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Dissolution‐corrosion (DC) represents an important factor for speleogenesis, and can be measured monitoring weight variation over time of carbonate and gypsum tablets exposed in underground environments. The oxidation of H2S produces H2SO4, which in carbonate host rock induces the surface of carbonate tablets to be rapidly corroded by sulphuric acid, whereby CaCO3 is replaced by CaSO4∙2H2O, producing a significant weight gain. We describe preliminary results of DC monitoring in four still‐active SAS systems, including Ninfe Cave and Terme Sibarite (Calabria), Fetida Cave (Apulia), and Acqua Fitusa Spring Cave (Sicily). The tablets have been set inside the caves, in three different conditions of exposure (i.e. underwater, air, interface zone) in the winter 2015‐2016 to monitor DC in five years. The results show how the condition of exposure is an important control for the behaviour of weight variation. Tablets set underwater displayed significant weight loss during the first period of exposure, whereas those located at the interface zone exhibited a tendency of weight variation significantly dependent on time, and tablets in air showed weight gain.

Grazie ad approfondite ricerche di archivio e accurate indagini speleologiche, sono stati ispezionati e documentati diversi ipogei artificiali presenti nel comprensorio di Sutera (CL). L’area di Sutera, caratterizzata da affioramenti evaporitici messiniani e non lontana da importanti miniere di salgemma e di zolfo, ha subito una veloce corsa verso la ricerca di minerali pregiati intorno ai primi del ‘900. A memoria di queste attività sono rimaste diverse tipologie di cavità, quali: gallerie di carreggio, discenderie per ricerca mineraria, ma anche antiche cisterne per la raccolta d’acqua dove recentemente, a seguito di operazioni di ripristino e pulizia, sono stati effettuati importanti ritrovamenti archeologici. In questo contributo verranno descritti alcuni degli ipogei rinvenuti, mettendone in evidenza la tipologia e lo stato di conservazione In the Sutera (CL) area several man-made cavities were explored and studied after extensive archive researches and accurate speleological investigations. The Sutera area, characterized by evaporitic Messinian outcrops and not far from important salt and sulfur mines, underwent a rapid race to the mining activity in the early 1900s. Different types of cavities occur as memory of the mining practice, such as: carriageway tunnels, descendants for mining research, and old rainwater collection cisterns. In the biggest cistern restoration and cleaning activities led to discover important archaeological finds. Aim of this paper is to describe some explored underground cavities highlighting their typology and state of conservation.

Viene proposto un itinerario che consente di osservare alcune delle aree carsiche gessose più significative dell’intero Bacino del Mediterraneo per la eccezionale varietà e ricchezza di morfologie carsiche sia superficiali che sotterranee in esse presenti. L’itinerario si sviluppa in Sicilia occidentale e centro-meridionale e si articola in tre percorsi che possono essere realizzati in tre giorni, attraverso l’utilizzo dell’auto e tratti a piedi. Alcune delle aree, per la loro valenza scientifica e paesaggistica, costituiscono delle riserve naturali, istituite dalla Regione Sicilia, e/o Zone Speciali di Conservazione (ZSC) e Zone di Importanza Comunitaria (SIC).

Il percorso si svolge in territori pianeggianti e collinari attraversando, da sud a nord, la Conca d’Oro e addentrandosi nella valle del Fiume Oreto. Sarà possibile osservare aspetti stratigrafici, tettonici e geomorfologici, rappresentativi delle aree costiere e montuose della Sicilia settentrionale, che raccontano un’evoluzione geologica di oltre duecento milioni di anni. All'interno della città di Palermo saranno inoltre illustrati aspetti che riguardano i geomateriali locali, impiegati sia nella pratica edile ordinaria come nella costruzione di beni storico-monumentali, e le opere antropiche legate allo sfruttamento del sottosuolo e delle risorse geologiche in genere, evidenziando il forte legame tra la vita degli abitanti e le caratteristiche naturali del territorio che li accoglie. La percorribilità è agevole in tutti i periodi dell’anno e risulta rallentata all'interno del tessuto urbano della città di Palermo. Le possibilità di pernottamento sono numerose e diversificate. Per le escursioni fuori città e per le visite alle sorgenti e alle cave storiche è necessario un abbigliamento tecnico idoneo.

Le aree carsiche gessose della Sicilia hanno attirato l’attenzione di naturalisti e geologi sin dalla seconda metà del 1800. Tuttavia, gli studi sul carsismo nei gessi non hanno visto una costante evoluzione nel tempo; infatti, dopo un lungo periodo di indifferenza, è solo a partire dagli anni ’80 del secolo scorso, che si è assistito ad un rinnovato interesse verso questa tematica, inizialmente grazie alla realizzazione di numerose campagne di esplorazione in diverse aree carsiche gessose della Sicilia da parte di alcuni gruppi speleologici siciliani, e in un secondo momento grazie all’interesse mostrato dall’Istituto di Geologia (oggi Dipartimento di Scienze della Terra e del Mare) dell’Università di Palermo, che ha intrapreso una serie di ricerche sistematiche su differenti aspetti del carsismo nelle evaporiti siciliane. Tali ricerche condotte fino ad oggi, in collaborazione anche con altri Atenei e Istituzioni di ricerca italiani e stranieri e gruppi speleologici siciliani, hanno consentito di ampliare significativamente le conoscenze sui fenomeni carsici nei gessi della Sicilia. Le aree carsiche nei gessi della Sicilia rappresentano dei complessi di eccezionale interesse scientifico, paesaggistico e didattico sia per la grande abbondanza e varietà di forme carsiche superficiali e sotterranee, uniche in tutto il Bacino del Mediterraneo, sia per la loro collocazione geografica ed ambientale, che si estende dalle fasce costiere alle valli fluviali, dalle conche lacustri alle colline e agli altopiani. Le forme carsiche di superficie spaziano dalle piccole sculture in roccia (karren) alle forme di medie e grandi dimensioni, quali doline, valli fluvio-carsiche, polje. Oltre duecento grotte, con sviluppi fino a 2 km e profondità di oltre 100 m, sono state esplorate. Grazie all’intensificarsi degli studi che hanno avvalorato sia l’interesse scientifico, sia quello naturalistico e culturale del carsismo nei gessi siciliani, diverse aree carsiche gessose in Sicilia sono oggi sottoposte a tutela essendo state inserite nell’ambito di aree protette, quali riserve naturali, parchi regionali, siti della Rete Natura 2000, geositi e geoparchi. Attualmente ricercatori e speleologi cooperano, anche con gli enti gestori delle aree protette, per incrementare le conoscenze sulle aree gessose dell’isola e per favorire la loro valorizzazione, fruizione e tutela. The gypsum karst areas of Sicily attracted the attention of naturalists and geologists since the second half of the 1800s. After a long period of indifference, only since the 80s of the last century some Sicilian speleological groups and the Institute of Geology (now Department of Earth and Marine Sciences) of the University of Palermo, in collaboration also with Italian and foreign universities, conducted new researches increasing significantly the knowledge on gypsum karst phenomena. The gypsum karst areas in Sicily are sites of exceptional scientific and cultural interest, for the great abundance and variety of surface and underground karst forms and for their geographical and environmental position, extending from coastal areas to river valleys, from lake basins to hills and plateau. The surficial karst forms range from small rock sculptures (karren) to medium and large forms, such as dolines, fluvial-karst valleys and polje. Over two hundred caves, with developments up to 2 km and a depth of over 100 m, have been explored. Thanks to increase of studies that confirmed the scientific and the naturalistic and cultural interest of gypsum karst in Sicily, several areas are now protected as nature reserves, regional parks, sites of the Natura 2000 Network, geosites and geoparks. Actually, researchers and speleologists cooperate, also with the management of the protected areas, to grow the knowledge on the Sicilian gypsum areas and favor their exploitation, enjoyment and protection.

