1,720,974 research outputs found
Approccio multidisciplinare per la valutazione del degrado in murature storiche: il caso del Castello di Mesola (Ferrara).
No full textThe Uplift of an Early Stage Collisional Plateau Unraveled by Fluvial Network Analysis and River Longitudinal Profile Inversion: The Case of the Eastern Anatolian Plateau
Full text linkOrogenic plateaus of continental collision zones exhibit landforms and fluvial networks that retain first-order information on their topographic evolution and vertical growth. The inversion of river longitudinal profiles allows to reconstruct the base level fall history of plateaus, supporting the study of landscape evolution in the frame of geodynamic models. The Eastern Anatolian Plateau (EAP) of the Arabia-Eurasia collision zone is a plateau at an early stage of development. It stands at similar to 2,000 m, presents endorheic basins, and is drained by three main river networks. Seismic data indicate a thinned lithospheric mantle that explains the late Cenozoic volcanic activity. Despite the number of studies on the EAP uplift, its history is still debated. In this study we investigated the EAP hydrography and topography, and we inverted the longitudinal profile of one of the main rivers: the Arax River. The results describe a high-standing, low-relief plateau drained by a hydrography, controlled by active tectonics. Longitudinal profiles and ?-plots illustrate rivers in disequilibrium with channel steepness increasing downstream. The elevation of marine deposits indicates a surface uplift of similar to 2,000 m, similar to 500 m of which are of residual topography. This upheaval occurred by two increases: the first one at 10-11 Ma with the opening of a slab window and the arrival of a mantle flow from Arabia and the second one at similar to 5 Ma with the continued inflow coupled with isostasy. Our results describe the early stage of collisional plateau development, distinguishing the contribution of deep processes and isostasy to the topographic growth
Editorial: Reaching New Heights: Recent Progress in Paleotopography
No full textAlthough mountain belts and orogenic plateaus occupy only a limited portion of the Earth's surface (about 4% above 2 km in elevation), they are among the most prominent landscape features with global implications for tectonic deformation, climate, hydrology, and biodiversity. Topographic growth locally modifies the crustal stress field and the locus of active deformation; it re-arranges fluvial networks and atmospheric circulation patterns; it generates highly asymmetric precipitation and marked temperature gradients, and favors the development of diverse ecosystems over geographically limited areas; it thus dramatically impacts biodiversity and the evolution of flora and fauna over geological scales.
In recent years, a growing number of studies have tried to investigate the chronology and amplitude of topographic growth in deep time (millions of years), using various field-, laboratory-, and computer-based approaches from a wide range of scientific disciplines. The accuracy and uncertainty associated with these approaches are still being discussed, and studies providing quantitative paleoaltimetry estimates remain rare despite their relevance. Moreover, most quantitative studies so far have concentrated on the youngest and most extensive mountain ranges such as the Himalayas or the American Cordilleras, while the topographic evolution of smaller or much older orogens remain virtually undocumented.
This Research Topic contains 11 articles covering a wide range of paleotopography research, from short reviews and perspectives of either established or innovative paleo-topographic approaches, new datasets and syntheses of topographic uplift in well-known and understudied areas, and outlooks on the future development and improvement of paleoaltimetry.
Botsyun and Ehlers present recent advances and caveats in high-resolution isotope-based general circulation models (iGCMs) to calibrate stable isotope paleoaltimetry approaches, a growing and dynamic direction for paleotopographic reconstructions. Hren and Ouimet propose a new method to quantify paleotopography based on the isotopic signature of organic molecular biomarkers integrated over river catchments. Following the recent development of triple oxygen analysis, Chamberlain et al. review the application of this method to crystalline rocks and their high potential for paleoaltimetry on the crystalline cores of mountain belts. Ibarra et al. propose to use triple oxygen on lacustrine sediment as a paleoaltimetry tool, which they combine with carbonate clumped isotope data to reconstruct the paleoelevation of Eocene Nevadaplano rocks (North American Cordillera).
