Eastern Po Plain Research Articles

Constraining a bioavailable strontium isotope baseline for the Lake Garda region, Northern Italy: A multi-proxy approach

The evidence of prehistoric long-distance exchange networks in northern Italy is overwhelming, attested by several finds of non-local raw materials in Bronze Age pile-dwelling settlements of Lake Garda and eastern Po plain, like amber beads and bronze artefacts. Metals are dispersed throughout Bronze Age Europe from mining communities within the Alpine regions, and possibly local artefacts, like the Peschiera-type daggers, are known from archaeological records throughout Europe. This positions the region as part of organized networks of trade and communication connecting prehistoric Europe from north to south. This, however, does not in itself indicate a similar long-distance mobility of prehistoric individuals. To investigate individual, human provenance and mobility, the strontium (Sr) isotope methodology compares strontium isotope analysis of human remains to bioavailable strontium isotope baselines characterizing the regions of interest. We present here environmentally based, multi-proxy (water, soil leachates and plants) Sr baselines from the Lake Garda region. Our results show two separate baselines, roughly corresponding to the geographical distribution of rock types and erosional products thereof. One baseline is valid for the Lake Garda region, where Mesozoic carbonates are a dominant surface-near strontium source, and for the central Po plain north of River Po. We constrain this to 87Sr/86Sr = 0.7088 ± 0.0014 (2σ; n = 44) when including 9 compatible samples reported previously. The second Sr-baseline is valid for Alpine areas dominated by magmatic (basalts excluded) and metamorphic bedrock around the Fersina valley. We constrain this to 87Sr/86Sr = 0.7146 ± 0.0058 (2σ; n = 22) when including 11 compatible samples reported in previous studies. The baselines are compatible with previously reported results of other Sr proxies such as snails, archaeological fauna, and agricultural soils and products from the region.

Late Glacial and Holocene buried black soils in Emilia (northern Italy): genetic and paleoenvironmental insights

PurposeThe existence of black horizons (BHs) is often highlighted in European soils, and in the Po River plain of northern Italy. Nevertheless, BH chronological frameworks and genetic models are still debated. The present study investigated the genesis of BHs in the eastern Po Plain where they are buried at various depths.Materials and methodsSoil sequences were investigated with a multidisciplinary approach integrating geomorphologic, stratigraphic, pedologic, geochemical, isotopic, palynological, and radiometric analyses.Results and discussionThe formation of the studied BHs was scattered over time from the Last Glacial Maximum to at least the middle Holocene. The new data indicate that BHs developed when the landscape was dominated by coniferous forest during conditions that were totally different from the current pedoclimatic setting. The recurrent presence of black particles indicates that this vegetation cover was systematically affected by fire episodes that induced soil degradation and mineralization processes of the original organic compounds, thus contributing to darkening of the upper soil horizons.ConclusionsBH formation clearly coincided with cold time lapses. Evidence for repeated fire events (natural or human-induced?) provides insights for the controversial debate on early anthropogenic impacts on the environment.

The Neolithisation of the Adriatic: Contrasting Regional Patterns and Interactions Along and Across the Shores

Abstract The beginning of the Neolithic in the Adriatic region dates back to approximately 6000 cal BC, and the appearance of Impressed Ware pottery marks its generic development. By combining lithic, economic, and paleoenvironmental data, we propose a new arrhythmic model for the chronology of Neolithisation in the Adriatic. On the one hand, the available data suggest that in the south-central part of the basin (Dalmatia and Apulia) the transition to farming was relatively quick, resulting from the colonisation of an open landscape (seemingly linked to the “8.2 ka event” and the onset of a drier climate). These newcomers mostly settled in the fertile plains of the Dalmatian and Apulian hinterlands, basing their subsistence almost exclusively on agriculture and livestock, while lithic blade production in cherts from Gargano (southern Italy) indicates important social aspects and complex management strategies (mining activities, more complex modes of pressure flaking, and specialised distribution networks). However, on the other hand, in the northern Adriatic (Istria, Karst, eastern Po Plain, and Marches), the Neolithic emerged somewhat later, possibly as a result of some form of acculturation. Although available data are still scarce, some evidence suggests that the last Mesolithic groups played an active role in the process of Neolithisation in these areas, where certain Castelnovian traditions have been identified in the lithic production accompanying Impressed Ware (the use of local cherts, lamellar production by indirect percussion, and “simpler” forms of pressure flaking) and in the economy, e.g. importance of fishing.

