16 research outputs found
Quaternary hydrostratigraphy in the Po Plain: multiscale geology and forward modelling
No full textHydrogeological modelling at different scales is best performed if the hydrostratigraphic architecture is well described, accounting for the hierarchic arrangement of heterogeneities and the multiple scales of the geological features. To this purpose, an efficient combination of surface geology data (high detail and accuracy, 1D - 3D data, small to large-scale, low-rank) with subsurface borehole/geophysical data (1D - 2D, very small to very large scale, low detail and accuracy, undistinguished rank) is mandatory. The management of such a multi-scale and heterogeneous dataset is the starting point of this work. The aim is to define a 3-D stratigraphic framework at different scale, constrained by all the available data, as a mean to validate the different evolutionary and geometrical hypotheses formulated in the 1 - and 2-D data analysis carried out in a GIS environment. The study area is a 25x50 km, N-S transect of the Central Po Plain, the widest alluvial basin of Italy hosting multi-layered aquifers of Quaternary age. A reliable geological reconstruction in this area contributes to better define the 3-D geometries of the stratigraphic units, verifying the existent 2-D geological maps and sections. It also contributes to validate the evolutionary history of the Basin, as the result of the interaction of Quaternary Alpine glacial cycles (North), tectonic evolution driven by the Apennine thrusts (South), and changes in the accommodation and sedimentation rates. The method relies on the integration of geological, field-based “hard” data, interpretative cross-sections and maps, geo-history and evolutionary hypotheses, with GIS and GeoModeller software. GIS is dedicated to data management and pre-processing for the 3-D analysis; GeoModeller permits to simulate and visualize the stratigraphic/tectonic relations rapidly, honouring the geological constraints, in order to elaborate several forward models comparing contrasting architectural end evolutionary hypotheses. The dynamic approach I want to discuss is multi-scale and hierarchical. It refers to i) the hierarchic order of the different “geological entities” and ii) the nature/number of constraints that have to be taken into account at each scale of reconstruction, by the integration of both surface and subsurface geological data
Modelling complex geological structures in alluvial hydrostratigraphy : constraints from surface geology and subsurface data
No full textMorphostructural evidence of Late Quaternary tectonics at the Po Plain-Northern Apennines border (Lombardy, Italy)
No full textThe landscape of foreland basins adjacent to active mountain ranges evolves under the control of basinward tectonic propagation of the structural fronts, in competition with climate dynamics. The resulting palimpsest landscapes record the sequence of geomorphic evolutionary steps, and the spatial-temporal relations between the active geological processes. However, a precise evolutionary sequence is hard to decipher from low-relief settings, like the wide alluvial plains worldwide. About these topics we investigate the sequence of tectonic- and climate-driven processes which shaped the palimpsest landscape of a large Quaternary foreland basin, the Po Plain in Northern Italy. Above the average glacio-fluvial and alluvial plain of the basin, Late Quaternary intra-basin reliefs emerge, owing to syndepositional ramp folding and uplift driven by N-wards propagation of the outermost thrust fronts of the active N-Apennine chain.
The incremental tectono-morphological and depositional history of the region permits to describe the propagation of the structural front as a polyphase process, involving uplift, wrenching and late collapse of the reliefs. This history is documented by: relicts of uplifted planation surfaces covered by latest Pleistocene weathered loess units; polygonal facets, landslides and slope wedges along faults delineating the slopes of the largest among the intra-basin reliefs (San Colombano hill); hydrographic anomalies on the relief network (river diversions, piracy and perching of valleys, paleovalley fills), river diversions and cross-cut relations on the adjacent alluvial plain. These features testify the thrust-fold-related, pre-LGM uplift of the Late Pleistocene alluvial stratigraphy, the subsequent segmentation of the relief in differently uplifting blocks along Riedel faults, owing to activation of a transfer fault zone, and the LGM extensional collapse of the relief, along inherited fault systems. A late, post-glacial outwards propagation of the Apennine thrusts was buttressed by the opponent Alpine thrust-belt front and induced the entrenchment of the river network. River diversions on the plain were controlled by the orientation of the San Colombano hill fault systems. The distribution of historical earthquakes and the present-day geodetic data are coherent with this evolution.
