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Preservation of the Miocene Atacama Gravels in Vallenar area, Northen Chilean Andes: Climate, Stratigraphic or Tectonic control?
No full textThe dynamics of back-arc extension: a laboratory approach to the opening of the Tyrrhenian Sea
No full textSedimentation and preservation of the Miocene Atacama Gravels in the Pedernales-Chañaral Area, Northern Chile: Climatic or Tectonic Control?
No full textIn recent years, longitudinal changes on the thin/thick-skinned tectonic styles of the Central Andes has been
intensively discussedwhile other studies have considered the role ofmass transfers on the unloading of the
orogen, and on the stress regime along the plate interface arising from changes on the volume of sediment
arriving into the Peru–Chile trench. The search for paleo-climate records is therefore crucial for our
understanding of the history of the Central Andes. In this paper, we focus on the Atacama Gravels, an
extensive blanket ofMiocene continental deposits filling a Neogene paleo-valley systemalong the southern
Atacama Desert in northern Chile. An east–west transect, between Pedernales and Chañaral (26°30′S),
enabled us to carry out a sedimentological and tectonic study of the Atacama Gravels, based on logging and
field observations along the Rio Salado canyon. New 39Ar–40Ar ages obtained on intercalated and overlying
ignimbrites date the beginning of the Atacama Gravels sedimentation at around the Oligocene–Miocene
boundary and cessation of sedimentation in the Late Miocene. Thirteen lithofacies, included within five
facies associations (A1 to A5) were identified. Depositional environments vary from proximal alluvial fan
(A1, A2) in the Precordillera through ephemeral fluvial (A3, A4) to distal playa lake (A5) in the Coastal
Cordillera. No evidences of synsedimentary deformation have been found, showing that the change from
sediment removal to sediment preservation cannot be explained by tectonic causes, and climate change
appears to be the dominant controlling factor of sediment preservation. A progressive change from semiarid
towards hyper-arid climatic conditions during theMiocene, led to a reduction on the transport capacity
of the fluvial system and sediment preservation along the paleo-valley system formed during the
Oligocene
The volcaniclastic series from the Luang Prabang Basin, Laos: A witness of a triassic magmatic arc?
No full textThe paleogeographic evolution of South East Asia (SEA) during the early Mesozoic is still poorly understood and a number of models have recently been put forward to account for the geodynamic evolution of SEA. The Luang Prabang Basin (north Laos), located in the core of a "paleogeographic jigsaw" in SEA, recorded a long lasting volcanism that spanned for ~ 35 my from the earliest Triassic up to Late Triassic as evidenced by combined stratigraphic and geochronological (U-Pb/zircon) analyses performed on both volcanic and volcaniclastic series. The volcanic rocks are arc tholeiites and calk-alkaline andesites to dacites. The volcaniclastic rocks contain, in part, volcaniclasts produced contemporaneously with sedimentation. Both the volcanic and volcaniclastic series display geochemical features characteristic of a subduction related volcanism. Therefore, the Luang Prabang Basin documents a magmatic arc in a good agreement with the recent recognition of neighboring ophiolitic rocks in the Luang Prabang area. Following a passive margin setting that prevailed from the late Carboniferous to the late Permian, an active margin then initiated along the western margin of the Indochina Block. This active magmatic arc developed as the result of an east-dipping subduction below the Indochina Block during most of the Triassic, at least from ca. 250 to 215 Ma. Subsequently, this oceanic subduction episode must have been followed by a continental collision of the Indochina Block with the eastern Simao Block, at a period that remains to be defined
THE INFLUENCE OF PRE-EXISTING THRUST PLANES ON NORMAL FAULT GEOMETRY: EXPERIMENTAL MODELLING AND GEOLOGICAL EXAMPLES
No full textPreservation of the Miocene Atacama Gravels in the El Salvador area, Northen Chilean Andes: Climate / Depositional-Erosional balance
No full text
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
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