The Ricker Hills Tillite provides evidence of Oligocene warm-based glaciation in Victoria Land, Antarctica

The relationship between the Ricker Hills Tillite (RHT), which represents the northernmost outcrop of lithified continental glacial deposits in Victoria Land, is discussed with respect to the glacial landscape assemblage of the Ricker Hills, a nunatak at the internal border of the Transantarctic Mountains. A warm-based ice sheet deposited the tillite and induced syn- to post-depositional glacial deformation under wet conditions both of the tillite and of the bedrock. The thickness of the ice sheet on the nunatak is estimated to have been 600 m, at most. The area had been deeply eroded before deposition of the RHT as documented by the low elevation of tillite outcrops located in overdeepened depressions of the nunatak. Micropaleontological analysis evidences only the presence of Permian to Jurassic palynomorphs. X-ray diffraction and SEM–EDS analyses of clay minerals in the RHT indicate continental chemical weathering under wet conditions after the RHT deposition. As documented by clay mineral assemblage variation in CRP drillholes, the progressive cooling of the Antarctic continent allowed chemical weathering in “warm” conditions until the Late Oligocene period in southern Victoria Land, leading to a chronological constrain for RHT deposition. Conservatively estimating the sea level to have been between the tillite outcrops and the erosional trimline limiting horns in the Ricker Hills, at the time of RHT deposition, we suggest that the maximum uplift of the area would not have exceeded 900–1500 m since at least Late Oligocene.     

Modelling river and riparian vegetation interactions and related importance for sustainable ecosystem management

We discuss the importance of modelling riparian vegetation and river flow interactions under differing hydrologic regimes. Modelling tools have notable implications with regard to the understanding of riverine ecosystem functioning and to promote sustainable management of water resources. We present both deterministic and stochastic approaches with different levels of simplification, and discuss their use in relation to river and vegetation dynamics at the related scale of interest. We apply such models to both meandering and braided rivers, in particular focusing on the floodplain dynamics of an alpine braided river affected by water impoundment. For this specific case we show what the expected changes in riparian vegetation may be in a ‘controlled release’ scenario for the postdam river Maggia, Switzerland. Finally, the use of these models is discussed in the context of current research efforts devoted to river restoration practice.     

The occurrence of Mt Barca flank eruption in the evolution of the NW periphery of Etna volcano (Italy)

Geological surveys, tephrostratigraphic study, and ⁴⁰Ar/³⁹Ar age determinations have allowed us to chronologically constrain the geological evolution of the lower NW flank of Etna volcano and to reconstruct the eruptive style of the Mt Barca flank eruption. This peripheral sector of the Mt Etna edifice, corresponding to the upper Simeto valley, was invaded by the Ellittico volcano lava flows between 41 and 29 ka ago when the Mt Barca eruption occurred. The vent of this flank eruption is located at about 15 km away from the summit craters, close to the town of Bronte. The Mt Barca eruption was characterized by a vigorous explosive activity that produced pyroclastic deposits dispersed eastward and minor effusive activity with the emission of a 1.1-km-long lava flow. Explosive activity was characterized by a phreatomagmatic phase followed by a magmatic one. The geological setting of this peripheral sector of the volcano favors the interaction between the rising magma and the shallow groundwater hosted in the volcanic pile resting on the impermeable sedimentary basement. This process produced phreatomagmatic activity in the first phase of the eruption, forming a pyroclastic fall deposit made of high-density, poorly vesicular scoria lapilli and lithic clasts. Conversely, during the second phase, a typical strombolian fall deposit formed. In terms of hazard assessment, the possible occurrence of this type of highly explosive flank eruption, at lower elevation in the densely inhabited areas, increases the volcanic risk in the Etnean region and widens the already known hazard scenario.     

Ecomorphodynamics of rivers with converging boundaries

Many rivers worldwide show converging sections where a characteristic limiting front for vegetation establishment on gravel bars is observed. An important conceptual model was advanced in 2006 by Gurnell and Petts, who demonstrated that for the convergent section of the Tagliamento River the downstream front of vegetation establishment can be explained by unit stream power. We introduce a theoretical framework based on 1D ecomorphodynamic equations modified to account for the biological dynamics of vegetation. We obtain the first analytical result explaining the position and river width where vegetation density is expected to vanish in relation to a characteristic streamflow magnitude and both hydraulic and biological parameters. We apply our model to a controlled experiment within a convergent flume channel with growing seedlings perturbed by periodic floods. For a range of timescales where hydrological and biological processes interact, we observe the formation of a front in the convergent section beyond which vegetation cannot survive, the location of which is explained by flow magnitude. This experiment confirms that the timescales of the involved processes and the unit stream power determine the existence and the position of the front within convergent river reaches, respectively. Copyright © 2014 John Wiley & Sons, Ltd.     