The study documents how, in foreland basins, the syndepositional propagation of “blind” orogenic fronts shapes the palimpsest landscape with superimposed morphological, tectonic, and stratigraphic features of paleoseismic significance, and permits comparisons with the other low-relief basin settings worldwide
Active thrusting and glacial controls recorded by stratigraphic unconformities in a Quaternary foreland basin (Po basin, Northern Italy)
No full textIn active foreland basins, stratigraphic unconformities develop on the flanks and crests of the uplifting thrust-related structures and correspond to correlative conformities in the adjacent depocenters. The geometrical, morphological, stratigraphic, sedimentological, and petrographic attributes of unconformities and associated sediments are highly variable from the uplifting to the subsiding basin sectors. In Quaternary continental foreland basins, landscape evolution, sedimentation, and the nature of the geological boundaries are controlled by the competing turnovers of climate (i.e. glacial advances and retreats) and tectonics (i.e. steady-state uplift/subsidence vs. unsteady deformation increments).
In order to recognize the fingerprints of tectonic and climatic factors on the nature of the stratigraphic unconformities, we studied the Pleistocene shallow marine (Calabrian) to alluvial and glacio-fluvial sediments (Calabrian-Latest Pleistocene) associated to the active external arc of the N-Apennine thrusts in the Quaternary Po basin of Lombardy (N-Italy).
A set of intra-basin reliefs corresponding to ramp-folds was the key-site to describe the nature and attributes of the exposed Pleistocene unconformities and stratigraphy. We integrated different-scale geological, sedimentological, stratigraphic, geo-pedological, geomorphological, and structural field surveys, constrained by C14 and OSL age determinations, to down-trace the stratigraphic boundaries to the subsurface and to assist correlation of borehole logs and geophysical images. The surface facies associations of the stratigraphic units were compared to the litho-textural associations of their subsurface equivalents to draw the best fitting surface-subsurface model, which was constrained to the geological evolution and chronostratigraphy. A hierarchic 3D geological model was computed by the potential field method, which includes the 4D attributes of the stratigraphic boundaries and unconformities organized into three hierarchic orders. Among them, five Quaternary high-rank, and seven intermediate-rank unconformities were recognized.
The high-rank unconformities (Gelasian, intra-Calabrian, Early-Middle Pleistocene, Late Pleistocene and Latest Pleistocene-Holocene unconformities) are erosional, angular (high angle), composite, diachronous surfaces. They originated in front of and above the uplifting ramp-folds, where the discrete, polyphase, and unsteady propagation stages of the blind outermost Apennines arc directly controlled sedimentation, erosion, and accommodation patterns. The intermediate- and low-rank stratigraphic boundaries are either: (i) stratigraphic surfaces of erosion and deposition, occasionally with low-angle unconformity; (ii) stratigraphic surfaces of aggradation (covered by late Pleistocene loess units at places); (iii) morphological surfaces of stabilization marked by (paleo-) soils. These attributes and the 3D relations with the high-rank unconformities show that these surfaces formed during steady uplift/subsidence increments and/or at times or sites of tectonic quiescence. In these cases, the development of erosion surfaces, facies and provenance changes are not associated to tectonic-induced angles, wedging or fanning of sedimentary units. Chronological constraints link these changes to the regional advances and retreats of the Pleistocene alpine glaciers, suggesting that the intermediate-rank surfaces are mostly dependent on the major climate changes, while the low-rank ones relate to depositional unsteadiness, either autocyclic or short-term allocyclic
CHARACTERIZATION AND MODELLING OF COMPLEX GEOLOGICAL ARCHITECTURES: THE QUATERNARY FILL OF THE PO BASIN AT THE PO PLAIN-APENNINES BORDER (LOMBARDY, ITALY)
