Alessandro Chelli

A conceptual hydrogeological model of ophiolitic aquifers (serpentinised peridotite): The test example of Mt. Prinzera (Northern Italy)

&NA; The main aim of this study is the experimental analysis of the hydrogeological behaviour of the Mt. Prinzera ultramafic massif in the northern Apennines, Italy. The analysed multidisciplinary database has been acquired through (a) geologic and structural survey; (b) geomorphologic survey; (c) hydrogeological monitoring; (d) physico‐chemical analyses; and (e) isotopic analyses. The ultramafic medium is made of several lithological units, tectonically overlapped. Between them, a low‐permeability, discontinuous unit has been identified. This unit behaves as an aquitard and causes a perched groundwater to temporary flow within the upper medium, close to the surface. This perched groundwater flows out along several structurally controlled depressions, and then several high‐altitude temporary springs can be observed during recharge, together with several perennial basal (i.e., low altitude) springs, caused by the compartmentalisation of the system because of high‐angle tectonic discontinuities.

Large-scale geomorphological mapping as a tool to detect structural features: the case of Mt. Prinzera ophiolite rock mass (Northern Apennines, Italy)

ABSTRACT This paper presents a geomorphologic map of the Mt. Prinzera ultramafic rock complex (Parma Province, Emilia-Romagna Region, Italy) mapped at large scale (1:2500). The map is the first contribution to the detailed geomorphologic knowledge of the area within the framework of a multidisciplinary approach used to analyse Mt. Prinzera as a hard rock aquifer case study. The geomorphologic mapping was carried out by field survey and aerial photograph analysis. All the surface processes and landforms were considered, with particular attention to structural geomorphologic features. The mapping of linear morphologic features was considered useful for revealing the presence of sets of joints otherwise difficult to detect due to surface weathering. Sets of rock discontinuities are important for water seepage and percolation and their identification is crucial for developing the hydrogeological conceptual model of the aquifer.

Assessing tectonic subsidence from estimates of Holocene relative sea-level change: An example from the NW Mediterranean (Magra Plain, Italy)

New sedimentological sea-level indicators are presented from the River Magra coastal plain, in NW Italy. Chronologically well-constrained paralic peats and organic sediments which had been deposited in a defined relationship with sea level were recovered in four of the seven boreholes considered in this work. Their evolution scatters in the time span of the past 6000 years. Since the cores are located within a single sedimentary basin, it was possible to correct the elevation of marker horizons for the effect of sediment compaction by means of both a field and a geotechnical method. Thus, seven reliable index points for the mid- to late-Holocene sea-level rise were obtained. The age–depth model derived from them was compared with that of sea-level predictions from two different Glacial Isostatic Adjustment (GIA) models available for the area. In both cases, the modelled sea-level estimates overlie the index points, suggesting lower relative sea-level elevation than the one predicted considering the combined eustatic and hydro-isostatic components. Based on the general tectonic setting of the area, this finding was interpreted as the effect of a tectonic subsidence of the basin, the rate of which can be quantified on average as 0.5 mm/yr since the middle Holocene, with a sharp increase after 2500 yr BP. By providing a reliable estimate of the rate of tectonic subsidence in a coastal area of NW Italy, this research contributes to refining the geodynamic model of this part of the Mediterranean basin.

The Geomorphologic Survey as Tool to Support Risk Management After Landslide Reactivation: The Case Study of Sauna di Corniglio Landslide (Northern Apennines, Italy)

During the period winter–spring 2012–2013, abundant rainfalls occurred in the area between Parma and Enza streams. In the first half of April 2013, the reactivation of a complex landslide involving a portion of the Sauna village (T Parma valley) occurred. Soon after the first rotational slide, the depleted mass started to move as a flow, progressively involving the western part of the settlement, destroying three houses, one cattleshed and many rural buildings. This paper reports the results of the geomorphologic survey performed in the days soon after the landslide reactivation. It has been aimed to describe the geomorphologic features of the landslide to support the risk management and mitigation.

Tectonics and Large Landslides in the Northern Apennines (Italy)

This work was aimed to highlight the spatial relationships between large-scale gravitational phenomena and tectonic uplifted structures in the area between Enza river valley and Taro river valley in the Northern Apennines. The structural-tectonic map of the investigated area and the inventory map of the large landslides and DSGSDs were made. The analysis of the structural map highlighted the existence of antiforms with axes roughly SE-NW. The comparison between the large landslides and the antiforms has shown that a spatial relationship between large complex landslides (earth/rock slides – earth flows) and positive geological structures exists.

Evolution of an Upper Pleistocene aeolianite in the northern Mediterranean (Liguria, NW Italy)

Based on a 19th century scientific report, a recent geological survey has highlighted the presence of a complex, mostly Aeolian deposit along the coast of Liguria (Laigueglia, Savona Province, NW Italy). This finding was recognized to be a relevant palaeoclimatic marker, being the northernmost aeolianite outcrop ever reported from the Mediterranean Basin. The investigated deposit is spread along a steep sea-facing slope from 2-3 m up to almost 60 m a.s.l.; it is strongly reworked due to recent urbanization of the area. Its stratigraphic features were recognized thanks to its exposure in different sections and analysed in order to obtain reliable indications on the sedimentary environments. Facies analysis suggests that the sedimentary body is a relict cliff-top dune evolved on top of a foreshore deposit in temperate-cold and moist climate conditions. Two samples from the upper, strictly aeolian part of the sequence were subjected to OSL (Optically Stimulated Luminescence) dating and yielded an age consistent with its deposition during the Marine Isotopic Stage (MIS) 5.2 and 5.1 substages (88-83 and 83-71 ka). This paper contributes to the increase of the number of Upper Pleistocene coastal aeolianites accounted for in literature. Being located at the northern border of the occurrence of aeolianites in the northern Mediterranean, it helps to outline climatic and environmental boundary conditions for the formation of this type of deposit.

