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

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

Hydrogeological mapping of heterogeneous and multi-layered ophiolitic aquifers (Mountain Prinzera, northern Apennines, Italy)

A few hydrogeological studies have been carried out worldwide in peridotite aquifer systems, despite their wide distribution. The ophiolites are one of the main groundwater reservoir within the northern Apennines (Italy). This paper suggests the graphical solution to set the hydrogeological map of heterogeneous, multi-layered ophiolitic aquifers mapped on large scale (1:1600). The site investigation area is an ophiolite outcrop of the External Ligurian of the northern Apennines: the Mountain Prinzera rock complex area (44°38′30′′N, 10°5′E; Parma Province, Emilia-Romagna Region). The hydrogeological characteristics of the tested aquifer system do not allow setting a hydrogeological map by applying usual graphical approaches. The hydrogeological map in such complex aquifer systems will show the classic hydrogeological data but must put in evidence above all (i) the main heterogeneities of the system, from the hydraulic point of view and (ii) the modifications of groundwater scenarios and pathways over time. The hydrogeological database of Mt Prinzera aquifer was managed in ESRI ArcGIS 10.0 software

Changes in high-intensity precipitation on the northern Apennines (Italy) as revealed by multidisciplinary data over the last 9000 years

Several record-breaking precipitation events have struck the mountainous area of the Emilia-Romagna region (northern Apennines, Italy) over the last 10 years. As a consequence, severe geomorphological processes such as debris avalanches and debris flows, shallow landslides, and over-bank flooding have affected the territory, causing severe damage to human-made structures. The unusual intensity of these phenomena prompted an investigation into their frequency in the past, beyond instrumental time. In the quest for an understanding of whether these phenomena are unprecedented in the region, peat bog and lake deposits were analyzed to infer the frequency of extreme precipitation events that may have occurred in the past. We present the results of a dedicated field campaign performed in summer 2017 at Lake Moo in the northern Apennines, a 0.15 km(2) peat bog located at an altitude of 1130 m a.s.l. During the extreme precipitation event of 13-14 September 2015, several debris flows generated by small streams affected the Lake Moo plain. In such a small drainage basin (<2 km(2)), high-density floods can be triggered only by high-intensity precipitation events. The sedimentary succession (ca. 13 m thick) was studied through the drilling of two cores and one trench. The sequence, characterized by clusters of coarse-grained alluvial deposits interbedded with organic-rich silty clays and peat layers, was analyzed by combining sedimentological, pollen, microanthracological and pedological data with radiocarbon dating (AMS C-14) in an innovative multidisciplinary approach for this area. Original data acquired during the field campaign were also correlated with other specific paleoclimatic proxies available in the literature for the northern Apennines area. We discover that the increase in extreme paleoflooding, associated with coarse-grained deposits similar to the ones observed recently, correlates well with the warm phases of the Holocene Thermal Maximum and with the ongoing warming trend observed that started at the beginning of the last century

Can we quantify sediment recycling in Italy's post-collisional subduction system?

Recycling of Earth's crustal components through subduction contributes to the observed geochemical heterogeneity in worldwide lavas, yet quantifying the in- and output fluxes is difficult because of the unknown compositions of subducted components and sediment transfer processes in subduction zones. Italian post-collisional magmatism is often mafic but potassiumrich, suggesting a significant contribution of subducted sediments in this complex geodynamic setting. Isotopic and elemental variability in the volcanic products across Italy likely reflects sediment recycling with variable composition and quantity from north to south. Here we report the geochemical compositions of sediments that accreted to the Apennine accretionary prism whose lateral counterparts have potentially subducted and contributed to the Italian melt source. The aim is to use the major-, trace- and Sr- Nd-Pb isotope compositions of the sediments and Italy's volcanic products to quantify subduction recycling through melt modelling. Sediments were collected from the northern-, central- and southern Apennines (Liguria, Emilia-Romagna, Umbria and Calabria) with a focus on exhumed units from below the various decollement levels. These included Triassic to Jurassic deep sea sediments in ophiolitic sequences deposited in the Ligurian- Piemonte Oceanic Basin, and Triassic to Neogene distal units of the Adria continental margin. End-member compositions are defined by deep sea clays and metapelites rich in K2O, SiO2, LILE, HFSE, REE with high 87Sr/86Sr (0.7458) and 206Pb/204Pb (19.4), and marls poor in K2O, SiO2, LILE, HFSE, REE, but rich in CaO and Sr, with low 87Sr/86Sr (0.7083) and 206Pb/204Pb (18.7). The geochemical compositions of the most primitive volcanics and olivine-hosted melt inclusions will be used to reconstruct subduction recycling processes by melt modelling of a sediment metasomatized mantle wedge. Sediment transport mechanisms, sediment/vein mineralogy, melting behavior, and melt extraction processes will be evaluated