What kind of calcite? Disclosing the origin of sparry calcite temper in ancient ceramics

The addition of temper in the pottery manufacturing process is attested since Prehistoric Times and is still a production choice adopted in the ceramic industry. When the temper is composed of minerals and rocks which outcrop in regions distant from each other, new questions about the production technology arise. Such situations can be explained by considering the recycling of imported rocks, including those used for architectonic elements or sculptures, mainly coming from contemporary or earlier buildings, a practice that was widely diffused during the Roman and successive periods. This study presents evidence of the deliberate addition of recycled white marbles and sparry calcite (probably from calcareous sinters/calcite alabasters) within the long-lived production (between the 4th and 14th century CE) of coarse and cooking ware in north-eastern Italy. The petrographic analysis of about 200 potsherds attested the use of marble as unusual kind of temper, in addition to fragments of sparry calcite, in about half of the repertoire. The occurrence of different types of marbles, associated with rocks and minerals typical of the alluvial deposits of the eastern Po plain as well as locally available rocks (Euganean Hills trachyte), clearly pointed to the intentional addition of recycled marble fragments from ancient spolia, excluding the hypothesis that the pottery was imported from other regions. Detailed petrographic and microstructural analysis, including maximum grain size (MGS), accessory minerals (when observed) and grain boundary shapes allowed us to limit the provenance of these marbles to the most important Mediterranean classical source regions. These conclusions have been confirmed by the oxygen and carbon stable isotope data derived from marbles and calcite fragments mechanically separated from the ceramic paste. Some fragments of sparry calcite were characterised by very negative δ13C values, significantly different from known marble varieties, and typical of calcite crystallised in superficial geological environments, consistent with calcareous sinters, such as calcite alabasters. Moreover, a series of firing experiments were carried out in the temperature interval between 450 °C and 800 °C, both reproducing oxidising and reducing conditions, on clay pastes tempered with Carrara marble, and fired, to evaluate whether these anomalous δ13C values observed in the ancient ceramic inclusions could also be related to the firing process.

Thermal model of the Piedmont Po Plain shallow aquifer (NW Italy) with the statistical temperature distribution

This study analyses the temperature distribution underneath the Piedmont Po Plain (NW Italy), where an important shallow aquifer exists due to fluvial and outwash deposits. A total of 118 thermal logs, for a total of 513 temperature measurements in spring 2008 and 585 in autumn 2008, were used to propose the conceptual thermal model of the vertical temperature distribution in the shallow aquifer of the western Po Plain. A constant temperature depth between 30 and 50 m below ground level was observed, under which aquifer temperatures were constant in the range 13−15 °C during the year independent of the external climatic condition. Above the constant temperature depth, the variable temperature zone, where the temperature is strongly influenced by external seasonal variations, was observed.Moreover, the collected thermometric data were processed, and the solution to the heat diffusion equation underground allowed us to determine the average distribution of temperature at different depths over time.This study provides a more detailed conceptual model of the temperature distribution in the Piedmont Po Plain. The model can be applied to other areas with similar hydrogeological characteristics (e.g., the eastern Po Plain or large plain alluvial aquifers). The paper also furnishes a description of the physical processes of heat diffusion in the shallow aquifer, as supported by statistical analysis. The proposed methodology may be adopted as a simple statistical method for the assessment of temperature values for the low-enthalpy geothermal exploitation of groundwater resources.

