The Verrucano Deposits of Southern Tuscany (Northern Apennines, Italy): a Record of the Mesozoic Continental Rifting

ORGANIZZAZIONE

Coordinamento Daniela Fontana

Segreteria Stefano Lugli

Comitato scientifico Milena Bertacchini Stefano Conti Daniela Fontana Stefano Lugli Simona Marchetti Dori

Collaboratori Elena Aldrovandi Massimo Barbieri Marco M. Coltellacci Veronica Padovani Edda Pattuzzi Manuela Zinanni

Progetto grafico Milena Bertacchini

Patrocinio Dipartimento di Scienze della Terra, Universtà di Modena e Reggio Emilia Provincia di Modena FIST, Federazione Italiana di Scienze della Terra

Sponsor Comune di Modena Comune di Spilamberto

1 Indice

ACCAINO F., BRATUS A., CONTI S., FONTANA D. & TINIVELLA U. Fluid flow pathway and configuration of buried structures in mud-volcanoes of the northern Apennines. Pag. 7

ALDINUCCI M. The Verrucano deposits of southern Tuscany (Northern Apennines, Italy): a record of the Mesozoic continental rifting. Pag. 8

ALDINUCCI M., BERTINI A., DA PRATO S., DONIA F., FORESI L. M., MAZZEI R., RIFORGIATO F., SANDRELLI F., SALVATORINI G. & ZANCHETTA G. Messinian events in Tuscany : insights from selected sections. Pag. 9

ALDROVANDI E. & LUGLI S. Evoluzione composizionale delle sabbie del fiume Po negli ultimi 30 ka: idagini preliminari sul paleoalveo di Bondeno (FE). Pag. 10

ALI ABDEL MEGID A. Modern sands composition, sediment budget and erosion rates of the Nile basin. Pag. 11

AMOROSI A Cyclic stratigraphic patterns from middle-late Quaternary deposits of northern Italy. Pag. 12

ARGNANI A. & ROGLEDI S. Stratigraphy and tectonics of the Pisa-Viareggio basin: hints on the evolution of the Neogene basins of Tuscany. Pag. 16

ARTONI A. & CONTI S. Seep-carbonates in intrabasinal highs of the inner foredeep: new insights from the middle Miocene Salsomaggiore Ridge (Northern Apennines, Italy). Pag. 17

BELLINO L. & FIORASO G. Quaternary evolution of the terraced fluvial succession of the Bormida River (Tertiary Piedmont Basin, North-Western Italy). Pag. 21

BENVENUTI M., MARIOTTI-LIPPI M., PALLECCHI P. & SAGRI M. Geoarcheologia oltre l'appeal: quali reali opportunità per la Geologia del Sedimentario? Pag. 22

BENVENUTI M. & MORONI A. Cambiamenti ambientali e presenza umana nel tardo Quaternario della Valtiberina Superiore (Toscana NE): Geoarcheologia e oltre . Pag. 23

BERNARDESCHI A., CATANZARITI R., MARRONI M., OTTRIA G., PANDOLFI L. & TAINI A. Mapping using Depositional Units inside of the Italian 1:50.000 CARG Project: an example from the Tertiary Piedmont Basin. Pag. 24

BERTACCHINI M. Osservazioni geoarcheologiche sul territorio di Nogna (Gubbio, Perugia). Pag. 25

2 BERTACCHINI M., FREGNI P. & PATTUZZI E. Nuove osservazioni litostratigrafiche sui depositi della conca di Gubbio. Pag. 26

BERTOK C., D’ATRI A., MARTIRE L., MUSSO A., PEROTTI E. & PIANA F. Depositional paleoscarps in the Meso-Cenozoic succession of the Marguareis Massif (Ligurian Briançonnais): recognition and implications. Pag. 27

BONCIANI F., CORNAMUSINI G., CALLEGARI I., CONTI P., FORESI L.M. & CARMIGNANI L. La “Coltre della Val Marecchia” nel quadro mio-pliocenico dell’Appennino marchigiano-romagnolo. Pag. 28

BUONOMO V., ORTOLANI F. & PAGLIUCA S. Climate change and beaches evolution in the Mediterranean area. Pag. 33

CACCHIO P., GIANIORIO L., ERCOLE C., DEL GALLO M. & LEPIDI A. Calcifying baceria and physicochemical parameters of three different soils of l’Aquila basin (central - Italy). Pag. 38

CAPEZZUOLI E., GANDIN A. & SANDRELLI F. Facies characterization of the Late Pleistocene-Holocene continental carbonates in southern Valdelsa Basin (Southern Tuscany). Pag. 39

CARANNANTE A. Le orictocenosi quaternarie dell’arcipelago flegreo e la lavorazione della conchiglia a Vivara (Procida, Napoli) nell’età del bronzo. Pag. 40

CARPENITO G., LEVI S. T., LUGLI S., MARCHETTI DORI S. & VEZZALINI G. Determinazione dei sedimenti utilizzati come frazione fine nella manifattura di ceramiche dell’età del Bronzo di Gorzano (MO). Pag. 41

CILUMBRIELLO A. Analisi stratigrafico-sedimentologica dei “Depositi marini terrazzati” della bassa piana metapontina tra i fiumi Basento e Cavone (Golfo di Taranto, Italia meridionale). Pag. 42

CLEMENTE P., IRACE A., NATALICCHIO M., TRENKWALDER S., MOSCA P., DE LUCA D. A., POLINO R. & VIOLANTI D. Deep hydrostratigraphy of Plio-Pleistocene successions in Western Po Plain. Pag. 46

CONTI S. & FONTANA D. I carbonati connessi ad emissioni di fluidi ricchi in metano:i risultati di dieci anni di studi nell’Appennino settentrionale. Pag. 47

CONTI S., FONTANA D., GUBERTINI A. & LUCENTE C.C. Authigenic seep-carbonates cementing coarse-grained deposits in a fan-delta depositional system (middle Miocene, Marnoso-arenacea Formation, central Italy). Pag. 49

DALLA VALLE G., GAMBERI F. & MARANI M. The Posada turbidite system (eastern Sardinian Margin): a mass-wasting affected system in a partially confined intraslope basin. Pag. 50

3 DEL CONTE S. Pliocene depositional evolution of the south-eastern Valdelsa Basin (Tuscany, Central Italy): tectonic and eustatic control on fluvio-deltaic depositional systems. Pag. 51

DELA PIERRE F., FESTA A., CAVAGNA S., CLARI P. & MARTIRE L. Cylindrical 13C-depleted concretions and chaotic deposits: a significant association in the Late Miocene of the tertiary Piedmont basin. Pag. 52

FALCINI F., MILLI S., MOSCATELLI M., SALUSTI E. & STANZIONE O. A simple three layers model for the behaviour of a turbidity current as a function of the Richardson number: sedimentological implication. Pag. 53

FIORONI C. & BERTOLINI G. L’alluvione tardo medioevale di Rubiera (Provincia di Reggio Emilia). Pag. 54

FUBELLI G., CIPOLLARI P., COSENTINO D., FARANDA C., GLIOZZI E., LIGIOS S., PASQUALI V. & SMEDILE A. Ricostruzione paleoambientale ed evoluzione stratigrafico-sequenziale della fascia costiera pliocenica compresa tra le foci del Paleo-Farfa e del Paleo-Corese (Sabina, Italia centrale). Pag. 57

GAMBERI F. Indication of seafloor instabilty in the upper part of the Marnoso-arenacea Formation of the Sintria, Lamone and Marzeno Valleys. Pag. 58

GAMBERI F. & DALLA VALLE G. The impact of margin shaping processes on the architecture of deep-sea depositional systems: the Sicilian and Sardinian margins (Tyrrhenian Sea). Pag. 59

GAMBERI F.& MARANI M. Carbonate hardground formation in the volcanic seamounts of the Tyrrhenian Sea. Pag. 61

GIUNTA S., MORIGI C., NEGRI A. , GUICHARD F. & LERICOLAIS G. Holocene biostratigraphy and evidences of paleoenvironmental modifications in the Black Sea based on coccolithophorids. Pag. 62

GUIDO A., GAUTRET P., JACOB J., LAGGOUN-DEFARGE F., MASTANDREA A. & RUSSO F. Organic markers as indicators of the depositional conditions of the Messinian Calcare di Base formation (Rossano Basin, Northern Calabria, Italy). Pag. 63

LABRIOLA M., TROPEANO M., MORETTI M. , PIERI P. & SABATO L. Prime considerazioni sugli apporti calcareo-clastici provenienti dall’Avampaese apulo nei “Depositi marini terrazzati” del bacino idrografico del Fiume Lato (Puglia). Pag. 64

MARCHETTI DORI S., LUGLI S. & FONTANA D. Segnali di controllo climatico sulla composizione dei depositi sabbiosi della pianura modenese: dati preliminari. Pag. 65

MIENERT J., GARCIA C. P., HAFLIDASON H., VANNESTE M. Gas blowouts and outer shelf cracking features of northern North Atlantic ocean margins triggered by gas-hydrate melting due to ocean warming? Pag. 70

G. MONEGATO The evolution of the valley of Tagliamento River from the Messinian Salinity Crisis onwards. Pag. 71

MORIGI C., JORISSEN F.J., HORTON B. P., SABBATINI A., CAPOTONDI L. & NEGRI A. The Holocene mud-belt and bathymetrical evolution in the central Adriatic Sea: benthic foraminiferal evidence. Pag. 72

NATALICCHIO M., IRACE A., TRENKWALDER S., CLEMENTE P., MOSCA P., POLINO R., VIOLANTI D. & DE LUCA D. A. Stratigraphic architecture of Plio-Pleistocene Savigliano and Alessandria Basins (Western Po Plain). Pag. 73

ONOFRIO V. Tectonic control on the stratigraphic setting of the northern Sant’Arcangelo Basin (Pleistocene- Southern Apennines, Basilicata). Pag. 75

ORTOLANI F. & PAGLIUCA S. Geoarchaeological evidences of cyclical catasthrophic events in the Neapolitan urbanised area. Pag. 76

ORTOLANI F. & PAGLIUCA S. Geoarchaeological evidences of cyclical climatic-environmental changes in the Mediterranean area (2500 bp-present day). Pag. 81

ORTOLANI F. & PAGLIUCA S. The climatic risk for the circummediterranean area on the base of geoarchaeological data. Pag. 86

PANIERI G. & SEN GUPTA B. K. Benthic foraminiferal colonization of a gas hydrate mound, Blake Ridge, western North Atlantic Ocean. Pag. 91

PARISI S., LONGHITANO S., MONGELLI G. & SPALLUTO L. Geochemistry and stratigraphy of the giurassic hard-grounds of the Rocca Busambra (west Sicily, Italy). Pag. 92

PEROTTI E., BERTOK C., D’ATRI A., MARTIRE L., MUSSO A. & PIANA F. Tectonic, seismic and hydrothermal events recorded in the Jurassic succession of the Marguareis Massif (Ligurian Briançonnais). Pag. 95

PIOVAN S., MARAGNO E. & MOZZI P. The Roman road “Via di Villadose” and its relations with the paleaeohydrography (Rovigo - Italy). Pag. 96

REDINI M., SARTI G., CONTINI S. & PIPPI G. La banca dati geognostica e la stratigrafia del sottosuolo come elemento di pianificazione del territorio: l’esperienza del comune di Pisa. Pag. 97

RUSSO F. Platform evolution in the Triassic of the Dolomites (Italy): from low relief carbonate banks to bioconstructions with a primary skeletal framework. Pag. 98

SAMPALMIERI G., COSENTINO D., CIPOLLARI P., SOLIGO M., LO MASTRO S. & LAURENZI M. Gamma-ray di superficie nel Miocene inferiore del Bacino Sabino: ciclicità e caratterizzazione dell’ambiente deposizionale. Pag. 99

SARTI G. & BERTONI D. Beach cusps and gravel deposits monitoring in a mixed sand and gravel beach from the Apuo- Versiliese coast (Tuscany, Italy): preliminary data. Pag. 100

SARTI G., ZANCHETTA G., CIULLI L. & CERRINA FERONI A. Facies analysis of the Late Quaternary deposits along the coast between Livorno and Piombino: paleoenvironmental and neotectonic implications. Pag. 104

SIMONE L. Carbonate Depositional Systems: new research approaches. Pag. 105

STANZIONE O., MILLI S. MOSCATELLI M. & FALCINI F. Tectonic and climate control on turbidite sedimentation: the Messinian deposits of the Laga Formation (Central Italy) . Pag. 107

TERUGGI, L.B., RINALDI, M. & COPPI, L. Revisione dell’instabilitá di sponde fluviali: applicazione al fiume Cecina . Pag. 108

TINTERRI R. Proposal for a classification scheme for combined flow sedimentary structures and the meaning of sigmoidal- and hummocky-cross stratification in facies analysis. Pag. 111

TINTERRI R. The relationship between flood hydrograph and facies sequences of delta-front sandstone lobes produced by hyperpycnal flows. Pag. 112

TROPEANO M., SABATO L., CILUMBRIELLO A. & PIERI P. Significato geodinamico dell'organizzazione stratigrafica dei depositi di chiusura del ciclo bradanico (Basilicata, Italia meridionale). Pag. 113

ZECCHIN M. Sequence-stratigraphic models in growth fault-bounded basins. Pag. 115

ZECCHIN M., BRANCOLINI G., DONDA F., RIZZETTO F. & TOSI L. High-resolution seismic stratigraphy in the Venice area. Pag. 116

ZEMBO I., BERSEZIO R. & TROMBINO L. Paleosols in a Pleistocene intermontane basin: a multidisciplinary approach to the study of the High Agri Valley (Southern Apennines, Italy). Pag. 117

Elenco dei partecipanti Pag. 118

6 Fluid flow pathway and configuration of buried structures in mud- volcanoes of the northern Apennines

ACCAINO F.1, BRATUS A.1, CONTI S.2, FONTANA D.2 & TINIVELLA U.1

1 - Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS) 2 - Dipartimento di Scienze della Terra, Università di Modena e Reggio Emilia

Mud volcanoes of Italy occur along the external compressive margin of the Apennine chain; they were described since long time by several authors. Italian mud volcanoes are usually small and unspectacular, when compared to other world examples. They rarely exhibit the periodic explosive activity, which is often related to important seismic activity. The Nirano mud volcanoes represent one of the best examples of Bulganaskshi category as reported in the Northern Apennines, even if the fluid pathways still is not well understood. In the frame of a co-operation between the Department of the Earth Science of the University of Modena and Reggio Emilia and the OGS, a geophysical investigation acquired geo-electrical profiles and a 3D seismic data in Nirano (Italy, Northern Apennine). The aim of this investigation is to determine the configuration of the buried shallow structures, and the detail of the fluid seepage until 50 m below the mud volcano surface, by using information obtained by tomographic inversion of first arrivals of 3D seismic data and models derived by 2D geoelectrical data. The seismic experiment was performed with the purpose of identifying the geometries of the shallower structure below a cluster of mud volcanoes of the area. The energy source was generated by a MiniVib with a sweep of 8 s ranging from 20 Hz to 250 Hz. The choice of the source has been made in order to reduce the environmental damages. The geophone pattern consisted of four lines spaced 12 m and crossing the greatest mud volcano; the hole of this mud volcano lies between the two central geophone lines, where no shots were performed to avoid environmental damage. Along a geophone line, the receivers with a nominal frequency of 10 Hz, were 6 m spaced with a total for the four lines. 23 shot lines, perpendicular to the geophone lines, was fired with a total of 111 shot positions. To obtain detailed information about the shallower structure under the studied mud volcano, the picking of the first arrivals of all the shots was performed. A total of more that 8000 picks was used simultaneously to perform the tomographic inversion. To avoid errors in the picking, the analysis of the apparent velocity of the pick was performed. The results obtained by tomographic approach indicate that the velocities vary from 450 m/s in shallower structures to 2000-2500 m/s at a depth of about 20-30 m. Particularly interesting is the resolution of the vertical conduit, representing the outlet leading to the surface vents of the mud-volcanoes, clearly evidenced by the low velocity anomaly. In the same area of the seismic experiment, three geo-electric lines were acquired. The acquisition was performed by using 64 electrodes spaced 3 m. Data were inverted using the commercial RES2DINV software, considering the effect of the topography. The resistivity models identify the presence of an area with high values in the south part, and probably corresponds to the south border of the mud volcano area. In the northern part, the presence of about 5 m in depth not interested by the presence of fluids is detected, while the resistivity values indicate that rising channels connected to a buried reservoir are present. In the central part of the investigated area, where the mud volcano is present, the resistivity values range from 3 to 5 Ohm·m, showing an area characterised by a high presence of fluids. In conclusion, the integrate approach of the geological study and different geophysical methods of the Nirano mud volcanoes in the external compressional front of the northern Apenninic chain furnished a detailed map of the buried structures in the first 30 - 50 m from the subsurface. This represents the first study showing the fluid flow pathway and the configuration of the volcanic subsurface structures in terrestrial mud volcanoes of the northern Apennines.

7 The Verrucano deposits of southern Tuscany (Northern Apennines, Italy): a record of the Mesozoic continental rifting

ALDINUCCI M.

Dipartimento di Scienze della Terra, Università di Siena, Via Laterina, 8 – 53100 Siena (Italy).

In the Alpine-Mediterranean region, the continental redbeds and shallow-marine siliciclastics that manifest the early depositional phases of the Late Permian-Mesozoic continental rifting are referred to as the “Verrucano Tectofacies”. Verrucano-type successions of southern Tuscany, Triassic to earliest Jurassic in age and now preserved in different tectonic units, are representative of the earliest ensialic rift-basin-fills that accumulated within the Tuscan Domain, a paleogeographic region of continental crust that subsequent to the opening of the Piedmont−Ligurian Ocean formed part of the Adria passive- margin. The Verrucano deposits of southern Tuscany belong both to the low-grade metamorphic Verrucano Group (Monticiano-Roccastrada Unit, mainly exposed along the Monticiano-Roccastrada Ridge) and to the non-metamorphic Pseudoverrucano Fm (Pseudoverrucano Unit, exposed in small outcrops along the coastal range of western Maremma). They rest unconformably on Late Palaeozoic-?Early Triassic successions, with the exception of the Pseudoverrucano successions, whose original substratum is nowhere exposed. Viewed overall, the Verrucano-type successions of southern Tuscany appear to manifest five episodes or pulses of the Mesozoic continental rifting. With the exception of the first episode that developed entirely within a terrestrial setting without marine incursion, each one is represented by basal Verrucano-type continental siliciclastics that grade up to compositionally-mixed marine deposits. These resulted from four diachronous, post-Middle Triassic marine-transgressions. The suite of tectonic pulses recorded by the Verrucano-type deposits produced the progressive westward widening (backstepping) of the Tuscan Domain. Older rift-basins underwent an overall subsidence regime which was primarily a consequence of the thinned continental-crust that had been produced during earlier episodes of extension. Nevertheless, each tectonic pulse rejuvenated older rift-basins and/or formed new-rift-basins within an enlarged region undergoing crustal extension. In this context it is noteworthy that exposures of much younger (i.e., Middle Jurassic) Verrucano-type siliciclastics are preserved on the eastern coast of Sardinia (e.g., the Bathonian−Bajocian Genna Sellole Fm at the base of the carbonate “Tacchi” succession). The Middle Jurassic opening of the Piedmont−Ligurian Ocean ultimately separated the Verrucano deposits of east Sardinia from those presently preserved in the Northern Apennines.

8 Messinian events in Tuscany : insights from selected sections

ALDINUCCI M.1, BERTINI A.2, DA PRATO S.3, DONIA F.1, FORESI L. M.1, MAZZEI R.1, RIFORGIATO F.1, SANDRELLI F.1, SALVATORINI G.1 & ZANCHETTA G.3

1 - Dipartimento di Scienze della Terra, Università di Siena, Via Laterina 8, 53100 Siena, Italy, 2 - Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira 4, 50121 Firenze, Italy; 3 - Dipartimento di Scienze della Terra, Università di Pisa, Via S.Maria 53, 56126 Pisa, Italy

In the Tuscan basins, as well as in other Mediterranean areas, Messinian deposits record dramatic changes in palaeogeography, palaeobiogeography and sedimentation, resulting from the complex interplay between regional and global factors. In order to define a high-resolution stratigraphic framework and recognize the effects of milankovich periodicity in sedimentation patterns, four selected stratigraphic sections were studied using a multidisciplinary approach, consisting of sedimentological, chemical, geophysical, palaeomagnetic and micropalaeontological analyses. The investigated sections are representative of the: i) pre-evaporitic phase (Gello section, Volterra Basin); ii) evaporitic phase (Faltona section p.p. and Migliarino section, located in the Volterra and Fine basins, respectively); and iii) post-evaporitic phase (Faltona section p.p. and Cava Serredi section p.p., latter located in the Fine Basin). Moreover, the Cava Serredi section encompasses also the Miocene/Pliocene boundary. A number of conclusions arise from this research: 1) In Tuscany, the onset of evaporitic deposition related to the Messinian Salinity Crisis is isochronous with the same event manifested by Mediterranean type-successions; 2) the pelite-gypsum couples (at least 11) exposed in the Migliarino section are thought to reflect an astronomical (precessional) periodicity; 3) a regional unconformity separates the evaporitic deposits below, from the overlying post-evaporitic successions; 4) lacustrine sedimentation of the post-evaporitic phase was characterized by microfauna of the Parathetyan realm; 5) Cyclical patterns of sedimentation, possibly related to a Milankovic cyclicity, have been recognised in the post- evaporitic deposits; 6) evidence of volcanic activity is present in the evaporitic and post- evaporitic successions; 7) the marine transgression marking the end of the post-evaporitic lacustrine sedimentation occurred at the Miocene/Pliocene boundary.

9 Evoluzione composizionale delle sabbie del fiume Po negli ultimi 30 ka: idagini preliminari sul paleoalveo di Bondeno (FE)

ALDROVANDI E. & LUGLI S.

Dipartimento di Scienze Della Terra – Università degli Studi di Modena e Reggio Emilia, Modena

Le ultime variazioni climatiche legate ai cicli glaciali-interglaciali e la presenza di una struttura tettonica quale la Dorsale Ferrarese, hanno particolarmente influenzato l’evoluzione idrografica e morfologica della porzione orientale del territorio padano. La recente fase di peggioramento climatico individuata a partire dal IX ed il IV secolo a.C. può essere considerata una causa del sovralluvionamento dei vari rami del fiume Po e delle sue relative numerose esondazioni. In particolare la “rotta di Sermide” fece abbandonare al ramo settentrionale del Po di Adria il suo corso e ne causò la confluenza nel ramo più meridionale del Po di Spina generando la struttura meandriforme del Poazzo nei pressi di Bondeno di Ferrara. Tra il IV-V secolo a.C. e l’età romana il corso del fiume si stabilizzò rettificando in parte il suo percorso attraverso salti di meandro; a questa fase può essere attribuito l’abbandono del tratto del Poazzo nei pressi di Bondeno. Il presente lavoro si prefigge lo scopo di illustrare le variazioni composizionali delle sabbie del fiume Po a partire dal tardo Pleistocene attraverso l’analisi di un sondaggio di quaranta metri a carotaggio continuo ubicato in località Ca’ Zarda di Bondeno (FE). Sui corpi sabbiosi individuati sono state condotte analisi granulometriche; la frazione sabbiosa compresa tra 0,500 e 0,250 mm, mediamente la più abbondante, è stata inglobata con resina epossidica per ricavare sezioni sottili per l’osservazione al microscopio ottico in luce trasmessa. Le sezioni sono state trattate per la colorazione selettiva dei carbonati e su di esse è stata effettuata l’analisi modale attraverso conteggio al tavolino integratore utilizzando il metodo Gazzi-Dickinson-Zuffa (Gazzi, 1966; Dickinson, 1970; Zuffa, 1985). L’analisi modale delle sabbie attuali dal fiume Po indica una composizione media di Qtot 80%, Feld 7% e Carbtot 4%. Le sabbie prelevate dal sondaggio di Ca’ Zarda mostrano sostanziali variazioni del tenore di carbonati in base alla profondità, oscillando tra un minimo di 3.7% ed un massimo di 33.3%. Nello specifico è possibile individuare un primo gruppo, fino alla profondità di –9,7 m, che presenta valori di Carbtot compresi tra 7.3% e 16.1%, un secondo gruppo, fino a –22,4 m, dove si registra un picco che raggiunge il 33.3% a –16,5 m dal piano campagna, ed infine un terzo, tra –22,5 e –40,0 m, con valori compresi tra 3.7% e 13.9%. Il quarzo totale presenta una variazione speculare rispetto a quella dei carbonati: i valori infatti oscillano tra un minimo di 52.7%, individuato alla profondità di –16,5 m corrispondente al massimo tenore di carbonati, ed un massimo di 84.3%. Il contenuto in feldspati non mostra variazioni rilevanti, attestandosi su valori variabili dal 3.9% al 16.0%. Le sabbie campionate in corrispondenza del picco minimo di quarzo e di quello massimo dei carbonati (–16,5 m), si collocano tra due datazioni al radiocarbonio, in un intervallo temporale compreso tra 3.000 e 30.000 anni B.P., (corrispondente alle profondità rispettivamente di -13,60 e -29,60 m). La forte variazione composizionale riscontrata comprende quindi l’ultima culminazione glaciale. I dati petrografici ottenuti, indicano un forte controllo climatico sui sedimenti sabbiosi deposti dal fiume Po negli ultimi 30.000 anni.

References

Dickinson, W.R., 1970, Interpreting detrital modes of graywacke and arkose: Journal of Sedimentary Petrology, v. 40, p. 695-707. Gazzi, P., 1966, Le arenarie del flysh sopracretaceo dell’Appennino modenese; correlazioni con il Flysh di Monghidoro: Acta Mineralogico-Petrographica, v. 12, p. 69-97. Zuffa, G.G., 1985, Optical analyses of arenites: influence of methodology on compositional results: G.G. Zuffa, Editors, Provenance of Arenites, Nato ASI series, D. Reidl Publishing Company, v. 148, p. 165-189.

10 Modern sands composition, sediment budget and erosion rates of the Nile basin

ALI ABDEL MEGID A.

Dipartimento di Scienze Geologiche e Geotecnologie, Università degli Studi di Milano - Bicocca, 20126 Milano (Italy), [email protected]

The aim of this work is to define sediment provenance and solid discharge of the Nile River as well as the erosion rate to give a tool to delineate water and land use. The Nile River has a basin of about three millions of square kilometres, ten percent of Africa, and its two principal branches of the Nile, the White Nile and the Blue Nile-Atbara, correspond to completely different hydrographical, climatic, topographic and tectonic regimes. The areas, which contribute significantly to the total water discharge of the Nile River, are relatively small and isolated, the East African lake region and the Ethiopian highlands, in comparison to whole basin in large extent occupied by the Eastern Saharan region. The compositional analyses is supported by a new and full-scale method of sampling modern sands, based on bed (longitudinal and point bars) and suspended (levee sediments) materials corresponding to the two principal transport modes, characterised by different sediments provenances. Nile sediments analyses, determinate for the first time by bulk petrography and subsequently associated with heavy minerals analyses, gives a quantitatively value of their cratonic (quartz dominated), mainly White Nile with minor supply from Saharan wadis and eolian dunes in Nubia and Egypt, and rift-derived components (plagioclase and augite dominated), essentially Blue Nile and Atbara, with minor supply from the Red Sea shoulders in Eritrea, Sudan and Egypt. Since the sixties, after the building of the Aswan High Dam in upper Egypt, the Roseires Dam on the Blue Nile and Khashm el Girba on the Atbara River, the sediment load of the Nile River has been reduced to almost zero, causing the destruction phase of the delta. Because of lack in direct measurements of sediment transport rate in the field, the sediment yield has to be recalculated from the amount of sediments deposited in natural sink and reservoirs occurring along the Nile system. The amount of sediment progressively stored within reservoirs in the last forty years, though the information is often heterogeneous and incomplete, provides a useful base to asses the Nile sediment load with greater accuracy than in the past, displaying a sediment transport rate from twice to five times over the load generally reported in literature and looked on dams constructions. Linking the petrographic and mineralogical data to the volumes of sediment transported by the rivers allows estimating the relative contributions from various detrital sources and sediment yield with an accuracy ever reached until now: the Blue Nile and the Atbara, giving the seventy percentage of annual Nile discharge, contributes is more than ninety-five percent of the Nile sediment load showing a focused erosion of the Ethiopian highlands.

Cyclic stratigraphic patterns from middle-late Quaternary deposits of northern Italy

AMOROSI A.

Dipartimento di Scienze della Terra e Geologico-Ambientali, Università di Bologna, Via Zamboni 67, 40127, Bologna

Detailed sedimentological and stratigraphic analysis of Middle-Late Quaternary fluvial to shallow-marine successions from hundreds of continuous cores, up to 200 m long, in Northern Italy reveals distinctive cyclic changes in lithofacies and channel stacking patterns, falling in the Milankovitch band. Transgressive surfaces represent the most readily identifiable features from core data. These surfaces constitute basinwide stratigraphic markers that show greater extent and correlation potential than sequence boundaries or maximum flooding surfaces. Accurate characterization of this prominent cyclicity can help significantly in developing conceptual models that can be used to portray the geometry, boundary characteristics and heterogeneity of aquifers and aquifer systems in a regional context. From the onset of the first major Pleistocene glaciation in the Alps, in the early late Pleistocene (Marine Isotope Stage 22 at 0.87 Ma - Muttoni et al., 2003), a distinctive cyclic organization of facies has been shown to characterize sedimentation in Emilia-Romagna (Regione Emilia-Romagna & ENI-AGIP, 1998), Lombardy (Regione Lombardia & ENI Divisione AGIP, 2002) and the subsurface of Venice (Massari et al., 2004). Stacked transgressive-regressive sequences (T-R sequences of Embry, 1993; 1995), referred to as “synthems” in the Geological Map of Italy to scale 1:50,000, can be generally correlated on a basin scale, and form the basic motif of middle-late Quaternary alluvial and coastal deposits of the Po Plain (Amorosi et al., 1999b, 2004; Amorosi & Colalongo, 2005) and the Arno coastal plain (Aguzzi et al., in press). In terms of sequence stratigraphy, these T-R sequences, which are 50-100 m thick and span intervals of time of about 100 ka, correspond to fourth-order cycles. Beneath the present north Adriatic and Tyrrhenian deltas and coastal plains, the lower parts of T-R sequences form thin transgressive systems tracts (TST), showing coastal-plain aggradation and rapid shoreline transgression (retrograding barrier-lagoon-estuary systems). Transgressive deposits are overlain by thicker shallowing-upward successions, interpreted to reflect delta and strandplain progradation (highstand systems tracts or HST). In highly subsiding areas, such as the Po Basin, subsequent long phases of sea-level fall are recorded by exceptionally thick (up to 60 m) successions of interbedded alluvial and coastal- plain deposits (falling-stage - FST - and lowstand - LST - systems tracts). After the early work by Bellotti et al. (1994; 1995) and Milli (1997) from the Tevere coastal plain, the first detailed facies documentation of a Late Quaternary incised-valley fill sequence in northern Italy has been recently shown from the subsurface of the Arno River (Aguzzi et al., in press). At this location, the Holocene succession is 51 m thick and includes, above a tidal ravinement surface, early transgressive estuarine deposits, about 20 m thick. These are overlain, through a wave ravinement surface, by a thin succession of late transgressive barrier-beach and inner-shelf deposits. Above the maximum flooding surface, highstand deposits are represented by a shallowing-upward succession of prodelta to delta- front sediments. The incised valley fill correlates laterally with an interfluve sequence boundary, overlain by just 17 m of Holocene sediments. At landward locations, within non-marine strata, the bounding surfaces of middle-late Quaternary T-R sequences are marked by abrupt facies changes from amalgamated fluvial- channel gravel and sand, formed mostly at lowstand conditions, to mud-dominated floodplain deposits, with isolated channel bodies and organic horizons (transgressive alluvial deposits or TST). This interval grades upward into thick alluvial plain deposits, showing increased channel clustering and sheet-like geometries (regressive alluvial deposits, including HST, FST, and LST). The sharp lower boundaries of T-R sequences identified within the alluvial

12 sections can be traced physically into the transgressive surfaces recognized at distal locations, allowing the establishment of the physical linkage between alluvial and marine deposits (Amorosi & Colalongo, 2005). This has important implications in terms of reservoir correlation. The cyclic pattern of facies described from the coastal and alluvial depositional systems is also identifiable close to the basin margin (e.g., Apennines foothills). In this area, a hierarchy of fluvial terrace sequences can be identified by successively thinner groupings of genetically-related fluvial terraces (Amorosi et al., 1996). Well-preserved fluvial terraces, developed mostly during interglacial periods, are clearly visible following a geomorphic approach in the valley landscape. These are split by steep escarpments formed during glacial times. Individual slopes are several tens of metres high, display very poor terrace preservation, and include outcrops of much older bedrock units. The repetitive alternation of coastal and alluvial deposits is paralleled by a distinctive pollen signature. Particularly, stratigraphic correlation with the marine oxygen-isotope record on the basis of pollen data, documents strict relationships between T-R sequences and interglacial/glacial cycles, showing that transgressive surfaces correlate invariably with the onset of forested conditions during interglacials, whereas return to alluvial sedimentation correlates with abrupt change to open vegetation conditions during glacials (Amorosi et al., 2004; Amorosi & Colalongo, 2005). Facies architecture within fourth-order T-R sequences has been described at length from latest Quaternary deposits (30 ka BP, from the Last Glacial Maximum to the Present) of the Po coastal plain (Rizzini, 1974; Bondesan et al., 1995; Amorosi et al., 1999a, 2003, 2005; Stefani & Vincenzi, 2005), the Venice lagoon (Mozzi et al., 2003), the Arno coastal plain (Aguzzi et al., 2005; in press), and the Ombrone river (Carboni et al. 2002; Bellotti et al., 2004; Biserni et al., 2004). A worldwide comparison of late Quaternary Po and Tevere subsurface stratigraphy with coeval deltaic succession has been shown by Amorosi & Milli (2001). Eustacy appears to be the major controlling factor of the retrogradational stacking pattern of parasequences within the TST. By contrast, a complex interplay of eustacy, sediment supply and subsidence, with an increasing influence of autocyclic mechanisms, such as channel avulsion and delta lobe abandonment, controlled facies architecture within the HST. The maximum flooding surface can not be assumed to be synchronous, its timing being strongly dependent upon local variations in sediment influx and subsidence. Very high-resolution stratigraphic studies of the Holocene succession have recently enabled the distinction, within TST and HST, of a series of small-scale, high-frequency cycles, about 3-5 m thick and spanning intervals of time of about 1,000 years (Amorosi & Milli, 2001; Amorosi et al., 2005). Interpretation of these cycles, which are invariably bounded by sharp flooding surfaces and generally show internal shallowing-upward trends (parasequences), indicates that relative sea-level change during the Holocene was episodic and punctuated by rapid phases of sea-level rise, followed by periods of stillstand (or decreasing sea-level rise). Parasequence boundaries record landward shifts in facies tracts that can be recognized with confidence only in shoreline and coastal plain successions. From seaward to landward locations, they document beach-barrier migration, bay-head delta abandonment and increasing accommodation in the coastal plain. The ensuing phases of sea-level stillstands, resulting in the progressive filling of the newly formed accommodation space, are characterized by beach progradation, extensive mud deposition in behind-barrier lagoonal (estuarine) and marsh deposits, and aggradation in bay-head delta systems at the head of estuaries. The impact of climatic changes on coastal systems in the near future must be judged in the perspective of predicting the possible scenarios of environmental changes under rising sea-level conditions. Studies about eustacy and coastal morphology provide evidence for the possible flooding of wide portions of the Italian coasts in the next decades. Detecting the sedimentary response of coastal systems to high-frequency climatic and eustatic variations, thus, is of vital importance for planning protection and management of these highly populated areas. In this respect, the study of past sea-level changes and, specifically, the

13 reconstruction of the palaeogeographic evolution of coastal systems during the Holocene can represent a powerful tool to predict how these coastal environments might alter in the future.

References

AGUZZI M., AMOROSI A. & SARTI G., 2005. Stratigraphic architecture of Late Quaternary deposits in the lower Arno Plain (Tuscany, Italy). Geologica Romana, 38, 1-10. AGUZZI M., AMOROSI A., COLALONGO M.L., RICCI LUCCHI M., ROSSI V., SARTI G. & VAIANI S.C. (in press) - Late Quaternary climatic evolution of the Arno coastal plain (Western Tuscany, Italy) from subsurface data. Sedimentary Geology. AMOROSI A., FARINA M., SEVERI P., PRETI D., CAPORALE L. & DI DIO G (1996) - Genetically related alluvial deposits across active fault zones: an example of alluvial fan-terrace correlation from the upper Quaternary of the southern Po Basin, Italy. Sedimentary Geology, 102, 275-295. AMOROSI A. & MILLI S. (2001) - Late Quaternary depositional architecture of Po and Tevere river deltas (Italy) and worldwide comparison with coeval deltaic successions. Sedimentary Geology, 144, 357-375. AMOROSI A. & COLALONGO M.L (2005) - The linkage between alluvial and coeval nearshore marine successions: evidence from the Late Quaternary record of the Po River Plain, Italy. In: Blum M.D., Marriott S.B. & Leclair S.F. Eds., Fluvial Sedimentology VII. Spec. Publs int. Ass. Sediment. 35, 257-275. AMOROSI, A., COLALONGO, M.L., PASINI, G. & PRETI, D. (1999A) - Sedimentary response to Late Quaternary sea-level changes in the Romagna coastal plain (northern Italy). Sedimentology, 46, 99-121. AMOROSI A., COLALONGO M.L., FUSCO F., PASINI G. & FIORINI F. (1999b) - Glacio-eustatic control of continental-shallow marine cyclicity from Late Quaternary deposits of the south-eastern Po Plain (Northern Italy). Quaternary Research, 52, 1-13. AMOROSI A., CENTINEO M.C., COLALONGO M.L., PASINI G., SARTI G. & VAIANI S.C. (2003) - Facies architecture and latest Pleistocene-Holocene depositional history of the Po Delta (Comacchio area), Italy. Journal of Geology, 111, 39-56. AMOROSI A., COLALONGO M.L., FIORINI F., FUSCO F., PASINI G., VAIANI S.C. & SARTI G. (2004) - Palaeogeographic and palaeoclimatic evolution of the Po Plain from 150-ky core records. Global and Planetary Change, 40, 55-78. AMOROSI A., CENTINEO M.C., COLALONGO M.L. & FIORINI F. (2005) - Millennial-scale depositional cycles from the Holocene of the Po Plain, Italy. Marine Geology, 222-223, 7-18. BELLOTTI P., CHIOCCI F.L., MILLI S., TORTORA P. & VALERI P. (1994) - Sequence stratigraphy and depositional setting of the Tiber delta: integration of high-resolution seismics, well logs, and archeological data. Journal of Sedimentary Research, B64, 416-432. BELLOTTI P., MILLI S., TORTORA P., VALERI P. (1995) - Physical stratigraphy and sedimentology of the Late Pleistocene-Holocene Tiber Delta depositional sequence. Sedimentology, 42, 617-634. BELLOTTI P., CAPUTO C., DAVOLI L., EVANGELISTA S., GARZANTI E., PUGLIESE F. & VALERI P. (2004) - Morpho-sedimentary characteristics and Holocene evolution of the emergent part of the Ombrone River delta (southern Tuscany). Geomorphology, 61, 71-90. BISERNI G., BERENDSEN H.J.A. & SANDRELLI F. (2004) - Shape Reconstruction of the Pleistocene/Holocene unconformity in the Grosseto Plain (Tuscany, Italy). Il Quaternario, 17, 443-451. BONDESAN M., FAVERO V. & VIÑALS M.J. (1995) - New evidence on the evolution of the Po-delta coastal plain during the Holocene. Quateranry International, 29/30, 105-110. CARBONI M. G., BERGAMIN L., DI BELLA L., IAMUNDO F. & PUGLIESE N. (2002) - Late Quaternary sea-level changes along the Tyrrhenian Sea. Paleoecological evidences from foraminiferal and ostracod assemblages. Geobios, 35, 40-50. EMBRY, A.F. (1993) - Transgressive-regressive (T-R) sequence analysis of the Jurassic succession of the Sverdrup Basin, Canadian Arctic Archipelago. Can. J. Earth. Sci., 30, 301-320. EMBRY, A.F. (1995) - Sequence boundaries and sequence hierarchies: problems and proposals. In: Steel R.J., Felt V.L., Johannessen E.P. & Mathieu C. Eds., Sequence Stratigraphy on the Northwest European Margin Spec. Publ. Norwegian Petrol. Soc., 5, 1-11. MUTTONI G., CARCANO C., GARZANTI E., GHIELMI M., PICCIN A., PINI R., ROGLEDI S. & SCIUNNACH D. (2003) - Onset of major Pleistocene glaciations in the Alps. Geology, 31, 989-992. MASSARI F., RIO D., SERANDREI BARBERO R., ASIOLI A., CAPRARO L., FORNACIARI E. & VERGERIO P. (2004) - The environment of Venice area in the past two million years. Palaeogeography, Palaeoclimatology, Palaeoecology, 202, 273-308.

