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Aquifer-building processes : unravelling allogenic controls to constrain 3D models of the Quaternary alluvial architecture in the Central Po Plain (Italy)
No full textThe Po Plain is the widest Quaternary alluvial basin of Italy. During the Pleistocene-Holocene, the stratigraphic architecture of its fill records the complex interplay between the tectonic evolution of the active Apennine thrusts to the South, rebound and isostatic response to deglaciations at the flexed Alpine margin to the North, Middle Pleistocene advances and retreats of alpine glaciers, changing local base levels, fluvial discharges, sediment textures, inflow and accommodation rates. All of these factors determined aquifer building processes, controlling geometry and stacking pattern of alluvial and glacio-fluvial bodies, hierarchic arrangement of aquifer vs. aquitard/aquiclude lithosomes, connectivity of the most and least pervious alluvial elements. Hydrostratigraphic models must account for the hierarchic nesting of heterogeneities; hence, the sedimentary history of aquifer building, the influence and hierarchy of the allogenic factors controlling these processes, and the multiple scales of sedimentological heterogeneity must be evaluated and quantified to constrain the 3-D reconstructions.
We apply this approach to a 50 km N-S belt in the Po Plain of Lombardy, from the northern alpine glacial amphitheatres to the southern Apennine foothills. The method we adopt combines field-based geological and modelling approaches with the multi-scale GIS management of the geological dataset. In particular, original geological mapping, stratigraphic,
sedimentological, pedological, paleontological, geomorphological and structural observations, integrated with OSL and C14 dating were combined to 1-D facies analysis of subsurface data and 2-D correlations. Surface maps and 2-D cross sections at different scales allowed to derive the controlling factors on the interpreted architecture, and to constrain the 3-D architectural reconstruction. GeoModeller software was selected because it permits i) to compare several different
realizations in a reasonably short time, ii) to visualize the stratigraphic relations honouring the geological constraints, to
compare the effect of the contrasting controlling factors on the sedimentary and morpho-tectonic history.
Within the mentioned transect of the Po Plain, at the present state of the research we are focussing on two key-sectors: 1) the glacio-fluvial and alluvial terraced landscape at the northern Alpine margin, directly influenced by the Pleistocene glacial pulses/retreats; 2) the Apennine tectonic reliefs which emerge in the southern Po Plain and involve the Quaternary, Alpinesourced alluvial succession in the Apennine folding and faulting.
The first results include: 1) new geological and geomorphological maps and subsurface reconstructions, which display the progressive modifications that affected the landscape of the study area during Quaternary. They resulted from the interplay of Alpine glacial cycles and the advance of Apennine thrusts. In particular i) syn-glacial fans and sandur progradation from the North built gravel-sand bodies with coarsening-upward stacking patterns and southward fining trends to the base-level, related to an unstable network of multiple braided rivers. ii) Non-synchronous, repeated entrenchment of river valleys occurred at different times in different sectors of the Plain. Deglaciation rebounding and tectonically induced forebulging acted in the North, whereas active folding and faulting, above all, controlled erosional cycles and riverine entrenchment in the South. Under- vs over-fitting of streams, recurrent avulsions, river diversions and piracy are some of the detectable modifications of the fluvial style. iii) Tectonic uplift and entrenchment resulted in erosion and reworking of older, coarsegrained sediments that were recurrently redeposited within the palaeo-valleys and the lowermost terraces in the central and southern sectors of the plain, in contrast with the regional southward fining of the syn-glacial bodies. 2) Comparison between depositional styles and architectures in the two most extreme sectors of the Central Po Plain, allows to associate the different allogenic controls to their peculiar hydrostratigraphic heterogeneity. Uplift, progradation, and entrenchment shaped mostly cross-cutting geometries of the downlapping gravel-sand bodies in the North. They form coarse-grained, complexly connected aquifers that develop above confined aquifer bodies within palaeo-valleys entrenched in a basal, gently tilted marine aquiclude. Contemporaneously in the South, tectonics shaped the pinch-out geometries of the alluvial bodies which onlap the folded units. Syntectonic erosional surfaces developed, merging into major composite unconformities. Consequently, aquifers were confined into different depocentres, and subsequent truncations enhanced the connectivity between alluvial entities of different ages. 3) The proposed integrated, multiscale methodology accounts for the geological constraints and the hierarchic arrangement of the stratigraphic units and surfaces; hence, it can be applied in different depositional settings, to constrain architectural and hydrogeological models independently from the scale of the work
The role of Late Quaternary incised valley systems in coastal-plain aquifer geometry: A case study from the Arno Plain (Ligurian Sea, Italy).
