1,721,070 research outputs found
Data for: Late Glacial to Holocene volcanism of the Jom-Bolok (Sayan Mountains, Siberia) recorded by microtephra layers of the Lake Kaskadnoe-1 sediments
No full textThis article presents first tephrochronological data on the volcanic activity in the valley of the Jom-Bolok River (East Sayan Mountains, Siberia), which is the largest manifestation of the Holocene eruptions in Central Asia. The data results from our study of the proglacial Kaskadnoe-1 Lake situated near the Jom-Bolok basalt field. The lake sediments include a series of tephra-rich layers. Radiocarbon dating of the lake sediments provided a robust age model which allowed us to build timing of eruptions formed the Jom-Bolok field. We recognize two large phases separated by almost 5 thousand years dormant phase. The first phase is traced back to ca. 14.3 cal ka BP and lasted until 6.3 ka BP. Ten clusters of microtephra layers in the sediments of the first phase show 300-800 years recurrence of the volcanic events weakening topward; the event of 14.3 - 13.3 cal ka BP probably represent the strongest eruptions of the Jom-Bolok. The second phase started ca. 1.6 cal ka BP and highly likely continues in our days. Its strongest eruptions occurred between 1.6 and 0.8 cal ka BP with periodicity of 200 years. This tephrostratigraphy shows a multiplicity of the Jom-Bolok volcanic events amplifying the earlier obtained scheme resulted from investigations of the stratified basalts, pyroclasts and lake damming events. Additionally, we indicate a possible influence of the Jom-Bolok volcanic activity on the regional and global climatic changes
Arshan palaeoseismic feature of the Tunka fault (Baikal rift zone, Russia)
No full textThe traditional concept of the rift development of flank depressions in the Baikal rift zone is now doubted in view of some indicators for compression deformations identified by the seismogeological and geodetic methods. Besides, the paleoseismological investigations revealed seismogenic strike-slips and reverse faults in the Tunka fault zone that is a major structure-controlling element of the Tunka rift depression. However, a detailed study of the upslope-facing scarp in the Arshan paleoseismogenic structure zone has shown that its formation might be due to rift mechanism of basin formation. Age estimation has been made for the previously unknown pre-historic earthquake whose epicentral area coincides with the western flank of the Arshan paleoseismogenic structure. Judging from previously determined ages of paleoearthquakes, the mean recurrence period for faulting events on the central Tunka fault is 2780–3440 years
LA‐ICP‐MS analysis of rare earth elements in tooth enamel of fossil small mammals (Ust‐Oda section, Fore‐Baikal area, Siberia): paleoenvironmental interpretation
No full textLate Quaternary geology of the Tunka rift basin (Lake Baikal region), Siberia, Russia
No full textThe objective of this research is to obtain a better understanding of the evolution of the Tunka rift basin, part of the Baikal rift zone, and how it relates to the overall geologic history of the region, particular for the Quaternary period. The tectonically active Baikal rift zone began forming over 50 million years ago and continues today. In the Tunka basin, during the Oligocene and Middle Pliocene, relatively weak tectonic disturbances took place and thick accumulations of organic-rich sands, silts, and clays were deposited in lacustrine–marshy subtropical environments. Tectonism increased between the Miocene and Pliocene and thick units of coarse alluvium and floodplain sediments were deposited. During the Late Pliocene–Quaternary, tectonism formed basins that are now filled with a variety of coarse clastic materials. Early and Middle Pleistocene sediments are poorly exposed, covered by widespread Late Pleistocene deposits. Three Late Pleistocene sedimentary facies dominate: boulder–pebble gravels (proluvial, glacial fluvial, and alluvial sediments), alluvial sand, and loess-like sediments with associated slope deposits altered by post-depositional wind erosion. The relationship between these complexes, including radiocarbon and other chronological data and fauna and flora remains, indicates that they began forming c. 70 000 yr ago. Paleosols, glacial deposits and cryogenic material indicate that at times the climate was cool or cold. During the early Late Pleistocene renewed tectonism took place causing increased deposition of coarse sediments. The middle Late Pleistocene deposits consist mostly of sandy, floodplain alluvium. By the end of the Late Pleistocene–Holocene, alluviation was reduced and replaced by a high degree of erosion and aeolian depositio
Late glacial and Holocene environmental change reconstructed from floodplain and aeolian sediments near Burdukovo, Lower Selenga River Valley (Lake Baikal region), Siberia
No full textFloodplain and aeolian sediment snear Burdukovo reveal a detailed record of Holocene environmental change in the lower Selenga River Valley (Lak eBaikalregion, Siberia). During the late Pleistocene and early Holocene fine-grained alluvium accumulated on the floodplain followed by a period of increased landform stability and subsequent pedogenic formation. This part of the stratigraphical sequence yielded rich assemblages of terrestrial molluscs, which increase in species diversity from early pioneer communities with about ten taxa to levels containing over twice that number. The land snail assemblages also record an episode of relatively drier local habitats prior to ?9.2 ka BP with subsequent wetter conditions lasting until ?8.0 ka BP. This was followed by an abrupt and sustained change in floodplain deposition, shifting from overbank alluvium to aeolian sedimentation, within which a series of weakly developed soil horizons formed during the middle and lateHolocene periods. The onset of aeolian processes and relatively drier conditions in the middle Holocene at Burdukovo coincides with major changes observed both in other regional palaeoenvironmental proxy records and in local archaeological sequences, although it is still not clear how the two are linke
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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