14 MILLI S. (1997) - Depositional setting and high-frequency sequence stratigraphy of the Middle-Upper Pleistocene to Holocene deposits of the Roman Basin. Geologica Romana, 33, 99-136. MOZZI P., BINI C., ZILOCCHI L., BECATTINI R. & MARIOTTI LIPPI M. (2003) - Stratigraphy, palaeopedology and palinology of Late Pleistocene and Holocene deposits in the landward sector of the Lagoon of Venice (Italy), in relation to the “caranto” level. Il Quaternario, 16, 193-210. REGIONE EMILIA-ROMAGNA & ENI-AGIP (1998) - Riserve idriche sotterranee della Regione Emilia- Romagna. A cura di G. Di Dio. S.EL.CA., Firenze, 120 pp. REGIONE LOMBARDIA & ENI DIVISIONE AGIP (2002) - Geologia degli acquiferi Padani della Regione Lombardia. A cura di C. Carcano e A. Piccin. S.EL.CA., Firenze, 130 PP. RIZZINI A. (1974) - Holocene sedimentary cycle and heavy mineral distribution, Romagna-Marche coastal plain, Italy. Sedimentary Geology, 11, 17-37. STEFANI M. & VINCENZI S. (2005) - The interplay of eustasy, climate and human activity in the late Quaternary depositional evolution and sedimentary architecture of the Po Delta system. Marine Geology, 222-223, 19-48.

15 Stratigraphy and tectonics of the Pisa-Viareggio basin: hints on the evolution of the Neogene basins of Tuscany

ARGNANI A.1 & ROGLEDI S.2

1 - Geologia Marina, ISMAR-CNR, Bologna 2 - ENI S.p.A., Exploration & Production Division, S. Donato Milanese, Milano

Several small sedimentary basins characterize the internal portion of the Northern Apennines. These inter-montane basins trend almost parallel to the Apennine range and are filled by Neogene sediments with thickness ranging between few 100’s m to few kms. Sediments belonging to these inter-montane basins crop out extensively in western Tuscany and often appear heavily deformed. Partly because of the intense deformation the early tectonic history of these basins is difficult to constrain; in fact, although classically interpreted as extensional basins, some recent papers call for an initial thrust-related origin, only later overprinted by extension. The debate about the origin of the Neogene basins of Tuscany has been going on for more than ten years, and in spite of recent field works the ambiguity remains still unresolved. This contribution aims at presenting the case of an internal basin, the Pisa-Viareggio basin, which is the northernmost one among the large inter-montane basins of Tuscany and which straddles the coastline, being partly buried underneath the alluvial sediments of the Pisa plain and partly extending offshore. This basin can be investigated only through subsurface data, and the current study is based on the interpretation of a grid of industrial seismic profiles covering the Pisa plain and tied to the stratigraphy obtained from exploration wells. In addition, the geology of nearby outcrops has been used to enlarge the regional scale picture. An extensional origin can be clearly proven for the Pisa-Viareggio basin, as seismic profiles show a west-dipping listric extensional fault that bounds the basin to the east. The basin is filled with up to 3 seconds of upper Messinian to Quaternary sediments, and extension mostly occurred during late Messinian-early Pliocene, although continuing with reduced intensity till the Quaternary. In spite of the extensional origin, the southern part of this basin shows indications of superimposed contractional deformation, possibly in the form of tectonic inversion, that progressively increases to the south, where the basin appears completely overturned and eroded in the Livorno Mountains. The basin-boundary fault trends roughly NNW-SSE and is buried in the Quaternary sediments of the Pisa plain, but it turns rather abruptly to N-S and NNE-SSW in the south, near Livorno. Inspection of the regional geological maps suggests that the fault plane may be possibly uplifted and exposed in the Livorno Mountains, located just west of Livorno. The timing of the contractional deformation that affected the southern part of the Pisa-Viareggio basin can be roughly constrained within the Pleistocene. We speculate on the possible causes of the intense deformation that affected the sourthern part of the Pisa-Viareggio basin and attempt to show that the tectonic history of this basin can possibly help understanding the evolution of the other Neogene basins, located further to the south, which suffered more widespread deformation and uplift.

16 Seep-carbonates in intrabasinal highs of the inner foredeep: new insights from the middle Miocene Salsomaggiore Ridge (Northern Apennines, Italy)

ARTONI A.1 & CONTI S.2

1 - Dipartimento di Scienze della Terra, Università degli Studi di Parma, Parco Area delle Scienze 157/A, 43100 Parma Italia. 2 - Dipartimento di Scienze della Terra, Università degli Studi di Modena e Reggio Emilia, Largo S. Eufemia 19, 41100 Modena Itali, [email protected].

Introduction

Fluid seeps and dewatering of sediments are fundamental processes along the world’s continental margins. Seep-carbonates, recognized worldwide from Devonian to Pleistocene, associated with mud diapirism, sediment instability and specialized seep ecosystem are important indicators of seafloor fluid expulsion often related to gas-hydrates dissociation. In convergent margins and accretionary wedges fluids expulsion is very efficient because of the considerable reduction in pore space of sedimentary sequences due to tectonic compression. In the Northern Apennines orogenic wedge, seep-carbonates occur in different settings of the middle-late Miocene foreland basin system and they are generally found in pelitic successions. Instead, in the Salsomaggiore area (Northwestern Apennines) seep-carbonates outcrop at the top of Serravallian foredeep deposits and they cement and/or encrust coarse-grained sandstones and conglomerates, a case that rarely occurs. This site provides a unique opportunity for analyzing depositional characters, three-dimensional distribution and evolution of the seepage system at the leading edge of an orogenic wedge. Fluid expulsions, strictly related to variable intensities in tectonic stresses, generate seepage-carbonates facies and sediment instabilities depending on the position of the feeding fluid pathways within the Salsomaggiore Ridge, a middle-late Miocene intra-basinal high. These newly described seep-carbonates precise better the Miocene tectono- stratigraphic evolution of the Salsomaggiore area, a key area to unravel the history of Northern Apennine orogenic wedge, and they present an evolution from slow to fast seepage; the latter in connection with a major tectonic pulse. Then, the studied seep- carbonates are also climatically-controlled as they develop during late Serravallian global high-frequencies climatic changes, Miller events. Therefore, the detailed analysis of seep- carbonates assumes a fundamental role in order to understand the feed-back between tectonic and climatic processes in orogenic wedges, which often preserve these types of seep-related deposits.

The evolution of the Salsomaggiore Ridge

The middle-late Miocene evolution of the Salsomaggiore Structure has been always debated because part of the sedimentary record is lacking. In fact, the Serravallian conglomerates and hemipelagic marls, enclosing seep-carbonates at the top, are the youngest stratigraphic deposits on top of the Salsomaggiore Ridge (Piola, 2003; Zanzucchi, 2000). The sedimentation starts again only during Messinian with a huge chaotic Unit (Intra- Messinian Chaotic Unit of Artoni et al., 2004) (Figs 1 and 3). During the missing geological record, between the end of the Serravallian and the beginning of the Messinian, the emplacement of the Ligurian tectonic Unit takes places. The study of the seep-carbonates made it possible to better precise the onset of the Ligurian thrust over the Salsomaggiore structure during the middle-late Miocene. The concentration of seep-carbonates and fluid expulsion processes at the top of the Serravallian testify an intense tectonic phase related to the Ligurian advancement and thrust activation propagation in deeper structural level. In middle Miocene, the leading edge of the Apennine orogenic wedge reached the Salsomaggiore area; Langhian hemipelagic marls were uplifted and Serravallian mixed turbidites were lapping onto the incipient Salsomaggiore Ridge (Fig. 1a). Tectonic uplift and

17 fold amplification should be mild during Serravallian; only a submarine slide, with intraformational sediments, glided on the northern limb of Salsomaggiore Ridge. Nonetheless, the relief was enough pronounced to decelerate and deposit the deltaic-related turbidites lapping against the southern flank where fast laden off of hyperconcentrated flows favoured localized seepage events of slow seepage phase (Figs 1a, b; Photos 1, 2). The seep-carbonates deposition started encrusting and cementing the deltaic-related turbiditic lobes, on the southern Ridge flank, and the slided masses, on the northern Ridge flank (Fig. 1b). Carbonate deposition firstly begins on the more external flank, with abundant and extensive micritic fossiliferous facies related to a prevalent moderate to slow seeping regime. Instead, on the southern flank, seep events began slightly later; they never reached large dimensions and they occasionally encrust coarse-grained turbiditic deposits which, continuing to be deposited, intermixed with slow seepage and fossiliferous carbonates (Photos 1, 2) and triggered fast fluids escapes. The fluid vents had spot distribution because they were driven by locations of more intensely fractured rocks at the thrust’s tip, on the northern flank, and by erosive depositional processes in the southern confined basin (Figs 1a, b). The coarse-grained siliciclastic input stopped during the deposition of late Serravallian hemipelagic/prodeltaic marls which probably represent mud drape deposition over the turbitite-filled southern flank and are laterally associated to carbonate mounds and patches of typical benthonic fauna (Fig. 1c; Photos 3, 4). Sediment starvation characterises the late Serravallian scenario and similar seep-carbonate deposits were active on both flanks of the Salsomaggiore Ridge, indicating a more prolonged slow seepage alternate to episodes of intense fluid emission and brecciation (Fig. 1c). The crest and the northern flank of the Salsomaggiore Ridge were sediments under-supplied and diffuse, slow-seepage was forming large carbonate mounds (Fig. 1c). At the end of the Serravallian, the northern and southern Ridge flanks are no more differentiated; a conglomeratic chaotic unit occurs on both flanks (Fig. 1d). It is characterised by local-, near-sourced and angular clasts; it erodes and remoulds the hemipelagic marls and the unlithified carbonates which are entrained in the debris; then, it contains a greater amount of Apennine-derived clasts (Photos 5, 6). Because of its depositional characters, this uppermost and extensive chaotic unit should have travelled a short distance and it is interpreted to express a major destabilization events of the seeping apparatus which undergone a fast seepage phase (Fig. 1d). This destabilization event, attributed to late Serravallian or early Tortonian, is considered to be triggered by tectonic stresses affecting, simultaneously, the Salsomaggiore Ridge, by thrust’s tip propagation, and the advancing allochthonous Ligurian units, which were approaching closer to the Ridge (Fig. 1d). At the same time, also high-frequency climatic changes could have favoured gas-hydrates destabilization. The same explosive or a later slow seeping event cemented this uppermost chaotic unit. Therefore, in the Salsomaggiore Ridge, seepage processes continued after late Serravallian but they were not anymore able to deposit the characteristic “Lucina limestones”. The plumbing system was completely rearranged by the emplacement of the Ligurian allochthonous units on top of Salsomaggiore Ridge crest (Fig. 1e). At this time, probably early Tortonian, the fluids likely started to be expelled at the submarine Cortemaggiore front which, now completely buried under the Po Plain, is the Tortonian-early Messinian leading edge of the Apenninic orogenic wedge (Rizzini et al., 2004; Artoni et al., 2004). Afterward, the Salsomaggiore Ridge becomes a thrust-anticline inside the Apenninic orogenic wedge and erosion made the seep carbonates to be exumed. The evolution depicted for the Salsomaggiore Ridge and Serravallian seep-carbonates does not differ from ancient thrust fronts affecting the foredeep deposits of Apennines, where “Lucina limestones” deposits outcrop (Conti and Fontana, 1998). Seep-related fauna and carbonates occur associated to foredeep units accreted to the orogenic wedge. During the middle Miocene, the formation of intrabasinal highs at the toe of the deformation front was a common feature of the Northern Apennine accretionary wedge (Conti and Fontana 2002; Conti et al., 2004).

Ridges and breached anticlines serve to trap fluids and gases through the sediment column and provide local extensional environments at their crests for fluid expulsion and deposition of authigenic carbonates inside turbiditic deposits with extremely heterogeneous porosity. The parallelism between the Apennine structural trends and the attitudes of intrabasinal highs enclosing seep-carbonates suggests a close relationship between tectonics and these particular deposits. Therefore, authigenic carbonates seem to be

19 indicators of the advancing deformational front of the chain, thus heralding the main Apennine tectonic phases (Conti and Fontana, 2002). These intrabasinal highs also play a complex role in conditioning the sedimentary infillings of the inner portion of the foredeep, and act as obstacles to extra-formational sediments deriving from the inner deformation fronts. This fact is proved by the abundance of extra-formational conglomerates cemented or encrusted by seep-carbonates on the southern flank of the Salsomaggiore Ridge: this flank is the nearest to the deformational front of Ligurian allochthounous units of the Northern Apennine chain. Increased tectonic stresses, i.e. paroxysmal tectonic pulses, and/or high-frequencies climatic changes, inducing changes in sea-level and water temperature, destabilize the seeping system which are prone to fast seepage (venting) and formation of chaotic deposits (Fig. 1d). Immediately after, the emplacement of the Ligurian nappe takes place and cap the pelitic deposition marking the end of seeping events; while, synchronously, a new and external foredeep was forming. In the Northern Apennines, seep-carbonates are important tracers for tectono- sedimentary evolution of the leading edge of the orogenic wedge; they mark the major tectonic and climatic phases shaping the orogen. Therefore, detailed studies on ancient seep-carbonates will contribute to unravel the complex feed-back between tectonic and climatic processes recorded in sedimentary successions of other convergent margins around the world.

References

Artoni, A., Papani, G., Rizzini, F., Calderoni, M., Bernini, M., Argnani, A., Roveri, M., Rossi, M., Rogledi, S. and Gennari, R., 2004. The Salsomaggiore structure (Northwestern Apennine foothills, Italy): a Messinian mountain front shaped by mass-wasting products. GeoActa, 3, 107-128. Conti, S. and Fontana, D., 1998. Recognition of primary and secondary Miocene lucinid deposits in the Apennine chain. Mem. Sci. Geol., 50, 131-150. Conti, S. and Fontana, D., 2002b. Sediment instability related to fluid venting in Miocene authigenic carbonate deposits of the northern Apennines (Italy). Int. J. Earth Sci., 91, 1030-1040. Conti, S., Fontana, D., Gubertini, A., Sighinolfi, G., Tateo, F., Fioroni, C. and Fregni, P., 2004. A multidisciplinary study of Middle Miocene seep-carbonates from the northern Apennine foredeep (Italy). Sed. Geol., 169, 1-19. Piola, G., 2003. Problemi geologico-stratigrafici collegati al tetto della struttura di Salsomaggiore Terme (PR). Unpublished Laurea Thesis, Università degli Studi di Parma, Parma, 123 pp. Rizzini, F., Argnani, A., Artoni, A., Manzi, V., Roveri, M., Rossi, M., Rogledi, S., Papani, G., Ricci Lucchi, F., Pini, G.A., Panini, F. and Bassetti, M.A., 2004. The Northern Apennines messinian deposits: paleogeography and tectono-stratigraphic implications. In: Milli, S. (Ed.), GESOSED 2004 - La geologia del sedimentario nella ricerca di base e nelle sue applicazioni, Roma, Italia, Atti, pp. 106-107. Zanzucchi, G., (ed), 2000. Note illustrative della Carta Geologica d'Italia 1:50.000, F. 198 Bardi. Carta Geologica d'Italia alla scala 1:50.000, Roma, 75 pp.

20 Quaternary evolution of the terraced fluvial succession of the Bormida River (Tertiary Piedmont Basin, North-Western Italy)

BELLINO L. & FIORASO G.

CNR - Istituto di Geoscienze e Georisorse, Via Valperga Caluso 35, 10125 Torino. E-mail: [email protected]

A detailed analysis of the quaternary fluvial successions preserved in the eastern sector of the Langhe Basin (Tertiary Piedmont Basin, TPB) have been carried out within the geologic survey of the Sheets 194 "Acqui Terme" and 211 "Dego" at scale 1:50.000 (CARG Project). The study has regarded the catchment of the Bormida River between Cengio and Cairo Montenotte, located along Bormida di Millesimo and Bormida di Spigno River respectively, and Castelnuovo Bormida, on debouching into the Alessandria Plio-Quaternary piggy back Basin. Bormida River is characterized by irregular sinuous pattern with asymmetric ingrown meanders deeply incised into the Eocene to Pliocene successions. The fluvial deposits are preserved in form of terraces perched along valley sides at elevation of 120-130 m above the valley bottom: these deposits, which mean color index ranges between 2.5-5Y to 7.5-10YR, are referred to Upper Pleistocene and Holocene and have been interpreted as river meanders inherited from a former surface of low relief. A second group of fluvial deposits is preserved on summit high plains visible along the watershed that extend between Bormida and Belbo Valleys. They have a petrographic composition similar to the former sediments and are distributed at elevation of 180-245 m above the valley bottom: these deposits show a mean color index of 5-7.5YR and are referred to Middle Pleistocene. For the interpretation of the stratigraphic framework a series of "allostratigraphic" profiles have been realized along Bormida di Spigno, Bormida di Millesimo and Erro Valleys. The correlations of sedimentary bodies and related basal erosional surfaces has been carried out considering their altimetric position, the pedogenetic evolution of soils and the degree of erosional dissection. This allowed to individualize a vertical succession of units corresponding to distinct erosional-depositional stages as a result of the uplift of this sector of the TPB. Moreover the analysis of the planimetric and altimetric distribution of the fluvial deposits stressed a differential behavior in the recent evolution of the Langhe Basin: - South of Acqui Terme the fluvial terraces assume a sub-parallel trend, in agreement with uniform uplift rates of the TPB; - along the hill front separing the Langhe reliefs from the Alessandria floodplain, the units gradually converge toward North in agreement with decreasing rates of uplift approaching to the depocenter of the Alessandria Basin. The distribution of fluvial deposits is compatible with a configuration of the Bormida River whose course changed in the time and in the space in responce to sin-morphogenetic tectonic activity that has imposed to the stream network a rapid entrenchment into the bedrock. This phase represents the response to a continuous deformative processes with differential character that has brought, during the Plio-Pleistocene, to the northward shifting of the depocenter of the Alessandria Basin and consequently of the hill front: this forced a gradual transition of the Bormida River from a free alluvial meanders configuration established into the floodplain before local uplift to an incised meanders pattern rapidly cuts down into the underlying bedrock.

21 Geoarcheologia oltre l'appeal: quali reali opportunità per la Geologia del Sedimentario?

BENVENUTI M.1, MARIOTTI-LIPPI M.2, PALLECCHI P.3 & SAGRI M.1

1 - Dipartimento di Scienze della Terra, Università di Firenze 2 - Dipartimento di Biologia Vegetale, Università di Firenze 3 - Laboratorio di Restauro, Soprintendenza ai Beni Archeologici della Toscana, Firenze

Negli ultimi anni la Geoarcheologia ha progressivamente attratto l'attenzione della comunità scientifica quale disciplina-ponte tra l'Archeologia, le Scienze Geologiche e Paleobiologiche. L' "operazione culturale" alla base della crescente popolarità della Geoarcheologia è un fatto decisamente apprezzabile. Esso tende, infatti, a colmare il gap, sempre più artificioso entro il corrente approccio sistemico allo studio del nostro pianeta, tra discipline storiche e scientifiche. A prescindere da questi elementi altamente positivi la Geoarcheologia, proprio in un momento di rapido sviluppo, corre il rischio di una banalizzazione. Da un lato essa rischia di apparire come un mero set di discipline mutuate dalle Geoscienze e applicate all’analisi dei siti archeologici. Questo ruolo di service svolto dalle discipline geologiche e paleobiologiche entro studi archeologici, potrebbe ingenerare una sorta di subalternità e perdita di motivazione nei geologi e di autoreferenzialità negli archeologi diventando geoarcheologi self-made. Queste conseguenze finirebbero per ostacolare l’auspicata integrazione culturale e metodologica tra due comunità che indubbiamente hanno background e specificità diversi. Per limitare questi rischi la Geoarcheologia deve scommettere sul suo attuale successo cogliendo la sfida di massimizzare le proprie potenzialità per rispondere al contempo a due principali esigenze: da un lato quella dell’Archeologia di contestualizzare i resti materiali dell’Umanità del passato entro l’ambiente naturale e dall’altro quella delle Geoscienze ed in particolare della Geologia del Sedimentario, di comprendere le dinamiche del cambiamento ambientale nel recente passato geologico. Questo secondo aspetto, ancora poco sviluppato, eleva la Geoarcheologia ad un importante ruolo nell’analisi e nella predizione del Global Change , priorità per lo sviluppo futuro delle società umane. Nella discussione di questi aspetti si presenterà un esperienza “geoarcheologica” che risponde alle due esigenze di cui sopra. Si illustreranno indagini, a diverso livello di approfondimento, su tre siti archeologici di età etrusco-romana posti in porzioni diverse del bacino idrografico del Fiume Arno (Toscana centrale). Oltre a rispondere alla domanda archeologica: “quali condizioni ambientali nel sito?” queste ricerche stanno contribuendo a ricostruire le dinamiche paleoidrologiche negli ultimi tremila anni con importanti implicazioni sui rischi idrogeologici del prossimo futuro.

22 Cambiamenti ambientali e presenza umana nel tardo Quaternario della Valtiberina Superiore (Toscana NE): Geoarcheologia e oltre

BENVENUTI M.1 & MORONI A.2

1 - Dipartimento di Scienze della Terra, Università di Firenze 2 - Dipartimento di Scienze Ambientali “G. Sarfatti”, Università di Siena

Si presentano i risultati preliminari di un analisi geoarcheologica effettuata a scala territoriale nell’Alta Valtiberina (Toscana NE). Questo territorio, che sottende la porzione prossimale del bacino idrografico del Fiume Tevere, individua una tipica conca intermontana analoga, in senso morfologico e stratigrafico-deposizionale, ai molti bacini presenti entro la catena nordappenninica, sviluppatisi fino dal Pliocene Medio. Il bacino in oggetto, riempito da circa 500 m di depositi prevalentemente fluviali e probabilmente lacustri di età Pleistocenica ed Olocenica, è controllato da sistemi di faglie normali che individuano un graben asimmetrico, più subsidente lungo il margine NO. Nelle colline di Anghiari-Citerna sono visibili oltre 250 m di depositi prevalentemente ciottoloso-sabbiosi fluviali che registrano tre principali fasi di deposizione in ampie pianure alluvionali. Sulla base delle frammentarie evidenze paleontologiche questi depositi vengono riferiti ad un periodo comprendente il tardo Pleistocene inferiore e medio. La presenza umana su questo territorio è documentata fino dal Paleolitico Medio ma si sviluppa più diffusamente e stabilmente a partire dal tardo Neolitico. Le evidenze materiali della presenza umana tardo preistorica, protostorica e storica, da tempo oggetto di raccolte e studi archeologici, sono diffuse sulle superfici ed entro i depositi alluvionali di età compresa tra la fine del Pleistocene superiore e l’Attuale che caratterizzano il fondovalle. Si illustrerà come il semplice e preliminare confronto tra i dati geomorfico-stratigrafici relativi a questi depositi e la distribuzione dei siti archeologici integri le ricerche geomorfologiche e archeologiche oltre gli attuali limiti della Geoarcheologia. Se, infatti, da un lato tale confronto rappresenta uno strumento di base per orientare future ricerche archeologiche e per meglio comprendere le relazioni Uomo-territorio, dall’altro esso offre spunti interessanti per correlare rapidi cambiamenti idrografici e attività tettonica recente con implicazioni sul rischio sismico dell’area alto-tiberina.

23 Mapping using Depositional Units inside of the Italian 1:50.000 CARG Project: an example from the Tertiary Piedmont Basin

BERNARDESCHI A.1, CATANZARITI R.2, MARRONI M.1,2, OTTRIA G.2, PANDOLFI L.1,2 & TAINI A.2

1 - Dipartimento di Scienze della Terra, Università di Pisa, Via S. Maria, 53. 56126 Pisa. e-mail: [email protected] 2 - CNR - Istituto di Geoscienze e Georisorse, Via S. Maria, 53. 56126 Pisa.

The Tertiary Piedmont Basin (TPB) represents an episutural basin developed from Late Eocene to Late Miocene, unconformably covering Alpine and Apenninic units previously deformed during the Eo-Meso-Alpine tectonic phases. Considered as part of a wider episutural basin, known as epi-Mesoalpine Basin, the TPB is filled by more than 4000m thick succession of predominantly siliciclastic deposits, that constitute a generally N to NW dipping monocline. The structural evolution in Paleogene-Neogene time, which led to the construction of the Apenninic chain, post Meso-Alpine phase, is characterized by the traslation to NE of the Ligurian tectonic units coupled with the TPB. The TPB recorded the same regional events as the apenninic tectonics, so, from a geodynamic point of view is important to individuate the major stratigraphic discontinuities which represent related markers of successive deformation phases. The study area is located in the eastern sector of the TPB, where is preserved the lowermost part of the TPB succession, represented by the Monte Piano Marls – Ranzano Sandstone succession, ranging from Priabonian to Early Rupelian. In this area the sedimentary succession, unconformably overlying the External Ligurian Antola Unit, is costituted by marine-marginal deposits characterized by strong lithofacies variation and by marked compositional changes. This kind of succension allows us to use an approach that provides the individuation of depositional units bounded by unconformity surfaces. The unconformity surfaces are characterized by the presence of: angular unconformities and continuos erosional surfaces; abrupt facies changes in contrast with Walther Principle; development of coarse turbidite systems; deposition of chaotic bodies; significant compositional changes. By using unconformity surfaces it is possible to individuate depositional units, with local chronostratigraphic value. These units can be defined as hybrid units, comprising either the charateristics of UBSU units and those of the allostratigraphic units, since the unit’s limits can be traced also where unconformity surfaces pass in paraconformity surfaces. Each units rapresent a stratigraphic succession constituted by a set of depositional systems genetically linked and are bounded by unconformity surfaces of local and/or regional significance and tectonic origin; so each units record an important step in the tectono-sedimentary evolution of the basin. A basic tool in the use of this approach derives from the careful biostratigraphic control of the units, assured by calcareous nannofossil analysis. The analysis of more than 500 samples allowed us to individuate 15 nannofossil events ranging from Early Priabonian to Late Aquitanian. Where the biostratigraphy was inadequate to characterized the depositional units we adopted a subdivision based on the compositional changes of the lithotypes feeding the basin. Moreover, each depositional unit was subdivided into various lithozones to show the characteristic lithologies constitutive of each unit. The result of the applied approach is represented by the definition of 11 depositional units represented in the map and in the explanatory scheme. The use of depositional units allows a better understanding of the basin architecture and of its time-space evolution, giving emphasis on the synsedimentary tectonics affecting the basin through time.

24 Osservazioni geoarcheologiche sul territorio di Nogna (Gubbio, Perugia)

BERTACCHINI M.

Dipartimento di Scienze della Terra, Università degli Studi di Modena e Reggio E., Modena; [email protected]

Il territorio di Nogna è situato in prossimità del margine settentrionale del bacino di Gubbio (Perugia) ad ovest dell’abitato di Mocaiana, nel versante in destra del fiume Assino. In un periodo di tempo compreso tra il I sec. a.C. ed il I-II sec. d.C., in quest’area fu iniziata la costruzione di un santuario mai terminato. Le vestigia del tempio di Nogna si ergono a circa 650 m di quota su un versante abbastanza acclive dominante l’intera pianura eugubina e circondato da contrafforti appenninici formati dalla Formazione Marnoso arenacea umbra. Il santuario, progettato nella seconda metà del II secolo a.C. come tempio italico ad alae sulla via di percorrenza transappennica, che in passato collegava Gubbio alla valle di Pietralunga, è stato oggetto di ripetute campagne di scavo condotte dalla Soprintendenza per i Beni Archeologici dell’Umbria dal 1998 al 2004. I materiali lapidei usati per la costruzione del santuario, analizzati dal punto di vista petrografico, sono riconducibili a due diverse litologie entrambe appartenenti alla Marnoso arenacea affiorante localmente e riconducibile al Membro di M. Urbino di Pialli (1966) e Ricci Lucchi e Pialli (1973); una si presenta arenaceo-quarzosa con mica biotite e muscovite e l’altra è calcarenitica ad elementi quarzosi. Le ricerche geologiche e petrografiche condotte su campioni raccolti nell’area del santuario unitamente ai numerosi elementi morfologici ricavati da foto aeree e rilevati sul terreno, hanno permesso di effettuare osservazioni di dettaglio sui depositi affioranti e sull’evoluzione geologico-ambientale del territorio di Nogna. Evidenti sono le tracce di un movimento franoso innescatosi a monte del tempio che interessò gran parte del versante coinvolgendo lo stesso santuario e provocando l’abbandono del sito. La comparsa di problemi di stabilità durante la costruzione del santuario è stata altresì confermata dalla realizzazione, durante il procedere dei lavori di costruzione, di un muro di sostegno e di un drenaggio ancora riconoscibili a monte del manufatto. Le cause che hanno contribuito a generare tale fenomeno di dissesto possono essere varie e non si può escludere una loro azione combinata. L’acqua, che tuttora è presente in abbondanza su tutto il versante, è sicuramente da considerarsi tra i principali agenti innescanti l’evento soprattutto se associata a periodi di piogge intense. Altrettanto plausibile è l’ipotesi di fasi di instabilità tettonica data l’elevata sismicità che caratterizza il territorio eugubino e in generale quello umbro, tuttavia l’assenza nella struttura muraria ancora conservata di fratture o lesioni riconducibili a terremoti non sembra supportare questa ipotesi. Non si può infine escludere che siano stati gli stessi interventi di sistemazione del sito per renderlo idoneo alla costruzione del tempio ad innescare condizioni di instabilità nel versante, opere che richiesero interventi di deforestazione e lavori di terrazzamento che crearono variazioni all’originale equilibrio del profilo topografico del pendio.

Bibliografia

Pialli G. (1966) – Osservazioni geologiche sulle formazioni flyscioidi di Castiglione Aldobrandi (foglio 123 IV NW). Mem. Soc. Geol. It., 5, 365-386. Ricci Lucchi F. e Pialli G. (1973) - Apporti secondary nella marnoso-arenacea: 1. torbiditi di conoide e di pianura sottomarina a est-nord-est di Perugia. Boll. Soc. Geol. It., 92, 669-712.

25 Nuove osservazioni litostratigrafiche sui depositi della conca di Gubbio

BERTACCHINI M., FREGNI P. & PATTUZZI E.

Dipartimento di Scienze della Terra, Università degli Studi di Modena e Reggio E., Modena; [email protected]

Lo scavo effettuato per scopi civili in località Branca, situata all’estremità sud-orientale del bacino di Gubbio, ha permesso di osservare in affioramento una successione continua di depositi continentali che in età pleistocenica hanno contribuito a colmare il bacino eugubino. Lo studio di dettaglio che ne è scaturito ha permesso di approfondire ed ampliare le informazioni geologiche relative a questo settore del bacino e di confrontare i risultati ottenuti con quelli indicati da GE.MI.NA (1963) e da Menichetti (1992). L’area oggetto della ricerca è posta in prossimità del fiume Chiascio immediatamente a valle della strada SP 219 Gubbio-Gualdo Tadino, lungo un versante che degrada con una discreta acclività verso la conca eugubina. Sono stati esaminati sia i campioni raccolti sul terreno, sia quelli provenienti dai segmenti dei carotaggi messi a disposizione dalla Ditta esecutrice delle indagini geofisiche effettuate nell’area. Tali analisi hanno preso in considerazione: la litologia, la granulometria, il colore, il contenuto in carbonati, la composizione mineralogico-petrografica, i microfossili presenti, le strutture sedimentarie, le caratteristiche micromorfologiche ed altri elementi diagnostici individuati durante la realizzazione dello studio. La comparazione ed il confronto dei risultati ottenuti dall’esame dei campioni hanno permesso la ricostruzione di una successione stratigrafica relativa al margine sud- occidentale del bacino di Gubbio sino ad ora mai osservata, confrontabile con quelle descritte da Martini e Sagri (1993) per i bacini distensivi tardo Miocenici-Quaternari dell’Appennino settentrionale, che ricalca, nei tre termini deposizionali più tardi, quella proposta da GE.MI.NA (1963). A contatto con il bedrock del bacino di Gubbio costituito dalla Formazione Marnoso- arenacea sono stati individuati: un potente deposito basale conglomeratico composto da clasti di provenienza locale e che costituisce il primo materiale di riempimento di un settore marginale del bacino progradante verso i sedimenti lacustri della parte più interna; a questo si sovrappongono depositi di ambiente palustre e lacustre (complesso argilloso-lignitifero), sedimenti di transizione fluvio-lacustri (complesso argilloso-sabbioso) e depositi detritici e fluviali (complesso alluvionale).

Bibliografia

GE.MI.NA. (1963) – Ligniti e torbe dell’Italia centrale. Pubbl. Soc. Geomin., ILTE Ed., Roma, 319p. Martini I.P. e Sagri M. (1993) - Tectono-sedimentary characteristics of Late Miocene-Quaternary extensional basins of the Northen Appennines, Italy. Earth-Science Reviews, 34, 197-233. Menichetti M., (1992) - Evoluzione tettonico-sedimentaria della Valle di Gubbio. Studi Geologici Camerti, Vol. Spec. 1, 155-163.

26 Depositional paleoscarps in the Meso-Cenozoic succession of the Marguareis Massif (Ligurian Briançonnais): recognition and implications

BERTOK C.1, D’ATRI A.1, MARTIRE L.1, MUSSO A.1, PEROTTI E.1 & PIANA F.2

1 - Dipartimento di Scienze della Terra, Torino 2 - CNR, Istituto di Geoscienze e Georisorse, Torino

The Marguareis-Cima delle Saline Triassic to Paleogene mainly carbonate sedimentary succession testifies a long-lasting (about 150 my) and complex evolutionary history that starts with the first phases of the continental rifting, continues with the formation of the paleoeuropean passive margin, linked to the opening of the Ligurian Tethys ocean, and ends with the beginning of the continental collision. This long lasting evolution is recorded by a thin (few hundreds meters), discontinuous and condensed stratigraphic succession. The succession hence records several structural reorganization phases, corresponding to important geometrical changes of the sedimentary basin, all observable in such a restricted area. The studied area is geometrically organized in domains bounded by two orthogonal systems of faults that may be followed for some km and show great offsets (up to several hundred metres) and that have been previously interpreted as either normal, inverse or transcurrent alpine faults. Our researches highlighted that some of these faults have a much older age; their syndepositional activity controlled sea-floor topography and hence sedimentation at different stratigraphic levels, from Middle-Late Jurassic to Eocene. This new interpretation is grounded on the following observations: large paleoslopes cutting down all stratigraphical units are still well preserved; their nature of depositional surfaces is demonstrated by: • the occasional presence of a mineralized crust (hard ground) • sediments ranging from Late Jurassic to Eocene overlie these surfaces with anomalous stratigraphic contacts, often forming thin and discontinuos lithosomes which drape them • the widespread occurrence of sedimentary breccias, locally showing evidence for being the direct result of the disruption of older cataclasites olistoliths of Jurassic limestons ranging in size from few m3 to thousands m3 are commonly found close to the paleoslopes preliminary results from petrographic and isotope analyses point to a hydrothermal circulation during Meso-Cenozoic sedimentation. According to the age of sediments resting on the paleoslopes, two main systems of paleofaults have been distinguished: the oldest (E-W striking) pre-dates the formation of the Aptian-Albian hard ground the youngest (N-S striking) follows the hard ground formation and is probably coeval to the deposition of the Eocene sediments. Rare evidence of Late Jurassic paleoslopes have also been found, but their occurrence is too discontinuos to recognize which kind of structures they were related to. According to these data a new model for the tectono-sedimentary evolution of the Marguareis-Cima delle Saline area has been proposed: the extensional tectonic phase related to the liassic continental rifting has not been the unique period of reorganization of the basin, neither the most important. During both Mesozoic and Cenozoic times, infact, sedimentation has been continuously deeply influenced by the activity of large normal faults, which controlled sea-floor topography and caused the formation of escarpments characterized by a strong gravity-driven instability.