Full text linkThe Late Quaternary subsurface successions buried beneath several delta-coastal plains exhibit distinct cyclic facies patterns
that reflect the predominant control exerted by climate-eustatic factors on sedimentation, at Milankovitch and sub-
Milankovitch scales. However, local subsidence co-operates with Late Quaternary glacio-eustatic fluctuations in determining
changes in accommodation space through time and space. During phases of sea-level rise (interglacial periods), subsidence
further increases the accommodation space. On the other hand, during the subsequent phases of sea-level fall (glacial periods) subsidence works to mitigate the accommodation space reduction, resulting in a better preservation of the
depositional record.
In the case of rapidly subsiding regions, such as the Po Plain (N Adriatic Sea, Italy), the combined tectonic-eustatic effect led
to a vertically stacked succession of transgressive-regressive (T-R) sequences forming a multilayered aquifer system (Amorosi
and Colalongo, 2005; Amorosi and Pavesi, 2010). In a hydrostratigraphic view, sheet-like, channel-belt fluvial bodies, tens of
m-thick in the regressive portion of the T-R sequences represent major aquifers. In contrast, pronounced fluvial incisions
occurred during glacial periods in coastal plains characterized by lower rates of subsidence, as those facing the Ligurian-
Tyrrhenian margin (e.g. Arno Plain, Ombrone Plain, Tiber Plain, Volturno Plain). These erosive processes led to the formation
of km-wide and tens of m-thick paleovalleys able to erode confined aquifers, reducing their lateral continuity. In these
contexts, the reconstruction of the aquifer systems is further complicated by the incised valley fill (IVF) successions formed
during the subsequent interglacial periods. These IVFs, which consist predominantly of estuarine muddy deposits, represent,
in fact, localized impermeable barrier to ground-water circulation. A high-resolution multiproxy approach (sedimentological,
faunal and chronological data) and the application of sequence stratigraphic principles can furnish a successful threedimensional
representation of such complex aquifer systems.
The Arno coastal plain (Ligurian Sea, Italy) represents an ideal setting where to investigate the hydrostratigraphic role of
incised valley systems (IVSs), as two well-preserved IVFs have been identified within the uppermost 100 meters and dated to
two non-consecutive interglacial cycles (MIS 7 and MIS 1; Amorosi et al., 2008; Rossi et al., in press). Based on a large
subsurface stratigraphic dataset, composed of hundreds of > 50 m long cores, 14C and ESR chronological data, and
stratigraphic correlation, a representation of the Arno Plain aquifer system is outlined. We focused on the identification and
mapping of potential aquitards/aquicludes (IVFs) and aquifers. These latter include: (i) laterally discontinuous gravel terrace
deposits developed at different stratigraphic levels along the paleovalleys flanks, (ii) lenticular channel-belt sand bodies
formed during the glacial phases that preceded IVSs formation, and (iii) post-valley fill coastal-marine sands showing a
landward-wedging geometry.
References
Amorosi A. and Colalongo M.L. (2005). The linkage between alluvial and coeval nearshore marine successions: evidence from
the Late Quaternary record of the Po River Plain, Italy. In: M.D. Blum, S.B. Marriott & S.F. Leclair (Eds.) Fluvial Sedimentology
VII. Int. Assoc. Sedimentol. Spec. Publ. 35, 257–275.
Amorosi A. and Pavesi M. (2010). Aquifer stratigraphy from the middle-late Pleistocene succession of the Po Basin. Mem.
Descr. Carta Geol. d’It. XC, 7–20.