Almost 20% of Italy is characterized by the outcropping of carbonate massifs ranging in age from Cambrian to Quaternary. Coastal karst is present in many Italian regions: from North-East to South and West: the Gulf of Trieste, the Conero (South of Ancona, Marche), the Adriatic coast of Apulia including Gargano, Murge and Salento, Maratea in Basilicata, Cilento in Campania, Circeo and Gaeta in Latium, Argentario and Giannutri Island in Tuscany, the southernmost part of the Ligurian Alps, Palermo Mts., San Vito Lo Capo, Syracuse coast and Marettimo Island in Sicily, and, especially, in Sardinia, which has carbonate rocks touching the sea along the coast of Balai near Porto Torres, Capo Caccia-Punta Giglio (Alghero), Sinis and Buggerru along the western litoral, Capo Teulada and Capo Sant’Elia at Cagliari, Capo Figari, Tavolara Island and the Gulf of Orosei along the eastern mountainside. Recent researches have revealed several coastal cave systems that have a clear origin by mixing corrosion, in which the aggressive solution derives from the mixing between saline and fresh water at the watertable interface (the so-called flank margin caves). Glacioeustasy and tectonic movements can control the position of sea level with respect to coastal carbonate outcrops. For this reason these coastal caves represent useful records of sea-level stillstands. These caves are normally organized in sub-horizontal levels, and are characterized by the lack of high flow velocity markers (scallops) and alluvial sediments. Instead, they show rounded cave passage morphologies, often with horizontal wall notches, a characteristic swiss-cheese or sponge morphology, and passages that narrow going away from the coastline (due to the decreasing of sea water influence and mixing-corrosion effect). This paper describes some flank margin cave systems found in Apulia, Sicily, and Sardinia. In particular, five cave systems are illustrated: Sant’Angelo caves (Apulia), Pellegrino and Rumena caves (Sicily), and Giuanniccu Mene cave and Fico cave (Sardinia), explaining their relationship with past sea levels and local uplift rate.

To test limitations and effectiveness of seismic tomography when coupled to geoelectrical technique for cavity detection 2D synthetic models were used. Synthetic models were created with different number of cavity and blocks of highly cohesive lithological material (high seismic velocity and resistivity values). A modified version of multiple gradient (Martorana et al., 2016) has been used for electrical sequence. The cluster analysis performed on static units defined by electrical resistivity values, P wave velocities, and seismic density on coincident sections, allowed to interpret subsoil structures. The use of the non-hierarchical clustering algorithm has been chosen because it is less influenced by abnormal values, and allows a statistical unit to change its cluster during the iterative process. Depending on the choice of the number of clusters to be identified, cluster distribution maps have been constructed in the multi-parameter space, allowing defining certain variability limits for the selected parameters, for synthetic and experimental data. Finally, experimental data show that electrical and seismic tomographies is not influenced by the presence of cavities without lateral continuity.

Geomorphological and geological studies have been carried out to contribute to the recognition of controlling causes and to the definition of genetic models for poljes of Sicily. A polje is a kilometric closed depression developed mainly on karst rocks, with a conspicuously flat and alluviated bottom affected by intermittent flooding. A polje is usually characterised by relatively steep slopes enclosing an almost perfectly horizontal floor, caused by lateral solution planation related to flooding events. The origin of a polje is due to dissolution of the land surface, although geological structure generally influences its genesis. These large depressions are often elongated according to the direction of main faults, in consequence of a control due to tectonics or to differential erosion. The performed researches have shown the existence of at least seven poljes located along the north-western (chain zone) and the southern (deformed foredeep zone) areas of Sicily. These large karst depressions are developed on Mesozoic limestone/dolomitic rocks within the chain zone and on Messinian gypsum rocks within the deformed foredeep zone. They are up to 4 km in length, can reach surfaces of 3-8 km2 and are around hundred metres deep, with steep slopes and a flat bottom. Generally, they are open, occasionally active depressions and their genesis seems to be strongly controlled by structure. In particular, the studied poljes occur in two different geological/geomorphological settings: a) in graben-like tectonic depressions, where important fault slopes/scarps border the flat bottom; b) in complex depressions controlled by structure, where wide fault line slopes/scarps or large inclined degraded structural surfaces mark the poljes. Finally, landscape analysis leads to the proposition of two main genetic models in which the development of poljes is primarily due to tectonics or differential erosion followed by dissolution.

Studies on surface denudation rate of karst rocks were carried out for many years with different methods, although researches on limestones are much more numerous than those on gypsum. In Sicily the most large and complete Messinian evaporite succession of Gruppo Gessoso – Solfifero outcrops and since 1993-1994 surface denudation measurements were performed on different types of gypsum by the Micro-Erosion Meter (M.E.M.) method. MEM stations were placed on natural sites representing different lithological features of gypsum outcrops of the Island: 1) selenite gypsum with centimetre-sized crystals; 2) selenite gypsum with sub-centimetre crystals; 3) gypsum arenite; 4) microcrystalline gypsum; and 5) gypsum laminite (balatino type). The measuring stations are positioned in three localities in western and central Sicily: Santa Ninfa (Trapani), Ciminna (Palermo) and Campofranco (Caltanissetta). The average lowering rates vary in the different lithofacies: from 0.25 mm yr1 in microcrystalline gypsum to 0.74 mm yr1 in selenite gypsum with centimetre-sized crystals. The average surface denudation rates are 0.40 mm yr1 in balatino gypsum and gypsum arenite, and 0.37 mm yr1 in selenite gypsum with sub-centimetre crystals. These different values are connected to several factors such as: rock texture, dip of gypsum surfaces, climatic conditions, troubles on the measurement sites (e.g.: presence of lichens, soil, remains of vegetation, etc.). The aim of this paper is to show the results of roughly twenty years of experimental measurements, and to compare the surface denudation rate of gypsum in Sicily with those of other evaporite areas characterised by different climatic settings.

Sulphuric acid speleogenesis (SAS) related to the upwelling of acid water enriched in H2S and CO2 represents an unusual way of cave development. Since meteoric infiltration waters are not necessarily involved in speleogenesis, caves can form without the typical associated karst expressions (i.e. dolines) at the surface. The main mechanism of sulphuric acid dissolution is the oxidation of H2S (Jones et al., 2015) which can be amplified by bacterial mediation (Engel et al., 2004). In these conditions, carbonate dissolution associated with gypsum replacement, is generally believed to be faster than the normal epigenic one (De Waele et al., 2016). In Italy several SAS caves have been identified, but only few systems have been studied in detail: Frasassi and Acquasanta Terme (Marche)(Galdenzi et al., 2010), Monte Cucco (Umbria) (Galdenzi & Menichetti, 1995), and Montecchio (Tuscany) (Piccini et al., 2015). Other preliminary studies have been carried out in Calabria (Galdenzi, 2007) and Sicily (De Waele et al., 2016). Several less studied SAS cave systems located in South Italy, and in particular in Apulia (Santa Cesarea Terme), Sicily (Acqua Fitusa, Acqua Mintina) and Calabria (Mt. Sellaro and Cassano allo Ionio) have been selected in the framework of a PhD thesis on SAS caves and their speleogenesis. Using both limestone tablet weight loss (Galdenzi et al., 2012) and micro erosion meter (MEM) (Furlani et al., 2010) methods the dissolution rate above and under water in the caves will be quantified. Geomorphological observations, landscape analysis using GIS tools, and the analysis of gypsum and other secondary minerals (alunite and jarosite) (stable isotopes and dating) will help to reconstruct the speleogenetic stages of cave formation. Preliminary microbiological analysis will determine the microbial diversity and ecology in the biofilms.

