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Alluvial fans along the coastal Atacama Desert - landforms, processes, and evolution
No full textAlluvial fans represent the dominant sedimentary systems within and along the margins of mountain regions where laterally confined, sediment-rich flows enter open plains or broader valleys. Successive aggradation creates a fan-shaped depositional landform featuring a complex internal architecture. Due to the direct coupling of alluvial fans to the source area, they are principally simple sediment routing systems and ideal archives to study local fluvial morphodynamics but also long-term landscape responses to (palaeo) climatic variability, tectonic activity, and base level changes. In most settings, however, it remained challenging to decipher these allogenic environmental controls. Along the coast of the hyperarid Atacama Desert in northern Chile (20.5°S-25.5°S), alluvial fans radiate from the steep western flank of the Coastal Cordillera, presenting the source area, over the narrow Coastal Plain, the sink. In the distal part, the coastal alluvial fans (CAF) interact with the marine environment, which forms an additional external control. In contrast to the last major alluvial activity in the interior Atacama Desert, dating back to the Miocene to Pliocene, the onset of CAF formation is much younger and CAF show a higher recent activity. However, the timing of their activity beyond the Holocene has barely received any attention yet. A major influence of climate on CAF formation has been proposed for a small part of the coastal Atacama; however, the interplay of climate, lithology, and tectonics in conjunction with strong, marine-driven base-level changes is still insufficiently explored. Hence, the CAF of the Atacama Desert are investigated in this comprehensive study as archives for recent to past sediment transport dynamics under coupled allogenic forcing. For this purpose, the CAF morphology as well as sedimentology, primary processes constructing the alluvial fans, relationships between the CAF systems’ hydromorphometry and the prevailing environmental characteristics (climate, tectonics, and source-area lithology), and the timing of their Quaternary evolution were assessed. While detailed field studies were concentrated on five key sites, overarching large-scale analyses of regional climatic and geologic geodata as well as geomorphometric analyses included 123 CAF systems.Results reveal that alluvial fans along the coastal Atacama Desert are in an overall advanced evolutionary state featuring voluminous aggradation and in approximately half of all cases also significant to deep entrenchment. Detailed geomorphological mapping and morphometric terrain analysis at the CAF complex Guanillos (21.97°S), enabled - besides the introduction of a multi-phase morphostratigraphic model comprising the fan’s prograde evolution and successive incision - to infer debris flows as the main depositional process in this hyperarid coastal setting. The morphological evidence is further supported by the CAF stratigraphy described in detail at five sites. Secondarily, hyperconcentrated flows were found to contribute to a large extent to the CAF aggradation. In contrast, sheetfloods are of negligible relevance, which is in accordance with previous sedimentological observations. Functional relationships between hydromorphometric catchment characteristics, the frequency of extreme precipitation events, fault density, and source-area lithology suggest a primarily climatic control on the CAF morphodynamics. Mostly restricted to catchments draining the western flank of the Coastal Cordillera, a higher frequency of precipitation extremes correlates positively with morphometric parameters indicating an increased susceptibility to debris flows (mean catchment gradient and basin relief ratio) as well as geomorphic catchment maturity. Spatial trends in catchment hydromorphometry and maturity reflect the major climatic source of rainfall events capable of creating effective sediment mobilization: frontal systems and cut-off lows which originate from the extratropical austral Westerlies and become increasingly rare towards the north. Furthermore, an increasing density of Loma vegetation can be observed towards higher latitudes so that possible feedback mechanisms of biota on sediment supply need to be considered for the southern CAF catchments. The relationships between climate and CAF morphodynamics are only seen in the geomorphometry of catchments characterized by a high degree of sediment connectivity and generally do not cut back far into the hinterlands of the Coastal Cordillera. Reflecting the strongly reduced influence of the Pacific precipitation source to the E, this sharp longitudinal climatic transition is governed by the orographic effect of the Coastal Cordillera’s steep topography. In contrast, source-area lithology could be excluded as a major controlling factor for CAF depositional processes along the coastal Atacama Desert. An important indirect influence of tectonics, however, can be seen in the long-term (neo)tectonic activity within the Coastal Cordillera, which in turn shapes catchments and controls the topography. CAF aggradation - those in the Late Pleistocene dated within the context of this study - shows peaks during the marine isotope stage (MIS) 5 (95-80 ka), MIS 3 (60-45 ka), Last Glacial Maximum (LGM) (35-20 ka), and Holocene (⪅7 ka). Those phases all coincide with more humid periods related to (i) warmer sea-surface temperatures (SST) of the SE Pacific provoking a southward shift of the Inter-Tropical Convergence Zone (ITCZ) in MIS 5 and parts of MIS 3, (ii) a weakening of the SE Pacific anticyclone and equatorward shift of the austral Westerlies during the LGM, and (iii) the onset of the modern El Niño-Southern Oscillation (ENSO) in the Middle Holocene characterized by positive SST during El Niño, which in turn favours convection of northward reaching atmospheric humidity and thus torrential rainfall. The coupling of CAF palaeoactivity to wetter phases implies that alluvial fan aggradation in the hyperarid Atacama Desert is primarily controlled by climate and is strongly transport-limited. At the CAF key site Botija (24.57°S), incision of the main channel occurred since the late MIS 3 to early LGM and can be interpreted as either a climate-driven effect due to the northward shift of the Southern Westerlies in MIS 2, the result of sudden base-level fall due to short-term megathrust earthquakes, or simply internal alluvial fan dynamics governed by autogenic controls. Regarding the onset of Pleistocene CAF formation, it cannot be excluded that remnants older than MIS 5 are buried under the younger, dated deposits. Further geochronological data along the coast is thus required to check, whether the widespread geomorphic changes of the CAF are a systematic response to an allogenic environmental control. Nonetheless, the CAF represent crucial archives for the Late Quaternary palaeoclimate of the hyperarid Atacama Desert, which preserve the climatic changes driven by the SE Pacific Ocean to a much higher degree than the interior alluvial fans. Besides the dominant control of climate on CAF evolution, tectonic impulses exert a significant short-term influence by sudden large-magnitude earthquakes changing the CAF base-level independently of eustatic sea-level changes. Against this background, mean Late Quaternary coastal uplift rates between ~0.06 and ~0.57 m/ka were derived from the datings of the elevated marine terraces
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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