1,720,981 research outputs found
Tidal sedimentation preserved in volcaniclastic deposits filling a peripheral seaway embayment (early Miocene, Sardinian Graben)
No full textThe Sardinian Graben System was a part of a NE-SW-oriented extensional basin, rotated counter-clockwise into a N-S-elongate basin, as consequence of the eastward migration of the Apennine orogenic front, in the western Mediterranean during the Neogene. Starting from the early Miocene, the Sardinian Graben was inundated by marine waters, turning progressively into a seaway, characterized by a tidal circulation as consequence of the connection between the Atlantic Ocean to the west and the Paratethys Ocean to the east. In this work, we investigate an area located marginally to the mid-seaway, whose well-exposed volcaniclastic deposits record the local expression of a tidal amplification occurring in a coastal peripheral embayment of the wider Sardinian Seaway. The studied succession is ca. 140 m thick and includes three main units: (i) the 20-m-thick lowermost unit consists of fluvio-lacustrine sandstones and conglomerates belonging to lower delta-plain and delta-platform environments; (ii) the second unit is 60–70 m thick and includes heterolithic sandstones and mudstones, exhibiting a variety of tidal sedimentary structures, and lies on the previous deposits through a tidal ravinement surface; these two units are mostly volcaniclastic in composition, reflecting the dominance of a magmatic source over other extrabasinal components; (iii) the uppermost unit is ca. 50 m thick, erosionally overlies the previous deposits and is made up of shoreface sandstones and open-shelf mudstones, whose composition indicates even less volcaniclastic elements and the prevalence of other clastic alongshore-derived components. Based on the results of the facies analysis, the study succession is interpreted as the infill of an incised valley along the southern flank of a structural high. The valley was excavated during a phase of relative sea-level lowstand (Aquitanian?) preceding a subsequent stage of major transgression (Burdigalian). Initially, a fluvial system impinged the valley from the west favoring the progradation of a deltaic system in a shallow-marine embayment. During an early stage of transgression, the isolation of a part of this coastal area generated by the building of a barrier island, produced the onset of a tidal-flat sedimentation over the previous deposits. A late transgression occurred through the inundation of this coastal area by marine waters and the consequent back-stepping of beach-barrier and open-shelf strata. The sedimentological features of this stratigraphic succession indicate as this valley was filled in a tectonic setting with a high rate of accommodation, where the tidal influence progressively increased during sediment accumulation, possibly due to the marginal position respect to a wider tide-dominated marine conduit. The present paper thus: (i) documents for the first time a tidal signature in the lower Miocene strata of Sardinia; (ii) indicates new possible relationships with other, coeval seaway successions of the western and northern Mediterranean area; (iii) suggests constrains for palaeogeographic reconstructions; (iv) and throws the basis for future researches on the Sardinian Seaway
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
Sedimentology and facies analysis of ancient sand ridges: Jurassic Rogn Formation, Trøndelag Platform, offshore Norway
Full text linkSand ridges represent a common type of sedimentary bedform of modern shelves seldom used as analogues to interpret isolated marine sandbodies recognised in the subsurface. Lack of extended literature on outcrop and subsurface examples limits the possibility for their recognition and seems one of the reason behind this underrepresentation. The Draugen discovery made in the early 80's represents an unicum in the Trøndelag Platform, offshore Norway. After more than 30 years the Froan Basin and Frøya High area are still underexplored and the Late Jurassic Rogn Fm play not well understood. Predicting reservoir distribution, and its internal architecture and properties requires the understanding of factors controlling sedimentation (e.g. palaeocirculation, depositional processes). North-south elongated sandbodies pertaining to the Rogn Formation are recognised in the Froan Basin and Frøya High encased within thick shaly deposits. Sandbodies develop above a ravinement or flooding surface (i.e. Callovian Unconformity) of regional extent where local depressions occur with a non-erosional concave-up top. Depressions representing the depositional loci for the accumulation of sand and development of the ridge. The presence of eastward and westward dipping reflections within the sandbodies allows identifying their large-scale architectures. Sediments form coarsening-upward vertical units characterised by a shaly base evolving upwards to medium- and coarse-grained sand forming tabular and trough cross strata. Locally, a fining upward trend characterised by plane-parallel stratification and coarse-grained massive layers is recognised. Sediments results well organised and sorted, which positively affects final porosity and permeability with values up to 30% and 6 Darcy, respectively - typical values for many sand ridges. Accordingly, sand ridges encased within thick shaly deposits can form stratigraphic traps with the potential for large hydrocarbon accumulations. The aim of the present study is to help the understanding of distribution, and internal architectures and properties of the Rogn Fm in the Trøndelag Platform
Miocene sedimentary sequences of the Sardinian Graben System as possible analogue for the Upper Jurassic Rogn Formation of the Norwegian Continental Shelf
No full textThe Rogn Fm is an Oxfordian to Volgian (Late Jurassic) sand-rich interval recognised in the offshore subsurface of the Norwegian Continental Shelf (Gjelberg et al., 1987, Dalland et al., 1988). In its type well the formation is up to 60 m thick and exhibits a coarsening-upward trend (Provan 1992) (Fig. 1). The Rogn Fm, which has found encased in shelf fines or adjacent to the flanks of structural highs, consists of well-sorted coarse-grained sandstones, made up of sub-angular clasts, diffusely cross laminated, and also including siltstones and shales (e.g., Elliott et al., 2015) (Fig. 1). The Rogn Fm has become even more renowned thanks to its good reservoir properties (P=29%; K=8 Darcy; N/G=0.7) and because it provided promising oil discoveries in the last twenty years. The more accepted interpretation on the depositional genesis of the Rogn Fm is the derivation from the erosion of several hundred of meters of pre-Permian to Upper Jurassic successions from the uplifted Frøya High, and the subsequent accumulation in sheltered coastal zones and/or in more distal ‘shelf ’ environments, tectonically shaped into narrow-elongate depocenters (Provan 1992). The recurrent motif of cross-bedding observable in the Rogn sandstones point out towards a general control exerted by tractional flows, whose strength was possibly influenced by lateral constrictions, generating a series of current-influenced subaqueous bedforms (i.e. in the southern-east Frøan Basin) or transported towards further to north on the Halten Terrace. However, a number of uncertainties related to the sub-seismic depositional architectures or lateral facies changes of the Rogn Fm call for evaluable outcropanalogue studies, useful to constrain or revise preliminary interpretations and, thus, to increase the exploitation
potential of the Rogn Fm
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
