1,721,028 research outputs found
Les bentonites, un outil de corrélation remarquable dans le Mésozoïque des bassins sédimentaires français : exemple des craies turoniennes du Bassin de Paris
No full textDeconinck Jean-François, Amédro Francis, Godet Alexis, Pellenard Pierre, Robaszynski Francis, Zimmerlin Irène. Les bentonites, un outil de corrélation remarquable dans le Mésozoïque des bassins sédimentaires français : exemple des craies turoniennes du Bassin de Paris. In: Documents des Laboratoires de Géologie, Lyon, n°156, 2002. STRATI 2002. 3ème congrès français de stratigraphie. Lyon, 8-10 juillet 2002. pp. 95-96
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
The Role of Tributary Inputs on the Downstream Fining Process in the Lower San Antonio River
Full text linkThe author has granted permission for their work to be available to the general public.Bed sediment tends to decrease in size systematically with respect to distance downstream but can be affected by lateral inputs that reset the downstream fining trend. To understand whether the downstream fining process is disrupted in the lower San Antonio River, bed sediment was evaluated in five reaches containing major tributaries (Cibolo, Ecleto, Escondido, Cabeza, and Manahuila) to determine the impact of the tributary sediment on the main stem. Field sampling involved collecting sediment upstream and downstream of tributaries as well as sediment from the tributaries. Data were analyzed using 50th and 90th percentiles of sediment at each respective site. Bed material metrics show a significant textural difference related to the Cibolo Creek tributary. Three models (exponential, logarithmic, and power) were utilized to observe fining trends within the study area. Low R2 values indicate that the conventional models of downstream fining fail to describe patterns in bed material texture, although the models perform somewhat better for the study reach downstream of the Cibolo Creek tributary. Confluence mixing models do not predict observed values well, as only one site within Ecleto is compatible with the 50th percentile but Manahuila values are successfully predicted for both percentiles. Overall, Cibolo Creek appears to be the only significant tributary within the study reach due to its sediment characteristics that cause a disruption to the downstream fining process.Geoscience
Quantitative approach to extension and fault characterization within the central and northern Llanos basin, Colombia
Full text linkThe author has granted permission for their work to be available to the general public.The early Llanos basin developed during the Paleozoic–Mesozoic in a volcanic back arc, formed by subduction along the northwestern corner of the South American plate. In the Cenozoic, accretion of the Panama arch uplifted the Cordillera and isolated the eastern side of the basin into the current configuration. Two major depocenters were present in the northern and central-western Llanos basin, respectively: the Arauca graben resulted from early Paleozoic rifting, and uplift of the Eastern Cordillera led to flexural depression of the lithosphere. Variations in basin depth between these two depocenters and the eastern forebulge, affected fault populations and the distribution of lateral extension within the basin. Extension was calculated from line length balancing along eight sections across the basin, and the results compared with thickness of basin fill, fault population, and basement structure. This study quantitatively demonstrates that extension is greater in areas of thicker basin fill, yet fault population (principally antithetic faults) increases within thinner sections. Distribution of oil fields apparently follows the areas of high fault population, rather than areas of high lateral extension. Overall, NNE–SSW fault orientations in the Casanare domain provide better seals for oil accumulation than the ENE–WSW fault orientations in the Arauca area.Geoscience
Geochemistry and Petrology of Dikes and Enclaves of the Mesoproterozoic Enchanted Rock Batholith, Llano Uplift, Central Texas
No full textThe author has granted permission for their work to be available to the general public.The Enchanted Rock Batholith (ERB) is a Mesoproterozoic-aged undeformed intrusive igneous body forcefully emplaced into the south-central portion of the Llano Uplift, Central Texas as the product of a Grenville-aged orogenic event. It is a metaluminous to marginally peraluminous fractionated A-type granite hosting ferroan to marginally magnesian, calc-alkalic to marginally alkali-calcic, peraluminous enclaves elongated parallel to the ERB's margins and a grouping of ferroan, calc-alkalic, peraluminous dikes, termed Marschall Creek Dike Complex, in the central-western portion of the batholith. Field, petrographic, and geochemical analysis suggests that the Marschall Creek Dike Complex and the enclaves of the ERB evolved through recharge fractional crystallization with limited magma mixing from ERB, undergoing similar processes during evolution evident