No full textObject of this work is the 3-D modelling of complex geological architectures in the Quaternary Po Basin (Lombardy, Italy). Reliable surface and subsurface models in Quaternary alluvial basins are important for several applications, including groundwater research and management, geohazard evaluation, exploitation and protection of other natural resources. The study area is the Po Plain-Apennine border in Lombardy (Italy), in a peculiar sector where the structural culminations of the buried Emilian Arc salient of the Northern Apennines determine the location of isolated reliefs in the Po Plain (i.e. San Colombano Hill and Casalpusterlengo – Zorlesco subtle relic reliefs). This area was selected because it permits to improve the 3-D modelling procedure in a complex tectono-stratigraphic-geomorphological setting, which is of interest for both the still controversial geological reconstructions of the Po Basin and the relevant issues in groundwater management and geothermal energy exploitation. The Quaternary sedimentary fill of the southern margin of the Po Basin in Lombardy records the complex interplay between active Apennine thrusting to the South, rebound and isostatic response to deglaciations at the flexed Alpine margin to the North and the dynamics induced by Quaternary glacial cycles. All of these factors produced the assemblage of nested stratigraphic, structural and geomorphological complexities which are the object of this work. Reliable 3-D models must account for multiple ranks and scales of sedimentary heterogeneity. To obtain such a result, this works attempts to compute 3-D models, constrained not only by the traditional explicit geological “hard” surface and subsurface data, but also by the implicit “soft” data represented by the increments of the geological evolution of the basin. At present, none of the available modelling methods incorporates geological evolution, hierarchy of stratigraphic and structural components of geological heterogeneity and uncertainty as formal rules of 3-D model building in a straightforward manner. Aim of the work is to propose an integrated, multidisciplinary methodology to combine both explicit and implicit geological knowledge as constraint for 3-D (4-D) architectural geological modelling of the study area. Specific aims of this work are: i) to reconstruct the surface and subsurface Quaternary geology of the study area at different scales; ii) derive the increments and the autogenic vs. allogenic controlling factors on the geological evolution; iii) develop alternative 3-D (4-D) models of the Quaternary sedimentary infill of the area, honoring the new maps and subsurface reconstructions and accounting for the incremental geological evolution; iv) contribute to improve and implement a method that combines explicit geological data with the implicit hierarchic and evolutionary constraints for 3-D geological modelling.
A multidisciplinary methodology has been set-up. It integrates i) classical geological, sedimentological, stratigraphic, geopedological, geomorphological and structural field surveys; ii) subsurface reconstruction based on stratigraphic correlation of borehole logs and geophysical images, along a fence of 2-D cross-sections over an area of 400 km2 and a maximum investigation depth of 150 m b.g.s.; iii) 3-D geological modelling based on integration of the GIS management of the multiple data-sets and the GeoModeller® 3-D modelling software. GeoModeller® was chosen for the feasibility to deal with the bounding surfaces, which is the key-concept to describe hierarchic frameworks and the key to introduce the genetic interpretation of the basin history (4th dimension) into 3-D representations. To do that, new software routines and novel concepts for the modelling rules were set-up and implemented in the commercial code.
Results of the work include: i) a new geological and geomorphological map of the San Colombano hill at 1:10.000 scale over an area of about 60 km2; ii) a hierarchic stratigraphic scheme of the surface-subsurface Quaternary succession of the southern Po Basin, integrated to the iii) incremental tectono-depositional evolution of the Po Basin-Apennine border, that relates the ranking and the significance of the stratigraphic and morphological boundaries to the hierarchy of the Quaternary increments of the geological evolution; iv) the conceptualization of the implicit hierarchic rules to be introduced into 3-D model building, and the procedure to progressively include the explicit and implicit geological rules within multi-scale realizations; v) some new computing routines which let GeoModeller® to manage the new rules and vi) alternative 4-D geological models accounting for different interpretations of the geological evolution.
