1,720,961 research outputs found
From orogen to passive margin: constraints from fission track and (U–Th)/He analyses on Mesozoic uplift and fault reactivation in SW Norway
No full textTectonic evolution of the SW Norwegian passive margin based on low-temperature thermochronology from the innermost Hardangerfjord area
No full textThe post-Caledonian structural and morphological evolution of the North Sea rift margin in southwestern Norway is largely unresolved. A comprehensive understanding of the importance of onshore fault reactivation and the magnitude of crustal uplift has been hindered by the near absence of post-Devonian sediments. This study aims to delineate the tectonic history of the passive margin hinterland from the Permian onwards by means of apatite fission-track (AFT) analysis and (U-Th)/He thermochronology. AFT analysis has been performed on 32 samples from the steep flanks of the innermost segments of the Hardangerfjord. The resulting cooling ages range from Late Triassic to Late Cretaceous and define a general positive age-elevation trend that is locally disturbed by large age offsets, suggestive of post-Mid Jurassic faulting on the order of several hundred metres. Four samples from the Eidfjord and Ulvik districts have been analysed by the (U-Th)/He method, giving primarily Cretaceous single-grain ages. Thermal history modelling reveals two distinct episodes of accelerated cooling (2-6 degrees C/Myr(-1)), confined to the Permo-Triassic and the latest Cretaceous to Cenozoic. The high Permo-Triassic cooling rates may be explained by flexural rift-flank uplift and increased tectonic activity onshore as a response to rifting in adjacent offshore areas. Rapid exhumation throughout the Cenozoic is consistent with sustained elevated topography and periodic rejuvenation of relief as a result of local fault activity. In combination with previously reported AFT data, the results presented in this contribution suggest that faulting has exerted a major control on the overall morphology of the passive margin. The Mesozoic-Cenozoic exhumation history reflects a complex interplay between tectonic activity, flexural uplift and erosion
K-Ar illite and apatite fission track constraints onbrittle faulting and the evolution of the northern Norwegian passive margin
Full text linkDetermining the timing of post-Caledonian brittle faulting in northern Norway is important for the understanding of the extensional tectonic evolution of the north Norwegian continental margin. Fault gouges from the Troms and Vesterålen regions of northern Norway yield Carboniferous to Permian and Carboniferous to Cretaceous K–Ar illite ages, respectively. The results show a contrast in fault activity and exhumation between the Troms and the Vesterålen regions: while major faulting in the Troms region appears to have ceased after the Permian faulting event, faulting continued into at least the Cretaceous in the Vesterålen region. The findings highlight the importance of a widespread Permian tectonic event followed by a distinct southwestward migration of post-Permian tectonic activity on the north Norwegian passive margin. Late Triassic to Early Jurassic apatite fission track ages do not show significant age offsets across major fault zones in Troms, indicating that most or all of fault activity took place prior to the Late Triassic. The thermal history models are consistent and indicate continuous cooling to about 60 °C in the Late Permian–Triassic
Tectonic evolution of the SW Norwegian passive margin based on low-temperature thermochronology from the innermost Hardangerfjord area
No full textThe post-Caledonian structural and morphological evolution of the North Sea rift margin in southwestern Norway is largely unresolved. A comprehensive understanding of the importance of onshore fault reactivation and the magnitude of crustal uplift has been hindered by the near absence of post-Devonian sediments. This study aims to delineate the tectonic history of the passive margin hinterland from the Permian onwards by means of apatite fission-track (AFT) analysis and (U-Th)/He thermochronology. AFT analysis has been performed on 32 samples from the steep flanks of the innermost segments of the Hardangerfjord. The resulting cooling ages range from Late Triassic to Late Cretaceous and define a general positive age-elevation trend that is locally disturbed by large age offsets, suggestive of post-Mid Jurassic faulting on the order of several hundred metres. Four samples from the Eidfjord and Ulvik districts have been analysed by the (U-Th)/He method, giving primarily Cretaceous single-grain ages. Thermal history modelling reveals two distinct episodes of accelerated cooling (2-6 degrees C/Myr(-1)), confined to the Permo-Triassic and the latest Cretaceous to Cenozoic. The high Permo-Triassic cooling rates may be explained by flexural rift-flank uplift and increased tectonic activity onshore as a response to rifting in adjacent offshore areas. Rapid exhumation throughout the Cenozoic is consistent with sustained elevated topography and periodic rejuvenation of relief as a result of local fault activity. In combination with previously reported AFT data, the results presented in this contribution suggest that faulting has exerted a major control on the overall morphology of the passive margin. The Mesozoic-Cenozoic exhumation history reflects a complex interplay between tectonic activity, flexural uplift and erosion
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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