Seismic Noise-Based Strategies for Emphasizing Recent Tectonic Activity and Local Site Effects: The Ferrara Arc, Northern Italy, Case Study

During the seismic crisis of May–June 2012, that strongly affected the central sector of the Ferrara Arc, relevant coseismic effects were observed, such as ground deformations and amplification phenomena due to low quality mechanical characteristics of the shallow subsurface (i.e. few hundreds of meters). This portion of the subsurface is not investigated by neither hydrocarbon explorations (too deep) nor geotechnical surveys (too shallow). Furthermore, direct analysis is not cost effective to carry out over such a wide area. To overcome these limitations, we exploited seismic noise-based strategies, which are not invasive and do not require expensive equipment. We carried out several single-station and array measurements (i.e. ESAC, Re-Mi, and HVSR), across some of the major tectonic structures of the eastern Po Plain, belonging to the most advanced buried sector of the Northern Apennines. Such investigations were performed along two profiles, about 27 km-long and oriented SSW–NNE, i.e. almost perpendicular to the regional trend of the Ferrara Arc structures. Our results clearly document lateral shear wave velocity variations and the occurrence of resonance phenomena between 0.52 and 0.85 Hz. Additionally, based on inversion procedures, we were able to infer the depth of the resonant interface(s) and we associated such interface(s) to the major known stratigraphic discontinuities, thus emphasizing the recent tectonic activity of the blind thrusts affecting this sector of the Ferrara Arc.

Late Holocene palaeo-environmental reconstruction and human settlement in the eastern Po Plain (northern Italy)

A sedimentary sequence comprising a Late Bronze age archaeological site located in the alluvial plain between Bologna and Ferrara (Northern Italy) was studied from geochemical, pedological and palynological points of view. Sediment geochemistry (in particular, the high content of Cr) indicates the existence of a thin set of Po River deposits coeval to the Bronze Age site, lying among alluvial sediments delivered from the Apennine chain. The soil corresponding to this chronological interval is also characterised by anomalous content of phosphorous and chalcophile elements (mainly Cu and Zn) that are clearly related to anthropogenic activities. The results were critically discussed to reconstruct the geomorphological and regional palaeo-hydrographic settings to support the existence of an unknown buried Po River course active during the late Middle Bronze Age in the southern part of the alluvial plain. The 14C and pollen analyses corroborate this interpretation, also providing clues on the genesis of more superficial peaty horizons. On the whole, the results provide fresh insights on the occurrence of ancient human settlements in the southern Po River alluvial plain.

The genusCyperusin the eastern Po Plain (Italy): historical and recent data

AbstractThe genus Cyperus L. is revised in the eastern Po Plain and in the Po Delta (Veneto and Emilia-Romagna Regions, Italy), based on historical data analysis, examination of public herbaria and field observations. The genus includes autochthonous, long-time naturalized and recently introduced species: 16 taxa are recognized as actually present in the study area, whereas two others were recorded only once. Most species of the genus live along the course of the Po river, e.g. the recently identified Cyperus odoratus L., and/or in the rice fields. Some naturalized species of Cyperus are considered invasive, e.g. Cyperus esculentus L. and Cyperus glomeratus L.; others, e.g. Cyperus microiria Steud., Cyperus eragrostis Lam. and even C. odoratus, have recently been spreading widely. Cyperus glaber L., Cyperus strigosus L. and Cyperus erythrorhizos Muhl. are rare species. The latter was only recently detected for the first time in Europe and is here reported from two additional sites, the oldest dating back ...

Evaluation of aquifer recharge and vulnerability in an alluvial lowland using environmental tracers

A multi-layered aquifer system (eastern Po plain, northern Italy) was investigated by means of isotopic data, with the goal of quantifying groundwater recharge from different sources and assessing the intrinsic vulnerability of aquifers to surface sources of contamination. The geology of the area is based on a stratigraphic alternation of several sandy aquifers and silty–clayey aquitards, down to a maximum depth of 200 m b.g.s. Water isotopes (δ18O, δ2H), and hydrochemical analyses were performed on groundwater samples collected from a regional network of 70 boreholes distributed on an area of almost 2000 km2. In addition to the regional sampling, detailed vertical isotopic profiling was performed in one location by means of groundwater and sediment samples collected through the whole sequence of aquifers and aquitards. Water isotopes indicated mixing from different sources of recharge (i.e., vertical recharge, Po river, deeper aquifers). Mixing calculations were used to quantify the contributions to the aquifers from the different sources. The vertical profiling allowed for integrating and validating the interpretations at a regional scale. The recharge pattern defined for the different aquifers was translated into an index of hydrogeologic interconnections with the surface, which represents a physically based proxy of the intrinsic vulnerability of the aquifers to surficial sources of contamination. The investigated setting can be considered to be representative of many other anthropized and groundwater demanding plain settings around the world. Thus, the proposed method represents a valuable approach for such settings both for recharge quantification (e.g., to be used as input for numerical modeling) and for a physically based assessment of the intrinsic vulnerability.