27 La “Coltre della Val Marecchia” nel quadro mio-pliocenico dell’Appennino marchigiano-romagnolo

BONCIANI F.1, CORNAMUSINI G.1, CALLEGARI I.1, CONTI P.1, FORESI L.M.2 & CARMIGNANI L.1

1 - Centro di Geotecnologie-Dipartimento di Scienze della Terra, Università di Siena 2 - Dipartimento di Scienze della Terra, Università di Siena

Introduzione

La Val Marecchia costituisce uno dei settori dell’Appennino Settentrionale caratterizzato da un’importante peculiarità geologica, qual’è la cosiddetta “Coltre della Val Marecchia”. L’assetto geologico e soprattutto le modalità di formazione e messa in posto di quest’ultima nel bacino di avanfossa, costituiscono tutt’oggi un elemento di dibattito. Tra i lavori più significativi e recenti, riguardanti tali problematiche, citiamo in particolare De Feyter (1991), Conti (1994) e Roveri et alii (1999). Viene qui presentata un’interpretazione relativa all’assetto stratigrafico e strutturale ed all’evoluzione della Coltre della Val Marecchia (CVM). I dati sono stati raccolti durante rilevamenti geologici svolti in più campagne di lavoro, ossia nell’ambito del Progetto CARG nazionale, del Progetto di Cartografia Geologica della Regione Marche e del dottorato di ricerca di uno degli autori.

Inquadramento geologico

Il quadro geologico dell’area, così come definito anche nell’ambito del Progetto CARG (vedi le Note Illustrative del Foglio 267-San Marino di Cornamusini et alii, in stampa) e nella Tesi di Dottorato di Ricerca di Bonciani (2005), risulta essere caratterizzato da un assetto complesso ed articolato in più unità stratigrafiche e tettoniche, di cui la CVM fa parte. La CVM è inserita nel sistema a thrust-belt appenninico esterno (Fig. 1) e separa l’Appennino umbro-marchigiano a sud-est, dall’Appennino romagnolo a nordovest. Nella Val Marecchia si individuano due principali unità stratigrafico-strutturali, rappresentative di successioni deposte in domini paleogeografici distinti: - l’insieme della “Successione umbro-marchigiano-romagnola” pre- e sin-evaporitica e della “Successione post-evaporitica del margine padano-adriatico”, in posizione sostanzialmente autoctona, deposte in un intervallo di tempo distribuito rispettivamente dal Burdigaliano superiore al Messiniano superiore e da questo al Pleistocene. Le due successioni sono separate da una discordanza stratigrafica angolare di importanza regionale, legata alla fase tettonica intra-messiniana (Vai & Castellarin, 1992; Roveri et alii, 1998); - la CVM, in posizione alloctona, costituita da Unità Liguri intensamente deformate e da una Successione Epiligure, con minore grado di deformazione, di età eocenico-pliocenica basale. Dal quadro geologico d’insieme, risulta evidente come la tettonica abbia influito sulla sedimentazione nell’avanfossa marchigiano-romagnola, durante il Miocene-Pliocene, determinando zone di alto a sedimentazione ridotta in cui si formavano durante il Messiniano depositi evaporitici primari e zone di basso bacinale, in cui si sviluppavano potenti spessori di depositi anche risedimentati (Roveri et alii, 2003, cum bib). Dai rapporti tra i depositi paleoautoctoni, neoautoctoni, semialloctoni e le unità alloctone, si può risalire alla definizione del timing della CVM. I lineamenti trascorrenti antiappenninici hanno complicato la struttura dei bacini stessi, determinando al loro interno ulteriori zone di basso e di alto morfologico, come bene evidente, rispettivamente nella zona di Sant’Agata Feltria e di Sapigno.

Figura 1 – Quadro geologico regionale dell’Appennino marchigiano-romagnolo. In evidenza con la linea tratteggiata l’area indagata, di cui fa parte la Coltre alloctona della Val Marecchia.

La faglia di Sant’Agata Feltria (FSA, Fig. 2) rappresenta uno dei principali elementi trascorrenti dell’area, ed ha fortemente condizionato la sedimentazione nel bacino di avanfossa, sin dal Messiniano inferiore. Questa sembra avere suddiviso l’avanfossa in settori, di cui quello a nord dato dalla sinclinale di Sapigno con deposizione dei Ghioli di letto in facies pelitica e successivamente delle evaporiti rimaneggiate provenienti dall’alto strutturale della “Vena del Gesso”. Diversamente, il settore a sud di tale faglia, è caratterizzato da una più potente successione pelitica dei Ghioli di letto, con alcuni livelli a slump ed intercalati livelli lenticolari di arenarie torbiditiche (Arenarie di Sant’Agata Feltria) e numerosi olistostromi liguri ed epiliguri, alla quale segue verso l’alto un potente stack di corpi alloctoni liguri, che costituiscono una porzione della CVM.

Caratteri della coltre della Val Marecchia

La CVM è costituita da una serie di scaglie embriciate, data da termini liguri e da depositi epiliguri, limitate da superfici di scorrimento listriche immergenti verso SW, con forma arcuata a scala regionale e convessità rivolta verso NE, ad indicare un senso di trasporto da SW verso NE. La geometria listrica delle superfici di scorrimento risulta evidente se confrontiamo l’inclinazione di queste nelle varie zone di ogni singolo “arco”: le parti frontali mostrano inclinazioni comprese tra 30° e 55°, mentre lateralmente le superfici passano ad inclinazioni minori (20°) per diventare suborizzontali nei pressi del contatto di base della coltre, al quale si raccordano senza mai dislocarlo. Le scaglie costituenti la CVM sono strutturate con una porzione basale data da termini fortemente deformati e plastici delle Argille varicolori, a cui seguono verso l’alto termini liguri più recenti e competenti (Formazione di Sillano e Formazione di Monte Morello) o direttamente placche epiliguri in

29 rapporti di discordanza angolare. Le placche epiliguri poggiano sempre sulle Argille varicolori, con termini oligocenico-burdigaliani nei settori interni della CVM, mentre poggiano con termini messiniani nei settori esterni. Lo spessore della CVM è maggiore nella porzione centrale, e va assottigliandosi sia verso ovest, sia verso est dove i termini assumono maggiore caoticità interna. La superficie basale della CVM, ben affiorante nell’area di Macerata Feltria, mostra la tendenza a seguire le irregolarità morfologiche di origine strutturale del substrato paleoautoctono, senza mai essere dislocata dalle faglie che interessano quest’ultimo. Questa situazione è evidente nella zona di Valle Avellana, dove la CVM, dopo aver “scavalcato” ed in parte “aggirato” l’alto di Macerata Feltria, si imposta nel bacino sinclinale di Montecalvo in Foglia, dove viene suturata dai depositi pliocenici della Zona a Globorotalia puncticulata. La CVM, si chiude quindi lenticolarmente verso NE all’interno della successione pliocenica, all’altezza della sinclinale di Montecalvo in Foglia. E’ quindi probabile, che considerate le differenze delle successioni di tipo bacinale e di alto, che l’anticlinale di Montefiore-Montescudo costituisse già una dorsale nel bacino durante il Messiniano, ed abbia rappresentato un ostacolo morfologico che ha agito da sbarramento/confinamento per il corpo alloctono in avanzamento, il quale sembra adattarsi alla morfologia del substrato della suddetta sinclinale. La geometria delle scaglie costituenti la CVM, i rapporti tra queste ed i depositi autoctoni (paleo- e neo-) ed i rapporti tra i depositi epiliguri, consentono la ripartizione della stessa, almeno in due corpi principali: uno settentrionale lungo l’allineamento Sant’Agata Feltria-Perticara-San Marino ed uno meridionale, lungo l’allineamento Sasso Simone- Mercatino Conca.

Evoluzione della coltre della Val Marecchia

L’interpretazione dei lineamenti cartografati, l’analisi della cronologia relativa degli eventi e delle successioni sedimentarie, hanno permesso di ricostruire un quadro dettagliato degli eventi deposizionali e tettonici che hanno interessato l’area della Val Marecchia tra il Miocene superiore ed il Pliocene medio, e di inserirli nel contesto evolutivo della parte esterna dell’Appennino Settentrionale. In particolare, sono stati riconosciuti quattro episodi principali. - Primo episodio del Tortoniano, che precede la strutturazione della CVM, durante il quale le Unità Liguri sono sovrascorse sulla Marnoso-arenacea interna dando luogo ad un fronte interno di sovrascorrimento a direzione appenninica (M. Fumaiolo), chiudendo il bacino di avanfossa interna, ed in cui i sedimenti epiliguri più recenti, implicati nella deformazione, sono attribuibili al Serravalliano. - Secondo episodio del Messiniano, durante il quale si è avuta la prima strutturazione della CVM all’interno del bacino di sedimentazione dei Ghioli di letto. Questo episodio è iniziato con la sedimentazione di depositi grossolani (Arenarie di Sant’Agata Feltria) e la messa in posto di olistoliti ed olistostromi provenienti dalla coltre alloctona in avanzamento, nell’ambito della depressione generatasi anche a seguito della tettonica trascorrente (faglia di Sant’Agata Feltria). La frequenza e l’entità degli olistostromi è aumentata nel tempo (parte sommitale dei Ghioli di letto), sino ad arrivare alla messa in posto di grandi lembi che andarono modificando la fisiografia di tale porzione di bacino (Fig. 2a). In questo caso i volumi coinvolti condizionarono fortemente la sedimentazione sino ad arrivare, per colmamento della depressione bacinale, ad interromperla. - Terzo episodio collocabile al passaggio Miocene-Pliocene, durante il quale il processo di messa in posto della CVM ha avuto un ulteriore sviluppo, probabilmente anche in semi- continuità con il precedente. In questo episodio si è avuta l’interazione nel bacino tra i lembi alloctoni ed i primi sedimenti pliocenici, i quali si caratterizzano in parte per il carattere autoctono, ed in parte per il carattere semiautoctono o addirittura semialloctono. - Il quarto episodio del Pliocene inferiore, segna il momento finale della messa in posto in posizione esterna della CVM, all’interno delle Argille azzurre. Nell’area settentrionale si ha un ulteriore impulso nell’avanzamento del corpo alloctono, con conseguente deformazione anche dei depositi pliocenici della zona di Perticara. La depressione che viene a crearsi tra il

30 primo corpo alloctono e l’alto di Macerata Feltria agisce da richiamo per un secondo e più importante lembo di materiale ligure, innescato dall’evento tettonico infrapliocenico, che determina la messa in posto della porzione meridionale della CVM (Fig. 2b), con direzione di movimento chiaramente condizionata dalla fisiografia del bacino pliocenico.

Conclusioni

Le geometrie dei corpi alloctoni e dei corpi semialloctoni, la presenza di numerosi olistostromi ed il quadro geologico-evolutivo che emerge, sono in sintonia con un innesco tettonico ed uno sviluppo di tipo gravitativo della CVM, a partire dal Miocene superiore sino al Pliocene inferiore secondo episodi deformativi e deposizionali appartenenti ad un processo semi-continuo. Dall’analisi dei dati ottenuti si ipotizza che le direttrici di trasporto gravitativo-tettonico e di strutturazione della CVM, siano state almeno due, parzialmente distinte per età e per disposizione. Infatti, sia il secondo episodio del Messiniano, che il terzo episodio del passaggio Mio-Pliocene, caratterizzano in particolare una direttrice di “flusso” antiappenninica settentrionale. Di questi sono caratteristici, rispettivamente i lembi alloctoni liguri-epiliguri all’interno dei Ghioli di letto ed i lembi alloctoni che hanno interagito con i sedimenti marginali del Pliocene basale.

Figura 2 – a) Pannello che mostra lo sviluppo della CVM nel bacino di avanfossa nel Messiniano superiore, secondo un “flusso” settentrionale; b) pannello che mostra lo sviluppo della CVM nel Pliocene inferiore secondo un “flusso” meridionale.

Diversamente, la direttrice di “flusso” del quarto episodio del Pliocene inferiore, probabilmente il più importante, sembra avere avuto simile direzione antiappenninica, ma con lo sviluppo di un “flusso” in posizione più meridionale, anche se accompagnato da un avanzamento del “flusso” settentrionale. Questa diversificazione può essere dovuta a fattori strutturali legati alla tettonica ed al fatto che probabilmente la depressione più antica e settentrionale si è colmata nel Pliocene basale, come indicano i sedimenti prossimali associati (Arenarie di Perticara), mentre si è sviluppata la depressione meridionale, che ha raccolto una parte consistente di lembi alloctoni della CVM. L’innesco della messa in posto della CVM può allora essere riferito a due fasi tettoniche principali, una del Messiniano superiore, responsabile anche della formazione della discordanza intramessiniana nella successione autoctona, ed una del Pliocene inferiore (Fig. 2). Si evince pertanto l’importanza della linea tettonica trasversale (linea Arbia-Val Marecchia), nel determinare le condizioni dinamiche e morfologiche necessarie alla messa in posto della CVM. Tale lineamento tettonico, che trova espressione superficiale in fasci di faglie subparallele ed in depressioni morfologiche, piuttosto che in dislocazioni lineari semplici, ha agito da innesco-richiamo, dapprima per i corpi clastici torbiditici e per i numerosi olistoliti ed olistostromi, ed in seguito per i corpi alloctoni liguri-epiliguri provenienti dal thrust-sheet presente in posizione più interna (fronte di Casteldelci). In definitiva, la messa in posto della CVM, è secondo noi caratterizzata da processi gravitativi, tipo enormi frane sottomarine, e risulta quindi guidata dalla morfologia del bacino mio-pliocenico, che

31 appare condizionata a sua volta della tettonica compressiva e trascorrente, attiva almeno fin dal Messiniano inferiore.

Bibliografia

BONCIANI F. (2005) – Approccio multidisciplinare (rilevamento geologico, geomorfologico ed applicazioni G.I.S.) per la ricostruzione dell’evoluzione di un settore dell’avanfossa nordappenninica (Val Marecchia-Montefeltro). Tesi di Dottorato inedita, XVII ciclo, Università degli Studi di Siena, 203 pp.. CONTI S. (1994) – La geologia dell’alta Val Marecchia (Appennino Tosco-Marchigiano). Note illustrative alla carta geologica 1:50.000. Atti Tic. Sc. Terra, 37, 51-98. CORNAMUSINI G., CONTI P., BONCIANI F., CARMIGNANI L., MARTELLI L. & QUAGLIERE S. (in stampa) – Note Illustrative della Carta Geologica d’Italia alla scala 1:50.000, Foglio 267-San Marino. A.P.A.T. Servizio Geologico d’Italia, Roma, 110 pp.. DE FEYTER A.J. (1991) - Gravity tectonics and sedimentation of the Montefeltro (Italy). Geol. Ultraiectina, 35: 1-168. ROVERI M., MANZI V., BASSETTI M.A., MERINI M. & F R.L. (1998) - Stratigraphy of the Messinian post- evaporitic stage in eastern-Romagna (northern Apennines, Italy). Giorn. Geol., 60: 119-142. ROVERI M., ARGNANI A., LUCENTE C.C., MANZI V. & RICCI LUCCHI F. (1999) - Guida alle escursioni nelle valli del Marecchia e del Savio. G.I.S. Riunione autunnale, Rimini 3-6 ottobre 1999. ROVERI M., MANZI V., RICCI LUCCHI F. & ROGLEDI S. (2003) - Sedimentary and tectonic evolution of the Vena del Gesso basin (Northern Apennines, Italy): Implications for the onset of the Messinian salinity crisis. Geological Society of America Bulletin, 115/4: 387-405. VAI G.B. & CASTELLARIN A. (1992) – Correlazione sinottica delle unità stratigrafiche nell’Appennino Settentrionale. Studi Geol. Camerti, vol. spec n.2 (1992): 171-185.

32 Climate change and beaches evolution in the Mediterranean area

BUONOMO V.1, ORTOLANI F.1 & PAGLIUCA S.2

1 - Department of Planning and Science of the Territory, University in Naples Fred II, Naples, Italy; [email protected] 2 - ISAFOM, CNR, Ercolano, Naples, Italy; [email protected]

The beaches represent the outcropping part of a geological prism, constituted by sandy/gravelly sediments, accumulated in the last thousand of years (Holocene) in concomitance with eusthatic sea waters rise, started around 15.000 years ago. The holocene coastal sediments can have a varying thickness from 15 to over 30 m along the shores that delimit the alluvial lowlands; the thickness is generally smaller along the Pocket Beach. The main result achieved with geoarchaeological research consists in the identification of cyclicity (period of about 1000 years) of the major climate and environmental changes that have resulted in real environmental crises lasting between 100 and 200 years in the Mediterranean area (fig. 1). There is clearly to close correlation between climatic and environmental changes and solar activity (concurrence of prolonged maxima of solar activity and warm increased greenhouse effect periods and concurrence of repeated minima of solar activity and cold periods, such as the Little Ice Ages).

Figure 1

Instrumental data chiefly concerning the last 150 years show, in the Mediterranean Area, consistently close correlation between environmental variations (increase in solar activity and temperatures and changes in the quality and quantity of rainfall). On the basis of scientific data acquired with geoenvironmental research conducted in the Mediterranean basin, it is possible to predict that the most serious environmental changes expected in coastal areas. During the warm periods (temperatures increased by 1-2° C) the coastal zones were affected by desertification up to latitude of about 42° N (Roman increased "Greenhouse Effect", 100- 300 A.D.; Medieval or Crusades increased "Greenhouse Effect", 1100-1270 A.D.).

33 The littorals with silicoclastic sands where affected by severe erosion while the beaches with bioclastic sands where characterised by evident progradation. During the decreases in temperatures the areas of the alluvial plains subject to human impact and settlements were affected by an accumulation of huge volumes of sediments with consequent aggradation and progradation of the coastlines in the northern part of the Mediterranean while severe erosion occurred along the beaches with bioclastic sands of the southern part (Archaic Little Ice Age, 500-300 B.C.; Dark Age Little Ice Age, 500-750 A.D.; Little Ice Age, 1500-1830 A.D.). It is possible to predict that the beach erosion, prevalently caused by the climate variation, will be active for 150 years at least.

Figure 2

Many thousands of kilometres of the Mediterranean coastline are affected by serious erosion which undermines not only the anthropised area, that has taken place up to few metres from the sea, but also the social and economic structure of entire regions whose economy is largely based on seaside tourism. It is undeniable, in fact, that coastline economy based on quality tourism, fostered by beautiful beaches, has contributed to the improvement of the social and economic position of the coastal regions. The beach erosion, consequently, represent a direct economic danger for the national and regional economic condition. Without effective and coordinated planning of the safeguarding, improvement and protection of the coastal areas, deterioration accentuated by predictable defence work made necessary by local emergency situations, will become more and more seriuos. The economic importance of the beaches is increased especially in the last 50 years in concomitance with the aggravation of the erosion. The palaeoenvironmental reconstructions put in evidence that the actual period of climatic variation represents the period of transition between the Little Ice Age and the following increase of the Greenhouse Effect, as cyclically and naturally is already verified in the past millennia (figs. 1 and 2).

34 An impact of notable importance interests the shores. It is evident that for the first time, in the last 1000 years, the man is found to face a natural, serious and general problem with a consistent negative impact on the environment and on the economy: that of the erosion and destruction of the beaches. The construction of the shores has happened during the cold-humid periods, that is during the past Little Ice Ages. The last natural nourishment is occurred between 1500 and the end of 1800 (fig. 1). In Italy, particularly, the shores fed by sediments by the rivers have been supplied abundantly primarily between the beginning of 1700 and the end of 1800. From the beginning of 1900 the natural feeding has been more and more progressively scarce and the beaches have begun to "to grow thin" especially in correspondence of the delta areas of the rivers where the erosive phenomenons have, often, provoked the destruction of over 1000 meters of beach in the last 100 years. Big part of the beaches currently is insufficiently nourished of sand, only thanks to the erosion or “cannibalisation” of the sediments of the delta areas that are those interested by very serious erosion. The search has reserved a particular attention to the individuation of the natural physical characteristics of the stable and not fed beaches, of elevated environmental and economic value, that characterize the coasts of Campania, Basilicata and Calabria, in Southern Italy. The acquired original environmental data have allowed to individualize suitable interventions (lasting nourishment) that allow to guarantee the defense and the geoenvironmental sustainable restauration of the Pocket Beachs, of varying length from some hundred meters to around 5 km, and of parts of long shores particularly interested by the erosion. The most evident and documented example of recent natural and lasting nourishment is represented by the beach of Vietri on the Sea (near Salerno in Campania Region) that in October 1954 was interested by the very rapid (few hours) accumulation of about 300.000- 400.000 meters cubes of sediments transported by many debris flows that devastated the basin slopes in the night among 25 and 26 october. The deposits (gravels and sand) determined an instant nourishment that increased of over 100 meters the beach. From 1954 to today the beach (constituted by gravel with sandy matrix) has suffered a middle withdrawal of around 20 meters, as easily verifiable from the comparison of the topographical maps and aerial photo. The research confirmed that the gravelly-sandy beaches similar to those of Vietri on the Sea, characterising the Amalfi coast and the Cilento (Southern Campania), the Maratea coast (Basilicata Region), and the Calabrian coast, are the most stable; in fact, the coarse sediments, heavier than the sand, are not eroded and dispersed towards the open sea by the tides induced by the strong sea storms. In relationship to the climatic variation the erosion of the beaches will last at least 100 - 150 years. In this picture, a role of primary importance is represented by the individuation of the "streets of concentrated oblique dispersion" of the sand, with the purpose to mitigate the losses, especially in the Pocket Beach. In fact, our researches have pointed out that the longshore sand transport is transformed in oblique sand dispersion in corrispondence of natural and artificial change of the beach morphology. The most meaningful data to be kept in mind to individualize lines of intervention to preserve and to restore, in lasting way, the beaches, are the followings: - the last natural nourishment is occurred between 1500 and the end of 1800. - the beaches, currently, are partially and insufficiently fed of sand from the river; there is a partial feeding, within the shore, thanks to the erosion or “cannibalisation” of the sediments of the delta areas. - the period in which erosion prevails, like the present one, constitutes a multicentennial natural phase within the evolution of the beaches. - in relationship to the climatic variation, the erosion of the beaches will last at least 100-150 years. The climatic variation, as happened in past, should behave an increase of the winds of southern origin and a consequent modification of the transport of the

35 sediments along the shore (that is from the southern quadrants toward the northern ones). - the artificial protection of the long shore anthropised environment reduce the cliff erosion and consequently the sediment feeding; - the artificial beach nourishments with sand are very expensive and not lasting; - the marine sands layers are absolutely insufficient for the nourishment of the various thousand of kilometers of shores interested by the erosion. - in correspondence of morphological interruptions of the beaches, natural (for example promontories) or artificial (docks), the sand transported longshore is dispersed irreversibly toward the open sea. The destruction of the beaches can effectively be opposed, and in lasting way, without altering the beauty of the beaches, only artificially supplying the shores of sediments. Till now have been performed various artificial nourishment of sand. Nobody has been lasting despite the elevated cost. The nourishment with sand would be the ideal intervention to effect, repeatedly.

Figure 3 – Rapid beach erosion in the touristic coast of the Cilento Natural National Park.

The true problem is represented by the elevated cost of the intervention, from the limited duration in the time and from the lack of marine layers of sandy sediments to satisfy the various thousand of kilometers of beach seriously affected by the erosion. Only in the Lazio, Liguria and Tuscany the requirement esteemed, within the European project Beachmed, is over 150 million meters cubes of sand for the reconstruction and 1,7 million meters cubes the year for the maintenance. Considered the gravity and the predictable duration of many tens of years of the coastal erosion, the interventions of restauration of the beaches must be based on the followings aspects: a - immediate realization of the intervention; b - contained cost of the intervention (with interventions also performed with a sinergy between public institutions and privacies) through interventions inspired to the naturalistic engineering; c - restoration of lines of shore already existed in past; d - reconstruction of natural coastal morphologies without emerged or submerged artificial barriers ; e - duration of many tens of years of the intervention of restauration and nourishment. In the figures 3 and 4 are evidenced some example of rapid change of touristic and famous beaches along the Tirrhenian coast of Campania and Basilicata Region.

Figure 4 – Very rapid change of the littoral morphology in the touristic coast of Maratea, Basilicata, Southern Italy.

References

Ortolani F. & Pagliuca S. ( 2003) – Climate change and littoral evolution: impact on the regional economy. 4th Congress on Regional Geoscientific cartography and information systems, Bologna 17-20 giugno 2003. Ortolani F. & Pagliuca S. (2004) - Littoral evolution and impact on the regional economy. 32° IGC Congress, Florence 19-28 August 2004. Ortolani F. & Pagliuca S. (2004) - Valorizzazione delle risorse ambientali e sviluppo dell’area costiera di Napoli. Volume abstract Convegno Nazionale INU “METROPOLI IN TRANSIZIONE. Innovazioni, Pianificazione e Governance per lo sviluppo delle Grandi Aree Urbane del Mezzogiorno”, Napoli 10 Dicembre 2004. Ed INU pp. 19.

37 Calcifying baceria and physicochemical parameters of three different soils of l’Aquila basin (central - Italy)

CACCHIO P., GIANIORIO L., ERCOLE C., DEL GALLO M. & LEPIDI A.

Dip. of Basic and Applied Biology, University of L’Aquila, Coppito 67010, Italy e-mail: [email protected]

It is almost impossible to find natural environments where bacteria do not exist, grow and multiply. They are found in the ocean depths, the driest desert and in the coldest climates. They can grow in the absence of oxygen and in the absence of organic nutrients. The presence of microorganisms in almost all habitats means that any type of environment is subjected to microbial action. This action may range from soil formation to the degradation of historic buildings or the appearance and spreading of illnesses. Calcium carbonate precipitation in natural habitats is commonly considered to be an abiogenic process even if the presence of microbes in carbonate deposits is reported. Bacteria and fungi can in vitro precipitate calcium carbonate extracellularly through a variety of processes, correlated with 1) metabolic activities, involving: i) autotrophic pathways (non-methylotrophic methanogenesis, anoxygenic photosynthesis and oxygenic photosynthesis); ii) the nitrogen cycle (ammonification of amino-acids, dissimilatory reduction of nitrate, degradation of urea or uric acid); iii) the sulfur cycle (dissimilatory reduction of sulphate), and 2) cell-wall structure of microorganisms through mechanisms that have only partly elucidated. Microbial carbonatogenesis is of great interest from the point of view both of pedogenesis and CO2 trapping. We hypothesized that bacteria isolated from soil which are able to mediate CaCO3 precipitation in vitro, play a role in the mineralization process in soil. We investigated three different soils of L’Aquila basin, characterized by low (“Pizzoli” sample), medium (“Coppito” sample) and very high (“Picenze” sample) CaCO3 content. The relative abundance of calcifying bacteria among total cultivable microflora and the aptitude to calcification (time and yield) were found to be related to physicochemical parameters and, in particular calcium carbonate content of soil, implying that their presence was not occasional. We also hypothesized that the calcifying strains isolated from “Pizzoli” soil use different precipitation mechanisms since calcite crystals were precipitated both within the colony and far from the colony in solid growth medium. Most of calcifying isolates were Gram positive cocci strains.

38 Facies characterization of the Late Pleistocene-Holocene continental carbonates in southern Valdelsa Basin (Southern Tuscany)

CAPEZZUOLI E., GANDIN A. & SANDRELLI F.

Dipartimento di Scienze della Terra, Università di Siena, Via Laterina 8, 53100 Siena, [email protected]

Southern part of the Valdelsa Basin (Southern Tuscany) is characterized by wide Quaternary carbonate deposits. These are divided in six synthems on the relative stratigraphic, geomorphological and facies characterization: an Early-Middle Pleistocene palustrine/lacustrine synthem (Campiglia dei Foci Synthem -CDF), four terraced fluvial/palustrine synthems (Abbadia Synthem - ABB; Calcinaia Synthem - CAL; Torrente Foci Synthem - FOC; Bellavista Synthem - BEL) referred to Late Pleistocene-Holocene and one fluvial synthem (Poggibonsi Synthem - POG) corresponding to the recent alluvial deposits. The four fluvial/palustrine synthems are discontinuously outcropping along the flanks of the valleys of Elsa River and its tributaries (torrents Foci and Staggia). They are mainly formed by detrital deposits, composed of mixed, terrigenous-carbonate silty sands and lenticular beds of gravels, but along precise segments of the river valleys, they are composed by calcareous deposits, mainly represented by bodies of concretionary phytoclastic-phytohermal calcareous tufas associated with compact micritic limestone and occasionally dark silty clays with organic matter. Sedimentological and petrographic analyses on these calcareous deposits distinguished ten lithofacies: Phytoherm Framestone, Phytoherm Boundstone, Phytoclastic Tufa, Lithoclast Tufa, Oncoidal and Cyanolith Tufa, Peloidal Tufa, Sapropelithic Tufa, Palaeosol Tufa, Micritic Limestone and Microbial Travertine. Their relative assemblage and organization reflects four predominant facies associations: Thermal spring environment, Fluvial barrage environment, Paludal environment and Braided fluvial environment. Recognition of the Thermal spring environment facies association in the upstream sector of the calcareous deposits implies their hydrothermal origin from springs with highly concentrated CaCO3 waters. Distribution of diverse associations indicates a rapid cooling of the waters, with deposition of calcareous tufa along most of the valley. Downstream, encrusting capacity of the water was progressively diluted by low-concentrated CaCO3 waters inputs and calcareous tufa deposits gradually evolve in detrital deposits.

39 Le orictocenosi quaternarie dell’arcipelago flegreo e la lavorazione della conchiglia a Vivara (Procida, Napoli) nell’età del bronzo

CARANNANTE A.

Laboratorio di Bioarcheologia, Università degli Studi “Suor Orsola Benincasa”, Napoli [email protected]

Limitata attenzione è stata rivolta, nel passato, ai resti fossili rinvenuti in contesti archeologici, sebbene resti paleontologici di organismi marini, raccolti da affioramenti sedimentari, siano stati rinvenuti in numerosi siti pre-protostorici mediterranei. Tali reperti sono particolarmente diffusi nei siti ciprioti, egei e italiani dell’età del Bronzo. Raccolte probabilmente, nella maggior parte dei casi, come curiosità o come begli oggetti, le conchiglie fossili erano talvolta utilizzate per scopi ornamentali o anche come materia prima per la realizzazione di oggetti come tessere e sculture in rilievo. Un caso particolarmente interessante è quello del sito campano dell’età del Bronzo di Vivara-Punta d’Alaca, sull’omonimo isolotto tra Procida e Ischia. Vivara rappresenta il resto di un edificio vulcanico inserito nel complesso sistema vulcanico procidano. Nei livelli archeologici del villaggio preistorico vivarese sono stati rinvenuti diversi frammenti di conchiglie molto spesse che presentano evidenti tracce di lavorazione. Essi sono riconducibili a esemplari fossili di Glycymeris bimaculata di grandi dimensioni, che venivano segati, abrasi e rifiniti per ottenere tessere utilizzate come ornamento o come “gettoni” di computo. Il loro rinvenimento in un’area, come quella flegrea, dominata da depositi vulcanici ha spinto ad indagare circa le possibili aree di approvvigionamento di tale materia prima. Alcuni affioramenti di rocce sedimentarie di ambiente marino, individuati sulle vicine isole di Procida e Ischia, sono stati analizzati a tal fine. Nelle isole Flegree affiorano, infatti, depositi marini contenenti orictocenosi a molluschi, ostracodi, foraminiferi bentonici e planctonici riferibili ad associazioni dell’infralittorale profondo-circalittorale, di età pleistocenica e olocenica, portati in emersione dai complessi eventi vulcano-tettonici che hanno caratterizzato l’intera area. Alla luce delle analisi effettuate, uno di tali affioramenti, rinvenuto a Lacco Ameno sull’isola d’Ischia, contenente, tra le altre specie, grandi conchiglie fossili di Glycymeris, sembra essere il più probabile luogo di provenienza delle conchiglie lavorate nella preistoria vivarese sebbene non si possa escludere che eventuali analoghi affioramenti, nel corso della complessa evoluzione geomorfologica dell’arcipelago, siano stati distrutti da processi erosivi o sommersi nella rapida risalita relativa del livello del mare che ha caratterizzato il settore procidano-vivarese negli ultimi millenni.

40 Determinazione dei sedimenti utilizzati come frazione fine nella manifattura di ceramiche dell’età del Bronzo di Gorzano (MO)

CARPENITO G., LEVI S. T., LUGLI S., MARCHETTI DORI S. & VEZZALINI G.

Dipartimento di Scienze della Terra, Università di Modena e Reggio Emilia, Modena. Ceramiche “d’impasto” provenienti dalla Terramara di Gorzano (Modena; Bernabò Brea et al., 1997) sono state analizzate dal punto di vista fisico, chimico e mineralogico; tali risultati sono stati confrontati con le caratteristiche di sedimenti argillosi di cinque differenti unità geologiche circostanti tale sito, in modo da definire le materie prime utilizzate: Argille della Val tiepido Canossa (?Oligocene-Miocene), Formazione delle Argille Azzurre (Zancleano-Pleistocene Inf.), Formazione delle Sabbie Gialle (Pleistocene Inf.-Medio) sintema Emiliano-Romagnolo inferiore (Pleistocene Medio), unità di Niviano (Pleistocene Sup.). Per confronto sono stati analizzati anche i sedimenti attuali del Torrente Tiepido che scorre in prossimità dellla Terramara. Sono stati scelti 30 campioni rappresentativi della varietà di forme e funzioni: tazze, dolii, orci e scodelle. Le analisi eseguite sono poi stati messe in relazione con quelle di campioni di analoghe tipologie, provenienti da sei Terramare della stessa area (ad una distanza massima di 8 km) (Levi S.T., 1997). Tutti i sedimenti argillosi e i manufatti, sono stati sottoposti ad indagine minero- petrografica con microscopio ottico, analisi chimica (XRF) e diffrattometrica (XRPD). Su alcuni frammenti ceramici ed argille si è inoltre eseguita una analisi d’immagine computerizzata e l’analisi mineralogica quantitativa tramite metodo Rietveld, utilizzando due diversi programmi di calcolo: GSAS e TOPAS. L’osservazione al microscopio ha permesso di classificare le ceramiche in 4 gruppi principali: a) smagrite con cocciopesto e calcite; b) smagrite con cocciopesto; c) smagrite con calcite; d) solo frazione fine. I minerali sempre presenti, a granulometria generalmente seriale e minuta, sono: quarzo, plagioclasio, K-feldspato, muscovite e opachi. Dal punto di vista chimico le ceramiche di Gorzano risultano essere abbastanza omogenee. In particolare il gruppo di ceramiche che utilizza come smagrante cocciopesto è molto simile al gruppo di ceramica fine. Dal confronto coi sedimenti argillosi risulta evidente che la maggior parte delle ceramiche è chimicamente compatibile con i campioni dell’unità di Niviano. Il confronto delle ceramiche fini di Gorzano con quelle fini degli altri siti limitrofi indica un’alta omogeneità ed ancora buona compatibilità con le argille della stessa unità. L’analisi diffrattometrica ha confermato la presenza delle fasi mineralogiche riconosciute al microscopio, inoltre ha permesso il riconoscimento dei minerali argillosi presenti nei terreni. Attraverso l’analisi mineralogica quantitativa si è riusciti a definire con precisione che i sedimenti presi in considerazione differiscono principalmente nel rapporto tra minerali argillosi e carbonati e che le argille dell’unità di Niviano sono quelle più affini alle ceramiche, in particolare a quelle fini e quelle smagrite con cocciopesto. In conclusione si osserva quindi che la tecnologia di produzione delle ceramiche di Gorzano, basata sull’uso di sedimenti fini smagriti con cocciopesto e calcite, ben si adatta alla tradizione osservata nella valle del Po all’età del Bronzo. La produzione ceramica di numerose Terramare dell’area di Modena è ben standardizzata, chimicamente e mineralogicamente omogenea e ha probabilmente visto come fonte principale di materia prima i sedimenti dell’unità di Niviano.

Bibliografia

Bernabò Brea M., Cardarelli A., Cremaschi M. (1997). L’insediamento collinare e montano. In: Le Terramare. La più antica civiltà padana. Milano: 275-295. Levi S.T., Loschi Ghittoni A.G. (1997). Gli impasti ceramici di siti terramaricoli del territorio modenese. In: Le Terramare. La più antica civiltà padana. Milano: 497-506.

41 Analisi stratigrafico-sedimentologica dei “Depositi marini terrazzati” della bassa piana metapontina tra i fiumi Basento e Cavone (Golfo di Taranto, Italia meridionale)

CILUMBRIELLO A.

Dipartimento di Geologia e Geofisica, via Orabona 4, 70125 Bari ([email protected])

L’area di studio, ricadente nel territorio del comune di Pisticci (Mt), è ubicata nel settore meridionale della Fossa bradanica ed è compresa fra gli alvei dei fiumi Basento e Cavone (fig. 1). In particolare, lo studio effettuato in questo lavoro riguarda fondamentalmente i depositi costituenti la parte alta della serie bradanica che, nel settore meridionale della fossa, è rappresentata dai cosiddetti “Depositi marini terrazzati” (VEZZANI, 1967; COTECCHIA & MAGRI, 1967; BOENZI et alii, 1971; BRÜCKNER, 1980). Si tratta di depositi sabbioso-conglomeratici (trasgressivi su sedimenti argillosi infra-mediopleistocenici) riferibili secondo BOENZI et alii (1971) a brevi cicli sedimentari che determinano ad una morfologia terrazzata attribuibile ad azioni di abrasione e di accumulo da parte di un mare complessivamente in via di regressione.

Fig. 1 A) Carta strutturale dell’Italia; B) Carta geologica della Fossa bradanica (mod. da PIERI et alii, 1997); C) Distribuzione dei depositi della Fossa bradanica (PIERI et alii, 1996) con ubicazione dell’area studiata.