Six high-rank increments of the geological evolution (“stages”) punctuated by low-rank steps have been described in this work. During stages 1 and 2, N-ward thrusting along the blind Emilian Arc originated the Zanclean and the Gelasian Unconformities. On the San Colombano hill, the Calabrian shallow marine San Colombano Fm. (PL4 highest-rank succession) unconformably overlies the truncated deep-marine Miocene formations, up-thrusted during Mio-Pliocene. At stage 3, Early to Middle Pleistocene increments of thrust-folding at the northernmost buried reaches of the Emilian Arc induced erosion of the intra-Calabrian unconformity (U1) and separated local depocentres related to the San Colombano and Casalpusterlengo – Zorlesco structures. These were filled by transitional and alluvial units (PS1 highest–rank succession). These regressive deposits, lap onto the uplifting structures of San Colombano and Casalpusterlengo - Zorlesco, suggesting the onset of their structural separation. At stage 4, these latter two structures were separated from the San Colombano thrust, since the Middle Pleistocene, by means of a newly interpreted dextral lateral ramp (San Colombano lateral ramp), as testified by the delayed migration of the depocentres of the Middle Pleistocene glacio-fluvial units and by the time-shift of the onlaps onto the different structures. After folding of U1, at the base of these units, the Early-Middle Pleistocene unconformity U2 was carved, bounding the base of the PS2 alluvial and glacio-fluvial high-rank succession. During stage 5, Late Pleistocene alluvial and glacio-fluvial units (PS3 highest-rank succession, correlative to late Besnate and Cantù Alpine glaciations) covered, through the Late Pleistocene unconformity (U3), the older glacio-fluvial succession in the subsurface of Casalpusterlengo and Zorlesco areas, while they terraced the deformed marine succession in the San Colombano area, both on the uplifted hilltop and on the surrounding “Plain Main Level” (Castiglioni and Pellegrini, 2001). Syndepositional normal faulting, related to dextral wrenching regime, occurred during this stage. Fault-related offset of Late Pleistocene units, stratigraphic and morpho- structural evidences (facets, relic surfaces and drainage patterns), document ongoing transtension, at stage 6 (Latest Pleistocene – Holocene; U4 unconformity), plausibly relating to the NNW-wards thrusting and related wrenching along the Pavia-Casteggio lateral ramp (Benedetti et al., 2003). Field evidences suggest to propose a link between the entrenchment and the anomalies of the post-glacial river network at the southern margin of the Po Plain to this tectonic stage.
This reconstruction links the origin of the highest-rank unconformable stratigraphic boundaries to the Quaternary tectonic stages of Apennine thrusting, wrenching and extension. The intermediate- and low-rank unconformities relate to both minor tectonic increments and to the climatic-driven glacial cycles, because the bases of the glacio-fluvial units are nested within the highest-rank tectonic-induced unconformities. On the isolated reliefs, in situ paleosols testify the preservation of non-erosional surfaces, i.e. morphological surfaces, related to sites of morphological stability. These became the sites for loess aggradation during the Late Pleistocene, that means when the isolated reliefs had been already uplifted and the main controlling factor on deposition was climatic. The recognition of unconformable stratigraphic boundaries vs. conformable “morphological” boundaries permits to unravel the different chronostratigraphic significance of these two surface types (respectively time-transgressive and almost isochronous) and to use them to constrain the reconstruction of the chronological evolution of the basin and the 4-D model to be computed.
A novel approach in the use of GeoModeller® is proposed by implementing a model building procedure based on coded ‘hierarchic rules’, at present not encompassed in the modelling suite. A rigorous routine is proposed to apply these rules to obtain at least three ranks of visualization of the 3-D geological architecture of the study area. The ordering of the geological units in the stratigraphic pile, combined with the set of the reference surface (top/bottom) and the nature of the interpolation for each surface (erode/onlap) conceptualized the hierarchic rules valid to represent complex stratigraphic architectures at each scale. 1) The isopotentials of GeoModeller® (i.e. the lowest rank surfaces which can be computed and represented by this software) describe well the morphological surfaces, i.e. surfaces stable through time. Using the orientation of the morphological surfaces as reference top boundary for model computation means to constrain the isopotentials to the deformation history of the area. This concept strongly impacts on the 3-D model application to the simulation of internal facies, as it would be necessary to simulate the distribution of hydrostratigraphic parameters. 2) Since crossing the isopotential, the erode stratigraphic boundaries bring the significance of the time-transgressive unconformable surfaces, in accordance with the geological evolution. 3) By attributing erode nature to the high-rank surfaces, and onlap rules and reverse ordering in the stratigraphic pile to the intermediate-rank ones, the resulting 3-D model displays the high-rank surfaces as composite stratigraphic unconformities, like they have been described by the geological model, since they collect the minor increments of deformation, deposition and erosion through the geological time. As a result, the proposed 3-D models are multiscale and honour the explicit geological observations and the implicit geological evolution at each scale of observation. The intermediate-rank boundaries and sediment volumes represent the result of the intermediate-rank evolutionary increments. On larger spatial and temporal scales, they can be grouped and visualized into higher-rank boundaries (‘U’ unconformities) and volumes, related to the major tectono-depositional stages. The relationship between geological history and geometrical features, with the possibility to upscale and downscale the model according to its hierarchic configuration in view of any specific application, is one novelty of the modelling results here presented.