Gébelin et al. report present-day stream water isotopic lapse rates from the west facing slopes of the equatorial Andes in Ecuador, underscoring that tropical regions can be targeted for future paleoaltimetry studies. Ingalls and Snell provide an exhaustive review of state-of-the-art and emerging tools to investigate the diagenetic alteration of carbonates, a crucial step in stable isotope paleoaltimetry, with an illustration of their impact on Tibetan paleoelevation estimates. McLean and Bershaw investigate the isotopic composition of carbonates while Kukla et al. focus on authigenic clays in paleosols from the John Day Formation (Eocene to Miocene), United States, in the rainshadow of the modern Oregon Cascades, with contrasting interpretations regarding the evolution of regional topography.
Beyond stable isotope paleoaltimetry, Montes et al. combine field mapping and detrital zircon geochronology to show that the northern and central Andes were separated between ca. 13–4 Ma by lowlands that connected this region with western Amazonia at ca. 3°N, providing a pathway for biotic exchange. Fox et al. examine the role of fluvial reorganization in the formation of elevated landscapes that resemble uplifted formerly contiguous low-relief landscapes. Taking the southeastern Tibetan highlands as an example, they propose that an interpolated paleosurface across low-relief remnants cannot be used to robustly measure geodynamic processes in space and time. Finally, Heitmann et al. review the recent paleoaltimetry work from the Colorado Plateau and propose several test studies to fill the gap in its uplift history.
In summary, this research topic presents new ideas, tools, and results on a wide range of aspects of the paleotopography of mountain and plateau regions around the world. It emphasizes that the future of paleoaltimetry has to be interdisciplinary and combine multiple proxies, considering the numerous uncertainties of individual tools. To increase their robustness and accuracy, the next generation of paleotopography studies will have to incorporate results from a variety of approaches, which is well-illustrated by the array of methods and applications in the eleven articles of this research topic
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
Rock-uplift history of the Central Pontides from river-profile inversions and implications for development of the North Anatolian Fault
No full textMajor strike-slip fault systems on Earth, like the North Anatolian Fault (NAF), play an important role in accommodating plate motion, but surprisingly little is known about how such structures evolve through space and time. Along the central sector of the NAF in the Central Pontides, transpression and crustal thickening along the northward restraining bend of the fault are thought to have generated rock-uplift rates of 0.2-0.3 km/Myr since at least 400 ka based on Quaternary marine and river terraces, while data from low-temperature thermochronology suggest that an enhanced exhumation phase occurred within the last 11 Myr. However, the precise onset of this faster uplift phase, which likely reflects deformation associated with the development of the central sector of the NAF, is poorly constrained. Here we define the spatiotemporal pattern of rock-uplift rates within the Central Pontides over the last -10 Myr by performing linear inversions of 19 river profiles that drain the northern margin of the Central Pontides, from the Sinop Range to the Black Sea. We use 21 new 10Be-derived basin-average denudation rates to calibrate an erodibility parameter, which we use to convert our & chi;-transformed river profiles into rock-uplift histories. Our results document an increase in rock-uplift rates after 10 Ma, with peak rates of -0.15-0.25 km/Myr occurring between 4 and 2 Ma. Moreover, the spatiotemporal pattern of uplift suggests that faster rock uplift started in the eastern part of the Sinop Range and migrated westward over a period of ca. 2 to 2.5 Myr, which we relate to the westward propagation of the NAF through this sector at a rate of 74 & PLUSMN; 13 km/Myr. In the context of previously published constraints on the westward propagation of the NAF starting in eastern Turkey at -12 Ma, our results suggest differences in fault-propagation rates that coincide with differences in the orientation of the NAF relative to plate -convergence velocity vectors. Fault segments with higher obliquity appear to have propagated at rates up to 2-fold slower than those oriented more parallel to the plate-convergence vector. & COPY; 2023 Elsevier B.V. All rights reserved
