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40Ar/39Ar ages and duration across the Triassic-Jurassic boundary of the Central Atlantic Magmatic Province volcanism in Morocco and Portugal.
No full textThe Central Atlantic Magmatic Province (CAMP) is the world's largest known continental igneous province and is contemporaneous with the Triassic–Jurassic (T–J) boundary that marks one of the five largest biological extinctions in the last
600 Ma. Although constraints on the duration of the CAMP volcanism remain yet poorly defined, the assumption that the CAMP may have had a causal relationship with the climatic and biotic crisis was suggested [Marzoli, A., Bertrand, H., Knight, K., Cirilli, S., Buratti, N, Verati, C., Nomade, S., Renne, P.R., Youbi, N., Martini, R., Allenbach, K., Neuwerth, R., Rapaille, C., Zaninetti, L., Bellieni, G., 2004. Synchrony of the Central Atlantic magmatic province and the Triassic–Jurassic boundary climatic and biotic crisis. Geology 32, 973–976.]. In this paper, we present new 40Ar/39Ar ages on basaltic flows from Moroccan (central High Atlas, Oujda and Argana) and Portuguese (Algarve and Santiago do Cacém) basins where CAMP lava flows are interlayered with T–J sedimentary sequences.
In the Moroccan basins, where the basalts were erupted across the T–J boundary, well defined 40Ar/39Ar plateau ages (n=12)
for more than 90% of the total erupted volume of CAMP basalts range from 197.8±0.7 Ma to 201.7±2.4 Ma and display a main
restricted peak at 199.1±1 Ma providing a precise estimate of the 40Ar/39Ar age of the T–J boundary, concordant with the current U–Pb age [199.6±0.3 Ma; Pálfy, J., Mortensen, J.K, Carter, E.S., Smith, P.L., Friedman, R.M., Tipper, H.W., 2000. Timing the end-Triassic mass extinction: First on land, then in the sea? Geology 28, 39–42.]. The topmost lava flows (recurrent unit) yield a significantly younger mean age of 196.6±0.6 Ma, highlighting late episodic eruption of CAMP magmas. These late basalts represent a small magma volume (b10% of the total), which was erupted most likely due to asthenospheric upwelling and lithospheric extension within the T–J central High Atlas basins.
In the Portuguese basins, stratigraphical and palynological studies of the associated continental sedimentary sequence
underlying the volcanic units suggest an age close to the T–J boundary for the CAMP basaltic flows. This is confirmed by new
40Ar/39Ar data for the Portuguese basalts, which provide the first accurate radio-isotopic ages for lava flows in the European
CAMP, with two plateau ages yielding a mean value of 198.1±0.4 Ma. These plateau ages (plus three concordant mini-plateau ages) suggest synchronous rifting and volcanism both in south-western Europe and Morocco (central High Atlas and Oujda basins)
The Central Atlantic Magmatic Province (CAMP) on the African Continent. Overview and future works
No full text40Ar/39Ar ages and geochemistry of Maranhão CAMP tholeiites (Brazil): implications for low and high-Ti basalt sources.
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Ar-40/Ar-39 ages and geochemistry of Maranhao CAMP tholeiites (Brazil): Implications for low and high-Ti basalts sources
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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
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