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Geochemical characterization of beach sediments of the NW Borneo, SE Asia: Implications on provenance, weathering intensity and assessment of coastal environmental status
No full textThe bulk chemistry of coastal sediments is governed by the geochemical nature of the river basin, the physical and chemical processes involved during weathering, and transportation of these sediments to the coastal zone and the post-depositional diagenetic alterations. The geochemical study of coastal sediments helps to assess heavy metal contamination and risk of toxicity to coastal ecosystems, and thus, is often considered important in coastal zone management. The hydrocarbon-rich, thickly populated and industrialized city of Miri and its coastal region are among the rapidly developing urban-economic-industrial, yet ecologically fragile regions of Sarawak State in Malaysia. The coastal regions of Miri consist of sandy and rocky beaches with natural erosional features such as cliffs, sea caves, arches, sea stacks, and so forth. Three major rivers confluence into the South China Sea near Miri: (1) the Baram River (NE part), (2) the Miri River (SW part), and (3) the Sibuti River (further SW from the SW part). The study described in this chapter reports on the bulk geochemistry (major, trace, and rare earth elements) of the beach sediments to interpret source rock weathering, provenance, and the environmental significance of selected trace elements. The beach sediments are medium to fine grained sand in the NE part, and very fine sand-mud in the SW part. The bulk chemistry of the sediments is controlled by the source rock lithology (via. rivers), with additional input of selected elements by the geological processes and anthropogenic input. The beach sediments show Chemical Index of Alteration (CIA) values of 68 and 67 for SW and NE, respectively, suggestive of moderate intensity of weathering. The domination of recycling effects, more so than weathering intensity over the geochemistry of studied samples, as shown explicitly in the CIA/WIP ratio and Zr enrichment, is observed. However, selected samples from the NE part show a higher content of Zr concentration due to the addition of zircon minerals by the sorting process. Localized enrichments of a few elements, namely, Zr, Hf, Cu, and Zn, due to natural processes and anthropogenic input (Pb), are also observed. The SW part sediments are moderately to highly contaminated by Cu, Zn, and As; whereas NE part sediments are low to moderately contaminated by Cu, Zn, Cr, and Sn. The biological effect of trace metals linked to Cu and possibly to As are interpreted. These inferences are also supported by morphological deformities of microorganisms, such as foraminifera and ostracoda
Chemostratigraphy of Neoproterozoic Banded Iron Formation (BIF):Types, Age and Origin
No full textNeoproterozoic banded iron formations (BIFs) are not restricted to the middle Cryogenian, c. 715 Ma glaciation, occurring in Tonian, Cryogenian, and Ediacaran successions. Many Neoproterozoic BIFs were deposited in glacially influenced settings, such as the Rapitan Group (Canada), Jacadigo Group (W Brazil), Chuos, and Numees Formations (Namibia) and Holowilena Ironstone (Australia). However, many occurrences are not related to glacial processes and can be assigned to the Algoma and Lake Superior types. Neoproterozoic Algoma-type BIF includes the Wadi Karim and Um Anab (Egypt), the correlative Sawawin BIF (Saudi Arabia), and the Jucurutu Formation of the Seridó Belt (NE Brazil). Lake Superior type BIFs are represented by the Tonian Shilu Group (South China) and the late Ediacaran Arroyo del Soldado Group (Yerbal and Cerro Espuelitas formations, Uruguay).Useful chemostratigraphic tools for the study of BIFs include rare earth element distribution, especially Eu and Ce normalized concentrations, iron speciation, and Nd and Cr isotopes (δ53Cr). Whereas Rapitan type BIFs exhibit no Eu or Ce anomalies, the Algoma-type Neoproterozoic BIFs show both. Positive δ53Cr values characterize glacially influenced BIFs, and differentiates them from nonfractionated, mantle-like δ53Cr values of Algoma type BIF. The most positive δ53Cr values occur in the open-shelf, Lake Superior type BIF, especially that of Ediacaran age.We suggest that glaciation was not a prerequisite for deposition of BIF in the Neoproterozoic, and that hydrothermal activity related to Rodinia rifting played the key role in their reappearance after the Mesoproterozoic gap. Their deposition has more to do with the return to ferruginous conditions in the oceans than with near-global glaciation
Cretaceous sea level rise : down memory lane and the road ahead /