The uncertainties derived from the interpretation of the geological evolution gave rise to two alternative geological models of the San Colombano hill area. Both honour the input explicit data and differ on the interpretation of the extent of the conjugate fault systems that involved the Late Quaternary stratigraphy.
The final visualization of the 3-D, ranked stratigraphic units and surfaces highlights the basic role of consistent 4-D geological models as the best synthesis of heterogeneous and multi-scale datasets, that represent the base for several applications at different scale. The adopted approach yields a model that can be easily updated, as soon as new knowledge gets available and modified, and permits to test different hypotheses accounting for any new implicit geological constraints
Late Quaternary sedimentation and tectonics in the Po Basin: field evidences at the Po Plain-Apennines border (Lombardy)
No full textTopographic reliefs and terraced landscapes represent key-sectors to constrain recent geological evolution and subsurface stratigraphy in almost flat landscapes like the Quaternary Po Plain. Aiming to investigate the role of Late Quaternary tectonics on the complexity of stratigraphic and geomorphological features exposed at the Po Plain-Apennines border in Lombardy, we focus on a structural culmination of the Emilia salient, the San Colombano Hill ramp anticline.
Geological and geomorphological mapping at 1:10.000 scale, stratigraphic, sedimentological, paleontological, petrographic and morpho-structural analyses, complemented by C14 and OSL age determinations, show the incremental tectonic imprints on the Quaternary stratigraphy originating the present-day palimpsest landscape. Location of unconformable stratigraphic vs. conformable morphological boundaries, pinch-out and cross-cut relationships among alluvial sedimentary bodies, uplifted paleovalley fills, cannibalism of pre-existing alluvial clastics, colluvial wedges and sediment deformation structures highlight how, where and when tectonic-driven processes controlled the evolution of the Hill and the adjacent plain.
The S. Colombano ramp anticline underwent Early-Middle Pleistocene thrusting, which uplifted and folded the Gelasian regional unconformity between littoral Calabrian and deep-marine Miocene formations. Late Pleistocene, alpine-sourced alluvial and glacio-fluvial units, terraced the deformed marine succession through the composite Late Pleistocene unconformity. The mapped synthems progressively wedge, thin and amalgamate S-wards, suggesting the syn-sedimentary confinement by an uplifting mild relief ancestor of the present-day Hill. Relicts of syn-tectonic paleo-valley fills testify the first drainage pattern of this proto-hill, where also polycyclic loess-soil aggraded during early Late Pleistocene.
