Pini, R.

The Messinian succession of the Southern Alps is widely exposed in the Venetian-Friulian Basin, whilst more westwards in the Po Basin only isolated outcrops are preserved in the Lake Garda and Lake Como areas. The Alpine Messinian deposits are characterized by the lack of evaporites and Lago-Mare type sequences and, because of the lacking of marine deposits, their chronology is still loosely constrained. Pliocene marine deposits are located in very confined outcrops at the outlet of the main valleys, from Friuli to Piedmont. New investigations concerning many of these successions have yielded new chronological constraints for the stratigraphy of the upper Neogene in the Southern Alps area, as well as new provenance data, supporting the reconstruction of the drainage network evolution in response to the Messinian Salinity Crisis (MSC). In Friuli, deposits of early Messinian age exposed along the Tagliamento River show a petrographic evolution across the Messinian-Pliocene unconformity. The occurrence of clasts from the Paleozoic successions of the Carnic Alps (up to 15%), completely lacking in the Messinian deposits, pinpoints to a widening of the drainage basin during the MSC because of stream piracy and tectonic activity. Deposition continues with alluvial fan facies within the Tagliamento Valley and in the upper piedmont plain until the Late Pliocene. In the central Venetian sector, new provenance analyses on the Messinian conglomerate suggest a drastic drainage network reorganization, as a consequence of the MSC fluvial entrenchment. The Pliocene deposits at Cornuda, next to the present-day valley mouth of Piave River, indicate that the outlet of the river was still confined at that time several km to the east, and the southwestwards migration to the present location took place only later, during the Pleistocene. Westwards, in the catchment of the Brenta River an increase of crystalline rock fragments in the gross composition (from 30 to 60 %) is observed and interpreted as the enhancement of the crystalline basement exhumation, triggered by the system response to the sea level drop. In the Lake Garda area, new investigations on the Sirmione continental conglomerate, doubtfully ascribed to the Messinian, shows the existence of three superimposed units, different in petrographic composition and sedimentology. The lower body consists of poorly-sorted, matrix-supported, coarse-grained gravels, with blocks exceeding the 0.5 m size; sand and gravel petrographic analyses point to a provenance from the Adige catchment, with porphyries locally reaching the 80% of the whole petrographic composition in the pebble fraction. The middle unit displays clast-supported, crudely-bedded gravels with a better sorting and enrichment in carbonate pebbles (up to 70%). The upper body is totally characterized by well-sorted limestone and dolostone pebbles, pointing to a drainage confined in the Southern Alps. The geologic survey allowed to detect several clayey silt layers interbedded in the conglomerate lower and middle units, that have been sampled for pollen analyses. On the western bank of Lake Garda, the Mt. San Bartolomeo succession consists of Messinian?-Early Pliocene continental conglomerate with Melanopsis, overlain by Pliocene shallow-water marine clays and an upper conglomerate unit. The lower conglomerate is clast-supported and poorly-sorted and suggests alluvial fan/intra-valley deposition settings, locally confined. Calcareous nannofossil analyses allowed to refer the marine clays to the late Zanclean (biozones NN14 and NN15). Shallow-water marine settings have been inferred also for the upper conglomerate on the basis of the occurrence of marine algae (Tasmanaceae and Prasinophyceae) and stratigraphic data suggest an heteropic relationship with the marine clay. Petrographic analyses point to a local provenance for the whole Mt. San Bartolomeo succession, with dominant carbonates and subordinate porphyries and volcanoclastic rocks in the pebbles. The overall gathered data allow to cast light on the geomorphologic response of the fluvial systems to the MSC in the Venetian-Friulian Basin and on the Late Miocene paleodrainages in the Lake Garda area. In the Venetian-Friulian Basin the stratigraphic record documents the strong rejuvenation of the Tagliamento and Brenta rivers’ headwaters, leading up to a stream piracy and to the basement exhumation increase, respectively. Taking into account the post-Messinian tectonic shortening and the former Messinian coastline position, we can estimate roughly in the order of 0.1 m/yr the upstream migration of the erosional signal triggered by the MSC dramatic sea level drop (~1500 m). More westwards, in the Lake Garda area high percentage of porphyries in the Sirmione conglomerate suggests that the Adige River flowed in Late Miocene times along Lake Garda valley with likely the Chiese River as tributary of the main trunk. The huge sand-rich bodies observed in the Po Plain subsurface and related to the Garda entry-point could be therefore referred to the Adige River catchment.