HVSR technique in near-surface thermal-basin characterization: the example of the Caldiero district (North-East Italy)

In the present work, non-invasive microtremor survey is applied for the preliminary characterization of the thermal district of Caldiero, in the eastern Po Plain (Italy), a thermal resource known since the Roman times for the presence of warm springs. The work’s aim was to test the suitability of the microtremor passive technique for the preliminary characterization of a thermal basin, in terms of resonance properties between the alluvial deposit covers and the rocky bedrock. In particular, the horizontal-to-vertical spectral ratio (HVSR) single-station technique is adopted to estimate the resonance properties of the geothermal basin. More than 100 HVSR single-station measurements are collected and analyzed in the area studied. HVSR information is integrated with the findings of the analysis of the data relative to more than 20 deep wells. Such an integration permits the calibration for validation of the geophysical data. The correlation between the results from microtremor survey, LiDAR data analysis, and wells information highlighted the main geological structures of the site, which are potentially responsible for the thermal waters arising. HVSR results are then interpreted in terms of regional geological setting, textural, and hydrogeological properties of the superficial deposits and the underlying rocky bedrock. The results of this method confirm the existence of significant correlations between the resonance behavior of the basin, as determined by the HVSR technique, and the geological assessment. This suggests that the single-station technique could be a very promising tool for a rapid and preliminary non-invasive method for the near-surface general characterization of geothermal basins.

HVSR technique as tool for thermal-basin characterization: a field example in N-E Italy

The Euganean thermal basin, located in the Eastern Po plain (Italy), is one of the most important thermal districts of Italy (Euganean–Berician Thermal District). The presence of hot water in the basin has brought about its exploitation over time. The thermal area has been known since the Roman Empire and is still of crucial interest for the profitable use of its hydro-geological resources. For these reasons the water cycle of the thermal area has been thoroughly studied, in particular with regard to its chemical and hydrogeological properties. The effects of well pumping, such as subsidence and water temperature steadiness, have been monitored over time. In the present work, the Horizontal to Vertical Spectral Ratio (HVSR) single station microtremor technique was applied as a non-invasive geophysical tool for the characterization of a part of the Euganean–Berician thermal district involving the municipalities of Abano and Montegrotto towns. This study represents the first correlation between the results from microtremor geophysical surveys and the thermal basin geological structure, including remote sensing data and thermal well information. More than 50 HVSR measurements from single stations were collected and analysed, in close correlation with the vast amount of available borehole logs, well exploitation data and SAR interferometry measurements collected for the monitoring of land subsidence induced by thermal water pumping. The aim of the work was to evaluate the suitability of the microtremor technique for the preliminary characterization of a thermal basin, in terms of resonance properties of the alluvial deposits covering the rocky bedrock, evaluated by means of HVSR methods. HVSR results were interpreted in terms of regional geological setting and hydrogeological properties of the subsoil. Our field results confirmed the existence of significant correlations between the resonance behaviour of the basin determined by the HVSR technique and the geological structures, suggesting that single station measurements are a promising tool for creating a rapid and preliminary non-invasive contribution to the characterization of the geothermal basin.