Hydrogeological behavior of peridotite aquifers: the example of M. Prinzera (Northern Apennines, Italy)

L’obiettivo principale di questo studio è stato quello di (a) analizzare e comprendere il comportamento idrogeologico di un’idrostruttura peridotitica serpentinizzata, appartenente alle Unità liguridi esterne dell’Appennino settentrionale e, sulla base di quanto emerso, (b) mettere a punto un nuovo modello idrogeologico concettuale. A livello internazionale sono pochi gli studi idrogeologici condotti su questi mezzi. In particolare, esiste un unico articolo (Dewandel et al., 2005) che entra nel merito della caratterizzazione del mezzo e si spinge fino alla messa a punto di un modello concettuale di funzionamento, su base sperimentale. Per ottenere questo risultato è stata identificata un’area campione (il massiccio ultramafico del M. Prinzera), nella quale è stato messo a punto e sviluppato un iter sperimentale a forte connotazione interdisciplinare. L’area oggetto di studio (Lat. 44°38'30''N, Long. 10°5'E) è situato in vicinanza della confluenza del fiume Taro e del torrente Sporzana in provincia di Parma e ricade nei territori comunali di Terenzo e Fornovo di Taro. Sono state oggetto di monitoraggio n. 14 sorgenti (tra le n. 24 identificate), in parte perenni (disposte lungo la cintura basale al contatto tra le peridotiti e il complesso delle brecce argillose basali) e in parte stagionali di alta quota all’interno delle peridotiti. L’attività sperimentale è stata condotta con una forte impronta interdisciplinare. Nel dettaglio sono state eseguite le seguenti indagini: • Rilievi geologico-strutturali; • Studio geomorfologico; • Monitoraggio delle portate sorgive; • Monitoraggio dei caratteri chimico-fisici ed isotopici delle acque sorgive e delle precipitazioni; • Caratterizzazione microbiologica delle acque sorgive. Le attività di monitoraggio sono state effettuate con cadenze da giornaliera a semestrale, a seconda degli obiettivi specifici da indagare. In questo modo sono stati acquisiti elementi esaustivi al fine di esaminare le fenomenologie di interesse in un lasso di tempo più ampio di un intero anno idrologico. I principali risultati ottenuti possono essere così sintetizzati: • Il rilevamento geologico-strutturale effettuato alla scala della struttura del M. Prinzera ha evidenziato che il mezzo ultramafico è composto da unità litologiche distinte e tettonicamente sovrapposte; • La presenza di unità semi-permeabili, può generare una falda sospesa stagionale, a deflusso sub-corticale, su una falda basale, a deflusso più prolungato e profondo; • Inoltre, poiché le peridotiti sono geometricamente sovrapposte a corpi geologici a bassa permeabilità, la presenza di discontinuità tettoniche ad alto angolo e dal rigetto significativo, influenza l’idrodinamica sotterranea basale, inducendo una compartimentazione; • Questa compartimentazione, unita agli elementi di eterogeneità verticale, induce la frammentazione dei recapiti sorgivi, nonché una notevole diversificazione dei caratteri idrochimici delle stesse emergenze.A few studies have been carried out worldwide in peridotite aquifer systems (e.g., Dewandel et al., 2005), despite their wide distribution. The main aim of this study was the experimental analysis of the hydrogeological behaviour of a test system in Northern Italy. The test system is the ultramafic massif of Mt Prinzera (Lat.44° 38'30''N, Long.10°5'E), located close to the confluence of the rivers Taro and Sporzana in the province of Parma, in the municipalities of Terenzo and Fornovo Taro. An interdisciplinary approach has been utilised, due to the really complex scenario. The following main activities have been carried out: • Geologic and structural survey; • Geomorphologic survey; • Hydrogeological monitoring (the discharge of 14 springs has been monitored throughout a hydrologic year, on a weekly basis); • Physico-chemical analyses (major and minor constituents) of all springs (two times); • Isotopic analyses (18O and D) of spring- and rain-waters, on a weekly basis; • Isotopic analysis (tritium) of some representative springs; • Biomolecular investigations and microbial community characterisation. The main results of the study can be summarised as follows: The ultramafic medium is made of several lithological units, tectonically overlapped. Between them, a low-permeability, discontinuous unit has been identified in a wide portion of the system. This unit behaves as an aquitard and causes a perched groundwater to temporary flow within the upper medium, close to the ground surface. This perched groundwater flows out along several depressions, and then several high-altitude temporary springs can be observed during recharge, together with several perennial base springs. The existence of several base springs is caused by the compartmentalisation of the system, due to high-angle tectonic discontinuities. This complex hydrogeologic scenario leads to the coexistence of different hydrochemical facies and microbial communities, in some cases strictly linked one to each other. References DEWANDEL B., LACHASSAGNE P., BOUDIER F., AL-HATTALI S., LADOUCHE B., PINAULT J.L. & AL-SULEIMANI•Z. (2005) - A conceptual hydrogeological model of ophiolite hard-rock aquifers in Oman based on a multiscale and a multidisciplinary approach. Hydrogeology Journal, 13, 708-726