Marsala area, in the western end of Sicily, has been historically interested by quarry activities, both at surface and underground. The carved rocks are Lower Pleistocene calcarenites, defined as “Calcarenite di Marsala” and referred to the Marsala syntheme. These calcarenites are composed of three main lithofacies with vertical and lateral passages: a)coarse to fine yellow bio- and lithoclastic calcarenites, rich in macrofossils; b) sands; and c) gray sandy clays. According to previous authors, the calcarenitic lithofacies can be divided into three lithotypes: i) coarse calcarenites and calcirudites strata, from 10 to 100 cm thick; ii) fine to coarse calcarenites with thickened grains; iii) medium to coarse calcarenites in irregular strata with intercalations of thin silt beds. The subterranean quarries, now abandoned, show increasing instability signs becoming in time a risk factor for several causes, among which: a) breakdowns due to poor (weak) strength of rock and to large size of voids; b) progressive weathering of rock; c) relationship between the horst rock discontinuities and pillars and/or walls of the underground quarries. These factors contributed to enlargement of the subterranean voids and to their upward propagation, thus triggering several sinkholes. The fast urbanization of the city masked many subterranean quarries causing the loss of memory of their location. In the last decades, numerous sinkholes occurred both in urban areas and in areas designated for agricultural use, creating extensive damage to buildings and infrastructures. The latest sinkhole episode occurred in the Amabilina area, at the eastern suburbs of Marsala. Here, in the late afternoon of November 21st, 2013 a sinkhole of impressive dimensions formed affecting an agricultural area, where until a few minutes before the owner was working. The area is located in the neighborhood of small rural buildings, housing and factories. The depression shows an elliptical perimeter (100×70 m) and a depth of at least 15 m. At the bottom, some rooms up to 5 m high of an underground quarry, are visible. Since the first investigation, it was clear that the sinkhole was caused by pillars failure and the upward propagation of the voids. This last factor increased as soon as the void reached the portion of the calcarenitic lithofacies rich in fossils. From the evidences collected a few days after the event, it was possible to reconstruct the time sequence in the formation of the sinkhole. The collapse started due to the propagation of voids and a first failure of some pillars, and was subsequently followed by a second event, which caused a widening of the depression, due to the redistribution of the stress resulting after early failures.

Over the past 15 years several expeditions by French, American and especially Italian cavers have unveiled over 50 caves in the Cordillera de la Sal (Atacama Desert, Northern Chile). Many of these caves contain a variety of speleothems and minerals, some of which have rarely been observed within karst systems. Most of the secondary deposits in these caves are composed of halite, but also other halide, carbonate, sulphate, nitrate, phosphate, and silicate minerals have been found. Among the sixteen cave mineral species recognized, atacamite, darapskite, blödite, leonite, anhydrite, and especially antarcticite are worth mentioning. In one of the samples an unknown Ca-Sr-bearing chloride mineral has also been discovered, but it has not been possible to carry out detailed mineralogical analyses. These often-rare minerals have formed in this region due to the very extreme hyperarid and salt-rich environment. This research reports the mineralogical results and proposes the genetical mechanisms leading to the formation of antarcticite, powdery anhydrite, and the paragenesis of the halite-darapskite-blödite. This study also shows that Atacama caves may be excellent analogues to study weathering processes and subsurface secondary minerals in hyperarid and hypersaline environments on Mars.

As part of activities of the “Inside the Glaciers” project, managed by an Italian team of speleologists and geologists with the purpose of studying several ice-caves in Europe and South America, a research campaign was recently carried out in Mount Etna (Sicily, Italy). This volcano is the highest active in Europe and hosts more than 200 caves including Grotta del Gelo (Ice Cave) which is located on the Northern flank of Mount Etna at an altitude of about 2040 m a.s.l. This cave was formed during the Etna’s long and most destructive eruption dated from 1614 to 1624 and is one of the most famous because it hosts a small glacier, maybe the southernmost of the Northern hemisphere. Aim of this project was to realize a detailed survey of Grotta del Gelo using a Leica HDS 7000 terrestrial laser scanner in order to acquire precise data measurements of the ice deposits. This survey was the first step of a monitoring project that will be developed in the next years in collaboration with the Etna Regional Park, the Sicilian Regional Speleological Federation and the Centro Speleologico Etneo of Catania which by many years are involved in the topographic monitoring of this particular cave. The proposed article introduces the methods used for this first laser scanning survey campaign of Grotta del Gelo and the results obtained.

Karst in Sicily develops in both Messinian gypsum and Mesozoic or Tertiary limestone rocks. Caves are also found in the basalts of Mount Etna. Except for some rare cases, until recently most caves developed in limestone were considered to be of epigenetic origin. The discovery of gypsum in some of these caves, and especially detailed morphological studies, have allowed defining a hypogenic origin for a dozen of caves up to now. In some of these, the hypogenic evidences are very clear, while others remain in doubt because of the widespread presence of well-developed condensation-corrosion morphologies not necessarily related to hydrothermal fluids. This paper reports the present knowledge of hypogenic caves in the Island of Sicily.

This paper proposes a morphoevolutionary model for western Sicily. Sicily is a chain–foredeep–foreland system still being built, with tectonic activity involving uplift which tends to create new relief. To reconstruct the morphoevolutionary model, geological, and geomorphological studies were done on the basis of field survey and aerial photographic interpretation. The collected data show large areas characterized by specific geological, geomorphological, and topographical settings with rocks, landforms, and landscapes progressively older from south to north Sicily. The achieved results display: (1) gradual emersion of new areas due to uplift, its interaction with the Quaternary glacio-eustatic oscillations of the sea level, and the following production of a flight of stair-steps of uplifted marine terraces in southern Sicily, which migrates progressively upward and inwards; in response to the uplift (2) triggering of down-cutting processes that gradually dismantle the oldest terraces; (3) competition between uplift and down-cutting processes, which is responsible for the genesis of river valleys and isolated rounded hills in central Sicily; (4) continuous deepening over time that results in the exhumation of older and more resistant rocks in northern Sicily, where the higher heights of Sicily are realized and the older forms are retained; (5) extensional tectonic event in the northern end of Sicily, that produces the collapse of large blocks drowned in the Tyrrhenian Sea and sealed by coastal-marine deposits during the Calabrian stage; (6) trigger of uplift again in the previously subsiding blocks and its interaction with coastal processes and sea level fluctuations, which produce successions of marine terraces during the Middle–Upper Pleistocene stages.

Santa Cesarea Terme in Salento is the only area in which hypogenic caves have been recognized in the Apulia region. In this spa area, the rising of sulfidic thermal waters that mix with both recent fresh infiltration waters and coastal salt water has formed four active sulfuric acid speleogenesis (SAS) caves. These caves are characterized by the typical set of sulfuric acid meso- and micromorphologies, and also by the presence of both gypsum and native sulfur. In all caves, biofilms are visible in the sulfidic thermal waters and on the cave walls.

Italy is a country hosting a large number of hypogenic sulfuric acid (SAS) speleogenesis caves, mostly located along the Apennine chain, but also in Campania (along the coastline of Capo Palinuro), Apulia (along the coastline of Santa Cesarea Terme) and Sicily. Besides the typical morphologies related to their special geochemical origin (cupolas, replacement pockets, bubble trails, etc), these caves often host abundant secondary mineral deposits, mainly gypsum, being the result of the interaction between the sulfuric acid and the carbonate host rock. Native sulfur deposits are also well visible on the ceiling and roof, and peculiar sulfuric acid minerals such as jarosite, alunite, and other sulfates like copiapite, pickeringite, tschermigite, tamarugite (probably related to the weathering of native clay minerals) have been found in those caves. The presence of typical SAS minerals, together with the morphologies, testifies the influence of rising acidic waters, that likely interact with the deep-seated Triassic evaporite deposits (along the Apennine chain), with volcanic sources or hydrothermal springs in the Tyrrhenian sea (in Campania) and with marine waters that infiltrate on the sea bottom and rise through deep faults (in Apulia). This paper describes the secondary minerals discovered in several caves, and discusses their origin and possible use in reconstructing the evolution of these cave systems.