No full textCretaceous Sea Level Rise delves into the question of whether the observed short-term sea-level changes are regional (tectonic) or global (eustatic) and determines their possible relation to climate cycles; to assess the role of feedback mechanisms, i.e. thermal expansion/contraction of seawater, subsidence due to loading by water, changing vegetation of the Earth System and to investigate the relation of sea-level highs and lows to ocean anoxia and oxidation events, represented by black shales and oceanic red beds, and to evaluate the evidence for ephemeral glacial episodes or other climate events. Though research has been, and is being, conducted in these fields since the introduction of sea level cycles and sequence development concepts in the 1970"s, the available information is scattered. Cretaceous Sea Level Rise presents the current understanding and future directions of the research on Cretaceous sea level cycles in a single source, forming a reference work for beginners, graduates and postgraduates who are interested in this subject.Includes bibliographical references.Online resource; title from PDF title page (EBSCO, viewed November 24, 2015).Cretaceous Sea Level Rise delves into the question of whether the observed short-term sea-level changes are regional (tectonic) or global (eustatic) and determines their possible relation to climate cycles; to assess the role of feedback mechanisms, i.e. thermal expansion/contraction of seawater, subsidence due to loading by water, changing vegetation of the Earth System and to investigate the relation of sea-level highs and lows to ocean anoxia and oxidation events, represented by black shales and oceanic red beds, and to evaluate the evidence for ephemeral glacial episodes or other climate events. Though research has been, and is being, conducted in these fields since the introduction of sea level cycles and sequence development concepts in the 1970"s, the available information is scattered. Cretaceous Sea Level Rise presents the current understanding and future directions of the research on Cretaceous sea level cycles in a single source, forming a reference work for beginners, graduates and postgraduates who are interested in this subject.Front Cover; Cretaceous Sea Level Rise; Copyright Page; Contents; Preface; Acknowledgments; 1 Introduction; 2 Trends, Timings, and Magnitudes; 3 Causes and Mechanisms; 3.1 Endogenic Processes and Causes; 3.2 Eustasy and Related Causes; 3.2.1 Eustasy Under Greenhouse Conditions?; 3.2.2 Limno-eustasy; 3.2.3 Eustasy Due to Thermal Expansion-Contraction of Sea Water; 4 Methods, Tools and Techniques; 4.1 Sedimentary Proxies; 4.2 Physical Proxies; 4.3 Biological Proxies; 4.4 Geochemical Proxies; 4.5 Integrated Analyses for Documenting Sea Level Fluctuations; 5 Where It Stands and Where Is It Headed.Elsevie
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
Eustasy, high-frequency sea level cycles and habitat heterogeneity /
No full textEustatic High-Frequency Sea Level Cycles and Habitat Heterogeneity: Basinal-Regional-Global Implications presents the current understanding and future directions of the research on Cretaceous sea level cycles in a single source. This reference work is for beginners, graduates, and postgraduates who are interested in the subject and intend to venture into serious research. This hybrid text/reference is for beginners, academics, and professionals who intend to document sea level dynamics on long and short time scales and resultant habitat and paleobiodiversity changes.Includes bibliographical references.Front Cover; Eustasy, High-Frequency Sea-Level Cycles and Habitat Heterogeneity; Copyright Page; Contents; Preface; Acknowledgments; 1 Defining Habitat and Habitat Heterogeneity; 1.1 Introduction; 1.2 Definition of Habitat Heterogeneity; 1.3 Definition of "Space" in Habitat; 2 Sequences, Sea-Level Cycles, and Habitat Dynamics; 2.1 Sequences and Habitats; 2.2 Sea-Level Fluctuations and Environmental Parameters; 2.3 Environmental Perturbations and Habitat Changes; 3 Influence of Sea-Level on Facies and Habitat Heterogeneity; 3.1 Depositional Systems as Defined by End-Members.3.2 Scales of Depositional Systems3.3 Types of Depositional Systems; 3.4 Facies Types as Proxies for Habitat Heterogeneity; 4 The Cauvery Basin of South India: A Test Case; 4.1 Justification and Objectives; 4.2 Regional Geological Setting; 4.3 Material and Methods; 4.4 Tectonic Structures; 4.5 Lithofacies Succession and Distribution; 4.6 Barremian-Danian Relative Sea-Level Fluctuations; 4.7 Barremian-Danian Biotic Heterogeneity; 5 Depositional History and Habitat Heterogeneity; 5.1 Tectonic Influence on Habitat Dynamics; 5.2 Depositional History and Habitat Dynamics.6 Proxies for Habitat Heterogeneity and Dynamics6.1 Geochemical Indicators; 6.2 Chemostratigraphy as a Proxy; 6.3 Geochemical Proxies of Climate, Sea-Level, Sediment Influx; 6.4 Facies as Proxy for Habitat Heterogeneity and Dynamics; 7 Implications and Future Trend; 7.1 Biotic-Habitat Heterogeneity of the Cauvery Basin; 7.2 Local-Regional-Global Implications; 7.3 Future Trends and Recommendations; References; Back Cover.Online resource; title from PDF title page (EBSCO, viewed April 24, 2017).Eustatic High-Frequency Sea Level Cycles and Habitat Heterogeneity: Basinal-Regional-Global Implications presents the current understanding and future directions of the research on Cretaceous sea level cycles in a single source. This reference work is for beginners, graduates, and postgraduates who are interested in the subject and intend to venture into serious research. This hybrid text/reference is for beginners, academics, and professionals who intend to document sea level dynamics on long and short time scales and resultant habitat and paleobiodiversity changes.Elsevie
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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