1,720,985 research outputs found
Spatial and temporal variability of the benthic foraminiferal assemblage in a low salinity environment (Stavns Fjord, Denmark).
No full textModern analogue faunal distribution is increasingly being used in fossil foraminiferal studies to provide quantitative estimates of ancient environmental conditions, requiring an accurate assessment of modern taphonomic assemblages. The aim of this work was to create a local foraminiferal database for sea-level reconstruction. Over one year, we analysed living (stained) and dead benthic foraminiferal assemblages, including soft-walled
monothalamous taxa, along a transect (six sites at intertidal to subtidal elevations) in Stavns Fjord, a brackish microtidal shallow-water lagoon, located in the southern Kattegat Sea (Denmark). For each station, key environmental parameters like salinity, temperature, pH and vegetation cover were recorded. Loss on ignition and grain size of the sediment substrate were determined in the lab. Stavns Fjord has a diverse living foraminiferal assemblage with 39 species identified, of which 32 are soft-walled
species. The soft-wall foraminifera constitute more than >60% of the total assemblage except in the most landward station where their abundance varied between 0-18%. Most of the species counted in these samples are previously unreported from the Kattegat area; all are undescribed at the species level and in most cases also at the generic level. The dead foraminiferal assemblage yielded very low diversity assemblage with 6 agglutinated species
(dominated by Jadammina macrescens and Trochammina inflata) and two calcareous taxa (Elphidium williamsoni and Ammonia sp.).
The living agglutinated and calcareous species show a general distributional trend with J. macrescens dominating landward and the calcareous species (E. williamsoni and Ammonia sp.) dominating seaward. In the dead assemblage, the most landward station is still dominated by J. macrescens (abundance > 508 individual/10 cm2), whereas the other sites are barren or with less than 30 individual/10 cm2. The landward edge of the transect
shows the lowest interannual variability (128 to 152 individual/10 cm2) whereas a higher interannual variability is recorded on the sandflats further out in the lagoon. Major taphonomic changes occurred during the transition from living to dead assemblage in the seaward station:
all the soft-wall taxa disappeared, and calcareous species, as well as many agglutinated species were affected by intensive in situ dissolution. Nevertheless the taphonomical assemblages still gives a fairly reliable record of the ecology of the environments. This study demonstrates that it is important to compare data on living and dead assemblages in order to determine the pathways to fossilization and to evaluate the amount of information loss through taphonomic change before quantifying paleoenvironmental variations
Spatial and temporal variability of the benthic foraminifera assemblage in a low salinity environment (Stavn Fjord, Denmark).
No full textModern analogue faunal distribution is increasingly being used in
fossil foraminiferal studies to provide quantitative estimates of
ancient environmental conditions, requiring an accurate
assessment of modern taphonomic assemblages. We analysed
living (Rose Bengal stained) and dead benthic foraminiferal
assemblages, including soft-walled monothalamous taxa, at six
sites in Stavns Fjord during four different months (November
2011, May 2012, June 2012, and November 2012). Several
environmental variables were recorded: salinity, temperature,
pH, loss on ignition, grain size and vegetation cover. The aim of
this work was to create a foraminiferal database for sea-level
reconstruction in the Kattegat area. Stavns Fjord is a microtidal
semi-enclosed shallow-water lagoon, located in the southern Kattegat (Denmark). Stavns Fjord has a diverse living
foraminiferal assemblage with 39 species identified, of which 32
are soft-walled species. The soft-wall foraminifera constitute
more than >60% of the total assemblage except in the most
landward station where their abundance varied between 0-18%.
Most of the species counted in these samples are previously
unreported from the Kattegat area; all are undescribed at the
species level and in most cases also at the generic level. The
dead foraminiferal assemblage yielded very low diversity
assemblage with 6 agglutinated species (dominated by
Jadammina macrescens and Trochammina inflata) and two
calcareous taxa (Elphidium williamsoni and Ammonia sp.). The
living agglutinated and calcareous species show a general
distributional trend with J. macrescens dominating landward and
the calcareous species (E. williamsoni and Ammonia sp.)