The assessment of stability of man-made underground caves, excavated in the past and later on abandoned, represents a serious challenge for land and urban planning operations, especially for the areas of possible interaction of the caves with overlying structures and infrastructures. Several areas of Southern Italy are characterized by the presence of abandoned underground quarries for the extraction of soft calcarenite rocks, which now threatens the overlying environment due to the risk of collapse and the consequent generation of sinkholes. This work presents a back-analysis of a sinkhole occurred in 2011 in the town of Marsala, caused by the collapse of an underground quarry, as a representative case study of these phenomena. Based on the available geometrical and geological dataset as well as the field observations of the phenomenon, in this article the assumptions and the results about the genesis of the 2011 sinkhole, as derived from a three-dimensional finite element back-analysis aimed at reconstructing the stress-strain evolution that brought to the ground failure collapse, is discussed. In particular, the 3-D numerical analyses have been performed in order to identify the factors responsible of the genetic mechanism of the sinkhole. The finite element analysis has been carried out by accounting for the geotechnical characterization of the Marsala calcarenites derived from both specific laboratory tests performed on samples taken from the site and literature data available on the same rock material; the numerical results have been then validated by means of the comparison with field observations and also compared with those achieved through a 2-D model of the same case study.

none 16 si Although outcropping rarely in Italy, evaporite (gypsum and anhydrite) karst has been described in detail since the early 20th century. Gypsum caves are now known from almost all Italian regions, but are mainly localised along the northern border of the Apennine chain (Emilia Romagna and Marche), Calabria, and Sicily, where the major outcrops occur. Recently, important caves have also been discovered in the underground gypsum mines in Piedmont. During the late 80s and 90s several multidisciplinary studies were carried out in many gypsum areas, resulting in a comprehensive overview, promoting further research in these special karst regions. More recent and detailed studies focused on the gypsum areas of Emilia-Romagna and Sicily. Sinkholes related to Permian-Triassic gypsum have been studied in Friuli Venezia Giulia. This article reviews the state of the art regarding different aspects of evaporite karst in Italy focusing on the main new results. open De Waele, J.; Piccini, L.; Columbu, A.; Madonia, G.; Vattano, M.; Calligaris, C.; D’Angeli, I.M.; Parise, M.; Chiesi, M.; Sivelli, M.; Vigna, B.; Zini, L.; Chiarini, V.; Sauro, F.; Drysdale, R.; Forti, P. De Waele, J.; Piccini, L.; Columbu, A.; Madonia, G.; Vattano, M.; Calligaris, C.; D’Angeli, I.M.; Parise, M.; Chiesi, M.; Sivelli, M.; Vigna, B.; Zini, L.; Chiarini, V.; Sauro, F.; Drysdale, R.; Forti, P.

In the past 15 years several expeditions by French, American and especially Italian cavers have surveyed over 15 km of salt cave passages in the Cordillera de la Sal, close to San Pedro de Atacama village (Atacama Desert, Northern Chile). Over 50 caves have been explored up to now at an elevation around 2,500 m asl. These karst systems are characterized by in-cave temperature of around 17 °C and a relative humidity always very low, with a maximum of 15%. This extreme aridity is due to the severe conditions of the area with only a couple millimeters annual rainfall and several years without rain. Currently the rare precipitation events are enough to allow the dissolution of the salt rock and crusts, and the deepening of underground meandering river passages. Moreover, after the sporadic rain events, the water penetrating the cave’s host rock along fractures and bedding plains leads to the dissolution of primary minerals and allows the formation of seeping brines with dissolved salts. Both these processes selectively add solutes to the incoming undersaturated rainwater. The evaporation of these resulting salt-rich fluids at the cave atmosphere interface causes secondary minerals to precipitate. Mineral samples have been collected in eight caves, and include stalactites, flowstones, precipitates that form crusts in the streambeds and at the groundwater seeps, parietal coatings, earthy masses from the cave floors and efflorescence salts on ceiling rock outcrops. Most secondary deposits are composed of halite, but also other halides, carbonates, sulphates, nitrates, phosphates, and silicates have been discovered. Among the sixteen observed minerals, antarcticite, leonite, darapskite, blödite, atacamite and anhydrite are worth mentioning. The peculiar climate (extremely arid) and the very special environment dominated by NaCl and CaSO4, allow the crystallization primarily of halite. Atacamite was found where local enrichment in Cu (of hydrothermal origin) occurs, and antarcticite precipitates by the final evaporation of SO4-depleted brine (after early precipitation of anhydrite). Among sulphates, the metals necessary for the formation of these mineral species (magnesium, potassium, sulphate) derive from the cave sediments while nitrates are supplied by bird guano. Salt mineral precipitation is controlled by the temperature dependence solubility of the species in saline water, so that different secondary minerals were observed.

Caves formed by rising sulfuric waters have been described from all over the world in a wide variety of climate settings, from arid regions to mid-latitude and alpine areas. H2S is generally formed at depth by reduction of sulfates in the presence of hydrocarbons and is transported in solution through the deep aquifers. In tectonically disturbed areas major fractures eventually allow these H2S-bearing fluids to rise to the surface where oxidation processes can become active producing sulfuric acid. This extremely strong acid reacts with the carbonate bedrock creating caves, some of which are among the largest and most spectacular in the world. Production of sulfuric acid mostly occurs at or close to the water table but also in subaerial conditions in moisture films and droplets in the cave environment. These caves are generated at or immediately above the water table, where condensation-corrosion processes are dominant, creating a set of characteristic meso- and micromorphologies. Due to their close connection to the base level, these caves can also precisely record past hydrological and geomorphological settings. Certain authigenic cave minerals, produced during the sulfuric acid speleogenesis (SAS) phase, allow determination of the exact timing of speleogenesis. This paper deals with the morphological, geochemical and mineralogical description of four very typical sulfuric acid water table caves in Europe: the Grotte du Chat in the southern French Alps, the Acqua Fitusa Cave in Sicily (Italy), and the Bad Deutsch Altenburg and Kraushöhle caves in Austria. Caves formed by rising sulfuric waters have been described from all over the world in a wide variety of climate settings, from arid regions to mid-latitude and alpine areas. H2S is generally formed at depth by reduction of sulfates in the presence of hydrocarbons and is transported in solution through the deep aquifers. In tectonically disturbed areas major fractures eventually allow these H2S-bearing fluids to rise to the surface where oxidation processes can become active producing sulfuric acid. This extremely strong acid reacts with the carbonate bedrock creating caves, some of which are among the largest and most spectacular in the world. Production of sulfuric acid mostly occurs at or close to the water table but also in subaerial conditions in moisture films and droplets in the cave environment. These caves are generated at or immediately above the water table, where condensation–corrosion processes are dominant, creating a set of characteristic meso- and micromorphologies. Due to their close connection to the base level, these caves can also precisely record past hydrological and geomorphological settings. Certain authigenic cave minerals, produced during the sulfuric acid speleogenesis (SAS) phase, allow determination of the exact timing of speleogenesis. This paper deals with the morphological, geochemical and mineralogical description of four very typical sulfuric acid water table caves in Europe: the Grotte du Chat in the southern French Alps, the Acqua Fitusa Cave in Sicily (Italy), and the Bad Deutsch Altenburg and Kraushöhle caves in Austria.