Il bacino di Leonessa è una delle maggiori depressioni tettoniche intermontane dell’Appennino Centrale. A differenza delle altre depressioni, disposte in direzione appenninica con la faglia bordiera principale sul lato orientale, il bacino è orientato in senso WNW-ESE ed ha la faglia bordiera principale sul suo margine sud-occidentale. Questo studio ha permesso di ricostruire l’evoluzione quaternaria del bacino attraverso un approccio multimetodologico basato sull’integrazione dei dati provenienti dal rilevamento geologico e geomorfologico a scala di dettaglio (1:10.000), supportato dall’interpretazione di fotografie aeree, da analisi paleontologico-stratigrafiche, paleomagnetiche, palinologiche e mineralogico-petrografiche. I sedimenti affioranti all’interno della depressione sono stati distinti in sintemi. Quello stratigraficamente più basso è il Sintema di Villa Pulcini – Colle Montano, costituito da un alternanza di argille, argille torbose, marne e sabbie argillose di ambiente deposizionale da lacustre a piana alluvionale a canali intrecciati (braided plain), attribuibile alla parte alta del Pleistocene inferiore. Stratigraficamente superiore al Sintema di Villa Pulcini – Colle Montano, il Sintema di Leonessa è costituito da depositi di conoide alluvionale nel settore occidentale del bacino e da depositi lacustri nel settore orientale, ambedue contenenti, nella parte alta, intercalazioni di vulcaniti risedimentate. Il ritrovamento di un molare di Mammuthus (mammuthus) cfr.M. (M.) trogontherii (Pohlig) all’interno di depositi alluvionali e i risultati delle analisi paleomagnetiche e palinlogiche consentono di riferire al Pleistocene medio il sintema.I due sintemi precedenti sono coperti a tratti da sabbie e sabbie argillose rossastre (Sintema di Terzone), con spessore che raramente supera i 5 metri, ricche di elementi vulcanici rimaneggiati. I sintemi stratigraficamente più alti del bacino sono costituiti da tre ordini di terrazzi fluviali e da due ordini di conoide alluvionale denominati Sintema di Cerreto - Monte Tilia1, Sintema di Fosso della Ripa e Sintema di Villa Falcucci – Monte Tilia2. Questi sono probabilmente da riferirsi al Pleistocene superiore – Olocene. La definizione degli eventi erosivo-deposizionali che hanno contraddistinto l’evoluzione del paesaggio nel bacino di Leonessa costituisce un passo ulteriore verso un più preciso inquadramento temporale dell’attività tettonica distensiva, del sollevamento regionale e dei cambiamenti climatici che hanno portato all’attuale assetto geomorfologico dell’Appennino Centrale.

When coal seams are formed by compaction of plants, gases including methane are generated and accumulated into the coal cleats or adsorbed into the coal micropores. Such coalbed methane is normally recovered by means of reservoir-pressure depletion, i.e. by pumping out water and degassing the reservoir. A more attractive process with higher yields is the so-called Enhanced Coal Bed Methane recovery (ECBM), whereby carbon dioxide is pumped into the coal seam to displace methane thanks to higher CO2 adsorptivity. Injecting CO2 in unminable coal seams leads not only to methane recovery but also to CO2 sequestration. The factors still limiting the implementation of ECBM recovery are economical, i.e. lack of penalties for CO2 emissions, as well as technological and scientific, i.e. limited understanding of fundamental issues related to ECBM. Therefore, the goal of this study is to combine experimental measurements and modelling to characterize pure and multicomponent competitive adsorption of CO2 and CH4 on coal and study the coalbed dynamics using breakthrough experiments, including the effect of the injection of CO2 on matrix swelling and permeability. Since December 2004, a feasibility study throughout the Sulcis Coal Province in Sardinia [Quattrocchi, 2004] is in progress and one of its objectives is to correlate the results of the mentioned experiments with the compositional patterns of the coal, considering its role in the CBM-ECBM exploitation.

An ECBM feasibility study started for the Sulcis Coal Province (SW Sardinia, Italy): available geochemical, structural-geology, stratigraphic and reservoir engineering considerations as well as the newly gathered experimental data are discussed, including: fluid geochemistry (major and minor elements, dissolved gases, C and He isotopic ratios) of different strata/reservoir, coal composition and experimental data on CO2/CH4 adsorption-desorption on coal. A MapInfo GIS structure was built up including stratigraphic, geo-structural, hydro-geochemical, coal-compositional and environmental-impact information as well as the CO2 sources location and typology. Despite preliminary, these data highlighted both the challenging positive and negative aspects of the Sulcis Coal Province versus the exploitation of the ECBM technique. The most important objective of this phase I of the project is the selection of the best Sulcis ECBM test-pilot site, which will be followed (Phase II-2007) by the choice of a scaled up site and possibly by a future network (Phase III-2008). CO2 geological storage and CH4 production potentials in Sulcis have been grossly evaluated as a whole, in the frame of the Sardinia region CO2 sources, including the coal-fired power plants, both existent and foreseen (hundreds of millions of tonnes of CO2 are possible to be stored underground in the next decades).

An ECBM (Enhanced Coal Bed Methane) feasibility study started for the Sulcis Coal Province (SW Sardinia, Italy) in December 2004: geochemical, structural-geology, stratigraphic and reservoir engineering considerations are discussed. The first newly gathered experimental data are discussed, including: fluid geochemistry (major and minor elements, dissolved gases, C and He isotopic ratios) of the reservoir, coal composition and experimental data on CO2/CH4 adsorption on coal. A MapInfo GIS structure was built up including stratigraphical, geo-structural, hydrogeochemical, coal-compositional and environmental impact information as well as the CO2 sources location and typology. Even if these data could be preliminary with respect to the coal characteritics effectively located at the future injection depth, they highlighted both the challenging positive and negative aspects of the Sulcis Coal Province versus the exploitation of the ECBM technique. The most important objective of this phase I of the project is the selection of the best Sulcis ECBM test-pilot site, which will be followed (Phase II) by the choice of a scaled up site and possibly by a future network (Phase III). These phases are foreseen to be accompanied by the selection of progressively added CO2 industrial sources, to be used within the project economic spreadsheet model, actually in evolution. CO2 geological storage and CH4 production potentials in Sulcis have been grossly evaluated as a whole, in the frame of the Sardinia region CO2 sources, including the coal-fired power plants, both existent and foreseen (hundreds of millions of tonns of CO2 are possible to be stored underground in the next decades). The reservoir estimates, both for the CO2 injection and for the CH4 production are clearly involving to start the test-site phase exploitation, in the frame of an auspicabile international operative project.