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Physical stratigraphy, heterogeneity development and provenance evolution of the sand-rich pre-collisional Bordighera turbidite system
Full text linkL'unità di San Remo del Cretaceo superiore comprende un compleso basale (Fm. di San Bartolomeo) e due spesse sequenze torbiditiche, rappersentate da un sistema a bassa efficienza silicoclastico (Arenarie di Bordighera) che si interdigita con una sequenza torbiditica calcarea (Flysch ad Elmintoidi di San Remo) che, attraverso il dominio laterale e distale, diventa progressivamente più abbondante. Per poter valutare le potenziali analogie degli affioramenti della conoide altamente sabbiosa e di granulometria grossolana delle Arenarie di Bordighera, queste ultime sono state studiate con dettagliate analisi di facies. Molta enfasi è stata posta alla quantificazione delle eterogeneità “inter-sandbody” dovute allo sviluppo di hybrid event beds (HEBs). In una situazione di complesse deformazioni tettoniche e con una parziale esposizione laterale degli affioramenti, l'utilizzo di parametri sedimentologiche (tasso di amalgamazione, rapporto arenaria-argillite, trend di distribuzione delle granulometrie e proporzioni delle facies) forniscono uno strumento efficiente per determinare l'ambiente di deposizione. Inoltre, analisi statistiche dei trends di distribuzione orizzontali e verticali su scala di bacino hanno facilitato la valutazione quantitativa e posizionale nella distribuzione delle eterogeneità attraverso i corpi sabbiosi.
Lungo il transetto lungo corrente, tre domini deposizionali evidenziati in maniera sorprendente dalle proporzioni delle litofacies sono stati differenziati. Il dominio prossimale, interpretato come rappresentativo di un riempimento di canali a bassa sinuosità, è composto da successioni omogenee e massicce di sabbia pulita. Un dominio mediale carratterizzato da geometrie lenticolari e tabulari di breve estensione e minori proporzioni di sabbie argillose. Questo dominio è interpretato come la rappresentazione della transizione tra associazioni di facies canalizzate e non canalizzate. Contrariamente al precedente, il dominio distale è dominato da gruppi di corpi di arenaria laminati è intrpretato come una rappresentazione dei lobi terminali. Questi orizzonti sabbiosi tabulari (“sheet sands”) sono dominati da depositi di flussi transizionale quali livelli ricchi in clasti di argilla e HEB. Una relazione stretta tra incisioni a media scala e trasformazione di flussi rapidi può essere documentato dal cambiamento delle proporzioni delle facies osservato. La larga diffusione delle HEB nelle zone preservate di depositi allungati dell'asse centrale contrasta i modelli che definiscono gli HEB come peculiari dell'ambiente della conoide esterna. Inoltre, la atipicità di un sistema torbiditico a bassa efficienza (i.e. porzione di argille inizialmente ridotta) che diventa molto incline alle etereogeneità correlate agli HEB è interpretata come il risultato di una crescente disponibilità di fango coesivo dovuto alle intercalazioni eterotopiche con il Flysch ad Elmintoidi.
L'analisi multi-proxy della provenienza dei sedimenti dei due membri terrigeni - il complesso basale e le Arenarie di Bordighera - fornisce spunti per una miglior comprensione della complessa evoluzione pre-collisionale del dominio Ligure-Piemontese e i circostanti margini continentali. Analisi petrografiche identificano il complesso basale come un'arenaria tessituralmete matura e ricca in quarzo. Le Arenarie di Bordighera, sovraimposte in continuità a quest'ultime rappresentano arcose tessituralmente e composizionalmente immature. Queste osservazioni suggeriscono la graduale evoluzione della provenienza da un cratone stabile o transizionale verso un basamento in rapida esumazione. Nuovi dati geocronologici (datazioni U-Pb nei zirconi detritici) rivelano picchi di distribuzione nei detriti che suggeriscono una forte affinità con il marine Paleo-Europeo e mostrando che la placca inferiore (i.e. il margine passivo) debba funzionare come sorgente principale di detrito durante le fasi iniziali della convergena Alpina.The Upper Cretaceous San Remo Unit represents a trench fill that comprises a basal complex (San Bartolomeo Fm.) and two thick turbiditic sequences, a low-efficiency siliciclastic turbidite system (Bordighera Sandstones) that interfingers with a calcareous turbiditic sequence (San Remo Helminthoid Flysch) which becomes increasingly abundant towards the lateral and distal domains. In order to evaluate the outcrop analog potential of the sand-rich axial fan, the Bordighera Sandstones have been investigated by detailed facies analysis. Main emphasis was placed on the quantification of inter-sandbody heterogeneity due to hybrid event bed (HEB) development. In the context of complex tectonic deformation and limited lateral outcrop exposure, the use of sedimentological metrics (e.g. amalgamation ratios, sandstone-mudstone-ratios, grain size distribution trends and facies proportions) provided an effective tool for the determination of depositional environments. Basin-scale statistical analyses of horizontal and vertical facies distributions trends facilitated the quantitative assessment and spatial allocation of facies heterogeneity distribution