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
Middle to late Miocene Middle Eastern climate from stable oxygen and carbon isotope data, southern Alborz mountains, N Iran
No full textThe Alborz mountains of northern Iran intercept and divert the northern hemisphere westerlies carrying moisture from the Mediterranean and Black Sea, and form an orographic barrier to moisture sourced to the north in the Caspian Sea. This implies that terrestrial deposits along the southern Alborz mountains (leeward side of northerly winds and windward side of westerlies with the respect to Tibet and other mountainous terrain in the Himalayan-Karakoram realm) potentially track changes in past moisture and erosional regimes and mirror rainfall patterns. Here, we present results of a stable isotope analysis and clay mineral study of the Miocene (ca. 17.5-7.6 Ma) Upper Red Formation in the foreland of the southern Alborz mountains. The changes recorded by stable oxygen and carbon isotope data from pedogenic and lacustrine/palustrine carbonate in the southern Alborz mountains suggest: 1) an increase in aridity possibly related to the evolution of the Alborz orographic rain shadow, which became more efficient between 17.5 and 13.2 Ma; 2) a steady increase in precipitation between 13.2 and 10.3 Ma with a significant increase in rainout along the southern slope of the Alborz mountains between 11 and 10.3 Ma, possibly related to perturbations in atmospheric circulation pattern in the northern hemisphere as suggested by coeval wetter phases in southern Europe; and 3) a decrease in aridity from ca. 9.6 to 7.6 Ma, possibly reflecting an increase in the seasonality of precipitation. Based on environmental and climatic changes observed across southern Asia and India starting from ca. 10 Ma, we speculate that the topographic evolution of the Himalayan-Tibetan system might have affected the late Miocene climate in Middle East
Mineralogical study of historical bricks from the Great Palace of the Byzantine Emperors in Istanbul based on powder X-ray diffraction data
No full textThis study concerns the Quantitative Phase Analysis (QPA) of historical bricks coming from the complex of the Great
Palace of the Byzantine Emperors in Istanbul. The studied samples are characterised by different chemical compositions (low and high calcium content), variable firing temperatures and different amounts of soluble salts as damage products.
In the low-Ca samples, the decrease of the phyllosilicate content (from 23.4 to 6.9 wt%) is associated to the increase of the
amorphous fraction (from 24 to 48%). This clear negative correlation between the phyllosilicate content and the amorphous fraction indicates that in low-Ca systems vitrification processes are overwhelming with respect to nucleation and recrystallisation processes. By contrast, high-Ca samples present newly formed Ca(Mg) silicates (diopside from 5.7 to 27.2%; anorthite from 1.4 to 8.7%) and aluminium silicates (gehlenite only in two samples, 6.2 and 7.7%) associated to the decrease of quartz (from 27.7 to 11.5%), phyllosilicate (from 6.5% until complete break down) and amorphous (from 30 to 14%) phase fractions. These findings support the role played by the CaO(MgO) content deriving from carbonates decomposition which reacts with Al2O3 and SiO2 oxides from dehydroxylated clay minerals and quartz grains. The above results have been obtained by X-ray powder diffraction data using the combined Rietveld refinement – internal standard method in order to estimate both the crystalline and the amorphous phase fractions. In addition, the coexistence of two distinct plagioclases in high-Ca samples was modelled as follows: a primary albite, which tends to incorporate Ca during the firing process as demonstrated by the increasing of gamma crystallographic angle, and a newly formed anorthite. Finally, by difference between the X-ray fluorescence data and the chemical compositions inferred by QPA, it proved possible to roughly estimate the residual chemical composition attributable to the amorphous fraction. On the basis of our data,we believe that Rietveld refinement combined with the internal standard method represent a powerful tool to better characterise complex polycrystalline and amorphous mixture as in the case of historical bricks
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