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Supplementary dataset for the AGU publication 'Inherited Grain-size Distributions'
No full textThis repository contains supplementary datasets for the publication titled 'Inherited Grain-size Distributions: Effect on Heavy-mineral Assemblages in Modern and Ancient Sediments
Miocene provenance and drainage evolution of the northern Calabrian forearc basins, Southern Italy
No full textAbstract Northern Calabria forms part of the Calabrian Arc, a geologically complex region in southern Italy shaped by the convergence between the Eurasian and African plates. This convergence drove the closure of the Tethys Ocean and produced the subsequent phases of collisional and extensional tectonics. Thrusting during the Alpine orogeny produced extensive nappe stacking, followed by structural reorganization and exhumation during the Oligocene-Miocene. Tectonostratigraphically, the Apennine carbonate platform forms the lowest structural unit, overlain successively by the Liguride Oceanic Complex and the Calabride Complex, which includes the Sila nappe stack. Along Calabria’s eastern Ionian margin, forearc basins developed in response to the retreating subduction zone. To better constrain sediment routing pathways and regional uplift in northern Calabria from early to late Miocene, a multi-proxy provenance study was applied to four forearc basins: Rossano, Cirò, Crotone and Catanzaro. Quantitative heavy-mineral analysis, single-grain garnet and apatite chemistry, and apatite U–Pb chronology reveal spatial and temporal variations in sediment sources. Siliciclastic samples, spanning Aquitanian to Messinian in age, record changing contributions from a combination of low- to high-grade metamorphic and plutonic sources, including mafic Liguride units. Up-section shifts in sediment sourcing patterns indicate that Calabrian Arc exhumation and uplift, characterized by a rapid increase in the middle Miocene followed by a slow reduction in relief, played a pivotal role in controlling the timing and direction of sediment transport. This study demonstrates the benefits of multi-method provenance approaches to achieve valuable insights into relief build-up and demise, associated divide migration and sedimentary responses within a young and complex, zircon-poor orogenic arc system
Inherited Grain‐Size Distributions: Effect on Heavy‐Mineral Assemblages in Modern and Ancient Sediments
No full textHeavy‐mineral suites are used widely in sandstone provenance and are key when connecting source and sink. When characterizing provenance related signatures, it is essential to understand the different factors that may influence a particular heavy‐mineral assemblage for example, chemical weathering or diagenetic processes. Hydrodynamics, causing size‐density sorting, exert major control on the distribution of heavy minerals. Here, we highlight the effect of grain‐size inheritance, essentially the absence of certain grain sizes within a specific heavy‐mineral species, on two distinct types of sediments. Modern deposits from a high‐energy beach in NW Denmark give an analog for heavily reworked sediment, primarily controlled by hydrodynamic processes. In contrast, three Palaeogene turbidite successions in the Eastern Alps were sampled, presenting a more complex history that includes diagenesis. All samples were processed for their heavy‐mineral compositions using Raman spectroscopy, and several techniques applied to determine the effect of grain‐size inheritance. Results show that (a) even within the hydrodynamically well‐sorted beach and placer deposits, evidence of grain‐size inheritance is apparent, and (b) turbidites of variable heavy‐mineral composition show strong effects of grain‐size inheritance for several mineral species. Moreover, considerable intersample contrasts within single turbidite beds are observed. We enforce the importance of understanding grain‐size inheritance, as well as other processes effecting size‐density relations in clastic sediment that go well beyond purely hydrodynamic control of intrasample heavy‐mineral variability.Plain Language Summary
Heavy minerals are commonly found within sediments and sedimentary rocks and can tell us from which source regions the sediment may have originated. However, it is important to understand that the type, size, and abundance of particular heavy minerals can change depending on factors such as environmental conditions. The size, shape, and density of the heavy minerals also limits when and where they will settle and/or stay. A lack of big or small grains of a particular heavy mineral in the source rocks dictates the size of the minerals deposited; this is known as grain‐size inheritance. Using both ancient and modern sediment, we are looking for traces of grain‐size inheritance. Surprisingly, in all samples investigated we noted effects of grain‐size inheritance, for different heavy‐mineral types. The modern beach sediments, as expected, show more impact of hydraulic processes, but inherited grain sizes are still apparent. Within the ancient examples, grain‐size inheritance is more obvious, with further variations even observed between samples collected from the same area. Having identified this control on grain size, we can highlight the importance of understanding this effect when analyzing clastic sediments.Key Points
Understanding factors that can modify a heavy‐mineral assemblage is fundamental in provenance analysis
Heavy minerals of two distinct sedimentary environments were analyzed and compared to their “ideal” hydrodynamically sorted compositions
Several heavy‐mineral species of modern and ancient settings were identified to be influenced by grain‐size inheritance from the sourc
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
A Multi-Proxy Provenance Study of Eocene to Oligocene Sandstones in the Salin Sub-basin, Myanmar
Get PDFThe Salin Sub-basin, Myanmar, contains up to 15,000 metres of Cenozoic sediments, but their provenance remains ambiguous. Here, a multi-proxy provenance study that employed Raman Spectroscopy-assisted heavy mineral analysis, light mineral petrography, and U-Pb detrital zircon geochronology, is used to identify source areas and sediment pathways of nine samples from three formations of Eocene to Oligocene age. The heavy mineral assemblages are diverse and highly immature and indicate that sediments were principally provided from a range of igneous and metamorphic lithologies, with some recycling of older sediments. The metamorphic basement rocks in northern Myanmar are identified as a source in all three formations, suggesting that the headwaters of the sedimentary pathway were situated in this area. Detrital zircons overwhelmingly yield Cretaceous and Palaeogene ages. A population of Late Cretaceous and Palaeocene zircons could indicate input from the Mogok Metamorphic Belt, or a currently buried section of the Wuntho-Popa Arc; the diminishing of this signal by the end of the Rupelian suggests reduction in transport from the former, or burial of the latter. Late Cretaceous grains exhibit rounded and euhedral morphologies, suggesting input from recycled Wuntho-Popa Arc material via the sediments of the Chin Hills, and direct input from the Wuntho-Popa Arc, respectively. A persistent Palaeoproterozoic and Triassic signal in the Shwezetaw and Padaung Formations suggests provenance in the Pane Chuang Formation of the Indo-Myanmar Ranges, showing that by the early-mid Oligocene, the ranges were topographically prominent enough to be an important source of sediment for the Central Myanma
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