Pietro Di Stefano

Microfacies and depositional structure of allochthonous carbonate base-of-slope deposits: The late permian Pietra di Salomone megablock, Sosio Valley (Western Sicity)

SummaryThe carbonate breaccias and calcarenites of the extremely fossiliferous Pietra di Salomone megablock southwest of Palazzo Adriano, Sosio Valley (Monti Sicani, Western Sicily) represent debris-flow and turbidite sediments deposited in a base-of-slope position.Microfacies criteria (22 localities, 240 samples) and paleontological data (especially sphinctozoan and inozoan sponges,Tubiphytes, Archaeolithoporella, fusulinids, conodonts) provide evience of long- and short-lasting erosion of Middle to Upper Permian carbonate platform marginal reefs formed by binder/encruster and baffler guilds, probably on the uppermost slope. Subsequent to repeated reworking, lithified material (rudstones, boundstones) was transported downslope by sedimentary gravity flow processes and deposited, possibly, as fillings in channels incised in the deep-water basinal marly sediments of the Torrente San Calogero section adjacent to the Pietra di Salomone outcrop.The coincidence in the biostratigraphical age of the pebbles and the marly matrix of the breccias and of the basinal sediments indicates that the destruction of the platform margins and the platform lasted at least from the Murghabian to the Dzhulfian.The comparison of the reef biota preserved in the Pietra di Salomone limestone with reef biota occurring in Lower Permian allochthonous blocks within the Lercara ‘Formation’ (Cozzo Intronata, River San Filippo) points to a turnover in the composition of algal and sphinctozoan sponge associations after the Artinskian, probably during the lower Middle Permian (Kubergandian).RiassuntoLa Pietra di Salomone è il maggiore fra i famosi blocchi calcarei permiani della Valle del Sosio, ubicato a sudovest di Palazzo Adriano (Monti Sicani, Sicilia occidentale) e noto fin dal secolo scorso per la straordinaria ricchezza di fossili. Questo blocco calcareo risulta costituito da carbonati clastici risedimentati, prevalentemente da debris-flow, alla base di una scarpata.L’analisi delle microfacies e i dati paleontoloigici basati principalmente sulle spugne calcaree,Tubiphytes, Archaeolithoporella, fusulinidi e conodonti, indicano che le aree di alimentazione del materiale clastico erano costituite da complessi di scogliera ubicati al margine di piattaforme carbonatiche del Permiano medio e superiore.Il materiale clastico (per lo più elementi già litificati di rudstones e boundstones) prodottosi in seguito a ripetuti eventi erosivi, è stato trasportato lungo la scarpata mediante flussi gravitativi e potrebbe aver costituito il riempimento di canali incisi nei depositi permiani di bacino rappresentati nella sezione del Torrente San Calogero, contigua alla Pietra di Salomone.I dati biostratigrafici ricavati dagli elementi e dalla matrice marnosa delle brecce e quelli provenienti dai depositi di bacino, indicano che lo smantellamento dei margini della piattaforma si è protratto almeno dal murgabiano allo Giulfiano.Il confronto fra le faune di scogliera presenti nella Pietra di Salomone con quelle del Permiano inferiore presenti nei carbonati clastici della ‘Formazione’ Lercara (Cozzo Intronata, Fiume San Filippo) evidenzia una variazione nella composizione delle associazioni algali e delle spugne calcaree, variazione registrata dopo l’Artinskiano, probabilmente alla base del Permiano medio (Kubergandiniano).

New approach for quantifying water depth applied to the enigma of drowning of carbonate platforms

This research illustrates application of a fluid-inclusion technique for quantifying water depth of ancient carbonate platforms. Jurassic limestones of Monte Kumeta, Italy, were cemented with submarine calcite during a transition to carbonate platform termination. The calcite cements contain fluid inclusions consisting of Jurassic seawater and immiscible gas bubbles trapped during the growth and penecontemporaneous recrystallization of the cements. Crushing analysis indicates that gas bubbles are under pressures indicative of entrapment in water depths of 23–112 m. Assuming simple deepening and acknowledging chronostratigraphic errors, rates of relative rise in sea level were initially less than 7 m/m.y. followed by a rate of at least 33 m/m.y. These slow rates are evidence that the platforms demise was caused by an environmental perturbation other than rapid sea-level rise. The facies transitions and regional studies indicate that the perturbation resulted from nutrient excess or eutrophication in shallow water followed by deepening into ephemeral dysoxic waters at depths perhaps as shallow as 23 m.

Mesozoic and Paleogene megabreccias in Southern Sicily: New data on the Triassic Paleomargin of the Siculo-Tunisian platform

SummaryMesozoic and Paleogene clastic carbonates in deep-water successions outcropping in the Sicani mountains (central southern Sicily) represent debris-flow and turbidite deposits accumulated in slope/base-of-slope sectors of the Sicanian Basin, a Permian to Miocene deep-water sedimentary domain of Sicily. Reef-derived carbonates of late Triassic age are frequently found among the clastic elements of these deposits, in association with other shallow and deep-water Mesozoic carbonates. The provide us with new data on the stratigraphic setting of a platform paleomargin now buried beneath the Sicilian thrust and fold belt. This paleomargin bounded the wide middle and upper Triassic carbonate platform which is now known in the subsurface of the Southern Sicilian thrust and fold belt. This paleomargin bounded the wide middle and upper Triassic carbonate platform which is now known in the subsurface of the Southern Sicilian mainland and offshore in the Pelagian Platform, from the Malta escarpment to the Sciacca and Trapani areas through the Hyblean Plateau. The hinge zones between this platform domain and the Sicanian basin were particularly affected by the paleostresses related to the Mesozoic and Paleogene evolution of the Southwestern Tethys. The sedimentary successions of these areas recorded repeated episodes of progradation, aggradation, backstepping, uplift and erosion of the platform-basin system, under eustatic and tectonic forcing.

