1,721,082 research outputs found
Beyond the ice: shifts in productivity and carbonate oversaturation at the Eocene–Oligocene transition
Full text link: During the Eocene-Oligocene Transition (EOT; 34 Ma), Earth's climate shifted from a warm, unglaciated state to a colder, glaciated state, marked by the formation of large dynamic ice sheets on Antarctica. For decades, it was believed that calcareous nannoplankton showed little response to this transition, or where change was documented, it appeared to occur ~ 500 kyr before the EOT, suggesting that these key primary marine producers had a limited reaction to this climate transition. Here, we present morphometric and abundance data for the Clausicoccus subdistichus group from various sites across the Indian Ocean (Ocean Drilling Program [ODP] Site 756), Pacific Ocean (International Ocean Discovery Program [IODP] Site U1509; ODP Site 1209), and Atlantic Ocean (IODP Site U1411). Our findings reveal a synchronous increase in placolith size and abundance (acme interval) of this taxon. These records, investigated in different depositional settings worldwide, confirm the global nature of this event, at least at low to middle latitudes. Remarkably, this event serves as a distinctive global fingerprint of the EOT, even in poorly preserved sediments. We propose that the observed changes were primarily driven by oversaturation of carbonate ions [CO32-] in seawater and progressive eutrophication of the oceans, culminating in the "Early Oligocene Glacial Maximum" (EOGM)
Epilithic organisms in Priabonian marls with pillow lavas from the EuganeanHills (NE Italy)
Full text linkIn the Castelnuovo area of the Euganean Hills, upper Priabonian marls (referred to as Brendola Marl) are associated with products of submarine basaltic eruptions, including pillow lavas and lava flows, pertaining to the first, late Eocene magmatic phase in the district. A biostratigraphical revision of the marl by means of calcareous nannofossils allowed to ascribe the succession to the Priabonian Zone CNE19 (Agnini et al., 2014) and to the upper part of planktonic foraminiferal Zone E15, with an estimated age of 35.3-34.3 Ma (Berggren and Pearson, 2005). The benthic foraminiferal assemblage provided a palaeodepth estimation suggesting a deep neritic environment. A reconstruction of the late Priabonian events in the study area indicates various episodes of submarine eruptive activity with formation of pillows and associated hyaloclastic material, alternating with phases of colonization of the upper parts of the pillows and larger hyaloclasts by epilithic and vagile organisms such as cr..
Epilithic organisms in Priabonian marls with pillow lavas of Euganean Hills (NE Italy)
No full textIn the Castelnuovo area of the Euganean Hills, upper Priabonian marls (referred to as Brendola Marl) are associated with products of submarine basaltic eruptions, including pillow lavas and lava flows, pertaining to the first, late Eocene magmatic phase in the district. A biostratigraphical revision of the marl by means of calcareous nannofossils allowed to ascribe the succession to the Priabonian Zone CNE19 (Agnini et al., 2014) and to the upper part of planktonic foraminiferal Zone E15, with an estimated age of 35.3-34.3 Ma (Berggren and Pearson, 2005). The benthic foraminiferal assemblage provided a palaeodepth estimation suggesting a deep neritic environment. A reconstruction of the late Priabonian events in the study area indicates various episodes of submarine eruptive activity with formation of pillows and associated hyaloclastic material, alternating with phases of colonization of the upper parts of the pillows and larger hyaloclasts by epilithic and vagile organisms such as crinoids, cirripeds, brachiopods and cidarid echinoids, followed by their post-mortem disaggregation, dispersal and eventual burial due to the uninterrupted marly sedimentation. These episodes ceased with the emplacement of a lava flow, whose flat top was colonized only by sparse cirripeds
Middle Eocene large coccolithaceans: Biostratigraphic implications and paleoclimatic clues
Full text linkLate Miocene to Early Pliocene benthic foraminifera from the Tasman Sea (International Ocean Discovery Program Site U1506)
Full text linkModern and fossil benthic foraminifera have been widely documented from New Zealand, but detailed studies of material collected from drilling expeditions in the Tasman Sea are scarcer. This study aims to provide an updated taxonomic study for the Late Miocene–Early Pliocene benthic foraminifera in the Tasman Sea, with a specific focus on the paleoceanographic phenomenon known as the Biogenic Bloom. To achieve these goals, we analysed 66 samples from International Ocean Discovery Program (IODP) Site U1506 located in the Tasman Sea and identified a total of 98 taxa. Benthic foraminifera exhibit good preservation, allowing for accurate taxonomic identification. The resulting dataset serves as a reliable and precise framework for the identification and classification of the common deep-water benthic foraminifera in the region. The paleobathymetric analysis based on depth-dependent species indicates deposition at lower bathyal depths. Additionally, the quantitative analysis of the benthic foraminiferal assemblages allowed us to explore their response to the Biogenic Bloom at Site U1506. The paleoenvironmental analysis, focused on the Early Pliocene part of the Biogenic Bloom, points to high-productivity conditions driven by phytoplankton blooms and intensified vertical mixing of the ocean waters. These results provide valuable insights into the paleoceanographic events in the Tasman Sea, particularly the Biogenic Bloom, highlighting the significance of benthic foraminifera as reliable proxies for deciphering paleoenvironmental conditions. The taxonomic identifications and paleoenvironmental interpretations presented herein will aid in future paleoceanographic studies and facilitate comparisons with other deep-sea regions
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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