Assessment of the performance of hysteretic energy dissipation bracing systems

The advantages of passive supplemental dampers for performance enhancement of new and existing structures have been demonstrated extensively in the past. The big amount of experimental tests carried out all over the world on framed structures upgraded by energy dissipating bracing (EDB) systems based on hysteretic dampers (HDs), have shown their effectiveness in reducing seismic effects on buildings. The mechanical characteristics of the HDs in some cases may be different from those arising by the design procedure due to industrial tolerance or because of some damage suffered during previous earthquakes. In order to assess the robustness of this technique, in terms of capacity of seismic vibrations control even for significant changes in the mechanical characteristics of the EDB system respect to the design ones, in this paper experimental tests and parametric nonlinear time history analysis have been carried out changing the characteristics of the HD stiffness and strength. The experimental results refer to the shaking table tests performed at the Structural Laboratory of the University of Basilicata within a wide research program, named Joint Experimental Testing on Passive and semiActive Control Systems. The program has been completely funded by the Italian Department of Civil Protection within the activity of the Research Line 7 of the ReLUIS (Italian Network of University Laboratories of Earthquake Engineering) 2005–2008 project. A displacement-focused design procedure has been considered to evaluate the mechanical characteristics of the dissipating system, with the aim of limiting inter-storey drifts after frame yielding. From the experimental point of view, two design solutions have been tested for chevron braces equipped with HD, assuming the same stiffness but different values of both ductility demand and yield strength of the HDs. Moreover, parametric studies have been performed through numerical simulations. This paper provides an overview of the experimental set up and briefly summarizes the experimental outcomes and the comparison with the results of numerical nonlinear time history analysis. Moreover, the results of the parametric analysis for the assessment of the performances of the dissipating system in controlling structural response are presented.     

A unified framework for earthquake risk assessment of transportation networks and gross regional product

Natural threats like earthquakes, hurricanes or tsunamis have had serious impacts on communities. In the past, major earthquakes in the United States like Loma Prieta 1989, Northridge 1994, or recent events in Italy like L’Aquila 2009 or Emilia 2012 emphasized the importance of preparedness and awareness to reduce social impacts. In addition to that, earthquake damaged businesses dramatically reduced the gross regional product. Generating scenario earthquakes in a proper way is important to suitably assess the risk in bridge networks and social losses in terms of gross regional product reduction. Seismic hazard is traditionally assessed by means of probabilistic seismic hazard analysis (PSHA). Although PSHA well represents the hazard at a specific location it is not suitable for spatially distributed systems. Scenario earthquakes can overcome this problem; they represent the actual distribution of ground shaking for a spatially distributed system while being hazard consistent. In this work a methodology to generate scenario earthquakes has been proposed using a novel approach with the aim of being the basic step for investigating possible earthquake consequences in seismic areas and contributing to reduce losses.     

Large-scale circulation patterns and related rainfall in the Amazon Basin: a neuronal networks approach

This study describes the main circulation patterns (CP) in the Amazonian Basin over the 1975–2002 period and their relationship with rainfall variability. CPs in the Amazonian Basin have been computed for each season from the ERA-40 daily 850?hPa winds using an approach combining artificial neural network (Self Organizing Maps) and Hierarchical Ascendant Classification. A 6 to 8 cluster solutions (depending on the season considered) is shown to yield an integrated view of the complex regional circulation variability. For austral fall, winter and spring the temporal evolution between the different CPs shows a clear tendency to describe a cycle, with southern wind anomalies and their convergence with the trade winds progressing northward from the La Plata Basin to the Amazon Basin. This sequence is strongly related to eastward moving extra tropical perturbations and their incursion toward low latitude that modulate the geopotential and winds over South America and its adjoining oceans. During Austral summer, CPs are less spatially and temporally organized compared to other seasons, principally due to weaker extra tropical perturbations and more frequent shallow low situations. Each of these CPs is shown to be associated with coherent northward moving regional rainfall patterns (both in in situ data and ERA-40 reanalysis) and convective activity. However, our results reveals that precipitation variability is better reproduced by ERA-40 in the southern part of the Amazonian Basin than in the northern part, where rainfall variability is likely to be more constrained by local and subdaily processes (e.g. squall lines) that could be misrepresented in the reanalysis dataset. This analysis clearly illustrates the existing connections between the southern and northern part of the Amazonian Basin in terms of regional circulation/rainfall patterns. The identification of these CPs provide useful information to understand local rainfall variability and could hence be used to better understand the influence of these CPs on the hydrological variability in the Amazonian Basin.     

Late Holocene evolution of Tiber river delta and geoarchaeology of Claudius and Trajan Harbor,Rome

This study provides new information on the evolution of the Tiber delta during the late Holocene, and describes the record of sedimentation in the Port of Claudius and Trajan. The Tiber flowed into the Tyrrhenian Sea in the area of the Port of Claudius and Trajan between the 8th and 5th centuries B.C. The harbor basins excavated by the Romans during the 1st and 2nd centuries A.D. were filled with sediments containing saltwater fauna, then brackish‐water fauna, and finally by alluvial and marsh deposits. The Port of Claudius and Trajan was silted in as a consequence of episodes of alluviation that correlate with environmental events, possibly triggered by global climate changes. © 2009 Wiley Periodicals, Inc.