Amorosi A., Sarti G., Rossi V. and Fontana V. (2008). Anatomy and sequence stratigraphy of the late Quaternary Arno valley fill
(Tuscany, Italy). In: A. Amorosi, B.U. Haq & L. Sabato (Eds.) Advances in Application of Sequence Stratigraphy in Italy.
GeoActa Spec. Publ. 1, 55–66.
Rossi V., Amorosi A., Sarti G. and Mariotti S. (in press). Late Quaternary multiple incised valley systems: an unusually wellpreserved
stratigraphic record of two interglacial valley fill successions from the Arno plain (northern Tuscany, Italy).
Sedimentology
An interdisciplinary approach to the Arno palaeochannels reconstruction since the X century BC in the Pisa coastal plain (Tuscany, Italy)
No full textWe have used a interidisciplinary approach involving archaeology, geomorphology, stratigraphy, sedimentology, chronology, history sources and archaeogeography to infer paleochannels evolution of the Arno River. The traces of a centuriation (a method of land division and assignment used by the Romans), are still identifiable in the plain and constitute an important benchmark that helps to recognize the phases of channel migration across the centuries.
A wide shallow subsurface data set mainly coming from MAPPA project (www.mappaproject.org), has been used as reference for stratigraphic correlations. The target of the research looks at the upper 8-10 m of the subsurface succession that dates back to the Iron Age. Two new cores, 9 m long, were drilled and sampled using a percussion drilling technique (Vibracorer Atlas Copco, Cobra model), which supplied smaller diameter cores, qualitatively comparable to standard cores.
The description of cores lithofacies includes mean grain size, colour, sedimentary structures and accessory materials (shells and fragments; peat horizons or decomposed organic-rich layers; plant debris; wood fragments and calcareous nodules).
Facies analyses, archaeological data, and historical sources, have allowed: i) the identification of a paleo-Arno river branch, likely Roman in age, which flowed southernmost with respect to the present-day course and ii) the evidence of significant processes of meanders migration.
Moreover, this data opens up new prospects regarding the relationship between the evolution of the Arno River, in the coastal plain area, and the centuriation created by the romans
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
A low-cost technique to quantify river suspended sediment transport towards the assessment of coastal sediment budget
Full text linkDirect measurements of river sediment transport are required for several different activities, which span from the mere
scientific curiosity to the application of the collected data for management aspects. While the former drives the effort of the
scientific community to expand the knowledge about river dynamics, the benefits resulting from a successful quantification
of river sediment load would be mostly felt in terms of improving and optimizing the management of both river and coastal
systems. Many techniques involving various disciplines and different levels of technological solutions have been developed
ultimately, sometimes using cumbersome equipments that do not allow extended data collection or rather expensive
devices anyone cannot afford to employ. A low-cost instrument able to collect and transmit in real time the measurements
of river suspended sediment load is here presented.
The proposed device is essentially a densimeter based on the Archimedes’ Principle (Figure 1). The mechanical structure is
composed by two separate structures linked together: a device composed by four floats, whose immersion level varies
according to the density of water, and a floating structure storing the microprocessor and transmission unit, together with
the sensor in charge of measuring the immersion level of the other device. The immersion level is measured through an
ultrasound sensor that is able to calculate its exact distance from the upper surface of the four floats device. The microprocessor unit is composed by an
Arduino Mini board in charge of acquiring and
processing the collected data, translating an
immersion level information into a water
density data, while the transmission unit is
composed by an XBee Series 2 radio module,
in charge of transmitting the density
information to a data collection gateway
provided with GSM connection positioned
ashore. This gateway will transmit the locally
collected data to a remote data collection
centre that will store them in a database
making them available through the Internet.
The future applications of the technique
underlined by the development of the above
mentioned device involve the investigation of
the bedload transport, which is crucial for the complete definition of river contribution for sediment budget evaluation
purposes. Based on the source-to-sink concept, river sediment transport as a whole is among the primary factors controlling
the natural feeding of beaches: the lack of reliable measurements hinders the chance to adequately assess the sediment
budget of specific sectors of coast, which in turn prevents the coastal managers to take conscious, and possibly right,
decisions when the future of a coastal system (intended as catchment – beach – offshore) is on the line
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