The Marsala area, at the western end of Sicily, has been historically interested by quarry activities, both at surface and underground. The carved rocks are Lower Pleistocene calcarenites, defined as “Calcarenite di Marsala” and referred to the Marsala syntheme. The subterranean quarries, now abandoned, show increasing instability signs becoming in time a risk factor for several causes, among which: a) breakdowns due to poor (weak) strength of rock and to large size of voids; b) progressive weathering of rock; c) effects of the discontinuities in the rock mass with the pillars and/or walls of the underground quarries. These factors contributed to enlargement of the subterranean voids and to their upward propagation, thus triggering several sinkholes. The fast urbanization of the city masked many subterranean quarries causing the loss of memory of their location.In the last decades, numerous sinkholes occurred both in urban sectors and in areas designated for agricultural use, creating extensive damage to buildings and infrastructures.The latest sinkhole episode occurred in the Amabilina area, at the eastern suburbs of Marsala. The depression shows an elliptical perimeter (100×70 m) and a depth of at least 15 m.At the bottom, some rooms up to 5 m high of an underground quarry are visible. From the evidences collected a few days after the event, it was possible to reconstruct the time sequence in the formation of the sinkhole. The collapse started due to the propagation of voids and a first failure of some pillars, and was subsequently followed by a second event, which caused a widening of the depression, due to the redistribution of the stress resulting after early failures.

Il sistema carsico di Sant’Angelo Muxaro si sviluppa in corrispondenza del rilievo gessoso su cui sorge l’abitato omonimo, nel centro Sicilia, in provincia di Agrigento. Tale sistema è costituito da due inghiottitoi attivi (Grotta di Sant’Angelo Muxaro o localmente Grotta Ciavuli e Inghiottitoio Infantino), che si aprono al termine di due valli cieche alla base del versante meridionale del rilievo, e da una risorgenza attiva, ubicata alle pendici del versante nord-occidentale dello stesso rilievo. Le prime esplorazioni speleologiche e l’attività di ricerca in questo sistema nei gessi messiniani della Sicilia, escludendo le segnalazioni del geografo Olinto Marinelli, sono cominciate tra la fine degli anni ’80 e la metà degli anni ‘90, quando è stata topografata e descritta la Grotta di Sant’Angelo Muxaro ed esplorato l’Inghiottitoio Infantino. Solo a partire dal 2004 le ricerche si sono rivolte anche alla risorgenza. Nell’ambito di studi di carattere geomorfologico effettuati nell’area, è stato realizzato un nuovo rilievo topografico e geomorfologico della Grotta di Sant’Angelo Muxaro. In questa occasione sono stati scoperti alcuni rami nuovi, caratterizzati dalla presenza di particolari speleotemi gessosi. In questo contributo verrà descritto il sistema carsico nel suo complesso, anche alla luce delle nuove scoperte.

Cozzo Disi was one of the main sulphur mines in Italy, but after the closure and more than 10 years of desertion, urgent works are now necessary to save it from vandalism and flooding. This big mine contains geological and mineralogical peculiarities, so uncommon to be sometimes unique: this is the case of the “Grandi Garbere” at 3rd level, majestic karst cavities, containing magnificent selenite crystals documented by old miners. The possibility to have a “Sicilian Naica” attracted a multi-disciplinary underground task-force, now exploring the mine underground, in order to inspect old works and their good-safety conditions, and to achieve the rooms/caves of “Grandi Garbere”. This extraordinary discovery should be relevant for the future of this territory. In the past, the mine was characterized by huge safety problems: hydrogen sulfide, carbon dioxide and explosive atmospheres; so, the team involved in actual and future explorations has to move with caution, using adequate equipment and - if necessary - waiting for acceptable environmental conditions created by artificial tools (ventilation, pumping, etc.).

La Grotta dei Personaggi è localizzata in Sicilia occidentale, nei pressi di Monte Magaggiaro, a S del centro abitato di Montevago (AG). Nell’area sono presenti sorgenti termali, caratterizzate da acque cloro-solfate alcalino-terrose con temperatura di circa 40 °C e pH 7. La Grotta dei Personaggi, conosciuta già dai primi anni del 1900 e nota anche per ritrovamenti archeologici, non era mai stata dettagliatamente rilevata e studiata. La cavità si sviluppa prevalentemente in calcari di piattaforma della formazione Inici (Giurassico inf.) e in calcari di scarpata e pelagici della formazione Buccheri (Giurassico inf.-sup.). Si tratta di una cavità sub-orizzontale che presenta uno sviluppo di circa 1,7 km, un dislivello ascendente di 15 m e discendente di 32 m. Il pattern dei condotti è labirintico e strettamente influenzato dalla struttura geologica; non ci sono veri e propri pozzi, ma soltanto fratture che si restringono in profondità; i rami ascendenti sono caratterizzati da cupole che si compenetrano verso l’alto. Tra le altre morfologie si riconoscono buchi da stillicidio, canali di condensazionecorrosione, sfere di condensazione, bocche alimentatrici, pilastri e tramezzi. All’interno della cavità sono presenti anche una colonia di chirotteri e diversi depositi di minerali ancora in fase di studio. L’analisi delle morfologie a grande e media scala e la presenza di acque termali nell'area fanno ipotizzare che la genesi di questa cavità sia legata a processi ipogenici.

The application of numerical modeling to the analysis of the stability of both natural and man-made underground caves is rapidly increasing due to the availability of powerful numerical codes, that can account for either continuum or discontinuum behavior of the rock masses. Numerical methods allow to overcome traditional methods for cave stability analysis that assume too simplified geometrical, geological and geomechanical conditions. Further, they are also able to assess the potential failure mechanisms of underground systems. On the other hand, the application of numerical methods requires availability of a detailed geo-structural survey of the cave, as well as a proper geomechanical characterization of the rock and joint material properties for the pre-processing stage. The present contribution is aimed at describing some aspects related to implementation, and comparison of the outcomes, of two-dimensional or three-dimensional finite element analysis as regards artificial caves with complex geometries excavated within calcarenite rock masses. This type of man-made caves is very common in Southern Italy, and is at the origin of frequent sinkholes, often threatening the built-up areas. In particular, the results from 2-D and 3-D analyses of a case study represented by a cave with complex geometry are presented, showing that 3-D analysis leads to more stable conditions of the rock mass surrounding the cave. This is supposed to be the consequence of the different stress state as calculated by the two analyses, the 2-D one assuming plane strain conditions while the 3-D analysis assumes more general stress conditions.

La presenza di estesi sistemi caveali in sotterraneo, utilizzati nel secolo scorso per l’estrazione di materiale da costruzione in diversi contesti del territorio italiano, di frequente determina situazioni di pericolo per l’ambiente antropizzato, a causa dello sviluppo di processi di instabilità, che possono propagarsi verso l’alto, sino a raggiungere la superficie. Specialmente nei casi in cui la memoria storica della presenza ed estensione delle cave sotterranee è andata persa, lo sviluppo urbanistico dei centri abitati nel corso degli ultimi decenni può avere determinato la realizzazione di abitazioni ed infrastrutture al di sopra, o nelle immediate vicinanze, di zone interessate da complessi sistemi ipogei. Il territorio di Marsala, in Sicilia occidentale, è caratterizzato da numerose cave per l’estrazione della locale roccia calcarenitica, realizzate a profondità variabili da pochi metri a circa 15 m, su livello singolo o su due livelli, seguendo la tecnica di scavo a gallerie e pilastri. Dopo la cessazione dell’attività estrattiva, le cave sono state abbandonate e si è inevitabilmente avviato un processo di decadimento delle proprietà fisiche e meccaniche dell’ammasso roccioso, che spesso ha determinato l’occorrenza di fenomeni di instabilità in sotterraneo. Tali fenomeni, documentati per la zona in esame a partire dagli anni 1960, consistono essenzialmente in collasso e deformazioni delle volte e dei pilastri degli ambienti ipogei. In più situazioni, essi si sono propagati verso l’alto sino a raggiungere la superficie topografica, con formazione di sprofondamenti che hanno coinvolto anche aree urbanizzate, producendo significativi danni. L’ultimo evento è avvenuto nel mese di novembre 2013, ed è presentato nel dettaglio in un altro contributo di questo congresso. Il presente lavoro descrive le analisi numeriche 2D e 3D agli elementi finiti, eseguite su un interessante caso di studio avvenuto nel giugno 2011 nella zona orientale della città di Marsala, prodotto dall’instabilità all’interno di una cava sotterranea, e che ha provocato danni ad un edificio scolastico. La disponibilità del rilievo completo della cava sotterranea, eseguito alcuni anni prima dello sprofondamento, congiuntamente a specifici rilievi geologico-strutturali all’interno degli ambienti ipogei,hanno permesso l’esecuzione di analisi a ritroso per la comprensione dei meccanismi di rottura e l’individuazione dei fattori responsabili dei meccanismi genetici dello sprofondamento. In particolare, verranno evidenziate e discusse le principali differenze riscontrate nel corso dell’esecuzione di analisi bi- e tri-dimensionali.