Relativamente al numero di superfici terrazzate esistono discrepanze fra i diversi autori. VEZZANI (1967), COTECCHIA & MAGRI (1967) e BOENZI et alii (1976) concordano nell’individuare sette ordini di terrazzi marini di età compresa fra il Siciliano ed il Tirreniano. BRÜCKNER (1980) individua, invece, una successione di dieci ordini di terrazzi posti a diverse quote topografiche; questi vengono indicati, dalla costa verso l’entroterra, con le sigle T0- T10, dove T0 rappresenta la piana costiera e T10 è il terrazzo più elevato posto ad una quota di circa 400 m s.l.m. Secondo altri studi stratigrafico-sedimentologici, i “Depositi marini terrazzati” possono estendersi, verso l’entroterra del Golfo di Taranto, fino a comprendere i

42 depositi di colmamento della Fossa bradanica che si rinvengono a quota 430-400 metri (Pomarico e Matera) sul livello del mare (PIERI et alii, 1996; DOGLIONI et alii, 1996). A prescindere dal numero delle superfici terrazzate quasi tutti gli autori sono concordi nel ritenere che il meccanismo genetico sia l’interazione tra eustatismo e sollevamento regionale; BENTIVENGA et alii (2004) ritengono invece che i terrazzi marini siano il risultato dell’attività di sistemi di faglie dirette immergenti verso il Mar Ionio. Ai fini del presente lavoro è stato effettuato innanzitutto il rilevamento geologico alla scala 1:10.000 di un’area di circa 130 kmq, e successivamente l’analisi dettagliata di numerose sezioni stratigrafiche. In particolare lo studio delle sezioni stratigrafiche ha messo in evidenza un’estrema variabilità litologica e di facies, sia verticale sia laterale; ciò ha reso difficile la correlazione fra i depositi, anche a causa della mancanza di una continuità fisica fra gli affioramenti. Comunque, a partire dalla costa verso l’entroterra, nell’area di studio sono stati riconosciuti alcuni depositi terrazzati corrispondenti ad alcuni degli ordini di terrazzo già definiti da BRÜCKNER (1980) ed i cui caratteri stratigrafico-sedimentologici vengono di seguito brevemente illustrati a partire dal terrazzo più recente. Il “deposito terrazzato di Matine San Teodoro”, corrispondente al deposito marino terrazzato di I ordine (sensu BRÜCKNER, 1980), si sviluppa, procedendo da monte verso mare, da quota 35 metri a quota 15 metri s.l.m., con un’ampiezza trasversale alla costa di circa 1,70 Km. Tale deposito si raccorda all’attuale linea di costa mediante un’area sub- pianeggiante corrispondente alla piana costiera ionica. I caratteri stratigrafico- sedimentologici di tale deposito sono stati ricavati dallo studio di 4 sezioni stratigrafiche, che presentano spessori variabili da 2 metri ad un massimo di 8 metri, e sono rappresentate da sedimenti prevalentemente conglomeratici di ambiente marino poco profondo che verso l’alto passano a depositi conglomeratici e/o sabbiosi, di ambiente alluvionale. Il “deposito terrazzato di Masseria San Teodoro”, corrispondente al deposito marino terrazzato del II ordine (sensu BRÜCKNER, 1980), si sviluppa da quota 50 metri a 40 metri s.l.m.; ha un’ampiezza trasversale rispetto alla costa di circa 500 metri e presenta una buona continuità laterale. Le sezioni studiate nell’ambito di tale deposito sono 3, ed hanno spessore variabile da un minimo di 6 metri ed un massimo di circa 20 metri. Dal punto di vista litologico il deposito di Masseria San Teodoro risulta costituito da sedimenti prevalentemente sabbioso-conglomeratici di ambiente marino poco profondo, e solo subordinatamente da sedimenti di ambiente continentale (fig. 2), in erosione sui sottostanti.

Fig. 2 Depositi ghiaiosi di ambiente alluvionale in erosione su depositi ghiaiosi di ambiente marino poco profondo, affioranti nella cava di località “La Petrulla” e relativi al “deposito terrazzato di Matine San Teodoro”.

Il “deposito terrazzato di Masseria dell’Incoronata”, corrispondente al deposito marino terrazzato del III ordine (sensu BRÜCKNER, 1980), procedendo da monte verso mare, si sviluppa da quota 70 metri a quota 60 metri s.l.m. Anche tale deposito si raccorda al sottostante per mezzo di una superficie leggermente inclinata verso mare, e presenta un’ampiezza trasversale alla costa di circa 2 Km. Nell’ambito di questo deposito sono state

43 misurate 7 sezioni stratigrafiche aventi spessori variabili da un minimo di 8 metri ad un massimo di 24 metri. Tali sezioni sono rappresentate da depositi sabbiosi e sabbioso- conglomeratici (fig. 3) e presentano caratteri di facies attribuibili ad ambienti sedimentari variabili dal marino poco profondo al continentale. L’analisi di facies delle sezioni stratigrafiche relative a questo deposito terrazzato ha permesso una buona ricostruzione stratigrafica; sono stati riconosciuti, infatti, trends deposizionali sia di tipo shallowing-upward sia di tipo deepening-upward. In particolare si è osservato che a depositi di ambiente marino poco profondo (alternanze sabbie e ghiaie di shoreface superiore e depositi conglomeratici di beachface) sono intercalati depositi costituiti da sabbie molto fini, prive di strutture sedimentarie, con ciottoli alla base, e da argille molto ricche di materia organica, con ciottoli e frammenti di fossili, interpretati come depositi di ambiente continentale.

Fig. 3 Depositi sabbiosi di ambiente marino poco-profondo affioranti nella cava di località “San Teodoro” e relativi al “deposito terrazzato di Masseria dell’Incoronata”.

Il “deposito terrazzato di Marconia” corrisponde al corpo sedimentario terrazzato del IV ordine, (sensu BRÜCKNER, 1980), ha un’ampiezza trasversale alla costa di circa 1,30 Km e si estende da quota 103 metri sul livello del mare a circa 80 metri. All’interno di questo deposito è stato possibile misurare solo due sezioni stratigrafiche (Sezioni “Masseria dell’Incoronata 4” e “Marconia”) a causa della scarsità di tagli artificiali e di incisioni naturali. Tali sezioni hanno uno spessore abbastanza esiguo (circa 7 metri) e risultano quasi completamente rappresentate da depositi di origine marina ad eccezione della porzione sommitale. Quest’ultima è infatti costituita da un deposito sabbioso con ciottoli sparsi, dello spessore di massimo 2 metri, privo di strutture sedimentarie, fortemente arrossato e riferibile ad ambienti di tipo continentale. Il “deposito terrazzato di Tinchi”, corrispondente al deposito marino terrazzato del V ordine di BRÜCKNER (1980), si estende da una quota di circa 170 metri fino a circa 118 metri sul livello del mare, ed ha un’ampiezza massima, trasversale alla costa, di circa 3,5 km. Tale deposito terrazzato si raccorda al sottostante per mezzo di una superficie leggermente inclinata verso mare, che presenta una certa continuità, fatta eccezione per alcuni tratti dove non è visibile a causa di piccole incisioni naturali. Sono state misurate 6 sezioni stratigrafiche, di spessore variabile compreso tra un minimo di 12 metri ed un massimo di 30 metri, costituite da depositi prevalentemente sabbioso-conglomeratici di ambiente marino poco profondo (ambiente di spiaggia variabile dall’offoshore transition alla beachface) e/o continentale. Dalle analisi litologiche e sedimentologiche delle sezioni misurate è emerso che nell’insieme esse individuano sistemi deposizionali sabbioso-conglomeratici di ambiente marino poco profondo che verso l’alto evolvono ad ambienti di piana alluvionale. In alcuni casi si osserva la ripetizione ciclica di alcune facies fra cui sequenze deposizionali di spiaggia simili a quelle descritte da MASSARI & PAREA (1988) in aree limitrofe. I risultati preliminari di questo lavoro indicano che i depositi terrazzati dell’area metapontina sono costituiti da diverse litofacies e, contrariamente a quanto riportato in letteratura e a quanto indicato dal nome stesso, tali depositi sono relativi oltre che ad ambienti di tipo marino anche ad ambienti di tipo continentale; inoltre il riconoscimento di

44 particolari trend deposizionali, nell’ambito di successioni relative ad ogni singolo deposito terrazzato, potrebbe portare ad un dettaglio stratigrafico sequenziale attribuibile a cicli di altissima frequenza verificatisi durante il Pleistocene medio-superiore. Queste ultime considerazioni sono in via di elaborazione.

Bibliografia

BENTIVENGA M., COLTORTI M., PROSSER G. & TAVARNELLI E. (2004) – A new interpretation of the terraces in the Taranto Gulf: the role of extensional faulting. Geomorphology, 60, 383-402. BOENZI F., RADINA B., RICCHETTI G. & VALDUGA A. (1971) – Note illustrative della Carta Geologica d’Italia, F° 201 “Matera”. Serv. Geol. d’Italia, 48 pp. BOENZI F., PALMENTOLA G. & VALDUGA A. (1976) – Caratteri Geomorfologici dell’area del Foglio di “Matera”. Boll. Soc. Geol. It., 95, 527-566, 12ff., 1 tav. BRUCKNER H. (1980) – Marine terrasen in Süditalien. Eine quartärmorphologische. Studie über das Kustentiefland von Metapont. Düsseldorfer Geographische Schriften, 14, 235pp. COTECCHIA V. & MAGRI G. (1967) – Gli spostamenti della linea di costa quaternaria del mar Ionio tra Capo Spulico e Taranto. Mem. Soc. Geol. It., 24, 243-260. DOGLIONI C. TROPEANO M., MONGELLI F. & PIERI P. (1996) – Middle-late Pleistocene of Puglia: an “anomaly” in the Appenninic foreland. Mem., Soc., Geol., It., 51, 101-117. MASSARI F. & PAREA G. C. (1988) – Progradational gravel beach sequences in a moderate-to high- energy, microtidal marine environment. Sedimentology, 35, 881-913. PIERI P. SABATO L. & TROPEANO M. (1996) – Significato geodinamico dei caratteri deposizionali e strutturali della Fossa bradanica nel Pleistocene. Mem., Soc.,Geol.,It., 51, 501-515. PIERI P. VITALE G. BENEDUCE P., DOGLIONI C., GALLICCHIO S., GIANO S. I., LOIZZO R., MORETTI M., PROSSER G., SABATO L., SCHIATTARELLA M., TRAMUTOLI M. & TROPEANO M. (1997). – Tettonica Quaternaria nell’area bradanico-ionica. Il Quaternario 10, 535-542. TROPEANO M., SABATO L. & PIERI P. (2002) – Filling and cannibalization of a foredeep: Bradanic Trough, southern Italy. Geological Society of London, Special Publications, 191, 55-79. VEZZANI L. (1967) – I depositi plio-pleistocenici del litorale ionico della Lucania. Atti Accademia Gioenia Scienze Naturali, 18, 159-180.

45 Deep hydrostratigraphy of Plio-Pleistocene successions in Western Po Plain.

CLEMENTE P.1, IRACE A.1, NATALICCHIO M.1, TRENKWALDER S.1, MOSCA P.1, DE LUCA D. A.2, POLINO R.1 & VIOLANTI D.1,2

1 - C.N.R., Istituto di Geoscienze e Georisorse, Sezione di Torino, Via Valperga Caluso 35, 10125 Torino – [email protected] 2 - Università di Torino, Dipartimento di Scienze della Terra, Via Valperga Caluso 35, 10125 Torino

This work is a synthesis of preliminary results achieved in a wide project whose first aim is the definition of the hydrogeologic internal structure and outer physical shape of deep aquifers occurring in sedimentary Plio-Pleistocene successions of the Piedmont Plain. The project results from a C.I.P.E. financing that forecasts a close collaboration among Piedmont Region, CNR-IGG of Turin and the Department of Heart Sciences of Turin University. The Western Po Plain area represents the most important and large fresh-water reserve of the Piedmont region. However, only the first 200 m of the subsurface are well- known from a lithostratigraphic and hydrogeologic point of view. In contrast, informations about sediments beneath this depth are fragmentary because of the extreme lack of deeper wells. For this reason our researches, carried out through a multidisciplinary approach, have been focused on the definition of the hydrogeologic framework of deeper sectors. The identification of the stratigraphic architecture of a basin represents the first step to recognize the occurrence of aquifers and to define a conceptual model for groundwater flow. Initially the stratigraphic analysis has allowed to identify: geometry of six depositional sequences, the gross lateral-vertical arrangement of different depositional settings and their related lithologies (NATALICCHIO et alii, in this volume). In the second part of the work, mainly focused on the Savigliano Basin (SB), the integrated analysis of geological and lithologic data and their relative interpretations has allowed to recognize different aquifer complexes and their spatial distribution. Each complex, chosen like basic hydrogeologic units, groups more aquifers with similar sedimentological features, i.e. homogeneous facies association, referable to analogous but diacronus depositional environments. The choice of these units has allowed to propose a preliminary hydrogeologic model independent from a chronostratigraphic framework. In the SB, six complexes have been recognized and the distribution of the fresh- saltwater interface and its relationship with hydrogeologic complexes has been analyzed. Special attention has been focused on this interface that represents the lower limit of freshwater reserves and has been noticed in different stratigraphic sequences recognised in various sectors of the area. The main tectonic element of the SB is represented by the structural high of Saluzzo. This structure divides the examinated area into two different minor basins and also represents an important element that conditions the distribution of the fresh-saltwater interface that, in fact, is located in the two sectors almost at the same depth, but in different depositional sequences. In spite of this tectonical conditionings, it has been possible to assume that the distribution of the interface is mostly influenced by hydric flow in deep freshwater circuits overhanging this limit. The essential element of use and elaboration of lithostratigraphical, micropaleontological and hydrogeological data is represented by a database on purpose realized. Through the interpolation of the database data, it has been possible to carry out various texts on 3D graphical software to produce a series of fence diagrams and block diagrams in which are represented both steps of multidisciplinary analysis realized and final results of the interpretation.

46 I carbonati connessi ad emissioni di fluidi ricchi in metano: i risultati di dieci anni di studi nell’Appennino settentrionale

CONTI S. & FONTANA D.

Dipartimento di Scienze della Terra, Università di Modena e Reggio Emilia, Modena; [email protected], [email protected]

Durante l’ultimo ventennio, l’emissioni di fluidi freddi è stata ampiamente documentata lungo i margini continentali attivi. L’espulsione dei fluidi nei prismi di accrezione è favorita dalle sovrapressioni interstiziali indotte dal carico tettonico e le velocità di emissione sono legate all’entità dei processi tettonici. Ai processi tettonici si possono sovrapporre processi climatici, ed entrambi possono contribuire a fenomeni d’instabilità sedimentaria. L’emissione di fluidi freddi è evidenziata da vari indicatori quali: - depositi di carbonati autigeni, - fuoriuscita d’idrocarburi liquidi e gassosi, - vulcani di fango e strutture legate a processi diapirici, - presenza di depositi ricchi in clatrati, - deformazioni sinsedimentarie, - presenza di peculiari comunità bentoniche chemiosintetiche. Il riconoscimento di questi caratteri è importante per identificare i processi ed i meccanismi che controllano l’espulsione dei fluidi nei margini continentali. I depositi fossili, quali quelli presenti nell’Appennino settentrionale, sono importanti perché forniscono una documentazione temporale dei processi di espulsione dei fluidi: evidenziano la struttura e l’evoluzione del sistema di circolazione dei fluidi e soprattutto i rapporti tra tettonica e sedimentazione. I depositi fossili sono riconoscibili per la presenza di: - carbonati autigeni impoveriti dell’isotopo 13C, - peculiari comunità chemiosintetiche, - strutture sedimentarie legate a processi diapirici. In quest’ultimo decennio abbiamo esaminato i carbonati legati alle emissioni di fluidi ricchi in metano in numerosi affioramenti del Miocene medio-superiore dell’Appennno Settentrionale. Questi depositi si trovano in vari contesti geotettonici della catena appenninica: nelle zone più interne si concentrano nei bacini satelliti epiliguri, (Marne del Termina del Serravalliano superiore-Tortoniano inferiore) mentre in quelle più esterne dell’avanfossa sono presenti generalmente nella parte prospiciente il fronte deformativo. In particolare, nell’avanfossa sono concentrati in due distinte posizioni: - in intervalli pelitici legati ad alti intrabacinali intercalati nella successione langhiano- serravalliana delle Formazioni del M. Cervarola e della Marnoso-arenacea, - in emipelagiti di scarpata di età compresa tra il Serravalliano ed il Messiniano inferiore (Marne di Vicchio, Marne di Verghereto e marne di letto) che delimitano al tetto le sopra citate formazioni. In quest’ultima situazione, i carbonati autigeni sono situati poco al di sotto del contatto tettonico con le unità Liguri. I carbonati sono irregolarmente distribuiti nel sedimento in senso sia orizzontale che verticale; pur non essendo degli indicatori stratigrafici, si concentrano solo in particolari momenti della successione stratigrafica miocenica. Morfologia e litologia dei corpi cartonatici sono varie, come pure le facies presenti, caratterizzate da contatti complessi. I carbonati sono associati a sedimenti di prodelta, a facies di scarpata, e soprattutto a depositi torbiditici di piana bacinale. I carbonati sono prevalentemente inclusi in sedimenti pelitici, ma possono cementare o incrostare arenarie grossolane e conglomerati. Sono sia in posizione primaria che secondaria, per rimaneggiamenti intraformazionali. Al loro interno sono state riconosciute diverse facies, alcune ricorrenti e indicative di processi di tipo diapirico. Evidenze diapiriche sono rappresentate dalla mescolanza e rimaneggiamento di sedimenti e fossili di natura molto diversa, provenienti dalle rocce incassanti, dalle chemioerme stesse, e da sedimenti extraformazionali costituiti da olistostromi. Il regime e la tipologia delle emissioni dei fluidi varia, con evoluzioni da flussi concentrati a diffusi, da esplosivi a moderati e viceversa. Le emissioni lente e moderate sono responsabili della precipitazione di grandi spessori di carbonati autigeni, con sviluppo di facies micritiche riccamente fossilifere. Le fasi di emissione esplosive sono caratterizzate da

47 diversi tipi di autobrecciatura e dall’assenza di fossili in situ. Le facies brecciate per emissioni esplosive sono spesso marcate da valori molto impoveriti dell’isotopo 13C a cui si associano valori positivi del δ18O; questi caratteri potrebbero collegarsi a fasi di dissociazione di clatrati. I carbonati autigeni sono generalmente legati a caoticizzazione dei sedimenti incassanti: colate di detrito, slumps intraformazionali, frane in blocco extraformazionali, strutture caotiche e deformazioni sinsedimentarie. Gli episodi d’instabilità sedimentaria possono sia precedere che seguire la precipitazione dei carbonati, con la formazione di crescite multifase caratterizzate da diversi episodi di rimaneggiamento e cementazione di depositi risedimentati. La cessazione delle fasi di precipitazione autigenica dei carbonati coincide o con un’importante episodio d’instabilità sedimentaria o con un episodio tettonico. Nell’avanfossa i carbonati si associano di frequente a depositi a provenienza appenninica (arenarie grossolane e conglomerati calcarei), connessi con flussi iperpicnali in ambienti deltaico-torbiditici. I carbonati metano-derivati dell’avanfossa sono connessi con faglie inverse e thrusts a direzione appenninica, o con importanti contatti tettonici e fasi di accavallamento (Sestola- Vidiciatico-Cervarola, Liguridi su emipelagiti di chiusura), indicando una stretta relazione con le fasi tettoniche ed i principali accavallamenti miocenici appenninici.

48 Authigenic seep-carbonates cementing coarse-grained deposits in a fan-delta depositional system (middle Miocene, Marnoso- arenacea Formation, central Italy)

CONTI S.1, FONTANA D.1, GUBERTINI A.1 & LUCENTE C.C.2

1 - Dipartimento di Scienze della Terra, Università degli Studi di Modena e Reggio Emilia, Largo S. Eufemia 19, 41100 Modena Italy. 2 - Regione Emilia-Romagna, Servizio Tecnico Bacini Enza, Panaro e Secchia, sede di Modena, Via Fonteraso 15, 41100 Modena, Italy; [email protected].

The middle Miocene terrigenous succession of Deruta in central Italy, ascribed to the Marnoso arenacea Formation, encloses peculiar coarse-grained seep-carbonates within chaotic horizons. The sedimentary succession consists of two lithostratigraphic units. The basal unit A is made of gravelly and sandy high-density turbidites interpreted as a coarse-grained, mixed depositional system showing relatively immature facies characters with respect to true basinal turbidites . The main bulk of the overlying unit B is composed of fine grained sandstone beds and associated mudstones, alternated with lens-shaped coarse-grained bodies, interpreted as fan-delta deposits. Thick chaotic horizons occurring within the unit B, are the result of mass- failures ranging from sliding/slumping to debris and block avalanches; the emplacement of large mass-wasting deposits suggests a lower-slope prodelta environment. The superposition of the two systems reflects a strong tectonic phase of uplift and progradation of the prodelta slope. The tectonic activity is also indicated by the occurrence of slope-failures and huge supply of coarse-grained sediments reaching the prodelta slope Compositional data of arenites allow to outline diverse provenances: from Apenninic sedimentary rocks which supplied coarse-grained horizons of the unit A and B; from Alpine metamorphic rocks of various rank and dolostones, which contributed to the deposition of fine-grained turbidites in unit B. The recycling from older arenitic successions is accounted for localized arkosic source areas in turbidites up section. Seep-carbonates are present at different levels in unit B, associated with coarse- grained pebbly sandstones and conglomerates and included in the chaotic horizons. The occurrence of δ13C depleted carbonate rocks (hydrocarbon-seep carbonates) inside chaotic horizons is an evidence of presence and diffusion of methane-rich fluids pervading the sediments. Fluids reached the sea-bottom through thrust faults and pervaded selectively the more permeable, coarse-grained horizons along the prodelta slope. Carbonate blocks showing scattered chemosymbiotic vesicomyid-type clams indicate also that some of the coarse-grained beds were colonized, even if in stressed environmental conditions due to the recurrent mass flows. Cemented levels were involved in slope failures and accumulated at the lower slope. In situ cementation of coarse-grained blocks just accumulated at the lower slope is not excluded, due to remobilization of methane-rich fluids by mass-wasting processes and selective pervasion of such slide blocks.

49 The Posada turbidite system (eastern Sardinian Margin): a mass- wasting affected system in a partially confined intraslope basin

DALLA VALLE G.1,2, GAMBERI F.2 & MARANI M.2

1 – Università di Bologna 2 – ISMAR-Bologna)

High resolution multibeam data collected by Ismar (Istituto di Scienze Marine - Bologna) along the eastern margin of Sardinia island have been analysed to describe the morphology of the Posada turbidite system. The Posada turbidite system is located in the Baronie basin, a narrow intraslope basin in the northern sector of the eastern Sardinian margin. The basin is completely confined seaward by the Baronie seamount, a basement horst, inherited from the opening phases of the Tyrrhenian sea. The basin has a N-S trend deepening southward from around 1300 m to 1800 m depth, where it joins the northern reach of the Gonone-Orosei canyon system. In the shelf and continental slope, the system consists of a deeply (750 m) incised canyon, evolving at the base of slope into the Posada channel running on the proximal portion of a small (10 km) radial fan, with a sharp southward turn. The fan is bounded seaward by the Baronie seamount. An abandoned thalweg channel evidences that a westward migration of the Posada channel has occurred. The distal portion of the fan is affected by a 3 km wide, amphitheatre-shaped slide scar, that has strongly modified the morphology and the pathways of the actual Posada channel. Downslope of the slide scar, elliptical mounds are interpreted as part of the connected mass transport deposit. Further downslope the system evolves into a branching network of straight, low relief (<20 m) channels, running along the basin with a N-S trend, beyond the extent of the fan. Eventually, in the very distal portion of the Baronie basin, the channels join into a wide v-shaped valley, with an erosive relief of around 100 m, that joins the northern reaches of the Gonone-Orosei canyon system. The continental slope between the Posada Canyon and the Gonone-Orosei canyon, is characterized by steep sectors, due to the presence of small offset extensional faults. It is intensively affected by a wide network of slide scars, especially adjacent to the Posada fan, and represents the only sector of the entire Sardinian margin completely devoid of canyons. Likewise, the slope portion of Baronie seamount that faces to the east the Posada fan, is affected by instability processes, that could be triggered by the impact of the flows coming from the Posada turbiditic system. The morphology of the Posada turbidite system is the result of the complex interplay between the topography of the receiving basin, and the behaviour of the sedimentary flows. The topography of the basin has forced the Posada system to develop from an eastward to a southward trend, along the base of the continental slope. This setting has in turn, generate instability on the bounding slopes of both the Sardinia continental slope and the Baronie seamount. The slopes are affected by mass wasting processes triggered by turbidity currents that, through undercutting processes at the base of the slopes, promote sliding processes that involve even the upper sectors of the slopes.

50 Pliocene depositional evolution of the south-eastern Valdelsa Basin (Tuscany, Central Italy): tectonic and eustatic control on fluvio-deltaic depositional systems

DEL CONTE S.

Università degli studi di Firenze, Dip. Scienze della Terra, via La Pira 4, 50121 Firenze; [email protected]

A Pliocene succession exposed in the south-eastern Valdelsa Basin(VB) have been studied through high-resolution geological mapping and facies analysis. From the base of the succession the following synthems are distinguished: The Borro Strolla Synthem (BS) (uppermost Messinian-lower Zanclean) consists of alluvial deposits filling a valley incised in Messinian deposits and oriented NW-SE. Three subsynthems are distinguished: the lower BS1 and BS2 are referred to uppermost Messinian; the BS3, tentatively attributed to the lower Zanclean, is represented by gravels (indicating paleocurrent to W-SW) and subordinate sands which show horizontal and trough cross-stratification. These are abruptly overlain by inner shelf silty clays. The Talciona Synthem (T) (uppermost Zanclean?) consists of poor organised gravelly deposits, related to the proximal portion of an alluvial system draining toward S-SE. The Certaldo Synthem (C) (uppermost Zanclean-lower Piacenzian) is made of two vertically stacked lithofacies assemblages. The lower assemblage is represented by gravels, pebbles, and coarse medium sands alternating with massive silty clays bearing marine molluscs, referred to a delta front-inner shelf environment. The paleocurrents indicate provenance from E-SE. The upper lithofacies assemblage consists of silty clays with abundant marine molluscs and subordinately massive silts, referred to an inner shelf depositional environment. The Pietrafitta Synthem (uppermost Zanclean-Piacenzian) consists of two subsynthems. The lower one (PTF1) is made up of massive silty clays with abundant marine molluscs, indicative of an inner shelf, and fine to medium sands in horizontal or planar inclined beds, internally massive or normally graded, referred to as hyperpicnal flows. This subsynthem is unconformably overlain by a the following PTF2, consisting of alluvial deposits at the base, passing upward into medium to fine massive sands in tabular bedsets with abundant molluscan fauna dispersed in the sediment or concentrated in thin horizons. The Ponte a Elsa Synthem (PE) (Piacenzian) is made of fluvial gravel, sand and clay on the eastern side of the VB, passing gradually to deltaic and shallow marine sand and clay in the central-western portion of the basin. This stratigraphic architecture suggests interaction between tectonic and eustatic signals controlling the infill of the south-eastern portion of the VB between the Zanclean and the Piacenzian. The depositional dynamic was characterised by a partial connection between the VB and the Volterra Basin, lost at the end of Zanclean. More specifically: 1) During most part of the Zanclean (BS,T Synthems) a river system drained the NW margin of the basin, that was connected to the sea via the Volterra Basin. 2) In the latest Zanclean-early Piacenzian (C Synthem) the connection with the Volterra Basin was probably reducing as indicated by delta fronts prograding toward NW, i.e. in an axial direction. 3) The PTF Synthem records the renewed incision of deep valleys trending NW-SE. This evidence suggests that a residual connection with the Volterra Basin attracted the development of incised valleys during relative sea-level lowstand. 4) During Piacenzian (PE Synthem) a major reorganization of the drainage network occurred as a consequence of uplift and denudation of the north-eastern basin shoulders. The south-eastern part of the VB was conclusively isolated from the Volterra Basin and possibly characterized by dominant erosion.

51 Cylindrical 13C-depleted concretions and chaotic deposits: a significant association in the Late Miocene of the tertiary Piedmont basin

DELA PIERRE F.1, 2, FESTA A.1, 2, CAVAGNA S.1, CLARI P.1 & MARTIRE L.1

1 - Dipartimento di Scienze della Terra, Università di Torino, Via V. Caluso, 35 – 10125 Torino. 2 - CNR - IGG, Via V. Caluso, 35 – 10125 Torino.

Most of the Messinian sediments of the Tertiary Piedmont Basin (TPB) consit of a chaotic interval (recently named “Complesso Caotico della Valle Versa = CTV) that rests, through the Intramessinian unconformity, on marine sediments RANGING in age from the Oligocene to the Early Messinian and is followed, again unconformably, by Upper Messinian “Lago Mare” facies or directly by Lower Pliocene marine sediments. The main components of the CTV are huge blocks of gypsum and of evaporitic vuggy carbonates. However, blocks of strongly cemented CH4-derived carbonates are locally common and have suggested the possibile role of methane –rich fluid circulation and related shale diapirism in the genesis of the CTV. New data collected in the eastern part of the TPB, close to the Villalvernia-Varzi Line, confirm the relationships between chaotic deposits and CH4 - derived carbonates. In this area, CH4 - derived carbonate masses have been recently discovered in the CTV. They consist of strongly cemented mud breccias containing remains of chemosymbiotic organisms, both Lucinid bivalves and Vestimentiferan (?) tube worms. Moreover, cylindrical carbonate concretions have been recognised in the S. Agata Fossili Marls, about ten meters below the base of the CTV. The maximum length of the concretions is 80 cm whereas their diameter ranges from 5 to 10 cm. A roughly cylindrical axial portion, clearly distinghishable from the main body and generally reaching 1 cm across, is recognisable in all the concretions. Preliminary isotopic data indicate that these concretions are strongly 13C depleted (d13 C = -33,21 ‰ PDB), providing a compelling evidence that carbonate precipitation was driven by bacterial degradation of methane. Moreover, the positive d18 O values (+ 5,85 ‰ PDB) suggests that methane could be sourced from gas hydrate dissociation. Strikingly similar cylindrical concretions have been recognised in present day sites of shale diaprism and methane - rich fluid venting at the sea floor (e.g. Orpin, 1997; Diaz del Rio et al., 2003), and they have been interpreted as carbonate cemented fluid conduits originated below the sediment-water interface. In the fossil record, an identical association between cylindrical carbonate concretions and chaotic deposits has been recently described in Monferrato and interpreted as the record of the activity of a mud volcano (Clari et al., 2004). Two main conclusion can be drawn from these new findings: 1) methane- derived carbonates can be generated within the sedimentary column, below the sea floor. In this case they lack chemosymbiotic organism remains that are usually the most attractive evidence of a CH4 - related genesis; 2) the strict relationship between methane-derived carbonates and chaotic deposits is again confirmed and imposes to take into consideration a genetic linkage among sedimentary instability, fluid venting and shale diapirism in the interpretation of the Messinian chaotic deposits of the TPB.

References

Clari P. et al. (2004), Journal of Sedimentary Research, 74, 662-676. Diaz del Rio V. et al. (2003), Marine Geology, 195, 177-203 Orpin A.R. (1997), Marine Geology, 138, 51-67.

52 A simple three layers model for the behaviour of a turbidity current as a function of the Richardson number: sedimentological implication

FALCINI F.1, MILLI S.1, MOSCATELLI M.2, SALUSTI E.3 & STANZIONE O.1

1 - Dipartimento di Scienze della Terra, University of Rome “La Sapienza”, P.le Aldo Moro 2, 00185 Rome, Italy. 2 - Istituto di Geologia Ambientale e Geoingegneria (IGAG)-CNR, P.le A. Moro, 5, 00185 Rome, Italy. 3 - Dipartimento di Fisica – INFN – University of Rome “La Sapienza”, P.le Aldo Moro 2, 00185 Rome, Italy.

In this study, experimental data, analytical and numerical results about turbidity current are analysed and compared with field observation. This approach tentatively provides a simple scheme of the behaviour of a turbidity current flowing down of constant slope. The main features of the turbidity currents that appear from our analysis are: i) where available material is present, the erosive power due to the turbulence generated by the high shear stress in the basal layer between the bottom and the turbidity current; ii) the entrainment at the leading edge of the current, which may generate a turbulent diluite cloud over the turbidity current; iii) the laminar behaviour in the central layer of the current (namely the main part of the flow) which is able to transport the sediments. In order to provide a simple analytical model which takes into account the main characteristics above described, a three layer model for a turbidity current is here presented. The behaviour of the three layers is represented as a function of the Richardson number Ri. For each of the current layer one can analyse whether Ri >>1 or not. So, in the upper layer, the low gradient of the density, due to the entrainment (i.e. turbulent mixing) between the turbidity current and the environment water, yields Ri<<1. A turbulent flow occurs, where no horizontal transport of sediments is present (i.e. mean kinetic energy less than turbulent kinetic energy). In the middle layer Ri>>1 because of the high gradient of the density (namely high stratification) and the lack of velocity shear. In this layer the transport of sediment occurs. The behaviour of the basal layer is more complex. This layer is able to erode or deposit sediments on the sea bed, depending to the environment parameters (i.e. available particulate, grain size of sediments, slope of the bottom) and the value of velocity and concentration of the turbidity current (Parker, 1982). So, if the velocity shear (due to the bottom stress) is greater than the stratification (i.e. Ri<1) then the erosion of available sediments can occur. When the concentration of sediments contrasts the turbulence in the basal layer, Ri becomes ≈1 and erosion equals deposition. Finally, under condition of severe density gradient (i.e. high stratification), damping of the turbulence (i.e. Ri>1) may cause a net loss of sediments, as usually happens during the deceleration of the current over a flat bottom. The sedimentological implications due to the analysis above described take into consideration the flow condition during the depositional processes. From the model, it is important to note that loss of sediments in the basal layer occurs in laminar condition (Ri>1). So, turbiditic “massive” sandstones formation may be formed by a rapid temporal vertical aggradation of sediments during flow (in same cases probably due to a topography control), rather than by en masse deposition at the cessation of the flow. The presence of a crude lamination found in many turbiditic sandstones, bed originally interpreted as massive, observed into the Laga basin (Central Apennine), seem to confirm these results. Consequently, the thickness of the recorded deposits are linked to the deposition duration time of the sustained turbidity current rather than the height of the current itself.

53 L’alluvione tardo medioevale di Rubiera (Provincia di Reggio Emilia)

FIORONI C.1 & BERTOLINI G.2

1 - Università degli studi di Modena e Reggio Emilia, Largo S.Eufemia, 19, Modena, chiarafi@ unimore.it. 2 - Regione Emilia-Romagna, Servizio Tecnico dei Bacini Enza, Secchia e Panaro, Via Emilia S. Stefano, 25, Reggio Emilia

L’affioramento di Rubiera

Nel corso dell’anno 2003 il locale Servizio Tecnico di Bacino (Regione Emilia- Romagna) mise mano alla manutenzione straordinaria dell’alveo del Torrente Tresinaro nel tratto che scorre da Scandiano sino alla confluenza nel Fiume Secchia a valle di Rubiera. Si tratta di un canale artificiale pressoché rettilineo, esistente sin dal XIII sec. d.C., quando venne deviato verso Est già dal suo sbocco in pianura. I lavori comportarono scavi sui fianchi per l’allargamento del canale, portando all’affioramento del substrato sedimentario per sette metri di spessore, nel tratto tra Corticella e Rubiera. L’affiorare dei sedimenti fu temporaneo: già dopo pochi mesi la vegetazione riparia ed il suolo argilloso riportato artificialmente sulle rive erano tornati a nascondere completamente il substrato. Non prima però che fosse possibile raccogliere dati e fotografie che permisero interessanti deduzioni sull’evoluzione tardomedioevale di questa parte di pianura reggiano-modenese.

Stratigrafia

Lo scavo, presso il ponte in muratura di Rubiera, portò alla luce uno spessore di circa sei-sette metri di sedimenti di origine alluvionale, al di sotto dei quali affiorò il substrato romano di argille brune compatte, riconoscibile per la presenza di un manufatto in sasso e laterizi di grandi dimensioni (ancora esistente e visibile nell’alveo del torrente) e di resti di una probabile “domus rustica” (SOCIETÀ REGGIANA D’ARCHEOLOGIA, comunicazione personale). Il medesimo strato aveva restituito già in precedenza una piccola necropoli della fine I Sec-inizio II Sec d.C. con diverse tombe cinerarie e ad inumazione, portate alla luce da circa 4 metri di profondità sul fondo della cava per argille da ceramica posta circa cinquecento metri più a SW (siti 12 e 13 nella Carta Archeologica della Provincia di Reggio Emilia, PATRONCINI L. et Al, 1984; LASAGNA PATRONCINI e IORI, 1978, cfr anche “GAZZETTA DI REGGIO”, 28 Giugno 1971). Nel “nuovo” affioramento sul canale del Tresinaro, lo “strato romano” è sepolto da una lente di ghiaie di spessore sino a 2,5 metri. Tale lente affiora per una lunghezza di almeno 400 metri lungo entrambe le ripe del canale. Entro le ghiaie sono stati rinvenuti una grande quantità di resti di laterizi fluitati,in parte arrotondati, tra cui molte tegole e vasellame. Lo strato si interdigita con sottili livelli sabbiosi e mostra una rapida “fining upward”, passando verso l’alto a sabbie (per uno spessore minimo di circa due metri) e poi ai terreni di riporto degli argini del canale, che si elevano di circa mezzo metro sul piano campagna circostante.

L’alluvione di Rubiera - Mutina?

Lo strato ghiaioso rappresenta un evento alluvionale di carattere evidentemente “catastrofico” dovuto al vicino Fiume Secchia, che scorre a solo un chilometro di distanza. Con buona probabilità, si può ipotizzare che l’evento ghiaioso sia effetto di una rotta degli argini naturali del Secchia, il cui ventaglio alluvionò l’area posta in sinistra idraulica. Il rinvenimento di un grande numero di tronchi di albero coricati e sepolti sotto 5 metri di sabbie e limi nelle cave Elsa (periferia Nord di Rubiera, 2 km a NW rispetto al sito qui trattato, cfr. TIRABASSI, 1980) concorda con una tale ipotesi. La datazione di tre alberi, pubblicata in

54 ALESSIO et Al. (1981) fornisce un’età radiocarbonica –non calibrata- di 1460 +/- 50, 1350 +/- 50 e 1500 +/- 50 anni BP. Gli stessi autori attestano la presenza, nelle cave Elsa, di gran numero di “frammenti di cotto, tegole… e frammenti ceramici di età genericamente romana”. Risulta quindi estremamente probabile una correlazione fisica e cronologica tra i due rinvenimenti. E’ evidente anche la correlabilità cronologica con il seppellimento della Mutina romana (cfr. CREMASCHI E GASPERI, 1989)

Contesto climatico: l’alto medioevo

A quali eventi climatici dobbiamo imputare l’esistenza di un così vasto ventaglio di rotta quale risulterebbe dalla nostra ricostruzione? Occorre risalire a ritroso nella storia climatica di parecchi secoli, sino al periodo di deterioramento climatico che si protrasse dal 500 sino al 750 d.C., noto come “Piccola Età Glaciale Altomedioevale” (ORTOLANI E PAGLIUCA, 1998). In quel periodo grandi piene si succedettero con frequenza, causando un innalzamento degli alvei fluviali di diversi metri sul precedente piano campagna, mentre in pianura si depositavano nuovi strati di limi e di argille. Una gran serie di manufatti di epoca romana (ponti, strade, necropoli, etc), vennero sepolti dai sedimenti alluvionali. L’insediamento romano di Mutina (Modena) rimase abbandonato per quasi tutto il VI sec. D.C., anche perchè sepolto da alcuni metri di sedimenti depositati da quella che viene detta l’«Alluvione di Modena» (CREMASCHI E GASPERI, 1989). Esiste una folta bibliografia di eventi coevi ed analoghi nel Veronese (PAOLO DIACONO, Historia Longobardorum), nel Cesenate e Forlivese (VEGGIANI, 1973, 1958), nel Riminese presso S.Vito e a Ravenna (VEGGIANI, 1973). Le evidenze di campagna e le datazioni assolute suggeriscono la possibilità di attribuire il seppellimento del piano romano ad un singolo evento catastrofico o a pochi eventi concentrati in breve tempo, forse riconducibili all’alluvione che interessò tutta la nostra penisola verso la fine del VI Sec. D.C. Ricordiamo che proprio in quel periodo si situa il noto “Diluvium”, attribuito all’anno 589 d.C. e raccontato nella sua drammaticità da Paolo Diacono nella “Historia Longobardorum”. Lo spessore dei sedimenti alluvionali tende a ridursi a zero proseguendo verso N, come dimostra il ritrovamento della Domus Rustica di “Lograzzo”- Ergastulum (all’altezza dell’autostrada) a solo 2 metri di profondità (FERRABOSCHI, 1954).