along the sand fairway. Along a downstream transect, three main depositional domains - marked by strikingly contrasting dominant lithofacies proportions – have been differentiated. The proximal domain, interpreted as representing low-sinuosity channel fills, resembles homogeneous successions of massive clean sands. A medial domain of short basin-ward extent exhibits composite lenticular and tabular bed geometries. This medial realm, interpreted to represent the transition in between channelized and unchannelized facies associations, is defined by the presence of scour features. It comprises minor portions of bed types that account for facies heterogeneity. By contrast, the distal domain, dominated by laterally extensive, clustered sheet-like sandstone bodies, is interpreted as representing terminal lobes. These sheet sands are dominated by the presence of transitional flow deposits such as mudclast-rich beds and HEBs. A close environmental relationship between meso-scale scouring and rapid flow transformation could be documented that apparently controlled the shift in facies proportions. Remarkably, the widespread occurrence of HEBs within axial zones of the preserved elongated sand fairway contrasts models that predict HEB distribution to be characteristic of outer fan environments. The atypical nature of a low-efficiency turbidite system (i.e. defined by low initial mud concentrations) being highly prone to HEB-related heterogeneity is interpreted as the result of enhanced availability of cohesive mud due to the heterotopic intercalations of the calcareous Helminthoid Flysch. As the geodynamic evolution of the Western Tethyan realm during the incipient stages of Alpine convergence remains a matter of controversial debate, the multi-proxy sediment provenance analysis of the two terrigenous members, the basal complex and the coarse-clastic Bordighera Sandstones, provides insights towards a better understanding of the complex pre-collisional evolution of the Piemont-Ligurian domain and the bounding continental margins. Petrographic analysis characterizes the basal complex succession as texturally mature quartz-rich sandstones. By contrast, the conformably superimposing Bordighera Sandstones represent texturally and compositionally immature first-cycle arkoses. A gradual provenance evolution from a stable craton or transitional continental provenance setting towards a scenario defined by rapidly uplifted bedrock (granitoid plutons and low-grade metamorphic geobodies) is proposed. New geochronological data (U-Pb detrital zircon ages) reveal peaks in the detrital spectra that suggest the strong affinity of the clastic detritus towards the Paleo-European margin, documenting that the lower plate (i.e. the passive margin) provided the major sand supply into the subduction trench
Hybrid event bed distribution in a mixed siliciclastic-calcareous turbidite succession: a cross-current perspective from the Bordighera Sandstone, Ligurian Alps, NW Italy
No full textTransitional flow deposits (TFDs) and hybrid event beds (HEBs) form part of the high-density sediment gravity flow spectrum. They record flow characteristics intermediate between fully turbulent and laminar flow states. The transformation from initially frictional into transitional or quasi-laminar cohesive flow behaviour results from enhanced detrital clay concentrations that dampen flow turbulence, triggering the development of an argillaceous sandstone interval that displays characteristics of a cohesive debris flow deposit. Since excess detrital clay proportions reduce primary porosity and permeability, the presence of TFDs and HEBs hinders turbidite sandstone reservoir properties. In applied scenarios, understanding their spatial distribution is crucial for avoiding well misplacement. Spatial distribution models for TFDs and HEBs largely document them as a characteristic feature of distal and lateral outer fan environments. These models are compared with results from facies analysis conducted on a dataset derived from the detailed investigation of three stratigraphic sections, acquired along a cross-current transect of the distal depositional domain of the Bordighera Sandstone (BGS). In its distal domain, the sand-rich Bordighera turbidite system is characterized by direct interbedding with calcareous fine-grained turbidites of the San Remo Helminthoid Flysch, and features high proportions of HEBs and TFDs. Analysis of spatial trends in facies distribution allows the detailed allocation of intra- bed- to sandbody-scale heterogeneity to different axial and off-axis lobe sub-environments which are determined through quantitative sedimentological parameters. Results reveal that in the Bordighera turbidite system argillaceous sandstone bed types are not limited to lobe-fringe environments, but instead are primarily occurring in more proximal high net-to-gross zones of the largely unconfined terminal lobe domain. They account for more than 70% of stratigraphic thickness in axial zones (net-to-gross ratio = 0.87), whereas their proportions decrease towards off-axis lobe (36%; net-to-gross = 0.58) and marginal lobe to lobe fringe domains (23%; net-to-gross = 0.49)
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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