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Late-Quaternary incised valleys and tidal inlets of the northern Adriatic shelf and related alluvial plains
Full text linkThe reconstruction of the past sea-level changes and of their effects on the paleoenvironmental evolution are necessary steps for the modelling of the future sea-level rise and for the elaboration of management plans for the safeguard of the coastal systems. Such reconstruction is often hampered by the scarceness of adequate indicators as a consequence of the lack of formation/preservation or due to the low resolution.
This work focuses on the analysis of possible new paleo sea-level indicators. This research is essential in order to provide new data to constrain the marine transgression that took place after the Last Glacial Maximum (LGM) and to understand the consequent environmental evolution. A series of incised landforms that formed and were infilled during this period were therefore analysed. Incised landforms constitute one of the few available archives for the reconstruction of the past and especially for periods of high sea-level rise rate, which are usually characterized by few available paleo sea-level indicators as a consequence of the lack of formation or preservation.
The northern Adriatic shelf and the contiguous Venetian-Friulian Plain were chosen for this research due to their peculiar physiography, notably the low gradient of the continental shelf.
The northern Adriatic shelf was investigated through a series of high-resolution seismic profiles, allowing to document for the first time the presence of almost 100 paleo tidal inlets. Some of these have been investigated in detail, providing new pieces of evidence for the understanding of the evolution of the area during the early Holocene and the relation between the different rates of sea-level rise and the formation and preservation of lagoon environments.
The analysis of a large dataset of cores that sampled the infilling material of an incised valley located in the subsurface of the modern Venetian-Friulian Plain allowed a detailed reconstruction of the environmental evolution in the area since the Late Glacial. In particular, the switch from a fluvial freshwater environment to a brackish lagoon one was recognized and dated to Early Holocene.
Finally, this work presents some considerations and possible future developments for the use of such indicators in the reconstruction of timing and modes of the last marine transgression
Characteristics and potential application of Holocene Tidal Inlets in the Northern Adriatic Shelf (Italy)
No full textIn the last decades a series of offshore seismic and stratigraphic surveys revealed the presence of several infilled palaeo tidal inlets which punctuate the subsoil of the northern Adriatic shelf. The morphologic, morphometric and sedimentary characteristics of these landforms constitute remarkable database for the reconstruction of palaeo coastline positions and to constrain the post-LGM sea-level rise, especially during the beginning of the Holocene period. This work provides a first overview on the significance of the Adriatic tidal inlets and their response to the interplay between upstream and downstream controls
Incised Valleys of the Northern Adriatic Shelf: a Window on the Late-Quaternary Fluvial and Coastal Evolution
No full textOn a global perspective, marine regressions and low stands are associated to the widespread entrenching of fluvial networks through continental shelfs. The very low gradient that characterizes the Northern Adriatic shelf inhibited this scouring mechanism during the LGM. On the contrary, stratigraphic and chronological data highlight the occurrence of a set of LGM/post-LGM infilled incisions produced by different driving processes.
The wave and tidal action of the transgressive sea reworked and erased most of the units characterizing the former alluvial plain. Thus, the fillings of the Adriatic incisions constitute one of the few preserved deposits for investigating the morphological and environmental evolution of the period between the LGM and the phase of maximum flooding (i.e. circa 5.5 ka BP). The study was carried out through the analyses of a series of VHR CHIRP profiles, stratigraphic cores and radiocarbon dates.
