1,720,963 research outputs found
Deep-seated hydrocarbons in the seep “Brecciated Limestones” of the Maiella area (Adriatic foreland basin): Evaporitic sealing and oil re-mobilization effects linked to the drawdown of the Messinian Salinity Crisis
No full textThe 13C-depleted “Brecciated Limestones” record a hydrocarbon seep event that occurred between 5.56 and 5.532 Ma in the Maiella area. They unconformably overlie the “Primary Lower Gypsum” and crop out as carbonate buildups and authigenic patches fed by fluid migration pathways filled with flow-mobilized pelites. Tar occurs as solid bitumen shows, corresponding to pore-filling tar in the microfacies, and as a distinctive brown facies, resulting in finely impregnating patterns in thin section. Geochemical rock characterization confirmed that the measured Total Organic Carbon, with values up to 11.07%, mostly consists of migrated hydrocarbons in the carbonate buildups and the authigenic patches, while the flow- mobilized pelites are devoid of oil traces. Bitumen characterization showed an overall homogeneity among the samples, established by their similarities in the tricyclic fraction and their uniform bitumen d13C signals (␣26.3/␣28.66‰ PDB-1). Gas chromatographyemass spectrometry revealed five distinctive markers indicative of an oil that originated and migrated from a carbonate source rock: high C29/C30 hopane ratio; low Ts/Tm ratio; abundant C24 tetracyclic terpane; absence of diasteranes; and occurrence of methylsteranes. Considering the regional source rock setting, the carbonate source rock might pre- sumably be Upper Triassic/Lower Liassic in age. We favor a conceptual model that envisages a step-wise migration of hydrocarbons, which originated from a deep-seated source and migrated through a hydrofractured reservoir (Bolognano Fm.). The Primary Lower Gypsum of the Messinian Salinity Crisis provided an efficient seal until the major evaporative drawdown of the Mediterranean Sea at ~5.55 Ma triggered a renewed hydrocarbons migration, which occurred first with a vigorous gaseous release and then with a seeping oil flow. Oil impregnated the early cemented “Brecciated Limestones” and partly contributed to their precipitation, whereas a self-clogging effect supposedly prevented oil impregnation in correspondence with the feeder channels formed during the first gaseous migration phase
The late Messinian Lago-Mare biofacies in central Apennines: the ostracod perspective
No full text""The different phases of colonization of the Palaeo-. Mediterranean by the Paratethyan ostracods during the Lago-. Mare event of the Messinian Salinity Crisis, as recognized in the. whole Palaeo-Mediterranean area, are investigated in the central. Apennines. The studied localities showed the record of the first. colonization (5.59-5.40 Ma) by Loxoconcha mülleri and. Tyrrhenocythere sp. in the Majella Mt. area (Colle di Votta and. Decontra sections) and the arrival of the huge Paratethyan. contingent (5.40-5.33 Ma) made by several species of. Candoninae, Leptocytheridae and Loxoconchidae (among which. Loxocorniculina djafarovi, fig. 1) in the deposits of Latium (Cura. di Vetralla and Mondragone) and Abruzzi (Le Vicenne and. Majella Mt.). The latest phase of the Lago-Mare event (5.35-5.33. Ma) is documented in the Cura di Vetralla, Le Vicenne, Fonte dei. Pulcini and Decontra sections by the presence of Amnicythere. costata, A. litica, A. subcaspia, Pontoniella verrucosa,. Loxoconcha kochi and Tyrrhenocythere ruggierii."
A Messinian analogue for the subsurface plumbing of marine oil seeps (Maiella foreland basin, Central Apennine)
No full textA major evidence of fluid seepage in the Western Mediterranean margin during the Messinian Salinity Crisis: the tar-bearing Brecciated Limestones of the Maiella Basin
No full textSubsurface seepage dynamics and flow types in a Messinian paleoseep system (Maiella Mts., Central Italy)
No full textThe subsurface feeder complexes of mud volcanoes and seepage systems potentially provide valuable information on the evolution of seepage dynamics. Ancient seepage systems in outcrops allow for the observation of expulsion features, which are otherwise commonly beyond seismic resolution. In the Maiella hydrocarbon seep area, the evolution of fluid migration through the sedimentary column during the Messinian Salinity Crisis generated distinctive seep-plumbing features, geological responses, and geochemical signatures in the “Brecciated Limestones” unit. The fluid migration pathways evolved from funnel-shaped feeder channels (Flow-mobilized Sediments) into hydrofractured microbial carbonate buildups (Limestone Buildups), and finally into blow-out micropipes in the host sediment (Patchy Limestones), as overpressure dissipated through the plumbing system. The Flow-mobilized Sediments (δ13C down to − 24.5‰ PDB-1) correspond to the highest flow rates in the whole area, whereas the Patchy Limestones (δ13C down to − 39.3‰ PDB-1) correspond to the slowest flow rates within the intrusive zone. The Limestone Buildups show different degrees of hydrofracturing that reflect different flow rates (δ13C down to − 27.5‰ PDB-1). The fluid transport mechanisms evolved from focused venting through neoformed feeder channels, where sediments elutriated from depths were carried out (the sediment-prone response to fluid migration), to high-rate seepage triggering high hydrofracturation in the microbial buildups. While the hydrocarbon-rich fluids contemporaneously triggered authigenic precipitation (the mineral-prone response to fluid migration), progressive upward and lateral flow deceleration resulted in gradually weaker hydrofracturing of the microbial buildups and finally only local cementation in the form of carbonate patches within the host sediments
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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