A study of deep-seated gravitational slope deformation (DSGSD) phenomena affecting areas of various geological and geomorphological settings in western Sicily is described. Western Sicily is underlain by a thin-skinned imbricate wedge of Meso–Cenozoic carbonate and siliciclastic rocks that formed by the stacking of several thrust nappes over the Iblean foreland. Locally, the original thrust sheets are folded and cut by high-angle faults. Large areas of western Sicily now display high relief energy due to Plio-Pleistocene block-faulting and uplifting, and the Quaternary morphogenetic phases are characterised by incision, thereby triggering widespread DSGSDs. To identify controlling factors and triggering causes and to develop reliable morphoevolutionary models for the DSGSDs of western Sicily, a geomorphological study based on field surveys and aerial-photography interpretations was performed. Previous geomorphological data relating to well-known examples of DSGSDs were reconsidered, leading to remarkable revisions of the interpretative models in certain cases. New data were subsequently collected, enabling recognition of additional DSGSD phenomena. The whole body of data involves a total of 27 DSGSDs affecting areas in two specific geological settings: (1) areas with flat thrust surfaces, where differential settlements, back-tilting, lateral spreads in competent rocks overlying marls and clays, large topples, and/or block-type slope movements may develop; and (2) areas where deep-rooted carbonate units come into lateral contact with clayey–marly units along high-angle faults, where lateral spreads in brittle homogeneous rocks, sinking, and/or rock flows may occur. These DSGSD phenomena are associated with different evolutionary stages, allowing a morphoevolutionary model to be defined for the two geological conditions. For these two different morphoevolutionary models, the following structural features play an important role in the development of DSGSDs: (1) where carbonate bodies overlie clayey–marly rocks, triggering of the DSGSDs traces back to deformation of a ductile substratum that follows the exhumation of the flat thrust planes and the underlying clayey–marly rocks due to block-faulting and/or stream incision; and (2) where homogeneous carbonate rocks hundreds of metres thick crop out, the DSGSDs are triggered by very high relief energy and tensile stress that follow the combined actions of Quaternary block-faulting and stream deepening associated with differential erosion.

La presenza di estesi sistemi caveali in sotterraneo, utilizzati nel secolo scorso per l’estrazione di materiale da costruzione in diversi contesti del territorio italiano, di frequente determina situazioni di pericolo per l’ambiente antropizzato, a causa dello sviluppo di processi di instabilità, che possono propagarsi verso l’alto, sino a raggiungere la superficie. Specialmente nei casi in cui la memoria storica della presenza ed estensione delle cave sotterranee è andata persa, lo sviluppo urbanistico dei centri abitati nel corso degli ultimi decenni può avere determinato la realizzazione di abitazioni ed infrastrutture al di sopra, o nelle immediate vicinanze, di zone interessate da complessi sistemi ipogei. Il territorio di Marsala, in Sicilia occidentale, è caratterizzato da numerose cave per l’estrazione della locale roccia calcarenitica, realizzate a profondità variabili da pochi metri a circa 15 m, su livello singolo o su due livelli, seguendo la tecnica di scavo a gallerie e pilastri. Dopo la cessazione dell’attività estrattiva, le cave sono state abbandonate e si è inevitabilmente avviato un processo di decadimento delle proprietà fisiche e meccaniche dell’ammasso roccioso, che spesso ha determinato l’occorrenza di fenomeni di instabilità in sotterraneo. Tali fenomeni, documentati per la zona in esame a partire dagli anni 1960, consistono essenzialmente in collasso e deformazioni delle volte e dei pilastri degli ambienti ipogei. In più situazioni, essi si sono propagati verso l’alto sino a raggiungere la superficie topografica, con formazione di sprofondamenti che hanno coinvolto anche aree urbanizzate, producendo significativi danni. L’ultimo evento è avvenuto nel mese di novembre 2013, ed è presentato nel dettaglio in un altro contributo di questo congresso. Il presente lavoro descrive le analisi numeriche 2D e 3D agli elementi finiti, eseguite su un interessante caso di studio avvenuto nel giugno 2011 nella zona orientale della città di Marsala, prodotto dall’instabilità all’interno di una cava sotterranea, e che ha provocato danni ad un edificio scolastico. La disponibilità del rilievo completo della cava sotterranea, eseguito alcuni anni prima dello sprofondamento, congiuntamente a specifici rilievi geologico-strutturali all’interno degli ambienti ipogei, hanno permesso l’esecuzione di analisi a ritroso per la comprensione dei meccanismi di rottura e l’individuazione dei fattori responsabili dei meccanismi genetici dello sprofondamento. In particolare, verranno evidenziate e discusse le principali differenze riscontrate nel corso dell’esecuzione di analisi bi- e tri-dimensionali.

Although hypogene cave systems have been described since the beginning of the 20th century, the importance in speleogenesis of ascending fluids that acquired their aggressiveness from in-depth sources has been fully realized only in the last decades. Aggressiveness of waters can be related to carbonic and sulfuric acids and the related corrosion-dissolution processes give rise to different types of caves and underground morphologies. The abundance of hydrothermal springs and associated travertine deposits, and the widespread interaction between volcanic or sub-volcanic phenomena and karst in many sectors of the Italian peninsula are a strong evidence of hypogene speleogenesis. Furthermore, researches on secondary minerals have allowed to discover hypogene caves formed by highly acidic vapors in subaerial environments, also showing that most of these caves have extremely rich mineral associations.

Sulfuric acid caves can display a variety of forms, from 3D maze systems, to isolated chambers, and more or less maze-like water table caves. Most of the voids are normally generated at or immediately above the water table, where condensation-corrosion processes are dominant, creating a set of characteristic meso- and micromorphologies. This paper deals with the description of four very typical sulfuric acid water table caves: the Grotte du Chat in Provence (France), the Acqua Fitusa Cave in Sicily (Italy), and the Bad Deutsch Altenburg and Kraushöhle caves in Austria.