Estimation of effective recharge in hard rock aquifers based on spring discharge monitoring during the low flow season

Hard rock aquifers (or discontinuous aquifers) are commonly intended as igneous or metamorphic rocks with very low primary porosity and a significant however discontinuous and strongly anisotropic secondary porosity (i.e. fractures) due to tectonic stresses and weathering. In some cases, the term \u201chard rock aquifer\u201d is well suited also for sedimentary fractured rocks. This is the case of the turbiditic formations in the Northern Apennines (Italy), that represent the most valuable groundwater reservoir in the region. In such cases, the quantification of water resources hosted in the hard rock aquifers becomes of paramount importance. We propose a method to quantify the effective recharge occurring within a spring recharge area in a hard rock aquifer setting when only spring discharge monitoring during the low flow season (summer) is available. An empirical relationship was found between the average annual discharge of a spring and its average summer discharge, starting from a large database of 11 hydrologic years of discharge monitoring on more than 80 springs. Such relationship is linear on a log-log scale and changes according to the Maillet\u2019s recession coefficient. The average annual flow rate obtained from summer monitoring data (i.e. the average summer discharge and the Maillet coefficient) is considered as a proxy of the effective recharge occurring within the spring recharge area. The proposed method was tested both in turbiditic and ophiolitic hard rock aquifers in the Northern Apennines in different hydrologic years, providing an overall accuracy in the range of \ub115% with respect to the actual annual average spring discharges. Thus, this is a promising tool to support the application of hydrologic balances in hard rock aquifers. However, further tests should be carried out in different hard rock aquifer settings in order to form a basis for more realistic expectations about the overall validity of the method

Is there an ideal protocol for sampling macroinvertebrates in springs?

Sampling in springs has several technical problems due to their reduced dimensions and habitat heterogeneity. A standardized quantitative method for sampling crenic macroinvertebrates has never been proposed. The aim of this study was to compare different sampling methods and consider their environmental impacts. First, we present a review of sampling methods found in the literature and discuss their advantages and disadvantages with respect to selective collection of the target community and habitat disturbance. Altogether, 10 different methods have been reported, the use of nets being the most common protocol. Second, we report the results of macroinvertebrate samplings performed in three springs, each surveyed twice, using three different methods (multi-habitat proportional hand net, baited traps, and vegetation washing), in order to compare their effectiveness in collecting macroinvertebrates. Overall, 32 macroinvertebrate taxa, mostly identified at family level, were collected in the sampled springs. Significant differences in abundances were found using different methods, while results for community structure were comparable between the hand net sampling and the combined use of the other two methods, notwithstanding slight differences in the composition of Coleoptera and Diptera assemblages. The hand net, with a multi-habitat proportional approach, yielded more thorough results, making it suitable for biodiversity inventories but having some potentially negative effects on spring habitats. Traps and vegetation washing are also reliable methods with negligible impacts on spring ecosystems that can be conveniently used in ecological studies

Spring discharge and groundwater flow systems in sedimentary and ophiolitic hard rock aquifers: Experiences from Northern Apennines (Italy)

This chapter deals with hydrogeological characterization and springs/upreach streams monitoring activity on different test sites in Northern Apennines (Italy) where turbiditic and ophiolitic hard rock aquifers occur. The work aimed to define the investigation tools able to parameterize the aquifer and build-up a methodology for hydrogeological mapping. Hydrological analysis of base flow, tracer testing with fluorescent dyes and numerical flow modelling by the equivalent porous medium approach were used for the evaluation of direct recharge, quantification of flow and transport parameters and implementation of numerical models, calibrated by continuous discharge monitoring, finalized to define spring flow paths and protection areas. The ratio between direct recharge and total precipitation resulted in the range 0.13\u20130.17 for turbidites and 0.35\u20130.40 for igneous ophiolites. Groundwater average effective velocity ranges from 3.6 m/d in the thin-bedded pelitic turbidites to 39 m/d in the calcareous turbidites