Overview on the Strong-Motion Data Recorded during the May-June 2012 Emilia Seismic Sequence

Online Material: Supplemental table, figures. On 20 May 2012, at 02:03:52 GMT, an earthquake with M w 6.1 (Regional Centroid Moment Tensor [RCMT]; http://www.bo.ingv.it/RCMT) occurred in northern Italy striking a densely populated area. The mainshock was followed a few hours later by two severe aftershocks having the same local magnitude ( M L 5.1, Fig. 1a), and by hundreds of smaller aftershocks. Nine days later, on 29 May, at 07:00:03 GMT, a second event with moment magnitude M w 6.0 (RCMT; http://www.bo.ingv.it/RCMT) occurred to the west, on an adjacent fault segment. This event was also followed by hundreds of aftershocks, three of them having local magnitudes 5.3, 5.2, and 5.1 (Fig. 1a; locations from Istituto Nazionale di Geofisica e Vulcanologia, hereinafter INGV; http://iside.rm.ingv.it/; Malagnini et al. , 2012; Scognamiglio et al. , 2012). Despite the moderate number of casualties if compared to other major events in Italian history, the economic loss was extremely high, resulting in about EUR 5 billion (AON Benfield, 2012; http://www.aon.com/), as the majority of Italian industrial activities and infrastructure concentrate in this area, the eastern Po plain, which is the largest sedimentary basin in Italy. Figure 1. (a) Simplified geological sketch of the Po plain and surrounding northern Apennines and Southern Alps fold‐and‐thrust belts. Key to symbols: stars, earthquakes of M >5 of the 2012 Emilia–Romagna seismic sequence, dimension proportional to the magnitude; dark gray areas, Composite Seismogenic Sources (CSS) of the DISS database (http://diss.rm.ingv.it), the upper tip of the fault plane is highlighted in black. Focal mechanisms of the 20 and 29 May 2012 earthquakes are from the TDMT database (http://cnt.rm.ingv.it/tdmt.html). (b) Simplified geological sections crossing the Po plain and showing thickness variation of the Plio‐Quaternary sedimentary sequence correlated with syncline–anticline pairs of the northern Apennines and Southern Alps thrust belts. Modified from Cassano et al. (1986), sections 1, 2, …

Are the ancient forests of the Eastern Po Plain large enough for a long term conservation of herbaceous nemoral species?

We analysed the effects of patch configuration and site history on vascular plants in ancient forests of the Eastern Po Plain, documented back to 1740. Despite their reduced size, all the forests are part of Natura 2000 Network and significantly contribute to the maintenance of a threatened habitat and support biological diversity of the Continental biogeographic region. The presence of some functional ecological plant species groups was correlated with patch configuration and age. Habitat quality, in terms of suitability for forest species, was found to be important in explaining the presence of species of high conservation value, but patch age (as an indicator for habitat quality) played a major role too. For core forest species, patch area is a redundant variable in explaining species richness relative to habitat quality and patch age and the extinction of specialists seems to occur mainly in a deterministic way. Even small forest fragments can be very important for maintaining plant species diversity, at least if they are of high habitat quality and if the forest management is appropriate. However, to achieve a long term conservation, management plans should also aim at an improvement of the anthropogenic matrix surrounding forest remnants.

The MCS macroseismic survey of the Emilia 2012 earthquakes

<p>Most of the inhabitants of northern Italy were woken up during the night of May 20, 2012, by the Mw 6.1 earthquake [QRCMT 2012] that occurred in the eastern Po Plain. The mainshock was preceded a few hours before by a Mw 4.3 shock, and it was followed by a dozen Ml >4 aftershocks in May and June, amongst which 11 had Ml ≥4.5. On May 29, 2012, a second Mw 6.0 mainshock struck roughly the same area [QRCMT 2012], which resulted in further victims, most of whom were caught under the collapse of industrial warehouses. Such earthquakes are an unexpected event in this region, as testified by the lack of local epicenters in the Italian seismic catalog [Rovida et al. 2011: CPTI11 from now] and by the consequent low level of the local seismic classification (seismic zone 3) [DPC 2012]. Apart from the warehouses and hundreds of old, crumbling farmsteads, severe damage was focused on ancient, tall buildings, such as churches, bell towers, castles, towers and palaces. Residential buildings generally suffered only light and/or moderate effects, apart from some exceptional cases. Using the Mercalli–Cancani–Sieberg (MCS) scale [Sieberg 1930], we began a macroseismic survey in the early morning of May 20, 2012, that ultimately included visits to almost 200 localities, 52 of which were carried out before the second mainshock. […]</p><br />