The Map Sheet 1:50.000 595 ”Palermo” includes marine and land areas of the topographic map sheet “Palermo”. The map sheet “Palermo” (Palermo Province) covers a part of the Sicily Fold and Thrust Belt (FTB) which has developed along the plate boundary between Africa and Europe in the Central Mediterranean. The Sicily FTB links the African Maghrebide to the Calabrian arc and Southern Apennines. The FTB and its submerged western and northern extensions are part- ly located between the Sardinia block and the Pelagian-Ionian sector, and partly beneath the central southern Tyrrhenian Sea. In this sector of the Mediterranean area, the main compressional move- ments, after the Paleogene Alpine orogeny, began with the latest Oligocene-Early Miocene counterclockwise rotation of Corsica-Sardinia, believed to represent a volcanic arc, and its collision with the African continental margin. Thrusting oc- curred in connection with the westward subduction of the Adriatic and Ionian lithosphere beneath the Corsica-Sardinia block. Today, a westward subduction is indicated by a North-dipping Benioff zone, as deep as 400 km, west of Calabria and the Apennines, and the related calc- alkaline volcanism in the Eolian Islands. Subduction and thrusting are contempo- raneous with a back arc-type extension in the Tyrrhenian Sea.186 LAND AREAS geomorphoLogy Three different sectors can be distinguished in Sheet 595: 1) the Palermo and Bagheria coastal plains, characterized by several poly- cyclic marine terraces organized in different orders; 2) the isolated carbonate reliefs of Monte Pellegrino and Monte Catalfano; 3) the internal Belmonte Mezzagno highlands and the Oreto and Eleuterio river valleys. The geomorphological evolution of the area has been controlled by strong down-cutting and dismantling processes that have produced both the erosion of thick volumes of mainly Tertiary terrigenous deposits and the exhumation of mainly Mesozoic carbonate rocks. Due to tectonic uplifting, these proces- ses are intensely developed on ”soft rocks “(Numidian Flysch clayey deposits), producing large river valleys with slopes affected by water erosion and surficial landslides (valleys of Fiume Oreto, Fiume Eleuterio and Fiume Milicia); they have, however, considerably slowed down along the blocks of more resistant rock (Mesozoic-Tertiary carbonate units), forming the wide Palermo Mountains. At the present-day, relict (planation surfaces and abandoned valleys), structural (fault/fault-line scarps) and karst (sinkholes and polje) forms occur in the highlan- ds. The geomorphological setting of the coastal areas has been influenced more by significant Quaternary extensional tectonics that originated the drowning of the northern sectors of the Sicilian chain in the Tyrrhenian Sea above which the marine deposition was deposited (Marsala synthem). The uplifting, involving also the lowered blocks, has resulted in the progressive retreat of the sea that gave origin to a succession of marine terraces, Ionian-Latest Pleistocene in age, and fi- nally the emersion of the present-day coastal depressions (Palermo and Bagheria plains). During the Upper Pleistocene to Holocene, the uplifting rates reached values generally lower than 0.1 m/ky. stratIgraphy The carbonate and terrigenous rock facies analysis and stratigraphy led to the recognition of large Paleozoic to Miocene sedimentary bodies pertaining to diffe- rent and separate crustal paleogeographic domains; the former, developed along the African passive continental margin and the adjacent Tethyan ocean. The “Tethyan” successions correspond to the deep clayey carbonate and vol- canoclastic rocks known to have been deposited in the Sicilide Domain. The pas- sive margin rock bodies are shallow water carbonates, deep water carbonates and 187 siliceous carbonates that were deposited in domains, locally known as Panormide, Trapanese and, Imerese. Terrigenous, evaporitic and clastic-carbonate rocks, Miocene to Pleistocene in age, formed during the foredeep evolution of the Sicilian FTB. A detailed stratigraphy of the rock-successions is summarized in the paragraph “Legend of the Palermo Sheet”. Quaternary continental deposits have been mapped as unconformity-bounded stratigraphic units limited by lower and upper unconformities, locally marked by palaeosoils, due to erosion/depositional processes, marine/sub-aerial processes or non-depositional events. Locally, the upper boundaries are the present-day topo- graphic surface. The detection of some unconformities of regional extent allowed us to define several synthems. The Marsala synthem is a Lower Pleistocene body of marine/coastal deposits, with abundant fossils; its lower boundary is a mari- ne erosion surface cutting pre-Quaternary rocks. The Buonfornello-Campofelice synthem is composed of middle Pleistocene marine deposits covering abrasion surfaces above the coastal stepped blocks. The Polisano synthem is made up of aeolian sandstones and sands with intercalations of breccias talus, late Middle Pleistocene in age (OIS 6); its lower boundary is a non-depositional surface at the top of older rocks. Eleuterio and Milicia synthems are made up of Middle-Upper Pleistocene, mainly fluvial, deposits deposited on river terrace surfaces; their lo- wer boundary is a stream erosion surface. The Benincasa synthem includes colluvial Middle-Upper Pleistocene deposits of Qz-sandstones interbedded with stone-line, palaeosoils, Fe-rich layers and no- dular concretions. Its lower boundary is an unconformity above the Buonfornello- Campofelice synthem, the upper one is the base of the Capo Plaia synthem of the present soil. The Barcarello synthem encompasses marine/coastal conglomerates and are- nites, with a rich warm-temperate “Senegal fauna” including Strombus bubonius; it is located on two orders of marine terraces (OISs 5e and 5c or 5a) and laterally passes into welded colluvial deposits whose age is correlated with the OIS 5. The lower boundary of the synthem is a marine abrasion surface, laterally extending to a continental erosion surface; the latter is cutting the Polisano synthem or older rocks. The Raffo Rosso synthem consists of aeolian sandstones and sands, collu- vial or gravitational deposits and thick stratified slope deposits of the last glacial climatic event (OISs 4-2); the lower boundary is a non-depositional surface at the top of the Barcarello synthem or older rocks. The Capo Plaia synthem is made up of coastal to continental deposits of the last glacial climatic event of the end - Holocene age (OISs 2-1); its lower boundary is formed by variously origina- ted erosion or non-depositional surfaces; the upper boundary is the topographic surface.188 struCturaL graIn The Paleozoic to Cenozoic, mainly carbonate sedimentary bodies, developed in different sectors of the African passive continental margin and the adjacent Tethyan ocean and were progressively accreted in a pile of tectonic units and are now exposed to form the Sicilian fold and thrust belt. To define the extension and setting of these bodies versus their internal facies pattern, we individuate them as Structural-Stratigraphic Units (U.S.S.), described as large geological bodies per- taining to original paleogeographic domains from where they were removed and later deformed. These bodies are bounded by clearly mappable tectonic features (faults, thrust, etc.) and each of them is characterized by homogeneous lithologies and similar structural behaviours and settings. The outcropping tectonic edifice, in the “Palermo” Sheet, is composed of se- veral U.S.S., which can be locally subdivided into tectonic units of minor order. These subunits have been mapped on the basis of their tectonic relationships. Some U.S.S. have been identified, starting from the geometrically highest and most internal in the FTB. 1) U.S.S. deriving from the deformation of the Sicilide domain succession: - U.S.S. Tusa-Troina outcropping in the south-eastern sector, overlying the Numidian Flysch deposits. 2) U.S.S. deriving from the deformation of the Imerese domain succession and its overlying numidian flysch basin. The units widely outcrop in the cen- tral and southern sector of the geological sheet where Mesozoic deep water carbonates and their oligo-miocene numidian flysch covers are deformed, with the latter often slightly detached from the carbonate substrate. Among them we distinguished: - U.S.S. Sagana - Belmonte Mezzagno, in the western sector, where we indi- viduated the sub-unit Pizzuta-S.Cristina; - U.S.S. Monte Cane-San Calogero, in the eastern sector, subdivided into a) the subunit Monte Cane-S. Onofrio, overlying b) the subunit Bizolelli; 3) U.S.S. deriving from the deformation of the Panormide Domain. The U.S.S. consists of Meso-Cenozoic shelf to pelagic carbonates and the often detached nu- midian flysch cover, pertaining to the U.S.S. M. Gallo-M. Palmeto, forming the margin of the Panormide Platform. It outcrops only at Monte Pellegrino (subunit Pellegrino). 