen) and Corymbograptus v-fractus tullbergi (Monsen) are recognized and described in Argentina for the first time, reinforcing the graptolite faunal affinities with Baltoscandia. The studied specimens come from the Quinilican and Agua Chica sections, located at the northern extreme of the Aguilar Range in the Cordillera Oriental (Jujuy Province). The graptolites are preserved in fine to medium grained sandstones interbedded within a fine-grained succession of approximately 200m thickness, corresponding to the lower part of the Acoite Formation. The presence of Baltograptus vacillans (Tullberg), Acrograptus filiformis (Tullberg) and Expansograptus cf. holmi (Törnquist) allow to assign the studied levels to the Tetragraptus akzarensis biozone, which corresponds to the lower Floian. These levels are closely correlated with the lower part of the Lumara section located to the northeast of the studied area. The recognized species have been considered together with all the species previously documented in equivalent stratigraphic levels from the Argentine Cordillera Oriental and those recently reviewed in Baltoscandia, Great Britain and North America. A multivariate analysis (mvsp) was used and the determination of faunistic similarities was made with the classic Jaccards' index. The resulting affinity dendrogram shows stronger relationships between early Floian graptolite faunas from Northwestern Argentina and those coming from Baltoscandia. Great Britain is located in an intermediate position in the similarity dendrogram, and shows less affinity with northwestern Argentina. In addition, weak affinities with North American faunas are observed. The statistical analysis confirms the paleobiogeographic relationships previously established in other areas of the Cordillera Oriental, and supports the hypothesis that during the Early Ordovician, northwestern Argentina was located in middle to high latitudes, corresponding to the Atlantic Faunal Realm of cold water graptolite biofacies.Simposio I: 2º Simposio de bioestratigrafía y eventos del Paleozoico inferiorTrabajo subsidiado por ANPCyT-PICT 1272 y CONICET-PIP 112-200801-01994.Facultad de Ciencias Naturales y Muse

    A weak-coupling superconductivity in the electron doped NaFe0.95_{0.95}Co0.05_{0.05}As is revealed by ARPES

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    We report a systematic study on the electronic structure and superconducting (SC) gaps in electron doped NaFe0.95_{0.95}Co0.05_{0.05}As superconductor using angle-resolved photoemission spectroscopy. Hole-like Fermi sheets are at the zone center and electron-like Fermi sheets are at the zone corner, and are mainly contributed by xzxz and yzyz orbital characters. Our results reveal a ΔKBTc\frac{\Delta}{K_B T_c} in the range of 1.8-2.1, suggesting a weak-coupling superconductivity in these compounds. Gap closing above the transition temperature (TcT_c) shows the absence of pseudogaps. Gap evolution with temperature follow the BCS gap equation near the Γ\Gamma, ZZ, and MM high symmetry points. Furthermore, an almost isotropic superconductivity along kzk_z direction in the momentum space is observed by varying the excitation energies.Comment: 6 pages, 5 figures, Accepted by Phy.Rev.

    A Cambrian–Ordovician boundary section in the Rafnes–Herøya submarine tunnel, Skien–Langesund District, southern Norway

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    Rock specimens and contained fossils collected in 1976 from a submarine tunnel driven between Herøya and Rafnes in the Skien–Langesund area of southern Norway, have been restudied. The contained fossils include olenid and agnostoid trilobites, graptolites and brachiopods, groups described in detail for the first time from the area and documenting a Cambrian–Ordovician boundary section unique in the district where the upper Cambrian Alum Shale Formation is elsewhere overlain by the Middle Ordovician Rognstranda Member of the Huk Formation (Kundan in terms of Baltoscandian chronostratigraphy). The hiatus at the base of the Huk Formation is thus smaller in the section described herein, beginning at a level within rather than below the Tremadocian. Estimated thickness of the Alum Shale includes 10–12 m of Miaolingian and 20–22 m of Furongian strata with trilobite zones identified, and a Tremadocian section of 8.1 m identified by species of the dendroid graptolite Rhabdinopora in the basal 2.6 m and Bryograptus ramosus at the top. The Tremadocian section is preserved in a postulated zone of synsedimentary subsidence along the Porsgrunn–Kristiansand Fault Zone, while at the same time there was extensive erosion across an emergent, level platform elsewhere in the Skien–Langesund District and the southern part of the Eiker–Sandsvær District to the north. Aspects of stratigraphy and tectonics are highlighted together with a discussion on the Cambrian– Ordovician boundary locally and worldwide
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