Applying the Multiple Inverse Method to the analysis of earthquake focal mechanism data: New insights into the active stress field of Italy and surrounding regions

In order to obtain new insights into the active tectonic setting of the Italian territory and surrounding regions, the Multiple Inverse Method (MIM) has been applied to the analysis of fault plane solutions from more than 700 earthquakes with Mw≥4. The active stress field in the top 40km of the lithosphere has been defined for four 10km-thick layers, each including 810 square cells of 1.5° side. The obtained stress field maps point out that most of the upper crustal seismicity of the Western and Central Alps is controlled by a strike-slip regime, which is dominant also in part of the Dinarides, Albanides and Hellenides and in a large sector encompassing eastern Sicily and the Malta area to the eastern Tunisia offshore. On the other hand, the well-known extensional belt occurring in the interior of the Apennines appears to extend well beyond the backbone of Italy, potentially reaching the outer foothills of the northern Marche region, while the adjacent Adria block (extending to the eastern Po Plain and the outer Dinarides) sticks out as a major area characterised by dominant thrust faulting in the upper crust. A similar regime characterises also a large sector of the western Tyrrhenian Sea, from NE Tunisia through western Sicily and the west coast of Sardinia, to the Provence coast.Besides lateral variations, our analysis also points out a significant vertical heterogeneity of the stress field, the deeper levels (20 to 40km) investigated in this study being characterised by dominant horizontal maximum compression even in areas of upper crustal extension.The application of the MIM to a large seismological dataset, providing basic information for the compilation of active stress maps, contributes to a better understanding of active tectonic processes and may be used for improving seismotectonic zoning and reservoir management.

High frequency attenuation of shear waves in the southeastern Alps and northern Dinarides

SUMMARY We investigated the high frequency attenuation of S waves in the southeastern Alps and northern External Dinarides using waveforms from 331 earthquakes (3.0 < Mw < 6.5). The spectral decay parameter, k, was computed using 1345 three component high quality records, collected by the Italian Strong Motion Network (RAN) and by the Short-Period Seismometric Network of northeastern Italy (NEI) in the period 1976–2007. Weak motion data from 11 stations of the NEI network and strong motion data collected by five accelerometers of the RAN were analysed. The k parameter was estimated in the 0–250 km distance range, in a frequency band extending from the corner frequency of the event up to 25 or 45 Hz, using the amplitudeaccelerationFourierspectraofS waves.Theobservedrecord-to-recordvariabilityof k was modelled by applying a generalized inversion procedure, using both parametric and nonparametric approaches. Our results evidence that k is independent on earthquake size, while it shows both site and distance dependence. Stations of the NEI network present the same increase of k with epicentral distance, RE, and show values of the zero-distance k parameter, k0(S), between 0.017 and 0.053 s. For the whole region, the k increase with distance can be describedthroughalinearmodelwithslopedk/dRE =(1.4 ±0.1) ×10 −4 skm –1 .Assumingan average S-wave velocity, β = 3.34 km s –1 between 5 and 15 km depth, we estimate an average frequency independent quality factor, QI = 2140, for the corresponding crustal layer. The non-parametric approach evidences a weak positive concavity of the curve that describes the k increase withRE at about 90 km distance. This result can be approximated through a piecewise linear function with slopes of 1.0 × 10 −4 and 1.7 × 10 −4 sk m –1 , in accordance with a three layers model where moving from the intermediate to the bottom layer both QI and β decrease. Two regional dependences were found: data from earthquakes located westward to the NEI network evidence weaker attenuation properties, probably because of S-wave reflections from different parts of the Moho discontinuity under the eastern Po Plain, at about 25–30 km depth, while earthquakes located eastward (in western Slovenia), where the Moho deepens up to 45–50 km, evidence a higher attenuation. Moreover, the k estimates obtained with data from earthquakes located in the area of the 1998 (Mw = 5.7) and 2004 (Mw = 5.2) Kobarid events are 0.017 s higher than the values predicted for the whole region, probably because of the high level of fracturing that characterizes fault zones. The comparison between measured and theoretical values of k, computed at a few stations with available S-wave velocity profiles, reveals that the major contribution to the total k0(S) is due to the sedimentary column (from surface to 800 m depth). The hard rock section contribution is limited to 0.005 s, in accordance with a maximum contribution of 0.010 s predicted by the non-parametric inversion.