Conclusioni

Le evidenze stratigrafiche qui per la prima volta osservate e descritte, confrontate con quelle presenti in bibliografia, conducono al riconoscimento di un evento alluvionale di carattere “catastrofico” che seppellì l’area di Rubiera nell’alto medioevo. Tale evento trova una certa correlazione anche con l’evento del seppellimento della Mutina romana e probabilmente con quello citato da Paolo Diacono (Diluvium) nel 589. Si tratterebbe quindi di un grande evento alluvionale, di intensità mai più raggiunta nei successivi anni sino ai nostri giorni.

Opere citate

Alessio M., Allegri L., Bella F., Calderoni G., Cortesi C., Cremaschi M., Improta S., Papani G. e Petrone V. (1981) – Le datazioni C14 della pianura tardowurmiana ed olocenica nell’Emilia occidentale. Contr. Prel. Realizzazione Carta Neotettonica d’Italia, P.F. Geodinamica, 356. Roma. Cremaschi M. e Gasperi G. (1989) – L’Alluvione alto-medioevale di Mutina (Modena) in rapporto alle variazioni ambientali oloceniche. Mem. Soc. Geol. It. 42, pp 179-190. Diacono Paolo (traduzione a cura di F.Ronconi, 1971) – Historia Longobardorum (De Gestis Longobardorum) Vol. III, sez 23 e 24, Ed Rusconi, Roma. Ferraboschi P. (1954) – Le origini del “Fundus Erbaria”. Ritrovata una villa romana. In: La Libertà, Reggio E., 2 Maggio 1954. Lasagna Patroncini C. e Iori C. (1978) – Un’altra piccola necropoli a Corticella di Rubiera. In Quaderni di Archeologia Reggiana, 3/77, Reggio E.

55 Ortolani F. & Pagliuca S. (1997) – Evidenze geologiche di cicliche variazioni climatiche e modificazioni dell’ambiente fisico tipo “Effetto Serra” durante il periodo storico nell’area mediterranea. In: 1° Forum Italiano di Scienze della Terra. Bellaria, 5-9 Ottobre 1997. Patroncini L. (a cura di-1984) Carta Archeologica della Provincia di Reggio Emilia. Amministrazione Provinciale di Reggio Emilia – Società Reggiana d’Archeologia, Edita da stamperia Amm. Prov. Di Reggio Emilia. Tirabassi J. (1980) – Notizie geologiche ed archeologiche. In: “Storia Popolare di Rio Saliceto”, Reggio E. Veggiani A. (1958) – Cesena. Necropoli Romana sotto i depositi alluvionali. Accad.Naz. Lincei. Notizie degli scavi, 12, ser.8 (1-2). Veggiani M. (1973) -“Prove e considerazioni su due periodi di dissesti idrogeologici nella Pianura Padana”. Atti del 3° Convegno Nazionale di Studi sui problemi della Geologia Applicata, Firenze

56 Ricostruzione paleoambientale ed evoluzione stratigrafico- sequenziale della fascia costiera pliocenica compresa tra le foci del Paleo-Farfa e del Paleo-Corese (Sabina, Italia centrale)

FUBELLI G.1, CIPOLLARI P.1, COSENTINO D.1, FARANDA C.1, GLIOZZI E.1, LIGIOS S.1, PASQUALI V.1 & SMEDILE A.2

1 - Dipartimento di Scienze Geologiche, Università degli Studi Roma Tre 2 - Dipartimento di Scienze Geologiche, Università degli Studi di Catania

I recenti lavori eseguiti in ambito CARG per il rilevamento dei fogli 357-Cittaducale e 366-Palombara Sabina, della nuova cartografia geologica alla scala 1:50.000, ha permesso di raccogliere numerosi nuovi dati di superficie in settori in cui è da tempo nota la transizione tra facies continentali di piana alluvionale e le coeve facies marine costiere, legate, quest’ultime, alla trasgressione del Mar Tirreno che durante l’intervallo pliocenico ha interessato tutta l’area della Campagna Romana. In particolare, i risultati che vengono presentati in questo lavoro riguardano il settore compreso tra i paesi di Montopoli di Sabina e Montelibretti, a NE di Roma. Nella stessa area, una campagna di perforazioni effettuata per conto dell’Italferr S.p.A., a supporto del progetto esecutivo per la realizzazione della nuova linea ferroviaria regionale Passo Corese – Rieti, ha messo a disposizione, recentemente, un discreto numero di dati di sottosuolo, che unitamente ai dati di superficie consentono di ricostruire, con un certo dettaglio, l’evoluzione paleoambientale della fascia costiera pliocenica a ridosso dell’Appennino sabino. Le analisi paleoambientali sono state effettuate su campionature areali, in superficie, e campionature lineari, in sottosuolo, analizzando le associazioni a foraminiferi, nannofossili calcarei, ostracodi e molluschi. In particolare, le analisi effettuate su tre sondaggi (ARI1LGT16, ARI1LGT19 e ERI1LGT18), ubicati nella fascia di transizione, hanno consentito di evidenziare variazioni cicliche da ambienti marini litorali ad ambienti francamente dulcicoli, passando attraverso ambientazioni marino-marginali/salmastre. Le associazioni ad ostracodi marini risultano dominate da Loxoconcha diademata (91 % dell’associazione) e contengono, inoltre, Leptocythere aegea, Palmoconcha turbida e Xestoleberis dispar. Tali associazioni sono indicative di ambienti marini infralitorali. Le associazioni dominate da Cyprideis torosa indicano la presenza di acque salmastre, mentre quelle dominate dalle Candoninae [Pseudocandona marchica vel rostrata, Fabaeformiscandona fabaeformis, Candona (Neglecandona) neglecta] sono caratteristiche di specchi d’acqua francamente dulcicoli. La successione verticale di tali associazioni, unitamente alle caratteristiche sedimentologiche delle litofacies che le contengono, consentono di riconoscere almeno due cicli trasgressivo/regressivi, l’ultimo dei quali è stato responsabile dello spostamento verso mare della linea di costa, con il definitivo abbandono dell’ambiente francamente marino dal settore in esame. I rapporti laterali tra le facies, ricostruibili a partire dai dati di superficie, integrati con quelli di sottosuolo, mostrano situazioni riconducibili a sistemi deltizi, in cui migrazioni laterali di barre sabbiose determinano lo sviluppo di lagune costiere salmastre e/o specchi d’acqua francamente dulcicoli. Le analisi svolte nell’area in esame hanno consentito di individuare, attraverso il riconoscimento dei rispettivi apparati deltizi, la foce di due corsi d’acqua (il Paleo-Farfa e il Paleo-Corese) che nel Pliocene superiore interagivano con il sistema marino costiero del Mar Tirreno, attestato con la sua linea di riva sul versante occidentale dei Monti Sabini, all’attuale quota di circa 275 m s.l.m.

57 Indication of seafloor instabilty in the upper part of the Marnoso- arenacea Formation of the Sintria, Lamone and Marzeno Valleys

GAMBERI F.

ISMAR Sezione Geologia Marina Bologna

In the upper stratigraphic level of the Marnoso-arenacea Formation, of late Tortonian age, evidences of seafloor instabilities have been reported from the Santerno (Roveri et al. 2003) and from the Savio valleys (Ricci lucchi & D’Onofrio 1967, Lucente et al. 2002). The growth of a thrust related antlicine has been recently interpreted to be responsible for the seafloor gravitational deformation and for the emplacement of late Tortonian chaotic slump bodies with a thickness up to 300 m (Roveri et al. 2003). The same tectonic structure is present in the Sintria, Lamone and Marzeno valley, though no indications of seafloor instability have been reported. However, in the Lamone valley, few tens of meters below the base of the Gessoso- solfifera Formation, the upper part of the Marnoso-arenacea Formation is highly deformed. Deformation includes coherently rotated blocks up to 10 m large and 5 m thick sandwiched between subvertical faults, sheared sandstone beds and occasionally homogenized beds. Since the base and the top of the deformed interval are not exposed, a minimum thickness for the deformed unit can be estimated from the width of the exposure to be in the order of 10 m. In addition, since the two outcrops are spaced at about 500 m a similar minimum areal extent for the deformed unit can be advanced. At approximately the same stratigraphic level, in the Marzeno and Sintria valley, m-thick intervals with deformed, boudinaged and folded sandstone beds are found. In addition, in the same areas, mud clast laden debris flow deposits with an highly dishomogeneuos sandy to muddy matrix are also found. The new findings indicate that beside the Santerno and Savio Valleys, seafloor instability affected the Sintria to Marzeno valley sector of the Marnoso-arenacea Basin during the late Tortonian. In addition, they show that the style of seafloor deformation was both ductile and brittle generating respectively homogenized layers and debris flow deposits and relatively larger scale mass transport deposits consisting of choerent displaced blocks.

References

Lucente, C. C., Manzi, V., Ricci Lucchi, F., Roveri, M., 2002. Did the Ligurian sheet cover the whole thrust belt in Tuscany and Romagna Appennines? Some evidence from gravity emplaced deposits. Memorie della Società Geologica Italiana, Volume Speciale n. 1, 393–398. Ricci Lucchi F., D’Onofrio S., 1967. Trasporti gravitativi sinsedimentari nel Tortoniano dell’Appennino romagnolo (Valle del Savio). Giornale di Geologia, s. 2, 34, 1-44. Roveri M, Manzi V., Ricci Lucchi F., Rogledi S., 2003. Sedimentary and tectonic evolution of the Vena del Gesso basin (Northern Apennines, Italy): Implications for the onset of the Messinian salinity crisis. Geological Society of America Bulletin, 115, 387–405.

58 The impact of margin shaping processes on the architecture of deep-sea depositional systems: the Sicilian and Sardinian margins (Tyrrhenian Sea)

GAMBERI F. & DALLA VALLE G.

ISMAR, Sezione Istituto Geologia Marina di Bologna.

Multibeam bathymetric data, providing the details of the seafloor geomorphology, are influential for expanding our knowledge on deep-sea depositional systems. As a matter of fact, the recent extensive acquisition of multibeam data has shown that a higher variability in the style of deep-sea deposition along continental margins occurs than was previously thought. In particular, multibeam data have greatly contributed to enhancing our perception of the wide range of architecture and of component geomorphic elements that characterise present-day depositional systems along different stretches of continental margins. Moreover, the possibility of a direct study of the land and shallow water areas can lead to the establishment of a straightforward link between the processes acting in the source and transfer areas and the geometry of the observed deep-sea depositional systems. Such a study has been carried out on two portions of the Tyrrhenian Sea margin where multibeam bathymetric data have been recently collected. The Tyrrhenian Sea, located in the Mediterranean Basin, is enclosed by the islands of Sardinia and Corsica to the west, by the Italian peninsula to the east and Sicily to the south. The setting of Tyrrhenian region is the result of a complex recent geological history, characterised by the interplay of compression and orogenic processes and extension, arc volcanism and back-arc basin opening. As a consequence, the single margins of the Tyrrhenian Sea present highly variable geological features. In particular, since extensional tectonics has migrated with time toward the E-SE, a remarkably contrasting present-day geological setting characterises the Sardinian and Sicilian margins, located respectively to the west and to the south-southeast of the Tyrrhenian sea. In Sicily, extensional tectonics is still active and dissects the Maghrebian chain in a series of horsts and grabens, both perpendicular and parallel to the margin with high differential vertical movements and an uplift rate as high as 1 mm/year. A network of parallel, intermittent discharge rivers with small drainage basins develops; rivers run perpendicular to the margin in the tectonically depressed areas and enter the coastal region at intervals of less than 10 km. In addition, along the whole northeastern Sicilian margin, the shelf is always very narrow. On the slope, canyons face most of the river entry points; in general, the canyons are followed downslope by leveed channels. At the base-of-slope an apron consisting of laterally coalescing deposits of leveed channels is formed. However, in the eastern portion of the northern Sicilian margins, where the rivers have very small drainage basins and the rate of uplift is higher, a destructional apron consisting of a large mass wasting complex is developed. The eastern Sardinian margin, on the contrary, is a passive margin where extensional tectonics has been quiescent since the Early Pliocene, and is in general characterised by a negligible rate of uplift. Rivers have larger drainage basins than in the Sicilian margin and their feeding points to the coastal system are widely spaced at around 30 km. Furthermore, a wide shelf is present along the whole eastern Sardinian margin and in the northern area reaches a width of around 20 km. On the slope, the major canyons, being connected with the river entry points are widely spaced. Therefore, at the base-of-slope they feed isolated depositional bodies in the form of a series of small, radial or elongated fans developed at the mouth of the canyons. Large canyons also develop in the central part of the Sardinian margin where there are no large rivers; here they are likely due to slope instability following the uplift of the region because of recent volcanic activity. A strict application of the sequence stratigraphy models, would lead one to interpret the small fans of the Sardinian margin and the slope apron of the Sicilian one as representing deposition during different stands of sea level. On the contrary, the study shows

59 that the differences in the present-day Sicilian and Sardinian depositional systems are mainly due to the features of the sediment delivery systems developed in the two margins. Thus, the research shows that the distinct setting of each margin is a primary factor in controlling the architecture of the depositional systems and that it must be considered when predictive models for the distribution of deep-sea deposits are applied.

60 Carbonate hardground formation in the volcanic seamounts of the Tyrrhenian Sea

GAMBERI F.& MARANI M.

ISMAR Sezione Geologia Marina Bologna

Recent seafloor sampling campaigns have been carried out in the Vavilov and Marsili volcanic seamounts in the Tyrrhenian sea. Many samples of carbonate crusts have been recovered and a variety of types have been described. The first type of carbonate crust displays a smooth upper surface, inferred to be exposed at the seafloor due to the presence of encrustant organisms, and of a pervasive black Fe-Mn oxides coating; the lower surface is rough and no variations in the crust hardness are appreciable from the top surface toward the base. The carbonate crust is mainly composed of small bivalve, gasteropod and pteropod shells within a fine grained matrix mainly consisting of foraminifer tests. Boring is intense with vertical traces, up to few centimeters in diameter, that cut the whole crust. In section, the colour is dull brown with small scale bioturbations evidenced by black stainings and thin lineations. Horizontal traces, with length up to 10 cm and diameter of 2 cm, sometimes filled by an unconsolidated carbonate ooze, also occur along the lower surface of the crust. A second type of carbonate crust has an hard upper surface but its lower surface is not sharp and rather displays a transition between slightly cemented to soft foraminiferal ooze. We also recovered thin, ca 2 cm-thick, hard carbonate crusts, with sharp and tabular upper and lower surfaces and abundant bioturbation. These crusts do not present broken margins and have circular or ellipsoidal shapes with dimension up to 15x10 cm. These samples are interpreted as carbonate nodules forming within unconsolidated sediments in response to localized lithification at or below the seafloor. A fourth type of carbonate crust consists of a framework of corals and serpulids cemented by a carbonate matrix. Submarine carbonate lithification is a widespread phenomenon occurring on the Vavilov and Marsili Seamount, as documented by the ubiquitous presence of carbonate crusts. All the samples have been interpreted as representing different stages of hardground formation under sediment-starved conditions. Lithification occurring at or below the seafloor takes place under varying conditions leading to the formation of nodules, hardgrounds, and framework crust. A progression from nodule formation within unconsolidated sediments to thick hardground crusts, growing from the seafloor downward and resulting in a pavement at the seafloor is envisaged. Once the seafloor is lithified or where volcanic rocks crop out, corals can grow on the hard substratum and build cemented framework crusts. These findings confirm that lithified carbonate crusts are frequent in areas characterized by sediment-starved conditions, as already recognized in the Mediterranean Sea.

61 Holocene biostratigraphy and evidences of paleoenvironmental modifications in the Black Sea based on coccolithophorids

GIUNTA S.1, MORIGI C.1, NEGRI A. 1, GUICHARD F. 2 & LERICOLAIS G.3

1 - Dipartimento di Scienze del Mare, Università Politecnica delle Marche, 60131 Ancona, Italia 2 - LSCE, CNRS-CEA, Gif-sur-Yvette, France 3 - IFREMER, Centre de Brest, France

In the framework of the EU ASSEMBLAGE project (EVK3–CT-2002-00090), we conducted a detailed analytical micropaleontological work on four piston cores collected during the BLASON 2 cruise (B2 KS02, B2 KS24, B2 KS38, B2 KS33) and four piston cores collected during the ASSEMBLAGE 1 cruise (MD04 2754, MD04 2762, MD04 2770, MD04 2773), with the aim to investigate the Late Quaternary evolution of the Black Sea. The analyses performed on the coccolithophorids content of 270 samples aimed to refine biostratigraphy and explore the paleoenvironmental modifications that occurred in the Black Sea during the Holocene. The coccolithophorid analyses evidenced three intervals recognizable in all the studied cores, either collected in the basin or in the shelf, respectively characterized from the older to the younger by the spotty occurrence, the presence and the acme of Emiliania huxleyi. Moreover, in the older unit we observed the absence of the species Braarudosphaera bigelowii. This species is, on the contrary, occurring in the two younger units. The co- occurrence of these two marine species suggests a shift from fresh-brackish water to low- salinity marine conditions of the Black Sea. The spotty rare occurrence of E. huxleyi in the lower unit is an important feature never observed before. This could suggest two hypotheses: the presence of reworked specimens from Eemian outcrops, or the presence of low salinity waters also during the “lacustrine” phase of the basin. Another feature recognized in almost all the cores is the presence of a multi lamina aragonite level, always recorded in the upper part of the Ecozone 3 and thus useful for basin wide correlations. The parallel study of water samples and superficial sediment assemblages evidenced the presence of Syracosphaera lamina in the superficial water samples whereas this delicate form is not present in the sediments, suggesting dissolution through the water column. On the other hand the occurrence of B. bigelowii, in all cores, but its nearly absence in water and in recent sediment samples, suggests a change in the water condition during recent time.

62 Organic markers as indicators of the depositional conditions of the Messinian Calcare di Base formation (Rossano Basin, Northern Calabria, Italy)

GUIDO A.1, GAUTRET P.2, JACOB J.2, LAGGOUN-DEFARGE F.2, MASTANDREA A.1 & RUSSO F.1

1 - Dipartimento di Scienze della Terra, Università della Calabria, Via Bucci Cubo 15b I-87036 Rende (CS) - Italy 2 - ISTO, UMR 6113 - Université d’Orléans, Bâtiment Géosciences, BP 6759, F 45067 ORLÉANS Cedex 2 - France

A study with a multidisciplinary approach has been carried out on the Messinian Calcare di Base formation cropping out in the Northern Calabria. This research, developped through sedimentological, organic petrography and geochemistry analyses (palynofacies, Rock-Eval pyrolysis and Gas Chromatography/Mass Spectrometry analyses), aims at understanding the depositional conditions of these peculiar carbonate sediments, up to now interpreted as evaporitic limestone. Thin section observations put in evidence that carbonates of Calcare di Base are characterized mainly by peloidal microfacies and the absence of metazoan skeletons. Darkish peloids, cylindrical or subcylindrical in shape, are organized in clusters and dispersed in a lighter matrix (aragonite). The shape, mineralogical composition, dimensions and context suggest that some peloids can be interpreted as fecal pellets of unknown organisms. SEM observations at high magnification revealed two types of fecal pellets: those containing mainly silicoclastic particles and those with moulds of coccolithophorids but without relevant terrigenous component. We attribute the origin of coprolites with the terrigenous component to deposit feeders or grazers organisms and those with coccolithophorids to suspension-feeders or planktonic organisms. The Calcare di Base shows other two less common microfacies: i) detrital, sometimes bioturbated with very finely graded laminae, and ii) stromatolitic microbialites, with planar or more commonly gently ondulated fine lamination. A bright UV-epifluorescence indicates a high content of organic matter in both peloids and stromatolitic microfacies. Geochemical data (Rock-Eval pyrolysis) indicate a mixed (marine and continental) organic input. These data have been confirmed by organic petrographic observations with the presence of phytoclasts, amorphous organic matter, and variable proportions of zooclasts, pollens, spores and phytoplanktonic remains. The good preservation state of organic matter is highly favourable for studying the biochemistry of lipidic compounds. The detection of biomarkers, which provides the molecular signature of microscopically non- identifiable (non-preserved) organisms, revealed a reasonable biotic diversification in the depositional paleoenvironment. Organic geochemistry and petrography data suggest that the depositional environment became more and more restricted, allowing the survival of organisms adapted to stressed conditions. The presence of well preserved and bright-fluorescent spores and pollens indicate that these elements did not undergo degradation and oxidation, suggesting a sedimentary environment characterized by a stratified water column with periodic bottom dysoxic conditions.

63 Prime considerazioni sugli apporti calcareo-clastici provenienti dall’Avampaese apulo nei “Depositi marini terrazzati” del bacino idrografico del Fiume Lato (Puglia)

LABRIOLA M., TROPEANO M., MORETTI M. , PIERI P. & SABATO L.

Dipartimento di Geologia e Geofisica, Università di Bari

L’area oggetto di studio è costituita dalla porzione meridionale del bacino idrografico del Fiume Lato in Puglia. Tale area ricade lungo il margine esterno della Fossa bradanica, a cavallo fra le Murge, localmente rappresentate dall’Horst di Matera e dalla loro prosecuzione verso est (Murge di Laterza, Castellaneta), e l’avanfossa. L’evoluzione geologica plio-quaternaria di quest’area può essere sintetizzata come segue. Nel Pliocene i calcari mesozoici delle Murge, ribassati a gradinata verso W-SW, assumono il ruolo di avanfossa subsidente (Fossa bradanica). La successione del bordo murgiano del bacino bradanico è costituita dal basso verso l’alto dalla Calcarenite di Gravina che passa alle Argille subappennine. Questo tipo di sedimentazione era prodotta dalla subsidenza attiva in tutta l’area dal Pliocene superiore fino al Pleistocene inferiore. A partire dal Pleistocene medio, l’area è soggetta a sollevamento registrato stratigraficamente sia nella Fossa bradanica che nelle Murge dai “Depositi marini terrazzati” (Vezzani, 1967; Brückner, 1980). Tali depositi affiorano a partire dai dintorni di Pomarico (Mt) e Matera a circa 400-430 m s.l.m., sono deposti a quote sempre più basse fino a raggiungere pochi metri sul livello del mare lungo la costa ionica, e sono datati dal Pleistocene medio al Tirreniano (Cotecchia et al., 1969). Inoltre il sollevamento quaternario delle Murge è testimoniato dalla presenza di paleofalesie e piattaforme di abrasione nei calcari mesozoici posti a partire da circa 450 m s.l.m., fino a pochi metri sul livello del mare (Ciaranfi et al., 1994) e dalle profonde incisioni che alcuni corsi d’acqua hanno prodotto nei calcari mesozoici (i canyons chiamati “gravine”). Al fine di riconoscere l’evoluzione dell’area del bacino idrografico del Fiume Lato durante il sollevamento, è in atto uno studio dei più elevati “Depositi marini terrazzati” che si addossano ai calcari di avampaese. In particolare questi depositi sono posti a circa 70 m s.l.m. e corrispondono all’ordine di terrazzo T4/5 di Brückner (1980). Dallo studio preliminare di alcune sezioni stratigrafiche è possibile osservare, dal basso verso l’alto, facies marine e, in erosione sulle precedenti, facies continentali. Mentre le facies marine sono caratterizzate da conglomerati polimittici in assetto tabulare costituiti da ciottoli ben selezionati e arrotondati, e di dimensioni comprese tra 1 e 5 cm., le facies continentali sono contraddistinte da conglomerati oligomittici disorganizzati, massivi, i cui ciottoli presentano forma e dimensione variabile (da 1 a 15 cm). La natura litologica quasi esclusivamente calcarea dei ciottoli delle facies continentali lega geneticamente questi depositi all’attivazione del reticolo idrografico murgiano. Va ricordato che situazioni simili si registrano nei pressi di Matera e più a nord lungo il bordo occidentale delle Murge Alte. I dati preliminari indicano che il reticolo idrografico nell’area studiata e, più in generale, delle Murge si sia attivato in tempi successivi alle fasi iniziali di sollevamento dell’avampaese o per una risposta tardiva al fenomeno o a cause di variazioni nel tasso di sollevamento.

64 Segnali di controllo climatico sulla composizione dei depositi sabbiosi della pianura modenese: dati preliminari.

MARCHETTI DORI S., LUGLI S. & FONTANA D.

Dipartimento di Scienze della Terra, Università degli Studi di Modena e Reggio Emilia, Modena. [email protected], [email protected], [email protected]

Introduzione

Lo studio è incentrato sull’analisi composizionale dei depositi sabbiosi presenti nei primi 20 metri del sottosuolo della pianura modenese. La successione sedimentaria indagata copre l’arco temporale tardo pleistocenico e olocenico, e corrisponde all’ultima sequenza deposizionale trasgressivo regressiva (Gasperi et al, in stampa). Gli studi composizionali sono utili strumenti per la ricostruzione della storia sedimentaria di un bacino in funzione dei fattori climatici-fisiografici che controllano la produzione di sedimento, il trasporto e la deposizione (Basu, 1985; Critelli et al., 1997; Weltje et al., 1998). Questi studi hanno un particolare significato in aree come la pianura modenese, dove i sedimenti fluviali hanno sepolto siti archeologici del Neolitico, dell’Età del Bronzo, dell’Età del Ferro, Romani e Longobardi. L’evoluzione degli insediamenti umani nel tempo può essere indagata in dettaglio attraverso ricostruzioni della paleogeografia della pianura eseguite principalmente attraverso studi stratigrafici (Gasperi et al, 1989; Gasperi et al, in stampa) e geomorfologici (Cardarelli et al, 2004; Panizza et al, 2004). La dinamica fluviale è documentata dalla fitta rete di paleoalvei individuabili con le classiche tecniche di rilevamento geomorfologico che permettono la ricostruzione degli antichi reticoli fluviali. Solo l’ultima fase dell’evoluzione della pianura può però essere investigata in questo modo. Gli studi composizionali possono estendere le nostre conoscenze dell’evoluzione sedimentaria nel record stratigrafico, purché la composizione dei sedimenti fluviali sia riconoscibile. L’individuazione di corpi sabbiosi sepolti e la loro caratterizzazione da un punto di vista di facies deposizionale può permettere la localizzazione di canali fluviali o corpi di rotta sepolti, coadiuvando la ricostruzione della paleoidrografia. Il buon controllo cronologico disponibile per le stratigrafie dell’area permette inoltre di investigare in dettaglio la variabilità composizionale nel tempo attraverso l’ultimo ciclo glaciale-interglaciale.

Metodi

Questo studio è stato condotto attraverso lo studio di 150 campioni di sabbia provenienti da diversi contesti della pianura modenese (Fig 1): a) sedimenti attuali dei corsi d’acqua presenti nell’area di studio (41 campioni); b) sedimenti antichi riferibili ai principali corsi d’acqua (Secchia, Panaro, Tiepido) databili all’Olocene o al Pleistocene Superiore (24 campioni); c) campioni da carote e scavi archeologici provenienti dall’area urbana di Modena, da Cittanova, da Fossalta, Formigine e Baggiovara (56 campioni); d) depositi provenienti dalle trivellazioni per la linea ferroviaria ad Alta Velocità (comuni di Campogalliano, Modena e Nonantola; 29 campioni). La frazione granulometrica 250-125 mm delle sabbie è stata sottoposta ad analisi modale utilizzando la tecnica del conteggio per punti di sezioni sottili al microscopio ottico secondo il metodo Gazzi-Dickinson (Gazzi, 1966; Dickinson, 1970; Zuffa, 1985). Sono stati conteggiati oltre 300 punti per ciascun campione.

Figura 1: Ubicazione dei campioni di sabbia studiati. Con il cerchio vuoto sono indicate le sabbie attuali prelevate in alveo, con il cerchio pieno le sabbie antiche prelevate in corrispondenza di scavi, con l’asterisco serie di campioni provenienti da carotaggi o scavi archeologici: *1) Scavo di Cittanova, *2) Scavo di Via Emilia; *3)Carotaggio del Sant’Agostino; *4) Carotaggio 18; *5) Carotaggio dell’Ex Questura; *6) Carotaggi di Via Prampolini; *7) Scavo di Via Cesana; *8) Scavo di Via Giordano; *10) Scavo di Fossalta; *11) Scavo di Baggiovara; *12) Sondaggio TAV: S13-S14; *13) Sondaggio TAV: P143-S72; *14) Sondaggio TAV: P181; *15) Sondaggio TAV: P190;*16) Sondaggio TAV: P216; *17) P24-27; *18) P44-45.

Risultati

La caratterizzazione composizionale dei depositi sabbiosi ha portato contributi per la ricostruzione dei meccanismi deposizionali che agiscono e hanno agito nella pianura modenese, in termini di meccanismi di produzione del sedimento, trasporto, sedimentazione e diagenesi. L’analisi condotta sui campioni di sabbia attuale dei fiumi e torrenti presenti nell’area di studio ha consentito di individuare petrofacies caratterizzanti e distintive per ciascun corso d’acqua. La composizione della sabbia di ogni corso d’acqua descrive infatti campi composizionali discreti (Fig.2A) direttamente legati ai litotipi drenati nel bacino. Le variazioni composizionali lungo il corso dei singoli fiumi hanno permesso di verificare gli effetti sulla composizione della sabbia dovuti a trasporto e riciclo di sedimenti precedentemente deposti. L’analisi di successioni stratigrafiche chiave ha consentito di indagare le variazioni composizionali nel tempo. I dati ottenuti hanno mostrato che la composizione delle sabbie dei principali fiumi modenesi non è variata in modo significativo negli ultimi 7 mila anni (Fig. 2B). Questo periodo è caratterizzato da condizioni climatiche interglaciali temperato-umide e da aggradazione colluviale nelle aree montane e pedemontane, con sviluppo di estese coperture vegetali e conseguente maggiore alterazione chimica. La stabilità nel segnale composizionale negli ultimi 7 ka offre una chiave di identificazione per risalire alla provenienza dei sedimenti alluvionali recenti che costituiscono il primo sottosuolo dell’area modenese, attraverso il confronto diretto con le sabbie attuali. In questo modo sono state ricostruite variazioni subite dalla rete di drenaggio e evidenziati gli effetti di condizionamento esercitati dall’ambiente fisico sulle attività umane. Il passaggio alle sabbie pleistoceniche più antiche di 15-18 ka (unità di Vignola) nelle sezioni stratigrafiche analizzate, registra una significativa variazione composizionale,

66 consistente in un maggior contenuto in quarzo e feldspati, compensato da un decremento in frammenti litici, prevalentemente carbonatici extrabacinali (Fig. 2C, 3, 4, 5).

Figura 2: Diagramma ternario che mette in relazione i parametri Q+F (quarzo +feldspati), L(frammenti litici afanitici), C(Carbonati totali extrabacinali) nei campioni studiati di sicura attribuzione ai corsi d’acqua modenesi. A) campioni attuali; b) campioni olocenici; c) campioni pleistocenici.

Le variazioni composizionali in questi depositi sabbiosi non sono riconducibili a cambiamenti della litologia del substrato, né ad effetti diagenetici. Poiché queste variazioni sono registrate, più o meno marcatamente, al passaggio al tetto dell’unità di Vignola in tutti i contesti stratigrafici studiati, si può ritenere che siano legate al cambiamento drastico delle condizioni climatiche. Le variazioni nella composizione sembrano riflettere segnali climatici

67 ad alta frequenza (cicli glaciali-interglaciali) causati da variazioni nel tipo di apporto sedimentario collegati a processi di alterazione chimica di minore intensità, conseguenti alle condizioni di forte denudamento e di erosione/movimentazione di detrito dell’ultimo glaciale. Altri fattori quali la maggiore solubilizzazione dei carbonati e la più intensa disgregazione dei frammenti litici nei singoli componenti a granulometria fine, causata dell’elevata energia degli agenti di trasporto, possono aver contribuito a determinare la composizione dei depositi pleistocenici.

Figura 3: Variazioni delle principali classi petrografiche in funzione della profondità per i campioni del Fiume Secchia (Cava Pederzona a Magreta).

Figura 4: Variazioni delle principali classi petrografiche in funzione della profondità per i campioni del Fiume Panaro(Cava di Via Macchioni a Spilamberto). In asse delle ordinate sono stati usati valori positivi di profondità al fine di rispettare gli effettivi rapporti stratigrafici fra campioni.

Figura 5: Variazioni composizionali delle principali classi petrografiche per i campioni del Torrente Tiepido nelle varie unità stratigrafiche.

68 Conclusioni

Lo studio composizionale dei depositi sabbiosi del sottosuolo modenese ha permesso di ottenere fondamentalmente due indicazioni: 1) assenza di variazioni significative del segnale composizionale riconducibile a sostanziale stabilità climatica dell’Olocene; le fluttuazioni climatiche ad altissima frequenza hanno prodotto periodi di intenso alluvionamento alternati a periodi di stabilità morfologica e deposizionale, caratterizzate dallo sviluppo degli insediamenti umani. Il confronto diretto fra sabbie attuali e le sabbie delle alluvioni che hanno sepolto attestazioni archeologiche può permettere ricostruzioni paleoidrografiche e una miglior comprensioni dei rapporti fra sviluppo di un sito e ambiente fisico; 2) variazioni composizionali rilevanti al passaggio fra ultimo glaciale e condizioni interglaciali oloceniche. Tali variazioni suggeriscono un controllo climatico sulla composizione e forniscono uno strumento per individuare la discontinuità che separa l’Unità di Vignola dal sovrastante Subsintema di Ravenna anche in aree di media e bassa pianura ove essa non è riconoscibile, a causa dell’assenza di suoli e di netto contrasto litologico e di facies deposizionali, legata a un contesto di sostanziale continuità di sedimentazione.

Note bibliografiche

Basu A. (1985) - Influence of climate and relief on compositions of sands released at source areas: G.G. Zuffa, Editor, Provenance of Arenites - NATO ASI series, D. Reidel Publishing Company, 148, 1–18. Cardarelli A., Cattani M., Labate D. & Pellegrini S. (2004)-Archeologia e Geomorfologia. Un approccio integrato applicato al territorio di Modena – in: “Atlante Storico Ambientale Urbano”, Comune di Modena, Ufficio Ricerche e Documentazione sulla Storia Urbana, 65-77. Critelli S., Arribas J., Le Pera E., Tortosa A., Marmaglia K.M. & Latter K.K. (2003) - The recycled orogenic sand provenance from an uplifted thrust belt, Betic Cordillera, southern Spain - Journal of Sedimentary Research ,73, 72–81. Dickinson W.R. (1970) - Interpreting detrital modes of graywacke and arkose - Journal of Sedimentary Petrology, 40, 695-707. Gasperi G., Bettelli G., Panini F. & Pizziolo M. e con contributi di Bonazzi U., Fioroni C. & Fregni P. (in stampa) - Note Illustrative alla Carta Geologica d' Italia a scala 1:50.000. Foglio N° 219 "Sassuolo" - Regione Emilia-Romagna – Servizio Geologico d’Italia. Gasperi G., Cremaschi M., Mantovani Uguzzoni M.P., Cardarelli A., Cattani M. & Labate D. (1989) - Evoluzione plio-quaternaria del margine appenninico modenese e dell'antistante pianura. Note illustrative alla carta geologica - Memorie Società Geologica Italiana, 39, 375-431. Gazzi P. (1966) - Le arenarie del flysh sopracretaceo dell’Appennino modenese; correlazioni con il Flysh di Monghidoro - Acta Mineralogico-Petrographica, 12, 69-97. Weltje G.J., Meijer X.D. & De Boer P.L (1998) - Stratigraphic inversion of siliciclastic basin fills: a note on the distinction between supply signals resulting from tectonic and climatic forcing: Basin Research, v. 10, p. 129–153. Panizza M., Castaldini D., Pellegrini M., Giusti C. & Piacentini, D. (2004)-Matrici geo-ambientali e sviluppo insediativo: un’ipotesi di ricerca – in: “Atlante Storico Ambientale Urbano”, Comune di Modena, Ufficio Ricerche e Documentazione sulla Storia Urbana, 31-62. Zuffa G.G. (1985) - Optical analyses of arenites: influence of methodology on compositional results – In: G.G. Zuffa Editor, Provenance of Arenites, NATO ASI series, D. Reidel Publishing Company, 148, 165-189.

69 Gas blowouts and outer shelf cracking features of northern North Atlantic ocean margins triggered by gas-hydrate melting due to ocean warming?