The S. Colombano structure underwent dissection since latest Pleistocene along three fault systems, while LGM glacio-fluvial and alluvial units prograded from the NW. Evidences of Latest Pleistocene fault activity are observed as thickness variations of the LGM synthem, offset of the Late Pleistocene unconformity, paleosol reworking in colluvial wedges on the fault-block hangingwalls, marked by triangular facets and abrupt diversions of the river network. A late-LGM muddy flood plain developed N of the hill, owing to tectonic-induced subsidence. This was cross-cut by the meandering tributaries of the paleo-Po River during the Late Glacial. The post-glacial-Holocene entrenchment of the river network and river anomalies suggest an eventual latest phase of uplift and transtension of the San Colombano structure, plausibly related to the ongoing N-wards propagation of the Emilia salient. The progressing research is integrating the surface and subsurface field geological and evolutionary constraints into 3D(4D) geological models, as the basis for hydrogeological and geohazard applications
Landscape evolution and aquifer building processes in a carbonate fold‐and‐thrust belt, Italian Southern Alps: Insights from 3D geo‐modelling
No full textCarbonate aquifers of fold-and-thrust mountain belts supply a large amount of human water demand all over the world. Aiming to improve carbonate aquifer modelling, we investigated the relationships between landscape evolution and aquifer building processes in the Southalpine thrust belt of Lombardy Region. The rationale was to learn about the coevolution of tectono-stratigraphic, karstic and landscape genetic processes that led to the present-day carbonate aquifer configuration. Morpho-structural analyses and 3D geo-modelling permitted to relate the assemblage of aquifer heterogeneities to the geomorphological evolution of the Gaverina springs setting. Mesozoic pre- and syn-rift stratigraphy predisposed the future different limestone aquifer types (extensive cave vs. phreatic systems). The inherited Mesozoic extensional structures controlled alpine thrusting, shaping, sizing and deploying the different carbonate aquifers and shale aquitards. Coevolution of different karst systems and landscape started since the Neogene emersion above sea level. Three Miocene increments of slip and uplift rates, erosional unroofing of tectonic units, epi- and endokarst genesis and exhumation are recorded by landforms and sediments that witness the stabilization and raising steps of the relative base levels before the Pliocene marine transgression. The present-day elevation (350 m above sea level) of the late Pliocene coastal sediments onlapping the local relief, constrains the minimum estimates of Neogene and Quaternary uplift amounts, during which the karst systems developed downwards chasing the lowering of the reference base levels. Pleistocene glacial advances mainly acted on the valley floor, eroding and lowering the local base level. On the slopes, ablation tills and ice-contact deposits dammed some low-elevation springs, plausibly contributing to expand the phreatic zone upwards. The geo-morphological controls on hydrostratigraphy and the landscape–aquifer coevolution described at the Gaverina site are comparable to those of many settings of the Mediterranean peri-Tethyan fold-and-thrust belts, suggesting that this approach might find a broad application
Geology of the San Colombano hill, a Quaternary isolated tectonic relief in the Po Plain of Lombardy (Italy)
No full textThe 1:10,000 geological map of the San Colombano hill covers 60 km 2 in the Po Plain, south of Milan. The new and the historical surface geological data-sets are managed by a GeoDB aiming to contribute to re-interpret the Quaternary evolution at the Po Plain-Northern Apennine border. On the hill, the Calabrian shallow marine San Colombano Fm. unconformably overlies the truncated deeper-marine Miocene formations, up-thrusted by the external fronts of the Apennine Emilian Arc during Mio-Pliocene. Late Pleistocene alluvial units rest in unconformity above the marine succession both on the uplifted hilltop and on the surrounding plain. Fault-related offset of Late Pleistocene units, stratigraphic and morpho- structural evidences (facets, relic surfaces and drainage patterns), document the Quaternary tectonic history. Early to Middle Pleistocene ongoing thrust-folding at the northernmost buried reaches of the Emilian Arc was followed by Latest Pleistocene-Holocene transtension, possibly relating to the NNE striking Pavia-Casteggio lateral ramp
Geological constraints to model complex hydrostratigraphy: case studies from the Quaternary Po Hydrogeological Basin (Northern Italy)