Two different generations of infilled scours have been described. The older generation (Atl1) reach a depth of up to 30 meters below the modern sea floor and would have been formed during the peak of the LGM marine low stand (about 25-22 ka BP). The architecture of the infilling unit suggests that Atl1 incisions were abandoned by their formative river and therefore shifted into a fluvio-lacustrine environment, fed from distal fluvial systems. The scouring and infilling process appears to be stretch some 10,000 years. In contrast, the younger generation of infilled incisions (Atl2) is the legacy of the coastal-marine lagoon environment that existed in the study area for just a few millennia in the Early Holocene (10-8 ka BP). They are a network of tidal channels hinged on few deep tidal inlets, likely sheltered by sandy barriers. Atl2 incisions reach maximum depths of 20 m and they are completely infilled
LIDAR-DERIVED DEMS FOR GEOARCHAEOLOGICAL INVESTIGATIONS IN ALLUVIAL AND COASTAL PLAINS
No full textHere we present some Digital Elevation Models (DEMs) produced from airborne laser altimetry in the distal sector of the Venetian-Friulian Plain. The research considered some areas where the high detail of the surface landforms allows to evidence the oc-currence of some ancient anthropogenic features that normally are not detectable in the present landscape or have been eroded by recent human activity. Case studies are selected from NE Italy, but this work shows the potential of the use of LiDAR data for geoar-chaeological and geological mapping in alluvial environments
INCISED VALLEYS OF THE NORTHERN ADRIATIC SHELF: A MORPHOSTRATIGRAPHIC MARKER FOR THE LAST TRANSGRESSION
No full textIn a global perspective, fluvial incisions generally form on the continental shelfs during marine lowstand and they can be filled and partly eroded along the subsequent transgression by fluvial and estuarine deposition, as well as by sediment reworking (e.g. Maselli and Trincardi, 2013). A peculiar setting characterizes the Northern Adriatic shelf, that has a very low gradient and, apparently, it was not prone to significant incision during the LGM lowstand. On the contrary, stratigraphic and chronological data highlight the occurrence of fluvial erosive processes in the first part of the transgression.
After the LGM, the Northern Adriatic shelf, experienced a rapid submersion with dramatic environmental changes. The current morphology of the seabed above -45 m msl is the result of the strong shaping activity induced by the widespread erosive processes related to waves and currents activity after the transgressive submersion, whilst sedimentation occurred in very limited portions (Moscon et al., in press). This peculiar evolution heavily restricts the available sites that can supply information for reconstructing times and modes of the transgression. Together with the relicts of the coastal barrier systems, formed during pauses along the marine transgression, the fillings of these incised valleys are the only deposits preserved in the northern shelf between the end of LGM and the phase of maximum flooding.
The investigations carried out for the geological mapping of the sea floor recognized several completely filled incised valleys (Trincardi et al., 2011). The oceanographic cruises RISA2009, NAD2012 and ASCI2014 were partly devoted to the collection of high-resolution data (CHIRP seismo-acoustic profiles, multibeam bathymetries and stratigraphic cores) aiming at characterizing these sedimentary features.
In order to seize all the possible information out of these features a geodatabase is under construction: this database will collect all the information available for the incised valleys recognizable in the northern Adriatic area, between the Po Delta and the Slovenian-Croatian border, including VHR seismic data, shallow cores and radiocarbon dating. The preliminary work evidences several channel-like morphologies, few of them characterized by draped fillings, depth ranging from few to 20 meters, maximum widths of few hundred meters and a longitudinal development that can reach 10 kilometres. These paleo drainage systems can be generally associated to fluvial processes, but some of them underwent a shift to estuarine environments and, in some cases, lagoon tidal inlets. The analysis of their morpho-stratigraphy, along with radiocarbon dating, should offer new insights into the evolution of the area during the post-LGM transgression, providing constrains on the relative dating of these structures. Given the lack of the geological record, this approach may be of particular relevance in order to link the continental and the marine domains and to investigate the low order climatic fluctuation that strongly influenced the evolution of Lateglacial rivers
Geomorphological and Geoarchaeological Evidence of the Medieval Deluge in the Tagliamento River (NE Italy)
No full textBetween the second part of the sixth century
and the seventh century, many regions of
Europe have been characterized by dramatic
changes in the hydrographic setting, probably
related to a strong cooling phase. In northern
Italy, the chronicle of a huge flood event
referred by the Lombard historian Paul the
Deacon to the autumn of 589 AD has achieved
a major importance and induced many
researchers to attribute to this “deluge”
episode many of the floods occurred during
early Middle Age. In this paper, we consider
the alluvial system of Tagliamento, which is
one of the main rivers fed by south-eastern
Alps and experienced a strong avulsion phase
between the sixth and eleventh centuries. In
that period, the river activated up to three
branches and the hydrographical changes
strongly influenced the human activity. This
work critically reanalyses both published data
and new stratigraphic and archaeologic evidence
in order to assess and quantify the times
and modes of this instability phase. The data
suggest the occurrence of an extreme flood
event at the end of the sixth century, which
was also responsible for the burial of the
ancient city of Concordia Sagittaria. The
geochronological constraints suggest the possibility
that this catastrophic episode occurred
in 589 AD, thus confirming the Medieval
Chronicle. Anyhow, other alluvial events
occurred in the distal plain of Tagliamento
River slightly before and after that moment
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
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