Landslides types controlled by tectonics-induced evolution of valley slopes (Northern Apennines, Italy)

This paper investigates the role played by geomorphological and tectonic processes affecting a portion of an active mountain belt in causing the occurrence of different types of landslides developed in flysch bedrock. The adopted multidisciplinary approach (geomorphology, geology and geophysics) allowed to recognize in a portion of the Northern Apennines of Italy different types of landslides that developed in response to slope dynamics, in turn dependent on broader regional-scale tectonic processes. Sedimentary bed attitude, local tectonic discontinuities and lithology only partially influenced the type of landslides, which have been deeply affected by the activity of regional-scale antiform that controlled the hillslope geomorphic evolution in different ways. The growth of this structure and the tilting of its forelimb produced gently dipping slopes that approached the threshold angle that can cause the occurrence of (mainly) translational rockslides. Conversely, high-angle normal faulting parallel to the antiform axis (related to a later stage of activity of the antiform itself) strongly controlled the stream network evolution and caused the watercourses to deeply incise portions of their valleys. This incision produced younger steep valley slopes and caused the development of complex landslides (roto-translational slides-earth/debris flow). The results of the integrated study presented in this paper allowed to distinguish two main types of landslides whose development reflects the events that led to the geomorphological and geological evolution of the area. In this perspective, within the study area, landslides can be regarded and used as indicators of broader-scale recent tectonic processes.

A multidisciplinary procedure to evaluate and optimize the efficacy of hydraulic barriers in contaminated sites: a case study in Northern Italy

In the last decades, hydraulic barriers have been activated in a large number of polluted sites with the aim of preventing groundwater pollution outside the contaminated area. From a regulatory point of view, there is the need of evaluating the efficacy of these barriers. For this reason, the goal of the present study is to apply a coupled experimental modelling approach aimed at evaluating the efficacy of the barrier and providing management strategies. In particular, a case study in Italy is investigated. The study case is of main interest because of its complexity due to a heterogeneous aquifer and the presence of surface water that interacts with the below aquifer. The study has been carried out through the experimental characterization of the aquifer system (coupling the classic stratigraphic techniques with the results of radiocarbon dating, as well as through pumping and injection tests) and its hydrogeological behaviour (by means of hydraulic- and the stream-head measurements, as well as some isotopic investigations), and the implementation of a numerical model (through MODFLOW 2005). The results show the effectiveness of the coupled experimental modelling approach to analyse and simulate the hydrodynamics within the test aquifer system, as well as to evaluate the efficacy of the hydraulic barrier. Based on the results of the numerical model, easy solutions were designed to manage the barrier.

Development of Shore Platforms along the NW Coast of Italy: The Role of Wind Waves

ABSTRACT Pappalardo, M.; Cappietti, L.; Arozarena Llopis, I.; Chelli, A., and De Fabritiis, L., 2017. Development of shore platforms along the NW coast of Italy: The role of wind waves. This paper investigates whether waves are active morphologic agents capable of shaping the small shore platforms that characterize the rocky coast of NW Italy. Two study areas have been selected along this coastal tract: Calafuria (Livorno) and Lerici-Tellaro (La Spezia), located ca. 120 km apart, the first being shaped in sandstone and the second in dolomite bedrock. Propagation of waves in the nearshore has been simulated by numerical modeling. From wave model results, validated with data from an offshore wave meter buoy, it is inferred that waves break directly on the coast or very close to it at Calafuria, whereas for Lerici-Tellaro shores, waves mostly break up to 150 m seaward of the shore platform. This implies that the amount of energy delivered on the platform is much greater in the first case than in the second case. Given breaking depths and the height of breakers, maximum pressure and shear stress released at the breaking point were calculated for both areas. The results showed that wave forces released onto the shore platforms both at Calafuria and at Lerici-Tellaro never exceeded the compressive strength of the platform rocks, assessed using the Schmidt hammer test. It is concluded that, in the study area and with the present oceanographic conditions, wave forces are not directly capable of causing erosion on shore platforms.

Hydrodynamics in evaporate-bearing fine-grained successions investigated through an interdisciplinary approach : A test study in southern Italy-hydrogeological behaviour of heterogeneous low-permeability media

Messinian evaporates are widely distributed in the Mediterranean Sea as outcropping sediments in small marginal basins and in marine cores. Progressive filling of subbasins led to the formation of complex aquifer systems in different regions where hypersaline and fresh water coexist and interact in different manner. It also generates a significant diversification of groundwater hydrochemical signature and different microbial communities. In the case study, the hydrogeology and hydrochemistry of the whole system are influenced by good hydraulic connection between the shallower pyroclastic horizon and the underlying evaporate-bearing fine-grained Messinian succession. This is demonstrated by the merge of hydrogeological, chemical, isotopic, and microbiological data. No mixing with deep ascending waters has been observed. As shown by geophysical, hydraulic, and microbiological investigations, the hydraulic heterogeneity of the Messinian bedrock, mainly due to karstified evaporitic interstrata/lenses, causes the hydraulic head to significantly vary with depth. Somewhere, the head increases with the depth’s increase and artesian flow conditions are locally observed. Moreover, the metagenomic investigations demonstrated the existence of a poor hydraulic connection within the evaporate-bearing fine-grained succession at metric and decametric scales, therefore leading to a patchwork of geochemical (and microbiological) subenvironments.