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Changes in dolomitization patterns between Norian and Rhaetian in the Southern Tethys realm: clues to the dolomitization of the Dolomia Principale
No full textSpecial Publication of the International Association of Sedimentologists n°2
Crystallization pathways in the Great Artesian Basin (Australia) spring mound carbonates: Implications for life signatures on Earth and beyond
Full text linkRecent studies of continental carbonates revealed that carbonates with similar fabrics can be formed either by biotic, biologically-induced, biologically-influenced or purely abiotic processes, or a combination of all. The aim of this research is to advance knowledge on the formation of carbonates precipitated (or diagenetically altered) in extreme, continental environments by studying biotic versus abiotic mechanisms of crystallization, and to contribute to the astrobiology debate around terrestrial analogues of Martian extreme environments. Both fossil (upper Pleistocene to Holocene) and active carbonate spring mounds from the Great Artesian Basin (South Australia) have been investigated. These carbonates consist of low-Mg to high-Mg calcite tufa. Four facies have been described: (i) carbonate mudstone/wackestone; (ii) phytohermal framestone/boundstone; (iii) micrite boundstone; and (iv) coarsely crystalline boundstone. The presence of filaments encrusted by micrite, rich in organic compounds, including ultraviolet-protectants, in phytohermal framestone/boundstone and micrite boundstone is clear evidence of the existence of microbial mats at the time of deposition. In contrast, peloidal micrite, despite commonly being considered a microbial precipitate, is not directly associated with filaments in the Great Artesian Basin mounds. It has probably formed from nanocrystal aggregation on colloid particulate. Thus, where biofilms have been documented, it is likely that bacteria catalyzed the development of fabrics. It is less certain that microbes induced calcium carbonate precipitation elsewhere. Trace elements, including rare earth element distribution from laminated facies, highlight strongly evaporative settings (for example, high Li contents). Carbon dioxide degassing and evaporation are two of the main drivers for an increase in fluid alkalinity, resulting in precipitation of carbonates. Hence, although the growth of certain fabrics is fostered by the presence of microbial mats, the formation of carbonate crystals might be independent from it and mainly driven by extrinsic factors. More generally, biological processes may be responsible for fabric and facies development in micritic boundstone whilst micrite nucleation and growth are driven by abiotic factors. Non-classical crystallization pathways (aggregation and fusion of nanoparticles from nucleation clusters) may be more common than previously thought in spring carbonate and this should be carefully considered to avoid misinterpretation of certain fabrics as by-products of life. It is proposed here that the term ‘organic-compound catalyzed mineralization’ should be used for crystal growth in the presence of organic compounds when dealing with astrobiological problems. This term would account for the possibility of multiple crystallization pathways (including non-classical crystallization) that occurred directly from an aqueous solution without the direct influence of microbial mats
Changes in dolomitization patterns between Norian and Rhaetian in the Southern Tethys realm: clues to the dolomitization of the Dolomia Principale
No full textSpecial Publication of the International Association of Sedimentologists n°2
Late Holocene annual growth in three Alpine stalagmites records the influence of solar activity and the North Atlantic Oscillation on winter climate
No full textAnnual growth rates and the ratio of dark to light-colored calcite within single annual laminae in three
contemporaneously deposited Holocene speleothems from Grotta di Ernesto, an Alpine cave in northern Italy,
respond to changes in surface temperature rather than precipitation. Based on monitoring of present-day calcite
growth, and correlation with instrumental data for surface climatic conditions, we interpret a higher ratio of dark to
light-colored calcite and the simultaneous thinning of annual laminae as indicative of colder-than-present winters.
Such dark and thin laminae occur in those parts of the three stalagmites deposited from AD 1650 to 1713 and from
AD 1798 to 1840, as reconstructed through lamina counting. These periods correspond to the well-known Maunder
and Dalton Minima of solar activity. An 11-yr cyclicity in growth rate, coupled with reduced calcite deposition during
the historic minima of solar activity, is indicative of a solar influence on lamina thickness. Spectral analysis of the
lamina thickness data also suggests that the North Atlantic Oscillation variability influenced winter temperatures.
Based on the present-day controls on cave calcite formation, we infer that high-frequency changes in solar activity
modulated the seasonal duration of soil CO2 production
Climate variability in the SE Alps of Italy over the past 17000 years reconstructed from a stalagmite record.
No full textThe European Alps is a region very sensitive to Dryas (YD) marked the end of the Palaeolithic painclimatic
change (Beniston & Jungo 2002), and it is terso A better insight into the climate evolution of the
important to extend the existing climate records as far SE European Alps from the Last Glacial Maximum
back in rime as possible to detect any anthropogenic would greatly improve our understanding of Alpine
climate signals. At present, there is a large set of history. Rere we present an exceptional c. 17 kyr
palaeoclimate and climate data from the CentraI and speleothemr ecord from the southeasternm argin of the
Western Alps, but a fragmentary record from the ltalian Alps.
Eastern Alps (cf. Davis et al. 2003 and references
therein). A stalagmite record from northem ltaly
(McDermott et al. 1999) suggested that the CentraI. .
Alps had a similar Rolocene climatic evolution as the Samplmg and analytlcal procedures
JUTa Mountains and the French Alps. The eastern sec- G h. l tI ' tor of the ltalta..ne oAglrpasp ltes at the boundary between the lca se mg
CentraI and Southern European climate regions as The 27-cm-high, candle-shaped, stalagmite SVI was
defined by pollen data (Davis et al. 2003) and, there- sampled in Grotta Savi, a cave located at 441 m a.s.l.
fore, may show different climate evolution with north of Trieste (4S03ios"N, 13°S3'10"E) (Fig. l).
respect to the CentraI and Western Alps. The Eastern The outer surface of the stalagmite was whitish,
ltalian Alps bave great pre-history importance, which translucent and wet, a typical feature of active
is documented by abundant archaeological evidence stalagmites from the southem watershed of the Alps.
for both indigenous and imported cultural 'packages' At the time of removal, SVI was fed by a constant
(Mithen 2003). In the Dalmeri Shelter site, at 1240m drip (c. 10drops/min) from a stalactite growing about
a.s.l. in NE ltaly, a unique finding of painted stones 30m above the stalagmite. The Savi cave is cut in
dated at c. 13cal.kyr BP, which show lberian fissuredlimestoneoverlainbythin«SOcm)grassland
naturalistic influence (Dalmeri et al. 2004), seems to soil cover, a situation which optimizes the potential for
support Mithen's (2003) hypothesis that the Younger Dryas (YD) marked the end of the Palaeolithic painters. A better insight into the climate evolution of the SE European Alps from the Last Glacial Maximum would greatly improve our understanding of Alpine history. Here we present an exceptional c. 17 kyr speleothem record from the southeastern margin of the Italian Alps
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
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