Two‐ and three‐dimensional numerical simulations of the stress field at the thrust front of the Northern Apennines, Italy

Two‐ and three‐dimensional mechanical models simulating the seismic cycle along thrust faults are devoted to the active front of the Northern Apennines buried under the Plio‐Pleistocene sediments of the eastern Po Plain. The models aim at understanding two peculiar characters of the stress field in the region: (1) analyses of borehole breakouts and other well data, integrated with seismological information and field evidence, show along‐depth variations (from extensional to strike slip to compressional for increasing depth) of the stress style along the active Mirandola anticline and (2) seismic and borehole breakout data suggest strong lateral rotations of the stress axes along the frontal and lateral ramp portions of the Mirandola thrust fault. Modeling results allowed us to understand that the mechanical decoupling along faults strongly affects the stress distribution in their vicinity, under the form of strong rotations of the principal stress axes. As a consequence the slip (either fast or slow) along active blind thrust faults could drive to local stress fields very different from that associated with regional tectonics. This could explain, together with other processes (such as differential compaction), the along‐depth variation of the stress field observed in the Mirandola region and the strong lateral rotations of the principal stress axes observed along the lateral ramp of the Mirandola thrust fault. Finally, the seismic activity along one of the thrust fault ramps along the Apennines front should not interfere with the state of stress along adjacent ramps.

Sedimentary and tectonic evolution in the eastern Po-Plain and northern Adriatic Sea area from Messinian to Middle Pleistocene (Italy)

In the last 15 years, several Eni-Agip multidisciplinary studies were focused on the buried Messinian–Pleistocene succession of the eastern Po Plain and northern Adriatic Sea. A detailed revision of the biostratigraphy, chronostratigraphy, sedimentology, seismic interpretation and sequence stratigraphy was performed using the very large Eni subsurface dataset including regional 2D and 3D seismic surveys and over 500 deep wells. The new basin-scale geological model of the area is presented in this paper. During the Messinian and the Plio-Pleistocene the eastern sector of the Po Plain and the northern Adriatic Sea were part of the northern Apennine foreland basin. In this time span, the tectono-sedimentary evolution of the area largely coincides with the development of the Po Plain-Adriatic Foredeep (PPAF), of its ramp and foreland areas and of the related northern Apennine thrust-top basins. During latest Tortonian–Pliocene interval, as a consequence of the severe Apennine compressional tectonics, the PPAF underwent four major phases of deformation and depocenter migration towards the foreland (NE). These phases also generated four basin-scale tectonic unconformities referred here as Late Tortonian Unc., Intra-Messinian Unc., Intra-Zanclean Unc. and Gelasian Unc. The Messinian to Pleistocene PPAF sedimentary succession can be subdivided in four allogroups bounded by the basin-scale tectonic-generated unconformities: EM (pre- and syn-evaporitic Messinian), LM (post-evaporitic Messinian–early Pliocene), EP (early-middle Pliocene) and LP (late Pliocene–Pleistocene). The allogroup boundaries are produced by major compressional events generating phases of migration of the foredeep depocenters towards the foreland and abrupt changes in type and distribution of depositional systems. The foredeep succession is mainly composed of turbidites with prevailing highly-efficient Type I turbidite systems. Turbidite sand/sandstone lobes and turbidite basin plain deposits are the most common facies associations. Allogroup EM: the foredeep is subdivided in two different depocenters by the Emilia-Romagna arc. The foredeep succession is represented by the turbidite sandstones and shales of the Bagnolo Fm. Shelfal, marginal marine and evaporitic sediments are deposited in the Veneto and northern Adriatic foreland basin. Allogroup LM: during the post-evaporitic Messinian, the turbidites of the Fusignano Fm. are deposited within the foredeep basin, while most of the foreland area is subaerially exposed and eroded by deep incised-valleys. The base of the Pliocene corresponds to an abrupt eustatic rise. Poorly-efficient turbidites of the Canopo Fm. deposited within the foredeep basin. The foreland is interested by a rapid southward progradation following the transgressive phase. Allogroup EP: activation of the inner thrust of the Ferrara fold-belt and foredeep fragmentation. Deposition of highly-efficient turbidites belonging to the Porto Corsini and “inner” Porto Garibaldi Fms. Deposition of condensed shales in the foreland area. Allogroup LP: complete deformation of the Ferrara folds and of the northern Adriatic thrust-and-fold belt. Onset of a new foredeep basin in the eastern Veneto and northern Adriatic Sea and sedimentation of the highly-efficient turbidites of “outer” Porto Garibaldi and Carola Fms. During the middle Pleistocene the Po Plain progradation leads to the complete filling of the foreland basin.