dominating in the seaward side. In the dead assemblage, the
most landward station is still dominated by J. macrescens
(abundance > 508 individual/10 cm2), whereas the other sites
are barren or with less than 30 individual/10 cm2. The landward
edge of the transect shows the lowest interannual variability,
varying from 128 to 152 individual/10 cm2, where as higher
interannual variability is recorded in the tidal mud stations further
out in the lagoon. Major taphonomic changes occurred during the
transition from living to dead assemblage in the seaward station:
all the soft-wall taxa disappear, and calcareous species, as well
as many agglutinated species are affected by intensive in situ
dissolution. Nevertheless the taphonomical assemblages still give
a fairly reliable record of the ecology of the environments. This
study demonstrates that it is important to compare data on living
and dead assemblages in order to determine the pathways to
fossilisation and to evaluate the amount of information loss
through taphonomic change, before quantifying
paleoenvironmental variations
Coastal lagoon sediments and benthic foraminifera as indicator for Holocene sea-level change: Samsø, southern Kattegat
No full textCoastal lagoon sediments as a recorder of Holocene landscape evolution and sea-level development: Samsø, southern Kattegat Sea, Denmark.
No full textConfined shallow-water environments are encountered many
places along the coast of the inner Danish waters. Despite their
common occurrence, these environments have rarely been
studied as sedimentary archives. In this study we set out to trace
back changes in relative sea-level and associated geomorphological
responses in sediment cores retrieved from coastal lagoon
systems on the island of Samsø.
In the mid-Atlantic period, the post-glacial sea-level rise
reached central Denmark. Waves, currents and tides began to
erode the unconsolidated moraine and melt-out deposits. This
initiated the formation of coastal barriers and marine lagoonal
sedimentation. Until present day, the ongoing isostatic uplift
caused a gradual drop of relative sea-level resulting in shoreline
accretion and lagoonal infilling.
Stratigraphy, grain-size distribution, fossil and organic matter
content of cores retrieved from the lagoons were analyzed and
compared. Age control was established using radiocarbon and
optically stimulated luminescence dating.
Our data produced a surprisingly consistent pattern for the
sedimentary successions found in the lagoons. The period of
initial transgression can be identified as the onset of deposition
of fine-grained, organic-rich sediments. However, radiocarbon
dates evidence a punctuation of these deposits further upcore.
Grain-size analysis suggests that the reworking and abrasion of
the lagoon sediments resulted from the gradual lowering of the
wave-base. The core sequence is topped off-by marine sands
and wind-blown deposits. Based on these findings, we suggest
a conceptual model that allows inferring age and elevation of
transgressive and regressive stages from the lagoon cores.
The common occurrence of similar environments distributed
along gradients of isostatic uplift/subsidence (approximately
+0.7 to -0.5 mm/yr) in the south-western Baltic, makes coastal
lagoon systems a valuable archive for the reconstruction of Holocene sea-level and coastal evolution
Coastal lagoon systems as indicator of Holocene sea-level development in a periglacial soft-sediment setting: Samsø, Denmark.
No full textConfined shallow-water environments are encountered many places along the coast of the inner Danish waters.
Despite their common occurrence, these environments have rarely been studied as sedimentary archives. In this
study we set out to trace back changes in relative sea-level and associated geomorphological responses in sediment
cores retrieved from coastal lagoon systems on the island of Samsø, central Denmark.
In the mid-Atlantic period, the post-glacial sea-level rise reached what is today the southern Kattegat Sea. Waves,
currents and tides began to erode the unconsolidated moraine material and melt-out deposits. This initiated
sedimentation in adjacent coastal lagoons and further supported the formation of coastal barriers. Until present
day, the ongoing isostatic uplift caused a continuous drop of relative sea-level resulting in shoreline accretion and
successive lagoonal infilling.
Stratigraphy, grain-size distribution, fossil and organic matter content of cores retrieved from the lagoons were
analyzed and compared. Age control was established using radiocarbon and optically stimulated luminescence
dating.
Our data produced a surprisingly consistent pattern for the sedimentary successions found in the lagoons. The
period of initial transgression can be identified as the onset of deposition of fine-grained, organic-rich sediments.
However, radiocarbon dates evidence a punctuation of these deposits further upcore. Grain-size analysis suggests
that the reworking and abrasion of the lagoon sediments resulted from the gradual lowering of the wave-base.
The core sequence is topped-off by marine sands and wind-blown deposits. Based on these findings, we suggest
a conceptual model that allows inferring age and elevation of transgressive and regressive stages from the lagoon
cores.
The common occurrence of similar environments distributed along gradients of isostatic uplift/subsidence
(approximately +0,5 to -0,5 mm/yr) in the south-western Baltic, makes coastal lagoon systems a valuable archive
for the reconstruction of Holocene sea-level and coastal evolution
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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