4) U.S.S. deriving from the deformation of the Trapanese domain. It is recognizable only in the seismic profile crossing the eastern sector where it is overlain by the U.S.S. Sagana - Belmonte Mezzagno. Southwards, it oucrops at Monte Balatelle (U.S.S. Kumeta-Balatelle).189 Structural evolution The tectonic edifice outcropping and buried beneath the area of the Palermo Sheet is the result of several deformational events that have taken place since the Triassic, deforming complexly the sedimentary successions deposited during the Mesozoic-Pleistocene. After the detachment from their crystalline basement the original sedimentary bodies were progressively accreted in a pile of tectonic units now exposed in the Sicilian chain. Two main events have occurred during the Miocene and Pleistocene time interval. They are respectively characterized by compression and transpression. Contraction originally involved the Tethyan domains and the internal domains of the continental margin, whose deep water meso-cenozoic carbonates formed the structurally highest tectonic units in the chain. The occurrence of intrastratal decollement originated duplex geometries. Since the Messinian, the deformation moved at depth, progressively involving the carbonate platform rock bodies in large E-W antiforms that were successively (during Late Pliocene) folded by NE- SW structures. The transpressional event is proved by NNW-SSE and NE-SW transcurrent and transpressive structures (dextral); it involves the deep-seated car- bonate platform-forming fold structures and severe uplifting that induces reimbri- cation in the overlying Imerese deep-water units. This transpressive event accom- panies the paleomagnetically evidenced thrust rotations between the Late Miocene and the Early Pleistocene. An abrupt change in the tectonic transport direction of the two compressional structure systems is explained taking into account the 120° clockwise rotations based on the paleomagnetic results of ChanneL et alii (1980, 1990); speranza et alii (2000). As a consequence the present day outcropping structural attitude of the structures (and consequently of the deformation fields) do not coincide with the original trends. The compressional and traspressional structures are down faulted northwards by the extensional tectonics. MARINE AREAS In the marine areas, we distinguished different morphological environments, from beaches through the offshore (inner shelf), to the outer shelf and upper slope where two confined slope basins (Palermo and Termini basins, separated by the Monte Catalfano salient) represent the south-western margin of the large Cefalù basin. The substrate of these basins is represented by the Sicilian FTB tectonic units and their syn- and post-orogenic covers. The area shows a lateral variation from the rocky shores, in front of Monte Pellegrino and Monte Catalfano and in the eastern sector, to the beaches mainly in the central sector.190 Important physiographic changes, as shelf width and gradient and different coast orientations, characterise the continental shelf and slope and influence the hydrodynamic processes (wave activity and shelf current patterns). The continental shelf reaches 250 km2 and shows width values ranging from 1.5 km in the Capo Zafferano offshore to 8,0 km in the gulf of Termini, whereas gradient values range between 1° and 8°. The continental shelf has been subdi- vided into an inner infralittoral domain down to a 30 - 35 m water depth, which is characterized by an abrasion platform at different depths, and the outer shelf domain extends to the shelf edge. The shelf edge, which is both depositional and erosional, located at water depths between 120 m and 140 m, rises to lower depths at the canyon heads. Dominant morphological features along the continental slope are the submari- ne erosive conduits, locally interesting also the continental shelf. The heads of the conduits are characterised by severe episodes of retrogressive failure and incised by small gullies. Some (the Oreto and Eleuterio canyons) are directly linked to rivers and were connected during the last glacial maximum through incised val- leys, now buried by transgressive to highstand deposits. In the central sector of the Gulf of Palermo, we pinpointed almost three pockmarks, depressions tens of meters deep, originating from escaping fluids, while in the western sector of the gulf the same phenomena caused the occurrence of isolated or aligned, outcrop- ping or buried mounds. Finally anthropic features largely characterize the seabottom mainly in the inner shelf. seIsmostratIgraphy and stratIgraphIC settIng The buried sedimentary succession has been investigated by means of a close grid of single and multichannel seismic lines. On the whole, three seismic units (S, C and A) have been distinguished. The S seismic unit represents the offshore prolongation of the Meso-Cenozoic units of the Sicilian FTB and their syn- and post-orogenic cover. They are ge- nerally topped by a pronounced, erosive unconformity, correlated to the exten- sive Messinian horizon, generated during the last phases of the Mediterranean Salinity Crisis (5.5 Ma), and covered by a transparent seismic unit representing the Globigerina - bearing pelagic chalk (Trubi) and the Upper (?) Pliocene slope to shelfal deposits. The C seismic unit is represented by a prograding succession of 4° to 7° dip- ping horizons, which have been correlated with the regressive upper Pliocene- Pleistocene deposits, topped by the regional wide, erosional truncation related to the last glacioeustatic sea level fall, correlated with the δ18 O isotopic stage 2. The A seismic unit corresponds to the Late Pleistocene to Holocene 191 depositional sequence (SDTQ) with sigmoidal to tabular geometry; the deposi- tional sequence consists of a Falling Stage and Lowstand Systems Tracts with a progadational pattern controlling a relevant out-building of the shelf margin and a sedimentary wedge, of variable thickness, made up of the Transgressive (TST) and the Highstand (HST) Systems Tracts. The TST, developed during the Holocene sea level rise, shows a retrograda- tional stacking pattern, while the HST, deposited during the last 6 ka b.P., shows aggradational to faintly progradational geometries, related to the development of a littoral depositional system. Along the upper slope, turbiditic systems, characterized by erosive conduits and scattered mass wasting, developed extensively during the Late Pleistocene to Holocene. Surficial sediments of the continental shelf and slope The continental shelf and slope of the Palermo sheet are veneered with uncon- solidated, late Holocene in age, clastic and biogenic carbonate (Palermo gulf) and in second order, lithoclastic (Termini gulf) sediments. Deposits are composed of sands, relict Pleistocene and older carbonate parti- cles, abundant biogenic carbonate granules and algal-coated grains. In the outer shelf and upper slope, deposits are predominantly fine to very fine grained (silts and silty clays). The inner shelf is veneered by a mixture of gravel (rarely), coarse to fine sands, silts and clays, showing a general trend of decrea- sing size in a general seaward direction. From the sedimentary and the morphological features, four different depo- sitional systems have been distinguished: foreshore depositional systems, inner shelf depositional systems, outer shelf depositional systems and upper slope de- positional systems, mapped as g8 , g19 , g21 , m2 respectively. The systems are laterally gradational and linked by a variety of sedimentary processes. Shallow marine environments (up to a 50 m water depth) are generally characterized by biogenic sediments while terrigenous and carbonate clastic sedi- ments supplied by rivers or coastal erosion locally prevail. The most important facies of the infralittoral domain consists of Posidonia oceanica and Cymodocea nodosa meadows, which extensively cover the rocky substrate or the sandy floors the former and the muddy floors the latter. teCtonIC evoLutIon of the offshore areas The present day structural setting reconstructed in the Palermo sheet marine sectors appears the same as the tectonic edifice depicted on the mainland: it has 192 been interpreted as a consequence of the complex Neogene to Quaternary tectonic evolution. The compressive tectonics, responsible for the wedging of the present day submerged thrust sheets, developed during the Late Miocene span interval. This event was followed by transpressive tectonics that faulted and folded the Late Neogene to Pliocene infill by activation of high-angle, deep faults. During the Pleistocene, extensional tectonics accounted for opening and subsidence of structural lows. Present day active tectonics is still going on, as documented by compressive- transpressive focal mechanisms of shallow to deep, low amplitude earthquakes occurring along the offshore between the Sicilian coast and Ustica Island. A few middle-late Pleistocene marine terraces, outcropping along the coast at different levels, suggest a prolonged, faintly tectonic uplift. On the whole, the Plio-Quaternary geological evolution of the offshore area appears to be constrained by a strong interaction between eustatic sea level chan- ges, sediment supply and tectonics, recorded by strain features and enhanced un- conformities crossing the basin fill.