From thrust-and-fold belt to foreland: hydrocarbon occurrences in Italy

Abstract Italy is the most hydrocarbon endowed country of southern Europe, with total discovered reserves (produced+remaining) of 1840 million barrels of oil and 30 trillion ft 3 of gas. The production of oil amounts to 43.2 million barrels per year, about 75% of which comes from the Val d'Agri Field in the southern Apennines. The production of gas is 340 billion ft 3 per year, most of it coming from the northern Adriatic Sea. Hydrocarbon occurrences derive from a variety of petroleum systems which are the result of a complex geological history. At least five important source rocks have been recognized which are distributed in age from Mesozoic through Pleistocene. Three of them were deposited during Mesozoic crustal extension and are mainly oil-prone. Hydrocarbon occurrences associated with these sources are usually found in complex carbonate structures along the Apennines thrust-and-fold belt and in the foreland. Villafortuna–Trecate (Po Plain), Val d'Agri/Tempa Rossa (southern Apennines) and Gela (Sicily) fields represent the largest oil accumulations pertaining to these systems. Two other important sources rocks were deposited in the foredeep terrigenous units of the foreland basins which formed during the Cenozoic orogenesis. The older source is thermogenic gas-prone and is found in the highly tectonized Oligo-Miocene foredeep wedges: gas occurrences associated with this source are mainly concentrated along the northern Apennines margin (e.g. Cortemaggiore Field), in Calabria (e.g. Luna Field) and Sicily (e.g. Gagliano Field). The younger source is biogenic gas-prone and is situated in the outer Plio-Pleistocene foredeeps. The most important gas fields of Italy, located in the eastern Po Plain and northern Adriatic sea (Barbara and other gas fields), have originated from this source. Hydrocarbon exploration in Italy is overall mature, especially for gas, whose residual potential is estimated to be 6.0 trillion ft 3 of reserves. The remaining potential of oil is estimated to be 800 million barrels.

GPS-based monitoring of land subsidence in the Po Plain (Northern Italy)

We use regional and local networks of continuously-operating GPS stations (CGPS) distributed in the northern–central part of the Italian peninsula to investigate the subsidence phenomenon of the Po plain sedimentary basin and vertical movements of the surrounding areas. The observations of 146 scientific and commercial stations are analyzed and compared, adopting analytical techniques widely used to study GPS coordinate time series. The use of simple antenna supports in commercial installations, instead of a more rigorous geodetic monument, does not seem to induce significant differences in the noise characteristics and in the amplitudes of annual and semi-annual periodic signals. The vertical velocity field deduced from 129 sites with observation time spans greater than one year, located in the Central–Northern Italian Peninsula, indicates the presence of two mainly subsidence areas: the Po Plain and the Arno Plain, while the sites located in the Alps and Apennine domains show relatively low uplift. The areas of the Po Plain monitored by GPS seem to indicate that the subsidence rate is constant or, in some cases, decreasing with respect to the values obtained from the last measurements, performed up to 2006 by means of both SAR and levelling techniques. Only the central part of the eastern Po Plain close to the Apennine border (Modena city area) is characterized by a peak in subsidence consisting in a velocity of about 15 mm/yr.