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Phreatic overgrowths on speleothems: a useful tool in stuctural geology in littoral landscapes. The example of Eastern Mallorca (Balearic Islands)
No full textAlong the eastern coast of Mallorca, many littoral caves partly filled with brackish waters occur. The most peculiar aspect of these caves
is the presence of abundant phreatic overgrowths formed on pre-existing supports located at the underground pools’ water table, which
corresponds to the present sea level. Besides a specific geomorphological interest, these subaqueous speleothems provide an excellent record
of Quaternary sea level stands. The clear relation between phreatic speleothem growth and the contemporary sea level allows the control
of the tectonic evolution of an area, by comparing speleothems’ ages and heights with the regionally established eustatic curves. In the
studied region different altimetric positions of coeval phreatic speleothems suggest the existence of a recent tectonic activity. The
characteristics and chronology of this tectonic event are the objectives of this paper, pointing out at the same time the potential of phreatic
speleothems in structural geology investigations. Along the coastline of the studied area, alignments of phreatic speleothems attributed to
high sea stands 5a, 5c and 5e are recorded at increasing elevations northwards. This is an evidence of a significant tectonic tilting that took
place, at least partially, after substage 5a because phreatic speleothems of this substage are now located at different altitudes. Considering
that tectonic tilting has been continuous from post-substage 5a (approximately 85 ka) until now, and that normal displacement is
approximately of 1.5 m, the average minimum velocity of the tilting can be estimated about 0.02 mm/year in the southern part with respect
to the north end. Data obtained from phreatic speleothems have been compared with other regional, stratigraphical, geomorphological and
tectonic evidence that all together point to the same existence of the postulated tectonic tilting. Consequently, phreatic speleothem
investigation results in a new method that allows the quantification of average velocities of tilting as well as other tectonic movements with
high precision. This methodology can be extended to any littoral karstic landscape where phreatic speleothems are present
Late Quaternary Paleoclimatic and Paleoenvironmental changes in the Tyrrhenian Sea
No full textPaleoclimatic and paleoenvironmental changes that occurred in the Tyrrhenian Sea during the last 26 kyr are investigated in this paper. Isotopic and micropaleontological studies on foraminifers, supported by radiometric and sedimentological analyses, are carried out in a high-resolution core from the upper continental Tyrrhenian slope, near the Ombrone River mouth. The location of the studied core allows us to obtain both paleoclimatic data and results concerning the transgression caused by the last deglaciation, while previous paleotemperature reconstructions are based on deep-sea, or on coastal proxies like coral reefs and spelean serpulids. Cumulative curves of cold and warm-water species presented were derived from Hierarchical Cluster Analysis (HCA). Comparing these curves with those of Globigerina bulloides d18O and d13C results on paleoclimatic events of the Late Quaternary were obtained. Faunal and isotopic proxies concur and were used to isolate seven climatic zones, corresponding to the well-known climatic episodes of the last glacial—post-glacial cycle. During the Late Glacial, three main climatic episodes were recognised: Last Glacial Maximum (LGM), centred at about 22.5 kyr BP, during which our proxies indicate the lowest temperatures; Bølling-Allerød, between 15.0 and 12.5 kyr BP, characterised by rapid climatic fluctuations; Younger Dryas (YD), centred at about 11.4 kyr BP, with Sea Surface Temperature (SST) not dissimilar to that of LGM. A brief time span of about only 500 years separates the YD climax from the first appearance of seasonality that is typical of Holocene. On the whole, the transition between glacial peak and full Holocene conditions spans about 1000 years. Foraminiferal, isotopic and sedimentological data agree in excluding important bathymetric changes during glacial times. A rapid sea-level rise is recorded at the onset of the Holocene, with a mean rate of about 23 mm/yr calculated between 10.9 and 8.3 kyr BP. Three distinct phases of water circulation regimes were evidenced in the course of Holocene. During Pre-boreal and Boreal chronozones (10.9–8.3 kyr BP) a marked seasonality has been recognised. It corresponded to a homogeneous water column, favoured by efficient vertical mixing during the winter and by warm stratified water column and oligotrophic surface waters during the summer. Both faunal and isotopic record indicate, from 8.3 to 5.2 kyr BP, well-stratified water column witha low-salinity layer in surface waters, probably marking its climax at 6.2 kyr BP. Suchconditions correspond to the deposition of sapropel S1 in the eastern Mediterranean Sea. The subsequent paleoceanography is characterised by the establishment of the winter convection and vertical mixing typical of the Modern Tyrrhenian Sea
Dataciones Th/U de espeleotemas freáticos controlados por el nivel marino, procedentes de cuevas costeras de Mallorca (España)
No full textA 26 ky paleoenvironmental and paleoclimatic record using foraminiferal and isotope constraints from Tyrrhenian Sea core.
No full textNoves dades sobre el nivell marì a Mallorca durante el darrer interglacial: datacions Th/U d’alta precisiò d’espeleotemes freatics litorals.
No full textLate Pleistocene Paleoclimates And Sea-Level Change In The Mediterranean As Inferred From Stable Isotope And U-Series Studies Of Overgrowths On Speleothems, Mallorca (Spain)
No full textEls espeleotemes freatics de les coves litorals de Mallorca: canvis de nivell de la Mediterrania i paleoclima en el Pleistoce Superior.
No full text
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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