by disequilibrium textures present in nearly every sample and correspondingly negative trends of all major oxide vs. SiO2 plots, apart from K2O vs. SiO2, consistent with the fractionation of calcic plagioclase and biotite and, to a lesser extent, zircon, apatite, and titanite. This is supported by the negative trends in the compatible trace elements (i.e., Sr, Ba, Co, V, Zn, and Zr), the partition of LREE and HREE, and negative europium and cerium anomalies of REE. Biotite-rich margins, entrained host material, rapakivi texture, deformation of the enclaves, and undulated surfaces on the dikes are consistent with emplacement into a partially molten host. The doming and zonation of the ERB and orientation of the enclaves parallel to the structure's perimeter suggests that the batholith was emplaced by ballooning.Geoscience
Geochemistry, Petrology, and Thermal Properties of Lava from Fissure 17 in the 2018 Kilauea Eruption
No full textThe author has granted permission for their work to be available to the general public.In 2018, a complex lava erupted from Fissure 17 during the Lower East Rift Zone (LERZ) eruption of Kilauea, Hawaii. Fissure 17 was active from May 13-25 of 2018, and was more explosive than other vents, which produced fluid basalt. The Fissure 17 lavas plotted on a linear mixing trend between basalt and icelandite (iron-rich aluminum-poor andesite). Mixing of two different lavas is visible in hand specimen, with rigid crystalline inclusions in a microcrystalline groundmass that sheared around them. Our preliminary hypothesis was fresh basaltic lava encountering a cool crystal-rich evolved mush pocket from a previous magmatic episode; possibly a 1955 lava, creating icelandite inclusions in basalt. However, geochemical analyses indicate that the inclusions are basaltic and surrounded by andesitic lava. Fissure 17 lavas are consistent with the MELTS mixing model by Gansecki et al. (2019). Based on the petrography and thermal properties, a second source of basaltic material involved in mixing was added. This matches geochemically with the original (undifferentiated) 1955 lava. Calorimetry was used to determine the glass content of the icelandite groundmass (~50%) and the basaltic inclusions (undetectable). There is a possibility that inclusions could be xenoliths of 1955 lava. The conclusion is that, although in the field this lava is visibly hybridized, with numerous inclusions, these inclusions are not the major source of the geochemical variation in the suite. Instead of basalt containing andesitic inclusions, we have andesite / basaltic andesite containing basaltic xenoliths. The majority of the mixing occurred between two crystal-poor magmas, one already the product of mixing between two basaltic end-members and is now invisible. The broader implication is that visible evidence of mixing may tell a different story to the geochemical evidence in a single rift zone eruption.Geoscience
Quantifying Climate Change Over the Early Cretaceous Ruby Ranch Member of the Cedar Mountain Formation, East-Central Utah
Full text linkThe author has granted permission for their work to be available to the general public.The age of the Ruby Ranch Member (RRM) of the Cedar Mountain Formation in East-Central Utah was recently constrained using carbon isotope chemostratigraphy to span known excursions associated with the late Aptian. The RRM is characterized by calcrete horizons that are thought to occur across the C10 carbon isotope excursion. Along with carbonate stable isotope analyses and the region’s paleo-position in a depositional basin on the leeward rain shadow of the Sevier Orogenic belt, this interval is hypothesized to coincide with an aridification event. Our research objective is to quantify the extent of this aridity using clumped isotope paleothermometry (n = 7) and paleoprecipitation proxies (n = 51) for samples collected across the C10 chemostratigraphic interval. Two weathering indices, CIA-K and CALMAG, were applied to data obtained using X-ray fluorescence spectrometry. Using these proxies, we determined mean annual precipitation across the RRM at its type section. Precipitation values (n = 27) obtained through CIA-K for identified paleosol horizons ranged between 795 and 1275 mm/year, and through CALMAG ranged between 735 and 1042 mm/year. Precipitation values decreased through the C10 interval which may indicate increased aridity. Clumped isotopes provided Δ47 values ranging from 0.647 to 0.693‰. Paleotemperature measurements (n = 4) from accepted carbonate samples were between 27.9 and 46.3 °C. Isotopic compositions of water calculated from carbonates ranged between -4.4‰ and -1.9‰ VSMOW. Precipitation values and temperatures were not lowest during the C10 interval. Temperatures peaked at the end of the C10 interval and decreased afterward, indicating a potential for cooler, more arid conditions. These results suggest that carbon cycle changes during the mid-Cretaceous may have influenced paleoclimate conditions experienced in terrestrial settings.Geoscience
- …