No full textHydrogeological modeling of porous aquifers at different scales is best performed if the hydrostratigraphic architecture is well constrained to the geological history of aquifer origin and groundwater saturation. Reliable hydrostratigraphic models should account also for the tectono-sedimentary history of aquifer building and disruption. Critical controlling factors on good models are the hierarchy of sedimentary bodies, which depends on the intensity and duration of depositional/erosional processes, the resulting nested multiple scales of subsurface heterogeneities and the syn- to post depositional deformation history. Focusing on the best modelling procedure of the Quaternary hydrostratigraphy of the Po Hydrogeological Basin South of Milan, we chose two key-sectors to apply the method: i) the glacio-fluvial and alluvial terraced landscape at the northern alpine margin of the Basin, directly influenced by the Pleistocene glacial pulses; ii) the Apennine tectonic reliefs which emerge in the southern Po Plain and involve the Quaternary, alpine-sourced alluvial succession in Apennine folding and faulting. The specific aim of the work is to define a consistent 3-D stratigraphic framework of the two sectors at different scales, with the help of static geomodeling techniques, constrained by all the available data. Field-based geological reconstruction provided the entry data for multi-scale GIS management. Original geological mapping, stratigraphic, sedimentological, pedological, paleontological, geomorphological and structural observations were firstly carried out. Hundreds of subsurface borehole and geophysical data were also used, after normalized digitalization based on a specifically built litho-textural Code. Field-based ‘hard data’ were combined to 1-D facies analysis of subsurface logs, then correlated into a fence of 2-D geological sections. In this stages of pre-processing for the 3-D analysis, GIS software was interfaced with GeoModeller® software to rapidly simulate and visualize the stratigraphic/tectonic relations, honoring the geological constraints. Several forward models were computed to compare different and even contrasting architectures and evolutions. The 3-D results permit a first comparison between the contrasting hydro-stratigraphic architectures of the two sectors, in relation to the different geological evolutions. At the Alpine border, uplift related to glacio-isostatic and tectonic rebound determined nesting of entrenched pre-glacial valleys and glacio-fluvial terraces. At the Apennine border, thrusting and wrenching determined the palimpsest of tectonic culminations and depocentres, lately cut by the post-glacial river valleys. The 3-D model of this highest rank framework could be filled with the nested, low-rank hydrostratigraphic units, confining the potential field modelling within each highest rank geological volume, that means constraining the geological geometries to the shape of the top boundary of each unit, which is determined by the predating incremental geo-history. This attempt yielded a satisfactory image of the spatial arrangement of the different rank bodies; hence, it deserves to be taken in consideration to orient further simulations of the internal facies heterogeneities. The tectonically active sector at the Apennine border, permits also to deal with modeling of aquifer bodies whose geometries and thicknesses change dramatically within short distances owing to syn- and post depositional folding and faulting. The attempt to constrain the 3-D realizations with the incremental geological evolution required to model the geological hierarchy. Since ‘Hierarchic stratigraphic piles’ are not encompassed in the GeoModeller suite, we propose some hints to overcome this limit, starting from ad hoc scripts that we are carrying out at the present state of this ongoing research
Hydrogeological characteristics and water availability in the mountainous aquifer systems of Italian Central Alps: A regional scale approach
No full textGroundwater resources in mountain areas are strategically important to maintain adequate water supply for domestic uses, farming, industrial activities, and energy production, also considering the expected growing demand due to ongoing climate changes. Within this framework, the objective of the study is to develop a regional approach, compliant with the European requirements of the Water Framework Directive 2000/60/EC and Groundwater Directive 2006/118/EC, that could support public agencies and water companies to efficiently manage and protect the available water resources in mountainous environments.
The proposed approach identifies and delineates groundwater bodies by coupling a 3D hydro-stratigraphic model with the definition of the water budget and water hydrochemical fingerprints in a geologically complex Alpine environment in Northern Italy. Sixteen groundwater bodies (GWBs) have been identified all over the 10.290 km2 area, showing an average storage capacity of more than 500 Mm3 y−1 (about 3% of the average total inflow from precipitation and snowmelt), with differences up to four times between GWBs mainly constituted of carbonate rocks and those prevalently composed of crystalline or terrigenous rocks. Groundwater quality in the study domain is generally excellent, with few exceptions due to geogenic (i.e., natural) or anthropogenic sources of contamination. The results of this study show the advantages of coupling 3D hydro-stratigraphic modelling combined with meteorological, hydrological and hydrogeological information, which consist in: i) identifying the most Strategic Storage Reservoir both in terms of quality and storage capacity; ii) evaluating the present ground- and surface water availability; iii) detecting areas of specific interest for implementing groundwater monitoring networks; iv) recognising recharge areas of the most relevant springs, to implement protection strategies of the resource