MIENERT J.1, GARCIA C. P.1, HAFLIDASON H.2, VANNESTE M.1+

1 - Department of Geology, University of Tromsø, Dramsveien 201, N-9037 Tromsø, Norway; [email protected]; 1+ - Now at NGI, Oslo, Norway; 2 - Department of Earth Science University of Bergen Allégt. 41 N-5007 Bergen, Norway

Outer shelf cracks and elongated gas blow out features have been first discovered along a 40 km long section of the U.S. Atlantic margin. Her, individual cracks are several km long, 1km wide and up to 50 m deep (Driscoll et al., 2000, Hill et al., 2004). The cracks and depressions seem to be caused by "gas blow outs" related to the release of shallow trapped gas. The precise age of the blowouts and the origin of the gas remains unknown, but post- LGM formation of the blowout features suggest that ocean warming triggered methane hydrate dissociation processes. The fact, that the gas hydrate outcrop zones of the largest gas hydrate provinces in Europe are on the Norwegian-Barents-Svalbard (NBS) margin makes the U.S. Atlantic margin - Norwegian Atlantic margin reaction of potential gas hydrates fields to post- Last Glacial Maximum (LGM) climate conditions particularly important for studies of submarine slope failures, i.e. geohazards. The NBS margin is not only an important gas hydrate province but also an area where numerous seeps are documented, and we thus know that there is gas migration in the sediments. In particular the area, where the theoretical outcrop zone of the base of the gas hydrate stability zone (BGHS) and the geophysical evidence as a bottom simulating reflector (BSR) lies, we observe outer shelf cracking, gas blow outs, shallow faulting and fluid escape features such as pockmarks in sediments. Our presentation will draw attention (1) to a system of cracks associated with high pockmark density "gas blowout" features along the northern extension of the giant and retrogressive Storegga slide on the Mid-Norwegian Margin and (2) to a system of potential large blowout features and shallow faults influencing slope failures on the W-Svalbard margin. On the Mid-Norwegian margin a 50 km long and up to 3 km wide zone of approx. 10 m deep depressions occur. They line up with the northern edge of the Storegga headwall elongating in N-S direction. Within the uncertainty of the BGHS modelling the approx. 50 ms TWT cracking zone corresponds well to the belt of the BGHS outcrops, where they intersect the upper continental slope. Radiocarbon age dating of the cracking reveals the same age on the main crack as the Storegga Slide event, but due to the 14C dating uncertainties it remains unknown whether the cracking predates, occurs at the same time, or postdates the Holocene giant submarine sliding event. The cracks are associated with fluid escape indicated by pockmarks typically 50-300 m in diameter and 1-5 m deep. On the W-Svalbard margin outer shelf post-LGM faulting and large depressions occur. The depressions have a diameter of 6 - 10 km and a depth of up to 100 m but also smaller depressions (<20 m) exist. The presented post-LGM formation of cracks, faults and gas blow out features along U.S. and Norwegian Atlantic margin outer shelf areas may be the result of a time dependent response of ocean clathrate reservoirs to climate change and therefore a "climate induced geohazard".

70 The evolution of the valley of Tagliamento River from the Messinian Salinity Crisis onwards

G. MONEGATO

Dip. Georisorse e Territorio, Università di Udine, Via Cotonificio 114, 33100 Udine; Dip. Geologia, Paleontologia e Geofisica, Università di Padova, Via Giotto 1, 35122 Padova

As most valleys in the Southern Alps, the Tagliamento valley was heavily affected by the Messinian Salinity Crisis, with deep entrenchment as a result of Late Messinian sea level drop. At that time, the paleo-Tagliamento River fixed its course in a E-W direction along the boundary between Carnian Alps and Prealps. Downstream of San Simeone massif the valley was carved in a southerly direction into Mesozoic carbonate successions. In the valley-filling deposits three different Unconformity-bounded Stratigraphic Units have been distinguished, which can be traced along the valley for several kilometres. The first preserved post-Messinian valley fill (basal unit) is represented by intra-valley fluvial conglomerates and sandstones, which can be correlated on the basis of composition with coarse-grained middle Pliocene Gilbert-type deltas outcropping near Osoppo, NNW of the town of Udine. The deposits of this unit are deformed by two fold systems, which do not affect the younger deposits. At that time, the confluence with the Fella River, the main tributary of Tagliamento River, was located there, i.e. south of the present position. The second unit shows the same geographic distribution of the former. It is deformed by a general tilting towards NE. The deposits consist mainly of variably sorted and horizontally bedded fluvial conglomerates and sandstones, locally interfingering with landslide-related breccia bodies and coarse alluvial fan conglomerates, together with minor silty lacustrine deposits. The stratigraphic placement suggests a late Pliocene – early Pleistocene age for the deposits. The sandstone petrography evidences an increase in carbonate clasts, even though the reason of this change has not yet been clarified. During the deposition of the third unit some abrupt changes happened in the basin. This unit may be subdivided into two members, both characterised by an upward increase of clast size, a decrease in carbonate clasts and brittle deformation with main strike towards WNW-ESE. The river maintained its previous course during the deposition of the first member, which consists of fluvial conglomerates, generally sorted and horizontally bedded, as well as gravelly Gilbert-type deltas, landslide-related breccia bodies and laminated lacustrine muds. Pollen analyses in the lacustrine muds suggest a middle Pleistocene age. The second member embodies coarse fluvial conglomerates, badly sorted and crudely bedded, with subordinate sandstones. Before the deposition of the second member the river changed its course. The valley was affected by deep entrenchment and the axis shifted slightly eastwards i.e. toward the junction with Fella river near Carnia, as in the present-day location. This diversion caused the eventual abandonment of the western valley, which was filled only by a tongue of till during Late Pleistocene glacial expansions.

71 The Holocene mud-belt and bathymetrical evolution in the central Adriatic Sea: benthic foraminiferal evidence

MORIGI C.1, JORISSEN F.J.2, HORTON B. P.3, SABBATINI A.1, CAPOTONDI L.4 & NEGRI A.1

1 - Dip. di Scienze del Mare, Università Politecnica delle Marche, Via Brecce Bianche, Ancona, Italia. 2 - Laboratoire des Bio-Indicateurs Actuels et Fossiles, UPRES EA 2644, Université d'Angers, France. 3 - Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, USA. 4 - ISMAR - CNR, Via Gobetti 101, Bologna, Italia.

Detailed analyses of modern and fossil benthic foraminiferal assemblages collected in the central Adriatic Sea are used as tools to reconstruct the environmental changes that occurred between the Last Deglaciation and the Present (last 14 Kyrs); in particular we focus on the timing and formation of the mud-belt. The modern benthic foraminiferal assemblages display a parallel zonation to the Italian coast controlled by the interaction between food/oxygen availability and water depth. Cluster analysis of 4 sediment cores separates the fossil foraminiferal assemblages in 6 groups: Cluster A is dominated by three Ammonia species; Cluster B consists of Ammonia papillosa, Nonionella turgida, Elphidium advenum and Elphidium decipiens; Cluster C is composed of two taxa, Hyalinea balthica and Trifarina angulosa; Cluster D is dominated by 5 species, Cibicides lobatulus, Buccella granulata, Reussella spinulosa, Textularia agglutinans and Elphidium crispum; Cluster E contains Bulimina spp., Gavelinopsis praegeri, Bolivina spp., Cassidulina neocarinata and Asterigerinata mamilla; and Cluster F is dominated by Bulimina marginata, Valvulineria bradyana, Globocassidulina subglobosa and Melonis padanum. The cluster analysis and contemporary distribution patterns of these taxa are used together with ecological preferences of the most frequent species to reconstruct the spatial and temporal distribution of the different biofacies in the past. This reveals information about Holocene palaeoenvironmental changes that are related to water depth fluctuations and the instalment of the coast-parallel mud-belt. The benthic assemblage records the transition from a infralitoral environment (Biofacies I) to deeper marine condition (Biofacies III). After that the sea level reached about the modern level (Biofacies IV) the benthic foraminiferal community evidences the development of the mud-belt and the subsequent transformation of the ecological niches linked to the trophic evolution of the environment.

72 Stratigraphic architecture of Plio-Pleistocene Savigliano and Alessandria Basins (Western Po Plain)

NATALICCHIO M.1, IRACE A.1, TRENKWALDER S.1, CLEMENTE P.1, MOSCA P.1, POLINO R.1, VIOLANTI D.1,2 & DE LUCA D. A.2

1 - C.N.R., Istituto di Geoscienze e Georisorse, Sezione di Torino, Via Valperga Caluso 35, 10125 Torino – [email protected]. 2 - Università di Torino, Dipartimento di Scienze della Terra, Via Valperga Caluso 35, 10125 Torino.

This contribution presents geological interpretations inferred from the sequential analysis of Plio-Pleistocene successions of the Western Po Plain, carried out in a research program, whose principal aim is to define the geometry of deep fresh-water acquifers of the Piedmont Region (CLEMENTE et alii, in this volume). The integration of surface, deep well (ENI) and updated seismic data (MOSCA, 2006) has allowed to propose a revised stratigraphic scheme for Messinian-Pleistocene successions of Savigliano (SB) and Alessandria (AB) basins, that are bounded by the Monferrato and Torino Hill to the N, by the Tertiary Piedmont Basin s.s. (TPB) to the S and by the Alps to the W. Six stratigraphic sequences have been recognized, bounded by unconformities and correlative conformities, related to local and regional events that have controlled the physiography of the basin. The Late Messinian sequence (LM) is floored by an erosional surface associated with an angular unconformity that, in marginal settings, cut primary evaporites. The LM consists of resedimented evaporites and terrigenous sediments that reach a maximum thickness of about 600 m in depocentral zones, now buried under the thick Plio-Quaternary cover; this sequence is followed by Early-Pliocene marine deposits of eP1 sequence, whose base is a regional conformable surface (Miocene-Pliocene boundary), that corresponds to a sharp transition to open-marine environments. The eP2 sequence (Early-Middle Pliocene) testifies the beginning of a regressive stage, characterized at regional scale by the development of N-NE ward prograding systems, consisting of deltaic and shelf depositional settings, towards the S, and of slope to basinal environments towards the N. LP (Late-Pliocene) and Ple (Pleistocene) sequences are related to the ongoing regressive trend and represent the transition from marginal-marine (LP) to continental (Ple) depositional environments. These units reach an overall thickness of about 900 m in depocentral areas (SB and AB) and in marginal settings are split by an angular unconformity, associated to a temporal gap, spanning in age from Late Pliocene to Early Pleistocene (CARRARO et alii, 1996). The above described sequences are unconformably followed by The LQ (Pleistocene-Olocene) sequence and only consists of continental deposits; the proximal portion (near the Alpine chain) of LQ is composed of alluvial fan deposits, that eastward show a lateral facies change to alluvial plain deposits. In conclusion, the Early Pliocene-Quaternary evolution of the study areas has been strongly controlled by tectonic and it can be summarized in the following three evolutionary stages: Early Pliocene: the area experiences fast subsidence and basin enlargement; Middle Pliocene: this stage is marked by uplift and severe erosion of Western Alps, NW-ward tilting of the southern region of the TPB, S-ward tilting of the Monferrato-Torino Hill domains and by the onset of subsidence in the interposed areas (future SB and AB). Late Pliocene-Olocene: the Pliocene basin looses its continuity and is fragmented into two new strongly subsident depozones (SB and AB), surrounded by uplifting areas of Torino Hill, Monferrato and TPB.

73 References

CARRARO F.(1996) - Revisione del Villafranchiano nell’area-tipo di Villafranca d’Asti. Il Quaternario, 9 (1), 119 pp. MOSCA P. (2006) – Neogene basin evolution in the Western Po Plain (NW Italy). Insights from seismic interpretation, subsidence analysis and low temperature (U-Th)/He thermochronology. Ph.D. Thesis. Vrije Universiteit, Amsterdam, The Netherlands, 190 pp.

74 Tectonic control on the stratigraphic setting of the northern Sant’Arcangelo Basin (Pleistocene-Southern Apennines, Basilicata)

ONOFRIO V.

Dip. Geologia e Geofisica, Università di Bari, Via Orabona 4, 70125 Bari, Italy; [email protected]

The Plio-Pleistocene Sant’Arcangelo Basin is a wedge-top basin, located on the front of the Southern Apennines thrust belt. It is bounded to the E by the Stigliano-Rotondella ridge, which separated it from the Bradanic Trough. The stratigraphic framework of the northern part of the basin was well defined by PIERI et al. (1994, 1996), but new structural- stratigraphic data allowed to achieve more detail to better understand the tectonic control on sedimentation. The Sant’Arcangelo Basin in-fill, up to 5 km in thickness, is made up of some depositional sequences, late Pliocene to middle Pleistocene in age, bounded by unconformities (angular or progressive unconformities), and every sequence shows evidence of synsedimentary tectonics (growth faults or folds). In the northwestern margin of the basin, the older three sequences (A, B, C) are basically represented by systems of regressive fan-deltas, but during the later stage of the third sequence (early-middle Pleistocene) a continental system developed. The three sequences show a depocenter shifting toward E and, they record also a shifting of the source areas from W to N-NW. In particular, during deposition of sequence C, the northern part of the basin split into two sectors due to a transcurrent-fault system: the Guardia-Alianello-San Lorenzo system. The transcurrent system consists mainly of faults with a left-lateral movement. These faults, striking ca. N150-140, show left realising bends and confer an anastomosed geometry to the whole system. Transcurrent faults post-date anticline and syncline structure with NW-SE oriented axial planes and their tectonic activity caused the development of both a continental system (alluvial and lacustrine in origin) toward the W, and a marine system toward the E. Therefore, the sequence C is characterized by two different successions: a continental one to the W (C1), and a transitional to marine one to the E (C2). The C1 succession is located between two main transtensional faults of the Guardia- Alianello-San Lorenzo system: one toward SW, the other toward NE. The deposition of C1 succession was controlled by the activity of these two faults. In fact, unconformities on the edges of the lacustrine deposits have been locally observed in the neighbourhood of these faults. On the western edge, lacustrine deposits are characterized by an angular unconformity between a depositional system of coalescent small fan-deltas, and the alluvial conglomerates of C1 sequence. The angular unconformity was measured logging a series of successions, showing a change of the dip bed angle from 24°-20° at base of successions, to 10° at top near to the unconformity. In addition, throughout the successions the strata set make up a growth wedge. On the eastern edge, lacustrine deposits show growth strata that onlap conglomerate of C1 sequence. Other segments of fault system are visible in different localities, allowing to reconstruction of the whole structure and its activity. This transcurrent fault system belongs, together whit other structures recognized in the study area, to lateral ramp system separating two different structural domains.

75 Geoarchaeological evidences of cyclical catasthrophic events in the Neapolitan urbanised area

ORTOLANI F. 1 & PAGLIUCA S.2

1 - Dipartimento di Pianificazione e Scienza del Territorio, Università di Napoli Federico II, Napoli, Italy; [email protected] 2 - ISAFOM, CNR, via Cupa Patacca, Ercolano, Napoli, Italy; [email protected]

The physical environment of the Neapolitan Metropolitan Area is affected by several natural problems linked to the recent geological evolution of the area (fig. 1).

Figure 1

Sites with slopes greater than 60 percent are subject to sudden, fast and extremely dangerous mud flows ( for example, Sarno, May 1998 and Cervinara, December 1999) (fig. 1). The geoarchaeological research pointed out that many urban areas have been affected by the same local geological problems during all the historical period (figs. 1, 2, 3, 4, 5 and 6). Somma-Vesuvius and the mountains surrounding the Campanian floodplain are affected by an active erosion of incoherent terrains and soils by surface run-off. Local seismicity, concentrated within the area of the Somma-Vesuvius volcanic system is characterized by events that reached even the IX degree of MCS scale at the epicentres. Local seismicity is also connected to the Phlegrean Fields volcanic activity - with maximum predictable events of IX degree of MCS, at the epicentre - and bradyseismic activity, with a maximum of VI-VII degrees MCS.

Figure 2

Figure 3

Figure 4

Figure 5

A particular geoenvironmental problem is represented by the bradyseismic movements that affected all the Neapolitan urbanized surface coastal area (fig. 1); in fact the roman buildings are usually found some meters (fig. 6) below sea level. The last bradyseismic uplift happened in the Phlaegrean Phields in the period eigtheen eighty three- eighty five affecting an area densely populated around Napoli and also the western part of

78 Napoli. The urban area of Napoli, from Roman Period to the end of Middle Ages, was affected by three bradyseismic movements that lowered the roman soil of eight-ten meters maximum (fig. 6).

Figure 6

The bradyseismic movements are correlatable with the cyclical climatic variations (fig. 7). The soil uplift happened during the warm-arid period named “ Enhanced Roman Greenhouse Effect” and “Enhanced Crusades Greenhouse Effect”; the soil surface lowered during the cold-humid periods named “Dark Age Little Ice Age” and “Little Ice Age”. According to this ciclicity we think that in the near future the Phlaegrean Area will be affected by another soil uplift. The Buildings existing in the Phlaegrean Area are not structured to resist to the bradyseismic soil deformations characterized by anomalous expansion. Original researches evidenced that not well known Intraplinian Vesuvian eruptions alimented a lot of debris flows at the base of the calcareous mountains surrounding the Campanian Plane (fig. 2); in fact we found ten-fifteen meters of resedimented pyroclastic sediments and soils covering the roman anthropized surface (for example in Castellammare di Stabia, Sarno). The stratigraphic recostructions evidenced that all the ancient towns built in the alluvial plains areas where affected by contemporaneous catasthrophic flooding (figus. 2 and 8). We recognised three regional flood period. The first happened between the sixth and forth century Before Christ and we named it “Archaic Little Ice Age”; the second happened between the sixth and eight century A. D. and is named “Dark Age Little Ice Age”; the third happened between the sixtheenth and eighteenth century A. D. and is named “Little Ice Age”.

Figure 7

References

th Ortolani F. & Pagliuca S. (2003) – Geoenvironmental and urban evolution: past and future. 4 Congress on Regional Geoscientific cartography and information systems, Bologna 17-20 giugno 2003. Ortolani F. & Pagliuca S. (2004) - The Climatic Risk: a new risk for the cities of the Circummediterranean Area. 32° IGC Congress, Florence 19-28 August 2004. Ortolani F. & Pagliuca S. (2004) - 2600 BP-Present Day geoenvironmental and urban evolution of Naples (Italy). 32° IGC Congress, Florence 19-28 August 2004. Ortolani F., Pagliuca S. & Serva L. (2004) - Geological causes of last millennium tsunamis affecting the Italian coast. 32° IGC Congress, Florence 19-28 August 2004. Ortolani F. & Pagliuca S. (2004) - Geoarchaeological evidences of recent climatic changes and catasthrophic events in the Neapolitan urbanised area. 32° IGC Congress, Florence 19- 28 August 2004. Ortolani F. & Pagliuca S. (2004) - Urbanisation and man-geoenvironment relationships in Campania (Southern Italy). 32° IGC Congress, Florence 19-28 August 2004. Ortolani F. & Pagliuca S. (2004) - Variazione climatica, diminuzione delle risorse idriche e impatto sull’agricoltura dell’Italia meridionale. Atti dei Convegni Lincei, “Giornata mondiale dell’acqua” La siccità in Italia, Roma 21 marzo 2003, Accademia Nazionale dei Lincei 2004.

80 Geoarchaeological evidences of cyclical climatic-environmental changes in the Mediterranean area (2500 bp-present day)

ORTOLANI F. 1 & PAGLIUCA S.2

The Mediterranean area acts as a boundary zone between humid and desert zones and is highly sensitive to variations in climate and environment. Indeed, shifts in the climate bands towards north or south by only a few degrees of latitude may result in dramatic changes in soil surface conditions. This may cause, for example, desertification in areas that previously had a humid climate or vice versa (fig. 1).

Figure 1 - Climate zones in the circummediterranean Area. 1= present day limit between humid and arid zones; 2= northwards limit shift during muticentennial warm periods (enhanced Greenhouse Effect); 3= southwards limit shift during muticentennial cold periods (Little Ice Ages).

Figure 2 - Velia Geoarchaeological stratigraphy.

Multidisciplinary geoenvironmental research was carried out to shed light on the climatic signifi-cance of different sediment types that have accumulated over the last 2500

81 years (figs. 2, 3), located at various latitudes and in geographical areas with different morphoclimatic conditions (Ortolani et al., 1991; Ortolani and Pagliuca, 1993, 1994, 2001). The sediments, which cover many archaeological sites, were not affected by human impact between the Archaic Period and the Middle Ages.

Figure 3 - Sibari Geoarchaeological stratigraphy.

Figure 4 - Selinunte (SW Sicily) geoarchaeological stratigraphy.

In the Mediterranean area, the presence of windborne sand in coastal dunes (fig. 4) is the most significant geoenvironmental indicator linked to warm-arid climatic conditions. Under conditions of heightened aridity (rainfall lower than 200 mm, typical of desert areas), windborne coastal sand may even invade areas a considerable distance from the sea, forming windborne accumulations that cause the vegetation cover to disappear. This has

82 been widely shown in the literature and verified by direct research (Ortolani and Pagliuca, 2001).

Figure 5 - Northern Egypt Geoarchaeological stratigraphy.

The most typical sediment characterising wetlands consists of soil that allows the development of vegetation and which differs ac-cording to latitude, local climatic and morphological conditions, and substrate lithology (Ortolani and Pagliuca, 2001). The vegetation occurs both on the surface of coastal sand dunes, which are thus stabilised, and on the alluvial sediments of the plains and altered substrate of the rocks of hill and mountain slopes. The most significant sediments found in Mediterranean coastal dune zones in which severe climatic and environmental changes have occurred in the past consist of buried soils within layers of wind-borne sand (figs. 4, 5). The presence of buried soils indicates that precipitation increased appreciably for a sufficiently long period of time to allow soil formation. Hence, there was a change in climatic conditions from desert to humid. Sediments indicating considerable climatic changes in currently humid areas include wind-borne sand and alluvial deposits of considerable thickness that cover areas where human impact has occurred. The presence of wind-borne sand indicates that rainfall decreased sharply until desertification (rainfall below 200 mm) resulted (Ortolani and Pagliuca, 2001). During the peak of warm-arid climatic changes, enhanced “greenhouse effect” environmental conditions similar to those expected in the near future were established (figs. 4, 5). During the transition periods from humid to warm-arid and at the beginning of cold- humid climatic variations, other significant geoenvironmental variations (hydrologic and geomorphological instability) occurred concurrently with the marked increase in rainfall that took place after warm periods (figs. 2, 3). During periods in which the temperature increased by 1-2 °C, coastal zones were affected by desertification up to about latitude 42° N (fig. 4). During temperature decreases, the areas of alluvial plains subject to human impact and settlements were affected by an accumulation of huge volumes of sediments. This resulted in aggradation and progradation of the coastlines in the northern part of the Mediterranean (Figs 2 and 3), while soil formation occurred on the surface of the coastal dunes in the southern and northern parts (figs. 4, 5).

83 The main result achieved through geoarchaeological research is the identification of cyclicity (period of about 1000 years) of the major climate and environmental changes that have resulted in 100 to 200 year environmental crises (fig. 1). Paleoenvironmental, paleoclimatic and geoarchaeological data show that the Mediterranean area was chiefly affected by environmental conditions similar to those of the present day (fig. 6) (Ortolani and Pagliuca, 2001). There is clearly a close correlation between climatic and environmental changes and solar activity. Prolonged solar activity maxima coincide with warm “greenhouse effect” periods and repeated solar activity minima coincide with cold periods, such as the Little Ice Ages (fig. 6). The history of mankind and the environment in the last few millennia highlights progressive, cyclical climatic and environmental changes that consistently occur in multicentennial periods (fig 6).  Using instrumental data and those obtained from natural archives, we propose a climatic re-construction of the past 2500 years (fig. 6). Variations in rainfall are expressed as percentages of current values. A valid frame of reference for assessing and quantifying the changes that will occur at different latitudes during the enhanced Greenhouse Effect of the Third Millennium is provided by: (1) climatic and environmental data relating to the Warm Medieval Period in the Mediterranean area; (2) results achieved from research into geoenvironmental changes linked to historical climatic variations, especially those of the last few centuries, and; (3) various multidisciplinary data obtained from research conducted in various parts of the world. Instrumental data chiefly concerning the last 150 years in the Mediterranean show a consistently close correlation between environmental variations (increase in solar activity and temperature and changes in the quality and quantity of rainfall) and the period of transition from the cold-humid climatic conditions of the Little Ice Age to those that may probably characterise the Warm Period of the Third Millennium (enhanced Greenhouse Effect of the Third Millennium). If cyclical climatic variation as occurred in the past will continue, it might result in new environmental conditions along the belts bordering the current climatic zones. In particular, a large part of the areas that are currently subtropical deserts might be transformed into humid areas. These conditions may be at times better and at times worse than those of the Little Ice Age. This speculated shift in Mediterranean climatic conditions a few degrees to the north would cause an appreciable change in rainfall in central-northern Europe. Since the 18th century, this area has been characterised by an almost homogeneous distribution of rainfall over the year and consequently, a constant river water regime. Mediterranean-type rainfall could probably increasingly affect this area in the near future. This seasonalisation of rainfall would result in an increased frequency of bankful flow conditions. Ongoing millennial climatic cyclicity (fig. 6) forecasts that river valleys will be affected by repeated catastrophic flooding. Given that these valleys were urbanised on the basis of a constant river water regime, serious damage to the consolidated socio-economic organisation of central-northern Europe would therefore result.

Figure 6 - Correlation between geoarchaeological stratigraphy and solar activity

References

Allocca, F., Amato, V., Coppola, D., Giaccio, B., Ortolani F. and Pagliuca, S., 2000: Cyclical Climatic- Environmental Variations during the Holocene in Campania and Apulia: Geoarcheological and Paleoethnological Evidence. Mem. Soc. Geol. It., 55, 345-352. Ortolani, F. and Pagliuca, S., 2001: Le variazioni climatiche storiche e la prevedibilità delle modificazioni relative all’effetto serra. Asociazione Italiana Nucleare, marzo 2001, Roma. Ortolani F. & Pagliuca S. (2003) - Cyclical Climatic-Environmental Changes in the Mediterranean Area (2500 BP-Present Day). PAGES, Vol. 11, N. 1, April 2003, pp. 15-17. Ortolani F. & Pagliuca S. ( 2003) – Climate change and geoenvironmental evolution in the Mediterranean Area (2500 BP-Near Future). 4th Congress on Regional Geoscientific cartography and information systems, Bologna 17-20 giugno 2003. Ortolani F. & Pagliuca S. (2003) – Near-future climatic variations and water availability in Southern Italy. Managing water demand in agriculture through pricing, CNR-DAI-SMED Network “Factors limiting the agricultural productivity in the Mediterranean basin”, Proceedings Telese Terme – May 24-25, 2001. Ortolani F. & Pagliuca S. (2004) - Climate change, desertification and expected impact on agriculture in Southern Italy. 32° IGC Congress, Florence 19-28 August 2004. Ortolani F. & Pagliuca S. (2004) - Holocene-Present Day small scale, rapid and cyclical quasi- equilibrium and transient climate states in the Mediterranean Area: geoenvironmental effects and predictions for the near future. 32° IGC Congress, Florence 19-28 August 2004. Ortolani F. & Pagliuca S. (2004) - Climate changes scenarios and geoenvironmental impact in the Mediterranean basin. 32° IGC Congress, Florence 19-28 August 2004.

85 The climatic risk for the circummediterranean area on the base of geoarchaeological data

ORTOLANI F. 1 & PAGLIUCA S.2

Geoarchaeological studies carried out in the Circummediterranean Area evidence that, during the last thousands years, the beginning of each millennium has been characterized by rapid and severe change of climatic-environmental conditions, according to a millennial cyclicity. Correlation of the geoarchaeological stratigraphy with the reconstruction of multicentennial solar activity shows that significant and cyclical environmental changes occurred in the Mediterranean Area in concomitance with significant multicentennial changes in solar activity (fig. 1). During the periods in which the temperature increased by 1-2° C the coastal zones were affected by desertification up to a latitude of about 42°.

Figure 1

The acme of these changes was recorded during warmer periods of 100-200 years connected to a northwards shift of present day environmental conditions. We defined these climatic variations, similar to those expected in the near future (“Enhanced Greenhouse Effect of the third millennium”) and connected to the Greenhouse Effect increase, “Enhanced Roman Greenhouse Effect” (100-300 A.D.) and “Crusades Greenhouse Effect” 1100-1270 A.D. The palaeoenvironmental reconstructions evidence that during the past warmer periods all the Circummediterranean Area was affected by severe physical modifications due

86 to the variation of geomorphological equilibrium, pedogenetic processes, water availability, river discharge, cultivated areas. On the base of the results acquired with the geoarchaeological researches and evaluating the present day cities localization it is possible predict that many urban areas will be affected by severe modifications of the stable geoenvironmental conditions that have favoured the development of the anthropised areas, until present day. The predictable climatic risk that will affect the cities in the near future, during the climatic transition period, will be different according to the latitude. The Mediterranean cities will be interested by: - significant decrease of fresh water availability; - increase of groundwater and river pollution; - severe beach erosion; - slopes geomorphological instability. The shift of Mediterranean climatic conditions a few degrees to the north will cause an appreciable variation in rainfall in central-northern Europe and will cause a seasonalisation of rainfall with consequent periods of concentrated bankful flows which will be far greater than current levels. Given that the urbanisation of river valleys has up to now occurred in relation to the hydrological river regime, hence without alternating periods of marked lows and highs, it is forecast that river valleys will be affected by repeated catastrophic flooding that will result in serious damage to the consolidated socio-economic organisation of the cities (figure 1). On the basis of scientific data acquired, it is possible to predict climatic and environmental changes expected in the next 100 years. A- The most serious environmental changes are expected in coastal areas where a sharp reduction in rainfall and a marked temperature rise are expected, such as to cause climatic desertification (annual rainfall about 200-250 mm). According to the three- dimensional relationships, the alluvial aquifers in these belts may be naturally fed only by vertical rainfall (e.g. the northern and southern parts of the Sele river plain, the Alento and Bussento plains) or also by feeding from neighbouring limestone aquifers (e.g. the Campanian Plain and Agro Nocerino-Sarnese). The most serious water crisis may be forecast on those plains that do not benefit from the feeding of groundwater from confining limestone aquifers; the sharp reduction in water feeding into coastal aquifers will cause greater salt water intrusion into depressed retrodunal plains with a resulting crisis for agriculture. In Southern Italy considerable problems for irrigation, industrial and domestic uses will arise from the serious reduction in renewable water resources that will affect the limestone aquifers (over 50% less). Indeed, not only is the drinking water requirement but also industrial and irrigation requirements are based on spring water and on water extracted from alluvial aquifers. On the basis of the knowledge acquired on soil surface changes and short-term trends in water resources, it is possible to outline the main problems that will affect agriculture in relation to geographical position, morphology and the three-dimensional geological regime. The most significant expected environmental variations will occur on the eastern Southern Apennine belt, consisting of a chiefly clayey substrate, in which durum wheat cultivation is chiefly concentrated, representing a staple for pasta production which is known to play an important role in the Italian economy. From the predicted change in rainfall in the near future it is clear that in most of this area farmland there will no longer be the soil moisture needed throughout the durum wheat vegetative cycle. During the past warm periods the littorals with silicoclastic sands where affected by severe erosion while the beaches with bioclastic sands where characterised by evident progradation. During the decreases in temperature the areas of the alluvial plains subject to human impact and settlements were affected by an accumulation of huge volumes of sediments with consequent aggradation and progradation of the coastlines in the northern part of the Mediterranean while severe erosion occurred along the beaches with bioclastic sands of the southern part (Archaic Little Ice Age, 500-300 B.C.; Dark Age Little Ice Age, 500-750 A.D.; Little Ice Age, 1500-1830 A.D.) (fig. 1).

87 On the basis of scientific data it is possible to predict that the beach erosion, prevalently caused by the climate variation, will continue for 150 years at least. Many thousands of kilometres of the Mediterranean coastline are affected by serious erosion which undermines not only the aggressive anthropisation that has taken place up to a few metres from the sea, but also the social and economic structure of entire regions whose economy is largely based on seaside tourism. It is undeniable, in fact, that coastline economy based on quality tourism, fostered by beautiful beaches, has made a considerable contribution to the improvement of the social and economic position of the coastal regions. The beach erosion, consequently, represent a direct economic danger for the national and regional socio-economic condition. Without effective and coordinated planning of the safeguarding, improvement and protection of the coastal areas, deterioration accentuated by predictable defence work made necessary by local emergency situations, will become more and more seriuos. Studies on the stratigraphic and hydrogeological characteristics of the alluvial coastal plain of the River Volturno allowed the boundary to be drawn between seawater saline intrusion into the aquifer and the freshwater aquifer from inland sources and partly from precipitation (the more superficial part). The latter is decidedly brackish, caused by contamination due to intense groundwater use for agricultural purposes during the summer and the unsuitable drilling of wells. This situation affects much of the plain (at least 3000 hectares) and at least two-thirds of the plain may be said to be at risk, hence about 9000 hectares in all. Previous chemical, physical and hydrological studies from the 1950s to the 1970s highlighted the presence of soils affected by salinisation and alkalinisation. The chemical characteristics of the aquifers in the subsoils showed a medium-hoil soil salinity risk due to the large presence of chlorides. A soil survey showed, after sampling at over 100 water sources (wells) and measuring electrical conductivity, that many wells used for irrigation are affected by saline and/or brackish water and that the salt-water intrusion affects not only the low-lying retrodunal areas, as shown previously by some authors, but vast portions of the alluvial hinterland of the River Volturno. As regards the agronomic use of this water, in some cases, irrigation water was found to have conductivity levels that made it virtually unsuited to irrigation and, in other cases, conductivity values were detected that suggest mean productive losses ranging from 10% to 25%. The results of geoelectrical surveys show that the coastal plain of the Lower Volturno is affected by saltwater intrusion as far as 3 km inland from the coast. The problems affecting the area of the Lower Volturno are similar to those described, with the same study methods, by other researchers for other coastal plains in Italy (the coastal delta plain in Emilia-Romagna, the Veneto plain between the mouths of the Rivers Bacchiglione-Brenta, the southern area of Venice and Padua, the coastal plain of the Rivers Cecina and Albegna, the area close to the Po delta, the farmland around Bari, the coastal plain of northern Lazio, the coastal plains of south-eastern Sardinia). The beginning of the third millennium will be characterised by the climatic- environmental modifications, connected to the increase of the Greenhouse Effect, and by their impact on the urban areas. According to the different latitudes many urban areas will be affected, also, by new geoenvironmental problems (fig. 2), such as: - anomalous and instantaneous sea-water movements along the urbanised coastal areas; - decrease of the precipitation and of the fresh water availability in the Mediterranean area; - sea water intrusion and subsidence along the coastal alluvial plane; - beach erosion; - catasthrophic flooding in Central Europe; - cathastrophic landslides in the Alpine valleys; - catasthrophic very fast mud flows at the base of slopes characterised by rocky bedroch covered by loose water saturated sediment.

Figure 2

The geoenvironmental security of urban areas must be assured by a modern and advanced knowledge relative to this arguments: - Geoenvironmental evolution of the anthropised areas: including geoenvironmental knowledge relative the vasta area around the town having a potential influence on the security of the urbanised area (seismicity, volcanism, geomorphological instability of emerged and submerged area, surface hydrology, hydrogeology) and potentially influenced (natural resources, water availability and qualityt) by human activity (polluted water and trash discharge). - Urban Geology: including the geoenvironmental evolution of the urban area inhabited along a periods of many century where and for this reason representing an important archive containing informations relative to the impact of the geoenvironment on the urban area and viceversa. - Three dimensional Geology of Urban areas: including the reconstruction of the detailed three-dimensional geologic model of the subsurface, representing the phisical base of the town. It is possible to distinguish the modern urban area into two part: an “emerged” one, representing the surface urbanisation and a “submerged” one, representing the anthropised subsurface. It is evident that in the first century of the third millennium the importance of the submerged town will rapidly increase. In fact, the new urban frontier will be represented by the trhee dimensional plannig of the urban area.

References

Ortolani F. & Pagliuca S. (2004) - The Climatic Risk: a new risk for the cities of the Circummediterranean Area. 32° IGC Congress, Florence 19-28 August 2004. Ortolani F. & Pagliuca S. (2004) - 2600 BP-Present Day geoenvironmental and urban evolution of Naples (Italy). 32° IGC Congress, Florence 19-28 August 2004.

89 Ortolani F. & Pagliuca S. (2004) - Geoarchaeological evidences of recent climatic changes and catasthrophic events in the Neapolitan urbanised area. 32° IGC Congress, Florence 19- 28 August 2004. Ortolani F. & Pagliuca S. (2004) - Urbanisation and man-geoenvironment relationships in Campania (Southern Italy). 32° IGC Congress, Florence 19-28 August 2004. Ortolani F. & Pagliuca S. (2004) - Variazione climatica, diminuzione delle risorse idriche e impatto sull’agricoltura dell’Italia meridionale. Atti dei Convegni Lincei, “Giornata mondiale dell’acqua” La siccità in Italia, Roma 21 marzo 2003, Accademia Nazionale dei Lincei 2004. Ortolani F. & Pagliuca S. (2004) - L’evoluzione del clima in Italia dalla Piccola Età Glaciale (1500-1850) al prossimo futuro (Effetto Serra del Terzo Millennio). Atti dei Convegni Lincei, “Giornata mondiale dell’acqua” La siccità in Italia, Roma 21 marzo 2003, Accademia Nazionale dei Lincei 2004. Ortolani F. & Pagliuca S. (2004) - Il clima Mediterraneo: modificazioni cicliche degli ultimi millenni e previsioni per il prossimo futuro. Atti dei Convegni Lincei, “Giornata mondiale dell’acqua” La siccità in Italia, Roma 21 marzo 2003, Accademia Nazionale dei Lincei 2004.

90 Benthic foraminiferal colonization of a gas hydrate mound, Blake Ridge, western North Atlantic Ocean

PANIERI G.1 & SEN GUPTA B. K.2

1 - Dipartimento di Scienze della Terra e Geologico-Ambientali, Università di Bologna, Via Zamboni 67 - 40126 Bologna, Italy. E-mail address: [email protected] 2 - Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803. E- mail address: [email protected]

Contributions on benthic Foraminifera related to hydrocarbon environments (such as methane seeps and gas hydrates) have greatly increased in the last few years, because of the need for (1) an understanding of this unusual ecosystem and (2) identifying suitable microfossil markers of past methane release. Our present study is linked to both of these tasks. We examined living (rose Bengal stained) and dead benthic Foraminifera (>63 μm) taken from the Blake Ridge Diapir, off the U. S. east coast (Atlantic Ocean, 2250 m); the coring sites are within a major gas hydrate province. Twelve cores, collected from the submersible Alvin, were taken through (1) white bacterial mats composed of sulphur- oxidizing Arcobacter and sulphide-oxidizing Thiovulum, (2) from the edge of dense mussel beds, and (3) grey sediments away from such spots. The most significant difference among the surface samples is related to the highly variable foraminiferal density; the highest densities are from the bacterial mat sites. The distribution of species, i.e., the community structure, does not show any conspicuous difference among sites. However, the vertical distribution of foraminiferal density in the cores exhibits a more stable trend at the bacterial mat sites than in the surrounding sediments. Thus, the proliferation of foraminiferal species on this gas-hydrate seafloor is sustained best at dense white bacterial mats, which may act as oases of productivity and provide an enormous nutrient and energy pool for the Foraminifera.

