1,721,008 research outputs found
Preserved Ross-age(?) root beneath the Transantarctic Mountains and origin of the thinner crust beneath the northern Wilkes Subglacial Basin
No full textThe Wilkes Subglacial Basin, in the hinterland of the Transantarctic Mountains, represents one of the least un-
derstood continental-scale features in Antarctica. Aeromagnetic data suggests that this basin was imposed on a
much earlier Ross age back arc region that developed along the former active margin of the East Antarctic Craton
(Ferraccioli et al., 2009, Tectonophysics). However, the deeper crustal structure of the basin and its relation with
tectonic evolution remains both disputed and poorly constrained. Here, we present new airborne gravity data that
reveal the crustal architecture of the northern Wilkes Subglacial Basin. Our gravity models indicate that the crust
under the northern Wilkes Subglacial Basin is likely to be 30–35 km thick, i.e. 5–10 km thinner than imaged under
the adjacent Transantarctic Mountains, and
15 km thinner than predicted from some previous flexural and pas-
sive seismic models beneath the southern Wilkes Subglacial Basin region. We infer that crustal thickening under
northern Victoria Land reflects Ross-age (ca 500 Ma) orogenic events and accretion, followed by partial preserva-
tion of the orogenic root since then, as opposed to reflecting the edge of a Mesozoic plateau, which has previously
been inferred to have occupied West Antarctica (Bialas et al. 2007, Geology). Airy isostatic anomalies along both
flanks of the Wilkes Basin reveal major inherited tectonic structures, which likely controlled the basin location and
hence support aeromagnetic interpretations of the Wilkes Subglacial Basin as a structurally controlled basin. The
positive anomaly along the western margin of the basin appears to define the tectonic boundary between the East
Antarctic Craton and the Ross Orogen, and the anomaly along its eastern flank is interpreted as reflecting high-
grade and denser rocks of the central Wilson Terran,e with respect to lower grade meta-sediments and magmatic
arc rocks of the western Wilson Terrane and Wilkes Basin region. Our forward models indicate that the crust is
5 km thinner beneath the northern Wilkes Basin, compared to formerly contiguous segments of the Delamerian
Orogen in south-eastern Australia. We put forward four possible explanations for the thinner crust we modelled
beneath the northern Wilkes Subglacial Basin: i) back-arc basin formation or orogenic collapse processes, coupled
with major crustal-scale tectonic segmentation within the Ross
n
Delamerian orogens, ii) Jurassic to Cretaceous
intraplate extension in East Antarctica, prior to later break-up between Australia and East Antarctica, iii) major
glacial erosion within the Wilkes Subglacial Basin since East Antarctic Ice Sheet initiation, ca 34 Ma, or most
likely- iv) a combination of these tectonic and erosional processes and their associated isostatic response
BABOC: A new project aimed at analysing geological boundary conditions for the East Antarctic Ice Sheet in the Wilkes Subglacial Basin
No full textThe Wilkes Subglacial Basin extends for ca 1,400 km from George V Land into the interior of East Antarctica
and hosts several major glaciers that drain a large sector of the East Antarctic Ice Sheet (EAIS). The region is
of major significance for assessing the long-term stability of the EAIS, as it lies well below sea level and its
bedrock deepens inland. This makes it potentially prone to marine ice sheet instability, much like areas of the
West Antarctic Ice Sheet (WAIS) that are presently experiencing significant mass loss. This sector of the EAIS
has also recently become a major focus of research within IODP Leg 318 that aims to better comprehend the
initial stages of glaciation in East Antarctica and the subsequent history and stability of the ice sheet in response
to major paleoclimatic changes (Escutia et al., 2010 IODP Rep.). Understanding geological boundary conditions
in this region is therefore important to assess their influence on ice sheet dynamics and stability. Early geophysical
models inferred the existence of a major extensional sedimentary basin beneath the region, which if true, could be
similar to some areas of the WAIS, There thick subglacial sediments deposited within deep rift basins or forming
thin marine sedimentary drapes have been inferred to exert a key influence on the onset and maintenance of fast-
glacial flow. However, later geophysical models indicated that the Wilkes Basin contains little or no sediment, is
not rift-related and formed in response to Cenozoic flexural uplift of the Transantarctic Mountains (TAM). A major
joint Italian-UK aerogeophysical exploration campaign over parts of the Wilkes Basin is super-seeding these earlier
geophysical views of the basin: i) Precambrian and Paleozoic basement faults can now be recognised as exerting
fundamental controls on the location of the topographic margins of the basin; ii) the crust underlying the basin is
thinner compared to the TAM, but is unlikely to be Cretaceous or Cenozoic-age rifted crust and; iii) its bedrock is
composed of a variety of rocks of different ages and bulk composition, including inferred Proterozoic basement,
Neoproterozoic and Cambrian sediments intruded by Cambrian arc rocks, and cover rocks formed primarily by
Beacon sediments intruded by Ferrar sills of Jurassic age. Within the framework of the collaborative Italian-US-UK
BABOC project a new initiative has been launched to analyse and model variable geological boundary conditions
in the Wilkes Basin, by analysing both new and existing geophysical data. A couple of new flights over the region
were flown by the ICECAP team for BABOC during the 2010-11 field campaign from Mario Zucchelli Station.
ICECAP independently acquired a suite of extensive aerogeophysical observations over three campaigns, centred
in particular over the southern part of the basin, and some new profiles over the northern coastal margin of the
basin. We present an initial analyses and interpretation of the potential field signatures over the different parts of
the basin and assess regional geological controls on the subglacial topography of the basin
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
Recent aerogeophysical exploration sheds new light into the last frontier on Earth: East Antarctica
Full text link第7回極域科学シンポジウム:[OG] 地圏
11月29日（火）国立極地研究所 3階 セミナー室conference objec
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