A regional‐scale discontinuity in western Sicily revealed by a multidisciplinary approach: A new piece for understanding the geodynamic puzzle of the southern Mediterranean

The results of an integrated stratigraphic, structural, geophysical, and geochemical study reveal the presence of a crustal discontinuity in western Sicily that, at present, runs roughly N-S along a band from San Vito Lo Capo to Sciacca (SVCS). The boundary between the two zones of this discontinuity is nearly orthogonal to the main thrust propagation of the Sicilian thrust-and-fold belt. The different Permian to Tertiary sedimentary evolution recorded by the two zones appears related to this discontinuity, with thick carbonate platforms in the western sector facing deep-water successions in the eastern one. The presence of Upper Triassic reefs, huge megabreccias bodies, and widespread submarine volcanisms along the transition zone suggest the presence of a long lasting weakness zone. This zone has been reactivated episodically as transpressional and/or transtensional faults in relation to the different geodynamic stress acting in central Mediterranean area in different epochs. We speculate that this transition zone has represented a segment of the passive margin of the Ionian Tethys. During the Maghrebian convergence a different style of deformation has affected the two sectors floored by different sedimentary multilayers. The orthogonal-to-oblique differential convergence between the two sectors has resulted in right-lateral transpressional motions, leading to oblique thrusting of deep-water-derived thrusts onto platform-derived thrusts associated with clockwise rotations. The oblique convergence is still ongoing as demonstrated by the seismicity of the area, by the geothermal field with high mantle-derived helium fluxes and by the GPS measurements collected by different authors.

La Piattaforma Carbonatica Panormide: un caso anomalo nell'evoluzione dei bacini della Tetide giurassica

Negli ultimi anni sono state proposte diverse ricostruzioni paleogeografiche dell’area Centro Mediterranea durante il Mesozoico. La Piattaforma Carbonatica Panormide (PCPA) viene collocata tra la Tetide Alpina e la Tetide Ionica, in un’area geodinamicamente molto complessa. Recenti studi hanno documentato la presenza di superfici di discontinuita che caratterizzano l’evoluzione stratigrafica della PCPA rispetto alle adiacenti Piattaforme Carbonatiche Siciliane. La presenza di superfici di discontinuita negli intervalli Retico-Hettangiano e Giurassico Medio-Oxfordiano vengono messe in relazione, attraverso il confronto della storia della subsidenza tra le Piattaforme Carbonatiche, con gli stadi evolutivi della Tetide Alpina

MIDDLE TRIASSIC (LADINIAN) DEEP-WATER SEDIMENTS IN SICILY. NEW FINDINGS FROM THE MADONIE MOUNTAINS

A section of carbonate megabreccias grading upward to deep-water Daonella limestones is described from the locality of Sant’Otiero, near Petralia Sottana, in the Madonie Mountains (Sicily). The megabreccia mainly consists of neritic elements containing dasycladalean algae ( Diplopora annulatissima Pia) along with benthic foraminifers and problematics. The overlying calcilutitic strata are characterized by lumachella intercalations containing the bivalve Daonella tyrolensis Mojsisovics suggesting an early Late Ladinian ( Protrachyceras longobardicum ammonoid zone) age. We informally name the Daonella limestone as the calcare di Sant’Otiero (Sant’Otiero limestone). The Daonella limestones along with the neritic megabreccia extraclasts with Diplopora annulatissima represent a previously unknown component of the pre-Carnian stratigraphy from the paleo-Alpine Sicily.

LANDFILL SITE SELECTION FOR MUNICIPAL SOLID WASTE BY USING AHP METHOD IN GIS ENVIRONMENT: WASTE MANAGEMENT DECISION-SUPPORT IN SICILY (ITALY)

The goal of this work was to test a methodology, based on multi-criteria analysis and geographic information systems, aimed at identifying areas potentially suitable to host landfills for Municipal Solid Waste (MSW). Although the above-mentioned methodology was applied to three different areas (Western, South-western and Eastern) of Sicily, in this paper, we present the results of the western sector. The first step consisted of the division of the study area in excluded and potentially suitable sites, on the basis of the Italian current legislation. The suitable sites were subsequently re-evaluated based on additional criteria in order to choose the most suitable ones. This second step consisted of a multi-criteria analysis based on a scores and weights system. The Analytic Hierarchy Process (AHP) was applied to estimate the relative importance weights of the evaluation criteria. The suitability for landfill siting was finally evaluated with the aid of a simple additive weighting method. The resulting land suitability was reported on a scale of 0 to 10, respectively, from the least suitable to the most suitable sites. In order to reveal the most suitable sites, to provide a ranking and, consequently, a quick selection, a spatial clustering process was carried out. In relation to the data obtained, several suitable areas to host sites for MSW landfill in Western Sicily were identified. The application of multi-criteria analysis, together with the use of geographic information systems, provided a powerful tool for the identification of the most suitable site among those identified.