91 Geochemistry and stratigraphy of the giurassic hard-grounds of the Rocca Busambra (west Sicily, Italy)

PARISI S.1, LONGHITANO S.1, MONGELLI G.1 & SPALLUTO L.2

1 - University of Basilicata, Campus di Macchia Romana, 85100 Potenza (Italy) – [email protected]; [email protected] 2 - University of Bari, Via E. Orabona 4, 70125 Bari (Italy) - [email protected]

Hard-grounds, occurring on ancient and present-day carbonate from shallow- to deep- marine environments, represent an important lithofacies indicating relevant geologically conditions related to slow- or zero marine deposition (e.g. Friedman and Sanders, 1992). These layers, or crusty thin surfaces, are often observed along several succession of Mesozoic carbonate platforms of southern Italy, marking the abrupt transition between shallow-to-deep marine sedimentation (Catalano et al. 1991, 1993; Longhitano S., Montanari L., Punturo R., 1995). The study succession crops out near some quarries, along the western side of the RB (Rocche Argenteria and Drago). Our work mostly focuses on a ~1.5 m thick dark-coloured succession of hard-ground, occurring at the top of the Liassic carbonate platform, and cropping out near the western margin of the Rocca Busambra (RB), western Sicily (Fig. 1). The RB succession, some thousands of meters thick, pertains to the ‘Trapanese’ palaeodomain (Auct.), and represents a morpho-structural high of a strike-slip regional lines (Catalano et al., 1995; 1996). Here, stratigraphic and sedimentologic data were collected along several sections logged and sampled in detail. Microfacies elements, textures, sedimentary structures and early diagenetic features were analyzed in thin sections improving sedimentologic dataset in order to interpret paleoenvironments. In addition, the samples were analyzed by XRD analysis for the mineralogical paragenesis, and by the XRF analysis for both major- and trace elements distribution (FRANZINI M., LEONI L., 1972; FRANZINI M., LEONI L., SAITTA M., 1975; LEONI L., SAITTA M. 1976; MONGELLI G. 2002;). Detailed morpho-chemical analysis were carried out by SEM-EDAX.

Fig. 1 - Geological map (the regional location is shown in the inset), and geological profile of the study area (modified, after Grasso, 2001). 1) alluvial deposits; 2) Miocene marls and calcarenites; 3) “Numidian Flysch” unit (upper Oligocene to lower Miocene); 4) Sicani units (Jurassic-Tortonian); 5) Trapanese units (Jurassic-Miocene); 6) Marls and calcilutites (middle Triassic); 7) Main normal faults; 8) Main thrusts; 9) Geological profile.

92 The RB succession can be subdivided into two well-detectable members: a lower member (i), represented by some thousands of meters of shallow-marine peritidal limestones. This member, cropping out in the study area in its topmost part (Fig. 2), shows lithofacies associations characterized by mostly mud-supported textures in which barren mudstones, stromatolitic bindstones and loferites are the most widespread components. An upper member (ii) representing a condensed succession of deeper water carbonate sediments, characterized by a sharp-based, 1-2 m thick hard-grounds, rich of small-sized nodules. These beds, are followed by 3-4 m thick limestones, made up of biomicritic packstones with crinoidal plates, thin-shelled pelagic bivalves, rare brachiopods and planctonic foraminifers and by biomicritic mudstones/wackestones rich in planctonic foraminifers and by rare crinoidal plates and pelagic bivalves. The hard-grounds were morphologically distinguished into five facies: (A) 1 m thick calcareous dark beds (hard-ground s.s.); (B) Fe-Mn small-size nodules lying within the hard-grounds s.s.; (C) Fe–Mn crusts occurring between the bed discontinuities of the upper member carbonate succession; (D) ‘mushroom-shaped’ accretions, developing at the hard-ground/condensed-beds boundary, characterized by a suite of different sizes and morphologies; (E) Fe-Mn medium-size nodules randomly scattered within the deep-marine sediments (Fig. 3).

Fig. 2 – Outcrop photograph of the study succession near Rocca Drago. The dotted line indicates the lower/upper member boundary. Rocche di Rao in the background.

Fig. 3 – A) Boundary (dotted line) separating the lower- from the upper member forming the RB succession. The black arrows indicate small-size Fe-Mn nodules (facies B) scattered within the hard- grounds (facies A). B) Detail of the facies B. C) Fe-Mn crust occurring at the base of a bed within the upper member of the RB succession. This crust is covered by a paleosoil. D) “muschroom-shaped” Fe-Mn accretion typical of the facies D.

The mineralogical assemblage is made up of carbonate minerals, fluoroapatite, Fe- and Mn- oxihydroxides (Tab. 1). These phases are differently distributed within the five facies likely as a conseguence of different conditions of formation.

Tab. 1- Facies recognized for the studied hard-grounds and relative mineralogical paragenesis.

References

CATALANO, R., DI STEFANO, P., KOZUR, H., (1991) - Permian circumpacific deep-water faunas from the western Tethys (Sicily, Italy) - new evidence for the position of the Permian Tethys. Paleogeogr. Paleoclimatol. Paleoecol. 87, 75–108. CATALANO, R., DI STEFANO, P., NIGRO, F., VITALE, F.P., (1993) - Sicily Mainland and its offshore: a structural comparison. Geological development of the Sicilian–Tunisian Platform, Max, M.D., Colantoni, P. (Eds.). Unesco Report in Marine Science 58, 19–24. CATALANO, R., INFUSO S., SULLI A., (1995) - Tectonic history of the submerged Maghrebian Chain fro the southern Tyrrhenian Sea to the Pelagian foreland. Terranova 7, 1995, 179-188. CATALANO, R., DI STEFANO, P., SULLI, A., VITALE, F.P., (1996) - Paleogeography and structure of the Central Mediterranean: Sicily and its offshore area. Tectonophysics 260, 291–323. FINETTI I., LENTINI F., CARBONE S. & CATALANO S. E DI DEL BEN A., (1996) – Il sistema appenninico meridionale – Arco Calabro – Sicilia nel Mediterraneo centrale: Studio geologico geofisico. Boll. Soc. Geol. It. 115, 529-559, 12 ff. FRANZINI M., LEONI L., (1972) – A full matrix correction in x-ray fluorescence analysis of rock samples. Atti Soc. Tosc. Sci. Nat., Mem., Serie A, 79, 7-22, tab. 7. FRANZINI M., LEONI L., SAITTA M., (1975) – Revisione di una metodologia analitica per fluorescenza-X, basata sulla correzione completa degli effetti di matrice. Soc. Italiana di Mineralogia e Petrografia – RENDICONTI, 31, 365-378. FRIEDMAN M.G., SANDERS J.E., KOPASKA-MERKEL D.C. (1992) – Principles of sedimentary deposits. Stratigraphy and sedimentology. D.C. Kopaska-Merkel Eds., 649 pp. LEONI L., SAITTA M. (1976) – X-Ray fluorescence analysis of 29 trace elements in rock and mineral standards. RENDICONTI Soc. Italiana di Minaralogia e Petrografia, 32 (2) 497-510. GRASSO M. (2001) – The Appenninic-Magrebian orogen in southern Italy, Sicily and adjacent areas. Anatomy of an Orogen. The Appennines and Adjacent Mediterranean Basins. Kluwer Academic Publishers, 255-286. LONGHITANO S., MONTANARI L., PUNTURO R., (1995) – Tematiche genetiche sui filoni nettuniani della Rocca Busambra. Boll. Acc. Gioenia Sci. Nat. 349, 113-145. MONGELLI G. (2002) – Growth of hematite and boehmite in concretions from ancient karst bauxite: clue for past climate. Catena, 50, 43-51. PEPE F., SULLI A., BERTOTTI G., CATALANO R., (2005) - Structural highs formation and their relationship to sedimentary basins in the north Sicily continental margin(southern Tyrrhenian Sea): Implication for the Drepano Thrust Front. Tectonophysics 409 1–18.

94 Tectonic, seismic and hydrothermal events recorded in the Jurassic succession of the Marguareis Massif (Ligurian Briançonnais).

PEROTTI E.1, BERTOK C.1, D’ATRI A.1, MARTIRE L.1, MUSSO A.1 & PIANA F.2

1 - Dipartimento di Scienze della Terra, Torino 2 - CNR, Istituto di Geoscienze e Georisorse, Torino

The Marguareis Massif pertains to the Ligurian Briançonnais, i.e. a portion of the paleoeuropean margin of the Jurassic Western Tethys. Owing to a nearly absent metamorphism and confinement of deformation to discrete stratigraphic intervals, primary lithologic features and stratigraphic relations are preserved. The attention is here focused on the Calcari di Rio di Nava Limestones (CRN)(Middle Jurassic) whose features record a Jurassic syndepositional tectonic activity. The CRN, that mainly consist of thinly laminated, dark grey micritic limestones almost barren of fossils, show the following interesting features: 1) Intraformational unconformities: the middle part of CRN locally shows a wedge geometry with progressive reduction of original bed dip from base to top. It may be interpreted as the result of sedimentation within a small scale half graben related to a growth fault. The latter, which is not directly observable because of Alpine tectonics, caused a tilting of the hangingwall and generation of a certain relief of the sea floor that however was levelled still during deposition of the CRN. 2) Seismites: in all of the studied sections, the CRN show several beds affected by different degrees of postdepositional disruption. Most cases are represented by dm-thick pseudonodular beds. “Nodules” range in size from mm to cm, have sharp edges and an ellipsoidal shape flattened parallel to bedding, and are embedded in a more marly matrix. More calcareous layers are crossed by low-angle planes which subdivide beds in dm-sized portions slightly thrust the one over the other giving rise to an embricated structure. All these features suggest an early postdepositional sliding of a set of beds with different degrees of lithification resulting in boudinage and microfaulting. 3) Dolomitization: most of the CRN shows a certain degree of dolomitization that is locally complete. In general dolomite occurs as ehuedral to subhedral crystals scattered in the limestone bed and concentrated where the sediment has been more intensely chemically compacted. Cathodoluminescence (CL) reveals that dolomite is zoned: irregularly shaped, non-luminescent cores are overgrown by zoned, black to purple red luminescing, dolomite developing rombohedral crystal faces. The relationships with the compactional features of the surrounding limestones show that the dolomite overgrowths formed in an early stage of diagenesis. Moreover larger, sparry dolomite crystals with a comparable CL zoning occur within a network of polyphase veinlets crossing through the CRN. Finally, preliminary analyses of dolomite-bearing limestones show strongly 18O-depleted values that suggest the role of hot fluids flowing through shallow buried Middle Jurassic sediments. All the described features may be considered as the result of deformational processes related to Jurassic synsedimentary tectonic activity. Seismogenic extensional faults firstly generated small scale half-grabens giving rise to gentle slopes along which repeated seismic shocks triggered sudden dewatering of lime muds and consequent disruption and sliding. The faults and the associated fracture systems, moreover, acted as conduits for upward flow of hydrothermal fluids resulting in dolomite precipitation both as overgrowths and as vein fillings.

95 The Roman road “Via di Villadose” and its relations with the paleaeohydrography (Rovigo - Italy)

PIOVAN S.1, MARAGNO E.2 & MOZZI P.1

1 - Dipartimento di Geografia, Università degli Studi di Padova, via del Santo 26, 35100 Padova – Italy; e-mail: [email protected] 2 - Museo della centuriazione, piazza A. Moro 1, 45010 Villadose (RO) – Italy

The study area is about 30 km far from the Adriatic coast, between the cities of Rovigo and Adria, and delimited respectively to the north and to the south by the Adige and Po rivers. From the archaeological viewpoint the area is of great interest due to the presence of important Bronze and Iron Age sites and the existence of an exceptionally well-preserved roman centuria, which extends for 250 km2 from the city of Rovigo almost to the Lagoon of Venice and dates back to 1st century BC-1st century AD. Prominent is the case of Villadose which lies on a stretch of low plain consisting of Late Holocene fine sediments from both the Adige and Po system. The main archaeological feature is the Roman road “Via di Villadose”, that is the decumanus maximus of the centuria and runs north of the modern town. This research aims at understanding how the geomorphic and palaeoenvironmental evolution of the area influenced the pattern, typology and distribution of the ancient settlements and infrastructures. Our investigations are focussed on a crevasse splay which is crossed by “Via di Villadose” in the area called Ca’ Motte. The investigation takes advantage of microrelief survey, photo-aerial interpretation, analysis of boreholes obtained with Edelman hand auger down to the depth of 4-6 m and a methodic archaeological top layer survey of all the area, performed by Gruppo Archeologico di Villadose. A digital elevation model of the investigated area has been developed, based on contour lines with spacing of 0.5 m. For the construction of the contour lines, a manual interpolation of spot heights of the “Carta Tecnica Regionale del Veneto” at scale 1:5000 has been adopted. This method allows to discard the points that are related to present-day artificial structures and to reconstruct the natural swale-and-ridge systems. Aerial photographs were used to map natural morphologies such as the crevasse palaeochannels and splay and to help the analysis of their interaction with anthropic structures such as ancient roads, ditches and field patterns. Aerial photos and microrelief indicated also the convenience of drilling a set of boreholes across the crevasse splay placed north of “Via di Villadose” to develop a stratigraphical cross section that shows a complex sedimentary history characterized by different depositional environments before local centuriation took place. Periods of rapid aggradation due to the upbuilding of fluvial ridges and crevasse splays alternated with periods when overbank clays and peats accumulated with low depositional rates. Results will eventually indicate whether distribution of ancient settlement and infrastructures is casual or influenced by particular sedimentological conditions. The radiocarbon dating of the backswamp peats, currently under way, and the relative chronology based on archaeological evidences may help to date and understand the deposition of natural sediments and their interactions with the Roman settlements and structures.

96 La banca dati geognostica e la stratigrafia del sottosuolo come elemento di pianificazione del territorio: l’esperienza del comune di Pisa

REDINI M.1, SARTI G.2, CONTINI S.3 & PIPPI G.4

1 - Direzione Urbanistica, Comune di Pisa, vicolo del Moro 2, 56125 Pisa. 2 - Dipartimento di Scienze della Terra, Università di Pisa, via Santa Maria 53, 56126 Pisa. 3 - Gaia Servizi per il Territorio e l’Ambiente snc, via Angelo Battelli 39, 56127 Pisa. 4 - Località Santo Pietro Belvedere, Capannoli, Pisa.

Negli ultimi 60 anni il territorio del Comune di Pisa è stato oggetto di molteplici sondaggi e prove geognostiche volte alla definizione della stratigrafia del primo sottosuolo e dei relativi valori geotecnici. Tutti i dati raccolti in questi decenni sono stati strutturati in una banca dati geognostica finalizzata alla realizzazione di un progetto di modellizzazione stratigrafica, litotecnica ed idrogeologica del sottosuolo pisano. La banca dati è stata realizzata seguendo le specifiche tecniche nazionali di settore, prendendo come modello logico quanto già proposto dalla Regione Emilia Romagna (Servizio Geologico), dalla Regione Toscana, dalla Provincia di Pisa e dall’ARPAT. I logs stratigrafici sono stati georeferenziati in formato .shp adoperando la piattaforma ESRI (ArcGis version 9.0) come software GIS e la Carta Tecnica Regionale (scala 1:10.000) come base topografica. I dati, di differente qualità e provenienti da fonti diverse, sono stai uniformati, seppure sulla base di un primo passo interpretativo, attraverso un’ elenco di descrittori per poi essere restituiti graficamente attraverso l’elaborazione con il software DBSond32 della geo&soft. La banca dati geognostica ed il suo incremento rappresentano il primo passo, tuttora in corso d’opera, per la definizione di un modello della geologia del primo sottosuolo del territorio del comune di Pisa attraverso il software specialistico della Rockware (RockWorks v. 2006). Tale modellizzazione sarà ovviamente indissolubilmente collegata dallo studio di sondaggi a carotaggio continuo, tuttora in corso, che permetteranno di confermare, raffinare o modificare il modello stesso. Lo sviluppo della banca dati geognostica e del relativo modello geologico del sottosuolo comunale permetterà di arricchire le conoscenze scientifiche relative alla stratigrafia della pianura pisana. Inoltre, i dati inseriti potranno essere adoperati dall’amministrazione comunale come valido supporto alla pianificazione urbanistica e territoriale come ad esempio per la definizione dell’idoneità dei terreni di fondazione e la valutazione del rischio sismico.

97 Platform evolution in the Triassic of the Dolomites (Italy): from low relief carbonate banks to bioconstructions with a primary skeletal framework

RUSSO F.

Dipartimento di Scienze della Terra, Università della Calabria, Ponte Bucci 15B, 87036 Rende (CS), Italy. E-mail: [email protected]

The Triassic of the Dolomites includes many carbonate platform generations, ranging from Anisian to Norian-Rhaetian in age. After the the Permian-Triassic biological crisis “reef” communities reappeared during the Anisian time. These buildups were generally characterised by a limited relief, lacking any primary skeletal framework and evidence of syndepositional cementation. The microfacies are dominated by micrites, mainly allochthonous or detrital in origin. The sparse biota are generally binder and buffler organisms, as dasycladacean algae, sphinctozoans and briozoans. The second generation of carbonate buildups (late Anisian – early Ladinian, Sciliar Fm) are dominated by syndepositional cements (e.g. Marmolada Platform). These cements represent the main component of margin and upper slope facies. They form more or less isolated or laterally linked bodies: the “evinosponges”. During the late Ladinian and Carnian p.p., the post-volcanic platforms developed (Cassian Dolomite). The microfacies of these platforms manly consist of micrites, cements and skeletons. The automicrites constitute more than 50% of the rock volume, the cements the 20% and the skeletal organisms less than the 10%. The metazoan contribution is certainly subordinated to that of skeletal cyanobacteria, like Cladogirvanella cipitensis and microproblematica, like Tubyphites. The primary marine cements provide evidence of a widespread early syndepositional lithification. Towards the top of Julian Substage (Carnian), at the base of the Heiligkreutz/Dürrenstein Formation (i.e. Alpe di Specie), small calcareous bioconstructions (interpreted as patch-reefs) show much more “modern” faunal association. For the first time in the Triassic, a skeletal primary framework developed, largely formed by calcified demosponges and scleractinians. Corals were still subordinated to sponges. Taxonomic diversity increases greatly and the skeletal component exceeds the 50% of the rock volume. These biofacies anticipate the “modernization” of the reef-building communities, occuring at a global scale between the Late Carnian and the Norian-Rhaetian.

Gamma-ray di superficie nel Miocene inferiore del Bacino Sabino: ciclicità e caratterizzazione dell’ambiente deposizionale

SAMPALMIERI G. 1, COSENTINO D.1, CIPOLLARI P.1, SOLIGO M.1, LO MASTRO S.1 & LAURENZI M.2

1 - Dipartimento di Scienze Geologiche, Università degli Studi Roma Tre 2 - Istituto di Geoscienze e Georisorse, CNR-Pisa, Italy

In questo lavoro vengono esposti i risultati di uno studio riguardante il gamma-ray di superficie (integrato a studi di carattere biostratigrafico, geochimico geocronologico e mineralogico) operato su successioni stratigrafiche mioceniche appartenenti al Bacino Sabino, le quali si collocano in ambienti di sedimentazione che variano dal bacino distale sino alla rampa carbonatica media-interna. Il Bacino Sabino rappresenta un’area di raccordo tra la Piattaforma carbonatica laziale- abuzzese (PLA) a E, il Bacino Toscano a W e il Bacino Umbro-marchigiano a N e NE. La successione stratigrafica sabina, è assimilabile a quella pelagica del Bacino Umbro- marchigiano, dalla quale si distingue per importanti apporti carbonato-clastici provenienti dalla vicina PLA. I dati gamma-ray di superficie sono stati acquisiti attraverso l’utilizzo di uno spettrometro γ costituito da un detector, con cristallo 2"x2" NaI(Tl) che conta le emissioni γ in Cpm (colpi per minuto) e/o Cps (colpi per secondo). Inoltre, è stata effettuata una analisi spettrale (software AnalySeries 2.0, Paillard et al., 1996), utilizzando le letture gamma di terreno, al fine di evidenziare eventuali ciclicità nel gamma-ray. I risultati evidenziano come, sezioni di ambiente bacinale (di età Aquitaniano sup.- Burdigaliano inf.) mostrino un profilo γ con oscillazioni ad alta frequenza e un fondo del segnale gamma elevato (15-20 Cps). Sezioni in ambiente di slope (di età Burdigaliano inf.) mostrano, invece, un trend del gamma-ray con forti deflessioni dove il fondo del gamma-ray risulta essere più basso, tra 12 e 17 Cps. Le zone di minimo sono presenti in corrispondenza di risedimenti calcarei, mentre picchi di emissione gamma si localizzano all’interno di litologie marnose. Infine, profili gamma-ray relativi a successioni di rampa media-interna hanno mostrato trend del gamma-ray dalla forma piatta con oscillazioni molto ridotte, e fondo del segnale gamma tra i 5 e gli 8 Cps. L’analisi spettrale ha evidenziato in tutte le sezioni investigate una ciclicità legata alla precessione, fornendo valori di periodicità di 1,14 m/c in aree di bacino, di 1.4-1.6 m/c in aree di slope, e peridiocità di 3-3,4 m/c in ambiente di rampa medio-interna. In conclusione lo studio del gamma-ray di superficie ha evidenziato come distinti ambienti deposizionali, all’interno dello stesso bacino, siano caratterizzati da profili differenti: piatto in zone di rampa, con forti deflessioni sullo slope e con oscillazioni regolari in bacino. Inoltre, spostandosi da zone distali a zone più prossimali, si nota una diminuzione della radioattività imputabile sia all’aumento di sedimento carbonatico-clastico, che alla diminuzione della frazione pelitica. Infine l’aumento dei valori di periodicità precessionale, da 1,14 m/c in aree di bacino a 3-3,4 m/c in ambiente di rampa, si traduce in un più alto tasso di sedimentazione medio, in accordo con valori maggiori di produttività carbonatica di una rampa, rispetto a quelli delle aree bacinali.

99 Beach cusps and gravel deposits monitoring in a mixed sand and gravel beach from the Apuo-Versiliese coast (Tuscany, Italy): preliminary data

SARTI G. & BERTONI D.

Dipartimento di Scienze della Terra, via S. Maria, 53 – Pisa; [email protected] - [email protected]

Introduction

Beach cusps have undergone less intensive study as indicators of gravel movement with regard to sea-weather changes rather than about their morphology (Guza and Inman, 1975; Inman and Guza, 1982; Werner and Fink, 1993; Holland and Holman, 1996; Masselink et al., 1997; Masselink and Pattiaratchi, 1998; Nolan et al., 1999). Their erosive/accretionary character is also debated. We propose a case history of gravel monitoring on a beach subject to erosive processes. The studied mixed sand and gravel beach extends for 3 km ca. from Ronchi to Cinquale and is part of the physiographic unit comprised between the River Magra mouth and Livornesi Mounts (Fig. 1).

Fig. 1 – Map of the physiographic unit in which is comprised the study area (modified from Pranzini, 2004).

The limits of the investigated area are the groyne built at the mouth of the ditch Magliano (north, Ronchi) and the Cinquale pier (south). The littoral drift is directed to the

100 south throughout this area (Gandolfi and Paganelli, 1975; Pranzini, 2004). Gravel is composed of sandstones and marbles, and secondarily of ophiolites; sandstones and ophiolites stem mainly from the River Magra, while marbles have been largely discharged by human activity in recent years in order to protect these beaches from coastal erosion through nourishments. The study area is still subject to erosive processes in the northern part (Ronchi), while the southern (Cinquale) is going through a period of expansion due to the arrival of sediments eroded from the northern beach. Gravel accumulates on the foreshore, particularly on the step, and on the proximal portion of the backshore, where berm crests hardly develop. Coarse grains tend to decrease progressively towards the south: they disappear in front of Forte dei Marmi, according to the direction of the drift.

Methods

The activity was carried out mapping on a 1:630 scale map any gravel deposits found on the beach at the time of the observation. The elements mapped during the observations have been distinguished (Fig. 2) on a morphological basis (cusps or ribbon and lenticular deposits) and on a textural basis (clast- or matrix-supported deposits). These elements have been monitored considering sea-weather variations: thus, the observations were made following fair- and storm-weather cycles in order to understand how coarse grains behave during high- and low-energy episodes. Three phases of monitoring have been conducted between April 2005 and May 2006.

Fig. 2 – The elements mapped during the study: a) clast-supported deposit; b) matrix-supported deposit; c) gravel cusps; d) sand cusps.

Results

Fair-weather phase During fair-weather periods, lenticular gravel deposits are widespread all over the beach, while sand and gravel cusps are scarcely developed because during a fair-weather period wave energy could experience short oscillations that can obliterate elements previously present on the beach: cusps are in fact characters that quickly readjust to new wave energy conditions. Coarse grains slightly decrease towards the Cinquale pier according to the direction of littoral drift.

101 Storm-weather phase When wave energy is particularly high, sand and gravel cusps are quickly reworked by wave action and disappear just like most gravel deposits. During sea-storm events, when wave energy is highest, gravel deposits as a whole are almost totally absent: it’s then safe to say that during this phase coarse grains are no more present on the backshore.

Post-storm phase At the end of the sea-storm event, wave energy gradually decreases up to falling back to values typical of fair-weather periods. This phase is characterized by the largest amount of gravel deposits and cusps; gravel cusps are present on a big portion of the beach, while lenticular deposits are spread up to the Cinquale pier. Therefore, it’s possible to assume that coarse grains are more visible on the backshore on the days following a sea storm than in every other phase.

Conclusions

i) After a review of the collected data, it is clear that gravel is not present on the backshore during storm-weather conditions. ii) This process is probably related to wave runup, which increases during high-energy periods: the coastline is driven landward and water submerges the gravel, eventually causing the disappearance of coarse grains. iii) Accepting this kind of mechanism, gravel movement should be limited, especially cross-shore: at least it follows the “zig-zag” pattern typical of uprush and backwash (French, 2001), which is considered a slow type of movement. If gravel could move back and forth quite rapidly, we would expect to find it on the backshore even during particular strong storms (the available data cannot afford to predict the gravel offshore shift). iv) At the end of the storm-weather period, sea-level returns slowly to normal showing again the gravel. The deposits quickly reappear, especially in case of a short storm- weather period, further suggesting coarse grains have been undergone a weak cross- shore movement. v) After the high-energy event, gravel reappears as widespread ribbon deposits that assume a cusp-like form only after having been reworked by wave action: this process is very quick. Therefore, cusp formation can be considered in this case an erosive process rather than accretionary.

Acknowledgements

We are very grateful to Dr. Filippo Pelliccia for his critical review of the present research. Special thanks go to Prof. Mauro Rosi and Prof. Enzo Pranzini for their helpful comments throughout the drawing up of the paper. Finally, we are glad to thank Dr. Enrico Romiti for his support in editing the images.

References

FRENCH P.W. (2001). Coastal Defences. Processes, problems and solutions. Routledge. 366 pp. GANDOLFI G. and PAGANELLI L. (1975). Il litorale pisano-versiliese (Area campione Alto Tirreno). Composizione, provenienza e dispersione delle sabbie. Boll. Soc. Geol. It., 94, 1273-1295 GUZA R.T. and INMAN D.L. (1975). Edge waves and beach cusps. Journal of Geophysical Research, 80, 2997-3012 HOLLAND K.T. and HOLMAN R.A. (1996). Field observations of beach cusps and swash motions. Marine Geology, 134, 77-93 INMAN D.L. and GUZA R.T. (1982). The origin of swash cusps on beaches. Marine Geology, 49, 133- 148 MASSELINK G., HEGGE B.J. and PATTIARATCHI C.B. (1997). Beach cusp morphodynamics. Earth Surface Processes and Landforms, 22, 1139-1155

102 MASSELINK G. and PATTIARATCHI C.B. (1998). Morphological evolution of beach cusps and associated swash circulation patterns. Marine Geology, 146, 93-113 NOLAN T.J., KIRK R.M. and SHULMEISTER J. (1999). Beach cusp morphology on sand and mixed sand and gravel beaches, South Island, New Zealand. Marine Geology, 157, 185-198 PRANZINI E. (2004). Caratteristiche morfologiche e sedimentologiche di una zona di convergenza del trasporto litoraneo (Versilia, Toscana). Studi Costieri, 8, 135-149 WERNER B.T. and FINK T.M. (1993). Beach cusps as self-organized patterns. Science, 260, 968-971

103 Facies analysis of the Late Quaternary deposits along the coast between Livorno and Piombino: paleoenvironmental and neotectonic implications

SARTI G.1, ZANCHETTA G.1, CIULLI L.1 & CERRINA FERONI A.2

1 - Dipartimento di Scienze della Terra, Università di Pisa, Via S. Maria, 53, 56126 Pisa, Italy. 2 - Istituto di Geoscienze e Georisorse, CNR Pisa, Via G. Moruzzi, 1, 56124 - Pisa

The coast between Livorno and Piombino (Southern Tuscany) displays geological evidences of quaternary tectono-eustatic interaction. Through an accurate review of previous works and a detailed geological survey, 116 sites where outcrop Late Pleistocene deposits have been located. Facies analysis allowed the identification of 11 different lithostratigraphic units, constituting a larger number than the 3 or 4 units recognized in previous studies (Cortemiglia et al., 1983; Hearty & Dai Pra, 1987; Costantini et al., 1993 and Mauz, 1999).They are constituted by mainly sandstone levels formed in upper shoreface to foreshore/backshore and coastal dune environments, separated by silty and sandy pedogenized continental deposits. In particular, aeolian deposits have been documented in this area, on the basis of sedimentological features (e.g. presence of contorted bedding, pin stripe laminae, convex-upward stratification) and fossiliferous evidences (oligotipycal non-marine mollusc fauna, Caprid track-ways). A stratigraphical correlation sketches, based on recent chronostratigraphic data (Hearty & Dai Pra, 1987; Mauz, 1999), have been proposed for the study area and, compared with the last 130 ky global sea-level curves, suggest a tectono-eustatic interaction. The superposition of the 11 lithostratigraphic units laid between MIS5 and Holocene (MIS1), associated with their depositional environment interpretation, implies repeated phases of subsidence followed by a very recent uplift. Coastal sectors with differential subsidence/uplift rates have also been recognized along the study area. These data are in strong conflict with other neotectonic reconstructions, based on MIS 5.5 markers (Nisi et al., 2003; Ferranti et al., 2006), which suggest stability or gentle uplift for this area.

References

Cortemiglia G.C., Mazzanti R. & Parea G.C. (1983). Geomorfologia della Baia Baratti (Livorno- Toscana) e della sua spiaggia. Geografia Fisica e Dinamica, 6, 148-173. Hearty P.J. & Dai Pra G. (1987). Ricostruzione paleogeografica degli ambienti litoranei quaternari della Toscana e del Lazio settentrionale con l’impiego dell’aminostratigrafia. Bollettino del Servizio Geologico d’Italia 106, 189-224. Costantini A., Lazzarotto A., Maccantelli M., Mazzanti R., Sandrelli F., Tavarnelli E. & Elter F.M. (1993). Geologia della provincia di Livorno a sud del fiume Cecina. Quaderni del Museo di Storia Naturale di Livorno 13, 1-164. Mauz B. (1999). Late Pleistocene records of littoral processes at Tyrrhenian Coast (Central Italy): depositional environments and luminescence chronology. Quaternary Science Review 18, 1173- 1184

104 Carbonate Depositional Systems: new research approaches

SIMONE L.

Dipartimento di Scienze della Terra, Università Federico II, Largo San Marcellino n.10, 80138 Napoli, Italy. E-mail: [email protected]

Since the ‘60s great attention has been dedicated to the study of shallow-water carbonate successions also in the aim of oil research. A number of analyses have focused on large scale geometries and the evolution of carbonate platforms in order to create models to predict rock-property in reservoirs. For more than thirty years the tropical depositional systems (e.g.: Florida-Bahamas, Persian Gulf) have been the main reference models. Moreover these depositional models have appeared increasingly inadequate in interpreting some ancient limestones both in terms of grain composition and geometry of the depositional bodies. Despite the assumed homogenity in the aggrading carbonate shelves, it becomes more and more evident the internal complessity, shown by large carbonate systems in several time intervals. This called for new approaches in studing ancient carbonate systems. Since the last ‘70s, different research’s groups documented the difficulty of correlating ancient limestones with Recent deposits from the tropical depositional areas. These latter support photophilous biogenic assemblages typified by hermatypic corals and green algae (Chlorozoan Facies, sensu Lees & Buller, 1972),), and are rich in non skeletal grains. The related depositional settings normally show organogenic rims and/or bioclastic/ooidal bars. An alternative model from temperate/non tropical seas was suggested for limestones, characterized by more sciaphilous biogenic assemblages, including mollusks, benthonic forams, bryozoans and red algae (Foramol Facies, sensu Lees & Buller, 1972), and pertaining to open shelves devoid of bioconstructed margins (see: Barbera et alii, 1978; Carannante et alii, 1988, Nelson, 1988a,b-; James, 1997; James & Clarke, 1997, Simone et alii, 2003). Several ancient carbonate sequences (from the bryozoan-rich Palaeozoic limestones up to the Cretaceous rudist-bearing limestones, from the Neogene rhodalgal carbonate deposits up to the Quaternary ones) were interpreted on the basis of recent counterparts from cool up to warm-temperate carbonate-bearing continental shelves as well as from tropical shelves supporting cool/mesotrophic (tendentially eutrophic) water condition (see: Barbera et alii, 1978; Nelson, 1978;1988a,b; Carannante et alii,1988; 1995; 1997; 1999; Nelson & Bornhold, 1983; Brachert et alii, 1996; James & Clark, 1997; Pomar, 2001; Simone et alii, 2003; Pedley &Carannante, 2006 among others). Such carbonate depositional systems ruled by foramol or, in some cases, microbial communities differ markedly from the tropical chlorozoan ones. In the former the characteristics of production/dispersion of sediment drastically differ from those of the tropical model. The resulting sedimentary bodies, and consequently, the entire depositional system, present distinctly different 3D geometries and evolution. Significant differences in grain mineralogy, phisiography of the depositional settings, response to the hydrodynamic conditions, result in different response to the relative sea level variations. As a consequence a difficulty in interpreting some ancient carbonate systems, for which a significant internal heterogenity is frequently realized, occurs This call for a new approach of study which takes into account the wider spectrum of depositional conditions and analyses with greater details the sedimentary processes controlling the carbonate deposition. Recognition of the diagnostic characteristics of the different modalities of production/dispersion of the carbonate sediment and of the characterization of the carbonate bodies becomes essential for an accurate interpretation of their relative depositional systems, and provides the fundamental basis for any method of prediction. The onset, development and termination of the different depositional systems (chlorozoan, foramol, microbial-dominated) during different stratigraphic intervals was clearly conditioned by several interacting environmental factors showing complex feedback mechanisms. Deciphering such factors is a new relevant tool of research in order to predict the environmental meaning of peculiar alternanting carbonate facies. In some cases such

105 facies changes were coincident to dramatic variations of the overall, global-scale paleoclimatic and paleoceanographic conditions thus suggesting the changes in shallow water carbonate facies as a possible index of drastic changes in the water mass impinging on the marginal shelf/slope areas. Significant links between the environmental deterioration, hich controlled the inception of foramol-carbonate platforms and/or of systems dominated by cyanobacterial consortia, and the well known oceanic crisis events (OAEs, see Jenkyns 1980; Jenkyns et alii, 2002), responsible for the deposition of anoxic, organic Carbon-rich facies in basins and/or on slopes had to occur. A geochemical approach and related analyses on shallow water carbonate deposits may contribute in identifying these links.

References

BARBERA, C., SIMONE, L. & CARANNANTE, G. (1978) Depositi circalitorali di piattaforma aperta nel Miocene Campano. Analisi sedimentologica e paleoecologica. Boll. Soc. Geol. It., 97, 821-834. BRACHERT, T.C., BETZLER, C., BRAGA, J.C., & MARTIN, J.M. (1996) Record of climatic change in neritic carbonates: turnover in biogenic associations and depositional modes (Late Miocene, southern Spain): Geologische Rundschau, v. 85, p. 327-337 CARANNANTE, G., CHERCHI, A., & SIMONE, L. (1995) Chlorozoan versus foramol lithofacies in Upper Cretaceous rudist limestones: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 119, p. 137-154. CARANNANTE, G., ESTEBAN, M., MILLIMAN, J.D., & SIMONE, L.(1988) Carbonate lithofacies as paleolatitude indicators: problems and limitations: Sedimentary Geology, v. 60, p. 333-346. CARANNANTE, G., GRAZIANO, R., RUBERTI, D., & SIMONE, L. (1997) Upper Cretaceous temperate-type open shelves from northern (Sardinia) and southern (Apennines-Apulia) Mesozoic Tethyan Margins, in James, N.P., Clarke, J.D.A., eds., Cool-water carbonates: SEPM, Special Publication 56, p. 309-325. CARANNANTE, G., GRAZIANO, R., PAPPONE, G., RUBERTI, D., & SIMONE, L. (1999) Depositional system and response to sea-level oscillations of the Senonian rudist-bearing carbonate shelves. Examples from Central Mediterranean areas: Facies, v. 40, p. 1-24. JAMES, N.P.(1997)The cool-water carbonate depositional realm, in James N.P. and Clarke J.A.D., eds., Cool-water carbonates, SEPM Special Publication, v. 56, p. 1-20. JAMES N.P. & CLARKE J.A.D. (1997) Cool-water carbonates, SEPM Special Publication, v. 56, p. 1-20. JENKYNS, H.C., JONES, C.E., GROCKE, D.R., HESSELBO, S.P., PARKINSON, D.N., 2002. Chemostratigraphy of the Jurassic System: applications, limitations and implications for palaeoceanography. Journal of the Geological Society, London, 152, 351-378. JENKYNS, H.C. (1980) Cetaceous anoxic events: from continents to oceans: Journal of the Geological Society, London, v.137, p. 171-188. LEES, A., & BULLER, A.T.(1972) Modern temperate-water and warm-water shelf carbonate sediments contrasted: Marine Geology, v. 13, p. 67-73. NELSON, C.S. (1978) Temperate shelf carbonate sediments in the Cenozoic of New Zealand. Sedimentology, 25, 737-771 NELSON, C.S. (Ed.) (1988a) Non-tropical shelf carbonates – Modern and ancient. Sed. Geol., 60. 367 pp. NELSON, C.S. (1988b) An introductory perspective on non-tropical shelf carbonates. Sed. Geol., 60, 3- 12. NELSON, C. S. & Bornhold, B. D. (1983) Temperate skeletal carbonate sediments on Scott Shelf, Northwestern Vancouver Island, Canada. Mar. Geol., 52, 241-266. PEDLEY M. & CARANNANTE G. (eds) (2006). Cool-water carbonate ramps: a review. In: Pedley, H.M. & Carannante G. (Eds.) Cool-Water Carbonates: Depositional Systems and Palaeoenvironmental Controls, Geological Society, London, Spec. Publ.,255,1-9 POMAR L . (2001). Types of carbonate platforms: a genetic approach. Basin Research, vol. 13, 313- 334.Palaeo, Palaeo, Palaeo, 175, 249-272. SIMONE L., CARANNANTE G., RUBERTI D., SIRNA M., SIRNA G., LAVIANO A., TROPEANO M. (2003). Development of rudist lithosomes in the Coniacian-Lower Campanian carbonate shelves of central-southern Italy: high-energy vs low-energy settings. Palaeogeography Palaeoclimatology Palaeoecology. vol. 200, pp. 5-29 ISSN: 0031-0182

106 Tectonic and climate control on turbidite sedimentation: the Messinian deposits of the Laga Formation (Central Italy)

STANZIONE O.1, MILLI S.1,2 MOSCATELLI M.2 & FALCINI F.1

1 - Dipartimento di Scienze della Terra, Università di Roma “La Sapienza”, P.le Aldo Moro 5, 00185 Roma, Italy 2 - Istituto di Geologia Ambientale e Geoingegneria IGAG-CNR, Via Bolognola 7, 00138 Roma, Italy

The Laga Formation crops out in the more external sector of the central Appennine; it records the Messinian turbidite sedimentation in a complex foreland basin, characterized by an articulate substrate related to the incipient activation of compressional structures. A recent facies and physical stratigraphic analysis, based on the measure of 45 stratigraphical- sedimentological logs for a total thickness of about 7000 m, allow us to propose a new stratigraphic framework concerning the deposits of the Laga Formation. The analyzed succession has been subdivided in three superimposed units (Laga1, Laga2, Laga3) bounded by three unconformity and their correlative conformity surfaces, stacked to form a succession with a clear progradational trend, essentially related to the depocenter migration in the foreland basin system. These units are constituted by several turbidite depositional systems and singularly show a major thinning and fining-upward trend. Based on the new chronostratigraphic scheme proposed for the Messinian stage, the main unconformity surfaces (I1, I2, I3) bounding the recognized units have been dated 7,21 Ma, 5,96 Ma, 5,6 Ma respectively. The Laga1 unit shows erosive and depositional elements represented by canyons, channels, channel-lobe transition and lobes. Deposition in an articulated basin is evidenced by sedimentary structures and facies indicating deflection and reflection of the turbidite flows in correspondence of the lateral and frontal ramp of the Gran Sasso and Montagna dei Fiori- Montagnone slopes respectively. On the contrary, the turbidite deposits of the Laga2 unit were settled in a more flat basin with multiple point sources from which coeval turbidite depositional systems developed. Differently from Laga1, channels, channel-lobe transition and lobes deposits record a closer connection with the delta apparatus. Both Laga1 and Laga2 units onlapped onto the Montagna dei Fiori-Montagnone structure that represented the internal boundary of the early Messinian Apennines foreland ramp. The Laga3 unit was essentially deposited east to the Montagna dei Fiori-Montagnone structure and records the shifting of the foreland depocenter related to the infra-Messinian tectonic phase. Sedimentary characters of this unit indicates a transition, from base to the top, from channel-lobe transition and lobes turbidite deposits to slope deposits. The high thickness of this unit, about 4000 m, is related to the tectonic event that produced modification of physiography of the basin and the re-positioning of its internal slope in correspondence of the thrust-related folds. Several turbidite depositional systems have been recognized in these three units; at larger scale they record the activation of thrust system and the remobilization of the previous deposits that were principally deposited through failure processes and secondarily by hyperpicnal flows. At smaller scale the climate control the stratigraphic organization of the turbidite depositional systems through a variation of the sediment supply in turn related to the switching from warm and humid to a cool and dry conditions that produced drastic vegetation change revealed by palynological record.

107 Revisione dell’instabilitá di sponde fluviali: applicazione al fiume Cecina

TERUGGI, L.B., RINALDI, M. & COPPI, L.

Dipartimento di Ingegneria Civile, Università degli Studi di Firenze, Via S.Marta, 3 – 50139 Firenze. [email protected]

La variazione laterale dei corsi d’acqua è uno dei problemi principali che devono affrontare i responsabili delle risorse fluviali. Comunemente la protezione di un sponda in arretramento è stata la soluzione immediata al problema, tuttavia è stato dimostrato in molti casi che in questo modo il problema non viene risolto, ma soltanto ritardato o spostato verso valle (THORNE, 1992). Negli ultimi anni, in Italia, come in altri paesi di Europa, comincia ad essere diffusa la consapevolezza che in certe condizioni l’erosione di sponda può essere positiva da un punto di vista ecologico (PIÉGAY et alii., 2005) ed aiutare la rinaturalizzazione degli alvei. Per questo è importante conoscere e differenziare i diversi processi che provocano l’arretramento delle sponde. Lo scopo di questo lavoro è affrontare lo studio dell’arretramento di sponde fluviali secondo diverse scale di indagine, integrando un approccio sedimentologico - geomorfologico con tecniche di monitoraggio e modellazione numerica.

Area di studio e metodologia

Lo studio si è concentrato sul fiume Cecina situato nella Toscana meridionale. Il Cecina è un fiume ghiaioso a fondo mobile, con una lunghezza di circa 79 km ed un’area di drenaggio di circa 900 km². Le metodologie usate sono diverse secondo la scala dell’analisi. A scala di bacino sono state caratterizzate e misurate le sponde in arretramento e le variazioni laterali lungo tutto il corso d’acqua. A scala di tratto lo studio si è concentrato sul monitoraggio di una sponda localizzata presso la confluenza del fiume Cecina con il torrente Sterza (affluente di sinistra). La sponda monitorata presenta una altezza media intorno ai 5 m ed una lunghezza di circa 170 m, dei quali 70 m sono in erosione attiva. A scala locale è stata realizzata la modellazione di una sezione rappresentativa del tratto monitorato per un singolo evento di piena.

Aspetti sedimentologici e geomorfologici delle sponde

Durante il periodo di studio sono stati rilevati 32 tratti di sponda in erosione lungo tutto il corso del fiume. Per ognuna delle sponde analizzate è stata compilata una scheda di riconoscimento analoga a quella proposta da THORNE (1998), dove sono riassunte le caratteristiche morfologiche generali della sponda insieme ai processi di instabilità riconosciuti. Detta scheda è stata completata con i dati sedimentologici rilevati sul posto. Dalle caratteristiche sedimentologiche sono stati identificati nel F. Cecina tre tipi di sponde: Tipo 1: sponde omogenee costituite da materiale granulare (sabbia, ghiaia e ciottoli); Tipo 2: sponde composite, con un livello basale granulare (sabbia, ghiaia e ciottoli) ed uno superiore coesivo (sabbia fine, limo e argilla); Tipo 3: sponde omogenee composte interamente da materiale fine coesivo (sabbia, limo, argilla). L’analisi spaziale dei dati delle sponde rilevate mostra che: ¾ I tre tipi di sponda variano da monte verso valle: le sponde del Tipo 1 sono presenti verso monte, mentre quelle del Tipo 2 aumentano verso valle e quelle di Tipo 3 verso la foce (fig. 1a). ¾ Lo spessore del materiale coesivo presente nelle sponde aumenta da monte verso valle mentre lo spessore del materiale granulare è dominante a monte tendendo a sparire a valle (fig. 1a).

108 ¾ La granulometria dei sedimenti che costituiscono il piede della sponda tende a diminuire da monte verso valle (fig. 1b) ¾ La altezza media delle sponde presenta la tendenza ad aumentare da monte verso valle (fig. 1c). ¾ La pendenza media delle sponde presenta la tendenza a diminuire da monte verso valle (fig. 1d).

-9,0 6,00 Livello coesivo D50 Livello granulare -8,0 D90 5,00 Tipo 2 Tipo 3 -7,0 4,00 -6,0

3,00 -5,0 Tipo 1 (PHI)

TI φ 2,00 -4,0 Altezza spondaAltezza [m] 1,00 -3,0 -2,0 0,00 67 64 50 49 40 35 25 16 70,00 60,00 50,00 40,00 30,00 20,00 10,00 a) Distanza dalla foce [km] b) Distanza dalla foce [km]

6 100 90 5 80 70 4 60 3 50 40 2 Altezza media [m] media Altezza 30 Pendenza media [°] media Pendenza 1 20 10 0 0 70,00 60,00 50,00 40,00 30,00 20,00 10,00 70,00 60,00 50,00 40,00 30,00 20,00 10,00 c) Distanza dalla foce [km] d) Distanza dalla foce [km]

Fig. 1: Variazioni spaziale delle caratteristiche morfologiche e sedimentologiche delle sponde del fiume Cecina: a) tipi di sponde e spessori dei livelli sedimentologici, b) distribuzione del D50 e D90 del livello i inferiore delle sponde (piede), c) altezza media e d) pendenze medie.

Sono state identificati i vari processi attuanti in ogni sponda rilevata e aggruppati secondo le tre tipologie definite in precedenza.

Misura delle variazioni laterali

Le variazioni laterali sono state analizzate e quantificate comparando fotografie aeree di diversi anni e usando gli strumenti di analisi offerti da un GIS. L’ indagine è stata eseguita nel periodo compreso tra il 1994 e il 2004. I risultati evidenziano la distribuzione dei tratti più instabili: i valori massimi sono localizzati intorno ai 25 km ed ai 50 km dalla foce, mentre i minimi sono individuati tra la foce ed i 20 km verso monte e nel tratto incassato tra formazioni rocciose a nord di Pomarance. L’indice di mobilità del corso d’acqua (BLEDSOE & WATSON, 2001) e l’indice di erosione fluviale come proposto da PIÉGAY et alii. (2005) sono stati calcolati ai fini di verificare la possibilità di utilizzare tali indici per prevedere i tratti più instabili alla scala del sistema fluviale.

109 Sponda monitorata: misura dell’arretramento

L’arretramento di una sponda è stato monitorato attraverso rilevamenti fotogrammetrici terrestri che hanno permesso di stimare che il volume del materiale eroso durante un anno è pari a 470 m³. Integrando le sezioni ottenute dai rilevamenti fotogrammetrici terrestri con i dati sedimentologici rilevati nel campo, sono state analizzate le variazioni litologiche in ognuna delle sezioni ottenute dai rilevamenti fotogrammetrici. Dal confronto dei due primi rilevamenti fotogrammetrici si è calcolato il volume del materiale eroso per ognuna delle litologie presente. Inoltre si è potuto quantificare l’interazione tra i diversi processi responsabili dell’arretramento della sponda, vale a dire erosione fluviale e movimenti di massa. Di tale processi, i movimenti di massa sono risultati quelli dominanti.

Sponda monitorata: modellazione numerica

A scala locale è stata realizzata la modellazione di una sezione rappresentativa del tratto monitorato per un singolo evento di piena. Scelto un particolare evento di pioggia tra quelli monitorati, è stata condotta un’analisi delle pressioni interstiziali all’interno della sponda, tramite l’applicazione del software SEEP/W. Ha seguito un’analisi di stabilità della sponda, effettuata attraverso un software dotato della stessa interfaccia grafica SLOPE/W, in grado di valutare gli scivolamenti planari o rotazionali, e tramite un foglio di calcolo in grado di prevedere crolli di massa aggettante. Avvalendosi delle simulazioni effettuate si sono potuti modellare anche i principali effetti prodotti dalla vegetazione sulla stabilità di sponda.

Ringraziamenti

La ricerca è stata finanziata con fondi MIUR, progetto: ‘Incentivazione alla mobilità di studiosi stranieri e italiani residenti all’estero’. Gli autori ringraziano la Regione Toscana e la Provincia di Pisa, Servizio Difesa del Suolo, che hanno contribuito con materiale cartografico e foto aeree.

Opere citate

BLEDSOE B.P. & WATSON C.C. (2001) - Logistic regression of channel pattern thresholds: meandering, braiding and incising. Geomorphology, 38, 281-300. PIÉGAY H., DARBY S.E., MOSSELMAN E. & SURIAN N. (2005) - A review of techniques available for delimiting the erodible river corridor: a sustainable approach to managing bank erosion. River Research and Application, 21, 773-789. THORNE C.R. (1992) - Bend scour and bank erosion on the meandering Red River, Louisiana. In: Carling P.A. & Petts G.E. Eds., Lowland Floodplain Rivers: Geomorphological Perspectives, 95- 115. John Wiley & Sons, Chichester. THORNE C.R. (1998) - Stream reconnaissance handbook. Geomorphological investigation and analysis of river channels. John Wiley & Sons, Chichester.

110 Proposal for a classification scheme for combined flow sedimentary structures and the meaning of sigmoidal- and hummocky-cross stratification in facies analysis

TINTERRI R.

Dipartimento di Scienze della terra, Università di Parma; e-mail: [email protected]

The hummocky (HCS) and sigmoidal structures are among the most common bedforms that can be found in the stratigraphic record. These structures can, in fact, be recognized in all ancient sedimentary environments in which the deposition is governed by fluid mechanics. Their ubiquity, therefore, often poses the problem of their real stratigraphic and sedimentologic meaning in facies analysis. This problem became particularly important in the study of flood-dominated fluvio- deltaic systems in which it can be seen how this two types of structures are intimately associated to each other. On the basis of facies analysis of these systems, in fact, the sigmoidal bedding especially characterizes the facies sequences of fluvial systems and mouth bars whereas HCS is present particularly in delta-front sandstone lobes. Since different experiences inevitably lead to different points of view, in literature there are various hypotheses regarding these structures, mainly based on an actualistic approach to the problem. However, these hypotheses raise doubts in terms of environmental and hydrodynamic interpretation when they are seen within a more general stratigraphic framework. Although sigmoidal-cross stratification is generally interpreted as being associated to tidal currents and HCS to storm events, detailed stratigraphic and sedimentologic analysis of fluvio-deltaic systems show that these structures can be also deposited by various types of combined flows related to gravity flows produced by fluvial floods entering seawater. Hummocky structures, however, are common in many other depositional environments such as, for example, storm-dominated shorefaces and even in ponded turbidite basin plain. The starting point for a better understanding of the sigmoidal- and hummocky-cross stratification is to remember that they are multigenetic and ubiquitous structures since they can be found in numerous sedimentary environments and many are the processes that can produce them. Consequently they cannot be indicative of any depositional environments and processes if they are not viewed within their stratigraphic framework and facies association. On the basis of these concepts and of a comparison between experimental data available in literature and field data based on the facies tracts of many flood-dominated fluvio-deltaic systems, this study proposes a classification scheme for large- and small-scale combined flow structures. This scheme is based on the consideration that since there exists a continuum of types of flow that range from unidirectional (Uu) to oscillatory flows (Uo), there must exist a continuum of sedimentary structures which range from strongly asymmetrical ripple and megaripple related to unidirectional flow to symmetrical oscillatory ripple and HCS related to oscillatory flows. In particular, both at small and large scale, in the field of pulsating flows (Uu≥Uo) various types of bedforms with internal sigmoidal-cross laminae would be stable, whereas in the field of asymmetrical oscillatory flows (Uu≤Uo) different types of oscillatory ripple and hummocky structures characterized by different degrees of anisotropy would be stable.

111 The relationship between flood hydrograph and facies sequences of delta-front sandstone lobes produced by hyperpycnal flows

TINTERRI R.

Dipartimento di Scienze della terra, Università di Parma; e-mail: [email protected]

In the last ten years the interest in hyperpycnal flows and their deposits has progressively increased. Hyperpycnal flows are gravity flows triggered by fluvial floods entering a lacustrine or marine receiving basin in which the excess of density is due to the sediment trasported as suspended load. They are typical of small basins in tectonically active zones where the high rates of tectonic uplift, high gradients and short trasfer zones increase the sediment flux to the sea through the development of fluvial floods. The type of hyperpycnal flow, even if it is usually considered as a turbulent gravity flow, depends upon the type of gravity flow that enters seawater. For these reasons there can be various types of hyperpycnal flow and consequently of delta-front sandstone lobe that characterize fan-delta and river-delta systems whose facies are still relatively poorly studied. Recent works, moreover, interpret these deposits on the basis of the variations of steadiness and uniformity related to the rising and falling limbs of the flood hydrograph. According to these concepts, associated to the rising and falling limb of the hydrograph, a progressive forestepping and backstepping of the depositional zone is observed, which is recorded in the deposit, at a fixed position, by an inverse to normal grading respectively, generally characterized by continuous and gradual grain-size variations. Facies analysis of delta-front sandstone lobes of some particularly significant facies sequences deriving from various river-delta systems of the south-central Pyrenees leads to the following considerations: 1) The vertical grain-size variations which are interpreted as being associated to the variations of momentum related to the rising and falling limb of the hydrograph occur in a discontinuous way through sharp breaks in grain sizes often characterized by erosive surfaces that bounded laminasets of different grain-size populations and sedimentary structures. The erosive surfaces are particularly evident at the base of the coarsest laminaset that represents the peak flood. 2) Facies sequences of these beds present particular characteristics that depend upon their position along the depositional profile. In the proximal zone, with respect to the mouth bars, the beds are characterized by various laminasets that may show an inverse to normal grading in which the peak flood is represented by an erosive surface usually characterized by a residual pebble alignment. In the intermediate zone, by contrast, the beds are constituted by various laminasets showing the typical inverse to normal grading where the peak flood is indicated by an erosive surface and bypass strucures such as megaripples and/or anisotropic HCS in pebbly very coarse sandstones. At the end, the distal zones are characterized by only one laminaset or bed related to peak flood. These beds that are normally graded, sharp based and characterized by HCS are made up of fine sand that bypass the proximal and intermediate zones. In conclusion, the peak-flood phases are recorded by bypass structures in proximal and intermediate zones and by normally graded beds of fine sand with isotropic HCS in more distal zones.

112 Significato geodinamico dell'organizzazione stratigrafica dei depositi di chiusura del ciclo bradanico (Basilicata, Italia meridionale)

TROPEANO M., SABATO L., CILUMBRIELLO A. & PIERI P.

Dipartimento di Geologia e Geofisica - Università di Bari

Le unità formazionali definite e utilizzate nei lavori di rilevamento degli anni '60 relativi alla redazione della Carta Geologica d’Italia in scala 1:100.000, descrivono i depositi di riempimento della Fossa bradanica come una successione di età Pleistocene inferiore (Calabriano) composta da una semplice sovrapposizione aggradazionale di formazioni marine in assetto tabulare (Sabbie di Monte Marano, Calcareniti di Monte Castiglione, Conglomerato d’Irsina, Sabbie dello Staturo e Argille Calcigne) poggianti in conformità sulla formazione delle Argille subappennine (RICCHETTI, 1967; AZZAROLI et alii, 1968). In base a questa vecchia suddivisione formazionale e ad una diversa definizione di età degli stessi depositi, alcuni autori hanno attribuito alle fasi terminali di riempimento della Fossa bradanica il significato geodinamico di cessazione della subsidenza flessurale durante il Pleistocene medio, con tilting post-deposizionale causato dal sollevamento della catena (CINQUE et alii, 1993; PATACCA & SCANDONE, 2001). Una diversa interpretazione geodinamica basata sulla nuova suddivisione litostratigrafica proposta per gli stessi depositi, cui nell’insieme è stata attribuita la denominazione informale di “Depositi costieri regressivi” (PIERI et alii, 1996), ha portato invece a ritenere che tali depositi si siano formati durante il sollevamento e che la loro distribuzione altimetrica sia stata determinata da processi di terrazzamento deposizionale più che da tilting successivo alla loro deposizione (TROPEANO et alii, 2002a, 2002b). Le successioni affioranti sono infatti organizzate secondo cunei progradanti, costituiti da depositi di mare sottile passanti verso l'alto a depositi di transizione e/o continentali, cui erosivamente possono sovrapporsi altri depositi continentali non attribuibili alla serie bradanica s.s. (SABATO, 1996; SABATO et alii, 2004; PIERI et alii, in prep.). In particolare, nell'ambito dei cunei progradanti, è stata riconosciuta un’alternanza di prismi costieri in regressione deposizionale (rappresentati prevalentemente da successioni sabbiose di spiaggia) e prismi costieri in regressione erosiva (rappresentati prevalentemente da successioni conglomeratiche deltizie) formatisi progressivamente a quote inferiori nel verso della progradazione; tale tipo di configurazione (downward-shifting configuration) sarebbe legata all’interferenza fra oscillazioni relative del livello del mare di alta frequenza e sollevamento regionale, già in atto almeno a partire dal Pleistocene inferiore (Siciliano) (PIERI et alii, 1996; TROPEANO et alii, 2002a; SABATO et alii, 2004). Al fine di verificare il tipo di configurazione riconosciuto, nuovi studi sono stati condotti nell'area di Banzi e Genzano, adiacente a quella di Irsina, dove si sarebbero depositati i più vecchi "Depositi costieri regressivi" (PIERI et alii, 1996). Questi ultimi, pur se localmente caratterizzati da prismi costieri progradanti (LAZZARI & PIERI, 2002), risultano organizzati in una configurazione di tipo aggradazionale (CILUMBRIELLO, 2004; CILUMBRIELLO et alii, in stampa). In particolare si osservano depositi prevalentemente conglomeratici relativi ad ambienti continentali (area nord-occidentale - Banzi) che passano a depositi deltizi e che si interdigitano con depositi prevalentemente sabbiosi relativi ad ambienti marino-transizionali (area sud- orientale - Genzano). L'organizzazione stratigrafica riconosciuta viene attribuita all’interferenza fra subsidenza bacinale ed oscillazioni relative del livello del mare. In particolare, i corpi conglomeratici rappresentano il prodotto di sistemi deposizionali sovralimentati sviluppatisi durante fasi di relativo low-stand del livello del mare mentre i depositi sabbiosi di ambiente marino relativamente più profondo rappresentano il prodotto di sistemi deposizionali sviluppatisi durante fasi di trasgressione e relativo high-stand del livello del mare. Nel complesso questa porzione della successione indica che la sedimentazione, pur se caratterizzata da ciclicità di alta frequenza, avveniva in un bacino in cui il tasso di accumulo dei sedimenti compensava quasi totalmente il tasso di subsidenza (CILUMBRIELLO, 2004). In conclusione, confrontando l'organizzazione stratigrafica riconosciuta in diversi settori della Fossa bradanica, si può affermare che i "Depositi costieri regressivi" hanno registrato durante la loro sedimentazione un cambio di regime geodinamico, da testimoni di subsidenza

113 bacinale (area di Banzi-Genzano) a testimoni di sollevamento regionale (area di Irsina). Non è corretto quindi attribuire un significato geodinamico univoco ed una stessa età ai terreni in precedenza definiti come Formazione del Conglomerato di Irsina (in via di emendamento). A tale proposito, la datazione del momento di inversione di regime geodinamico dovrà prevedere una corretta attribuzione di età ai “Depositi costieri regressivi”, considerati siciliani, per l'area studiata, da PIERI et alii (1996), e di età mediopleistocenica, a livello di bacino, da PATACCA & SCANDONE (2001).

Bibliografia

AZZAROLI A., PERNO U. & RADINA B. (1968) - Note illustrative della Carta Geologica d'Italia, alla scala 1:100.000 del F° 188 "Gravina di Puglia". Serv. Geol. d'It.: pp. 35. CILUMBRIELLO A. (2004) - Caratteri stratigrafici dei depositi regressivi pleistocenici della Fossa bradanica nell'area di Banzi e Genzano di Lucania (Basilicata). Rilevamento geologico alla scala 1:10.000 delle tavolette 188 IV SW Genzano di Lucania (p.p) e 188 (p.p) III NW Oppido Lucano (p.p). Tesi di Laurea inedita, Università della Basilicata, Potenza: pp. 90. CILUMBRIELLO A., SABATO L. & TROPEANO M. (in stampa) - Problemi di cartografia geologica relativa ai depositi quaternari di chiusura del ciclo della Fossa bradanica: l'area chiave di Banzi e Genzano di Lucania (Basilicata). APAT Volume speciale in memoria del Prof. Iacobacci. CINQUE A., PATACCA E., SCANDONE P. & TOZZI M. (1993) - Quaternary kinematic evolution of the Southern Apennines: Relationship between surface geological features and deep lithospheric structures. Annali di Geofisica, 36, n.2: 249-259. LAZZARI M. & PIERI P, (2002) - Modello stratigrafico-deposizionale della successione regressiva infrapleistocenica della Fossa bradanica nell'area compresa tra Lavello, Genzano e Spinazzola. Mem., Soc., Geol., It., 57: 231-237. PATACCA E. & SCANDONE P. (2001) - Late thrust propagation and sedimentary response in the thrust-belt- foredeep system of the Southern Apennines (Pliocene-Pleistocene). In: G. B. VAI & MARTINI I. P. (Eds.): “Anatomy of Orogen: The Apennines and Adjacent Mediterranean Basins”. Kluwer Academic Publ.: 401-440. PIERI P., BOENZI F., GALLICCHIO S., SABATO L. & TROPEANO M. (in prep.) – Note illustrative del F° 471 “Irsina”. PIERI P., SABATO L. & TROPEANO M. (1996) - Significato geodinamico dei caratteri deposizionali e strutturali della Fossa bradanica nel Pleistocene. Mem. Soc. Geol. It., 51: 501-515. RICCHETTI G. (1967) - Lineamenti geologici e geomorfologici della media valle del fiume Bradano. Boll. Soc. Geol. It., 86: 607-622. SABATO L. (1996) - Quadro stratigrafico-deposizionale dei depositi regressivi nell'area di Irsina (Fossa bradanica). Geologica Romana, 32: 219-230. SABATO L., TROPEANO M. & PIERI P. (2004) - Problemi di cartografia geologica relativa ai depositi del F° 471 "Irsina". Il Conglomerato di Irsina: mito o realtà? Il Quaternario, 17 (2/1): 391-404. TROPEANO M., SABATO L. & PIERI P. (2002a) - Filling and cannibalization of a foredeep: Bradanic Trough, southern Italy. Geological Society of London, Special Publications, 191: 55-79. TROPEANO M., SABATO L. & PIERI P. (2002b) - The Quaternary "Post-turbidite" sedimentation in the south- Apennines foredeep (Bradanic Trough-southern Italy). Boll. Soc. Geol. It., Vol. Sp. n.1: 449-454.

114 Sequence-stratigraphic models in growth fault-bounded basins

ZECCHIN M.

Istituto Nazionale di Oceanografia e di Geofisica Sperimentale – OGS, Borgo Grotta Gigante 42/c, 34010 Sgonico (TS)

The stratal architecture of deposits accumulated in growth fault-bounded basins may be very different from that proposed by sequence-stratigraphic models developed for passive, divergent continental margins. Local factors, such as tectonics, sediment supply, and physiography may exert strong variability in stratal geometries and stacking patterns of systems tracts. The Pliocene succession of the Crotone Basin provides spectacular examples that show how normal fault-controlled subsidence and sediment supply may interact to produce sequence architectures that deviate from the original sequence- stratigraphic model. As the result, different sequence-stratigraphic models were developed for these successions. Peculiar stratal geometries and stacking patterns within systems tracts are commonly recognizable. Relatively thick transgressive systems tracts (TST) are common in the lower Pliocene Zinga 2 and Zinga 3 stratal units and in the middle Pliocene Strongoli stratal unit (Zecchin et al., 2004, 2006). Transgressive intervals are composed of lagoonal mudstones that are abruptly overlain by shoreface sandstones. A typical aggradational to progradational highstand systems tract (HST) is recognizable in the Strongoli stratal unit, whereas an aggradational highstand systems tract (AHST) is a characteristic feature of both Zinga 2 and Zinga 3 stratal units in half-graben basins. The AHST is defined as “an aggradational package of small-scale cycles deposited above a transgressive surface or a relatively thick retrogradational succession interpreted as a TST” (Zecchin et al., 2006). A distinct maximum flooding surface is not recognized at the base of the AHST, whereas thin forced regressive deposits (FRST) locally marked at the base by an erosional surface are present at the top (Zecchin et al., 2006). The AHST resulted from balanced conditions between the rate of sediment supply and the rate of creation of accommodation. Highstand deposits consist of shoreface to inner shelf sandstones and mudstones. Lowstand deposits (LST) have not been observed within these successions and are inferred to be located basinwards. Variations in the tectonic regime complicate the stratal architecture of sequences. This is the case of the continental to shallow marine Serra Piani stratal unit. Sedimentation was favoured by fault-controlled subsidence, whereas major unconformities were the product of regional uplift. The Serra Piani stratal unit exhibits an overall transgressive trend. The present cases provide interesting implications for sequence-stratigraphic analyses in extensional fault-controlled basins.

References

Zecchin, M., Massari, F., Mellere, D. & Prosser, G. 2004. Anatomy and evolution of a Mediterranean- type fault bounded basin: the Lower Pliocene of the northern Crotone Basin (Southern Italy). Basin Research, 16, 117–143.

115 High-resolution seismic stratigraphy in the Venice area

ZECCHIN M.1, BRANCOLINI G.1, DONDA F.1, RIZZETTO F.2 & TOSI L.2

1 - Istituto Nazionale di Oceanografia e di Geofisica Sperimentale – OGS, Borgo Grotta Gigante 42/c, 34010 Sgonico (TS) 2 - Istituto di Scienze Marine – Consiglio Nazionale delle Ricerche, San Polo 1364, 30125 Venezia

High resolution seismic profiles, which have been carried out within the Co.Ri.La. 3.16 Research Line, have evidenced the most significant elements of the late Pleistocene and Holocene geological evolution (last 20,000 years) of the Venice lagoon and offshore areas. The Holocene lagoon displays an abrupt difference between the lagoon mud-flat, characterized by fine-grained sedimentation and flat stratification, and the tidal channels, which commonly cut the Pleistocene-Holocene boundary and are only partially filled. The Pleistocene-Holocene boundary consists of an unconformity that is well recognizable in seismic profiles. It is located about 5 m below sea level in the area of the Venice city, and about 20 m in the southern lagoonal area. This surface tends to outcrop landward and seaward. The thickness of the Holocene succession increases from northern to southern locations up to about 20 m. Tidal inlets are highly dynamic, as evidenced by the presence of active erosional trenches in the Chioggia and Malamocco areas. Indications of active migration of a trench are found in the Chioggia inlet. Inlet deposits consist of accreting macroforms and dunes. The Holocene succession of the offshore area is characterized by channelized deposits separated by areas showing sub-horizontal reflectors in the lower part, and by a prograding marine wedge in the upper part. The base of these channels represents the Pleistocene-Holocene boundary in offshore locations. Present high-resolution seismic data and core data in the lagoonal area and the barrier island allow a sequence-stratigraphic interpretation of the Holocene succession of the Venice area. This succession is composed of a transgressive systems tract (TST) and of a highstand systems tract (HST). The TST, accumulated above the Pleistocene-Holocene boundary that is the sequence boundary (SB) of the Holocene sequence, consists of a retrogradational package formed by fluvial or estuarine channel fill deposits in the lower part and by fine-grained backbarrier deposits in the upper part. A wave ravinement surface (WRS) marks the marine ingression during the late transgressive phase, and is approximately coincident with the maximum flooding surface (MFS) in several places. The HST is composed of the marine prograding wedge and of the lagoonal mud-flat and tidal channel deposits in landward locations. The observed sequence-stratigraphic organization of the Holocene sequence in the Venice area is similar to that of coeval successions placed in the western side of the northern Adriatic epicontinental shelf.

116 Paleosols in a Pleistocene intermontane basin: a multidisciplinary approach to the study of the High Agri Valley (Southern Apennines, Italy)

ZEMBO I.1, BERSEZIO R.1 & TROMBINO L.1,2

1 - Dipartimento Scienze della Terra, Università degli Studi di Milano, via Mangiagalli 34, 20133 MI 2 - CNR - IDPA, via Mangiagalli 34, 20133 Milano; e-mail: [email protected]

The stratigraphic architecture of the Quaternary intermontane basin of the High Agri Valley (Lucanian Apennines) can be reconstructed by the integration of stratigraphical, sedimentological, geomorphological and geopedological methods. The exposed part of the syntectonic basin fill (with a thickness of more than 100 m) crops out in the south-eastern sector of the basin and is represented by a group of clastic units, of Mid-Upper Pleistocene age, which were deposited in alluvial fan, alluvial plain, fan delta and lacuo-palustrine environments. This succession consists of several units bounded by surfaces which can be associated with preserved weathering profiles and/or paleosols. The latter developed at the top of lateral alluvial fans (from both the northern and southern sides of the basin) and on the NW-SE axial alluvial plain, during geomorphological stability stages. Six weathering profiles, corresponding to truncated paleosols, have been chosen for a detailed geopedological characterization and stratigraphic correlations. The geopedological study was based on field-work, grain-size, chemical and mineralogical analysis, as well as micromorphological observations of thin sections. Field-based profile descriptions indicate that all the pedological bodies are incomplete due to the absence of topsoil. This is interpreted as a consequence of the post-stability erosion of the studied surfaces, suggesting that repetitive cycles of aggradation, stabilization, pedogenesis and subsequent erosion occurred both through the lateral alluvial fans and the axial plain settings. The lateral continuity and correlability of the weathering profiles is highly variable, ranging from tens to thousands of metres. This variability is due to differences in the relief, drainage, stability and sedimentation rates which characterize the fan and alluvial plain environments. Two profiles provided key-surfaces used for correlations at the basin-scale. One of these profiles consists of an andisol which developed as a result of the weathering of a tephra layer. This level is expected to offer a good geochronological marker as a result of the dating of the pyroclastic apatites currently in progress. The correlation of the pedological features of this weathered ash and volcanic glass layer with the equivalent paleosols developed on alluvial parent materials, provides a valuable marker bed of basinwide extension and chronological significance. Moreover, if available, age determination of the volcanic parent material will permit a more thorough evaluation of the duration and intensity of the pedogenetic processes. From the paleopedological point of view, all the paleosols show relict features, which can be related to pedogenetic processes not in equilibrium with the present-day environmental condition. In addition, they often show polycyclic characteristics too, attesting distinct pedogenetic phases, consistent with paleoclimates, spanning from semiarid to warm and, moderately wet, with clear seasonality of water deficit. The strongly weathered profiles appear to be related to long-cycle pedogenesis (i.e. some ten thousand years) rather than extreme paleoclimatic conditions. In conclusion, the combination of physical stratigraphy, facies analysis, geomorphological and paleopedological studies of the stratigraphic boundaries allow to: 1) improve correlation in a continental, tectonically mobile setting; 2) characterize stability of environments and deposition-erosion cycles; 3) define climate changes during the Quaternary, eventually providing a tool for regional characterization; 4) investigate the pedogenetic processes (rate and intensity) in an intermontane mobile basin.

117 Elenco dei partecipanti

Accaino Flavio [email protected] OGS - Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Trieste

Aldinucci Mauro [email protected] Dipartimento di Scienze della Terra, Università di Siena Ali Abdel Megid Ada [email protected] Dipartimento di Scienze Geologiche e Geotecnologie, Università di Milano Bicocca

Amorosi Alessandro [email protected] Dipartimento di Scienze della Terra e Geologico-Ambientali, Università di Bologna Argnani Andrea [email protected] CNR - ISMAR Istituto di Scienze Marine di Bologna

Aroldi Carlo [email protected] University Babes-Bolyai di Cluj-Napoca (Romania) Artoni Andrea [email protected] Dipartimento di Scienze della Terra, Università di Parma

Barone Mirko [email protected] Dipartimento di Scienze della Terra, Università della Calabria Bellino Laura [email protected] CNR - IGG Istituto di Geoscienze e Georisorse di Torino

Benvenuti Marco [email protected] Dipartimento di Scienze della Terra, Università di Firenze Bernardeschi Andrea [email protected] Dipartimento di Scienze della Terra, Università di Pisa

Bertacchini Milena [email protected] Dipartimento di Scienze della Terra, Università di Modena e Reggio Emilia Bertok Carlo [email protected] Dipartimento Scienze della Terra, Università di Torino

Bertoni Duccio [email protected] Dipartimento di Scienze della Terra, Università di Pisa Bonciani Filippo [email protected] Centro di Geotecnologie, Università di Siena

Cacchio Paola [email protected] Dipartimento di Biologia di Base ed Applicata, Universita' degli Studi di L'Aquila Cantalamessa Gino [email protected] Dipartimento di Scienze della Terra, Università di Camerino

Capezzuoli Enrico [email protected] Dipartimento di Scienze della Terra, Università di Siena Carpenito Giulio [email protected] Dipartimento di Scienze della Terra, Università di Modena e Reggio Emilia

Carannante Alfredo [email protected] Laboratorio di Bioarcheologia, Università degli Studi “Suor Orsola Benincasa” Napoli Chiarella Domenico [email protected] Dipartimento di Scienze della Terra, Università della Calabria

Cilumbriello Antonietta [email protected] Dipartimento di Geologia e Geofisica, Università di Bari Cipollari Paola [email protected] Dipartimento di Scienze Geologiche, Università di Roma 3

Ciulli lorenzo [email protected] Dipartimento di Scienze della Terra, Università di Pisa

118 Conti Stefano [email protected] Dipartimento di Scienze della Terra, Università di Modena e Reggio Emilia Cosentino Domenico [email protected] Dipartimento di Scienze Geologiche, Università di Roma 3

D'Atri Anna [email protected] Dipartimento Scienze della Terra, Università di Torino Dalla Valle Giacomo [email protected] CNR - ISMAR Istituto di Scienze Marine di Bologna

Del Conte Sara [email protected] Dipartimento di Scienze della Terra, Università di Firenze Dela Pierre Francesco [email protected] Dipartimento Scienze della Terra, Università di Torino

Dominici Rocco [email protected] Dipartimento di Scienze della Terra, Università della Calabria Falcini Federico [email protected] Dipartmento di Scienze della Terra, Università di Roma La Sapienza

Fantoni Laura [email protected] Dipartimento di Scienze della Terra, Università di Modena e Reggio Emilia Festa Andrea [email protected] Dipartimento Scienze della Terra, Università di Torino

Fioraso Gianfranco [email protected] CNR - IGG Istituto di Geoscienze e Georisorse di Torino Fioroni Chiara [email protected] Dipartimento di Scienze della Terra, Università di Modena e Reggio Emilia

Fontana Daniela [email protected] Dipartimento di Scienze della Terra, Università di Modena e Reggio Emilia Gamberi Fabiano [email protected] CNR - ISMAR Istituto di Scienze Marine di Bologna

Gennari Rocco [email protected] Dipartimento di Scienze della Terra, Università di Parma Giunta Simona [email protected] Dipartimento di Scienze del Mare, Università Politecnica delle Marche

Guido Adriano [email protected] Dipartimento di Scienze della Terra, Università della Calabria Invernizzi Giuliano [email protected] ENI Milano

Lirer Fabrizio [email protected] CNR IAMC Istituto per l'ambiente marino costiero, Sezione Geomare sud Napoli Longhitano Sergio [email protected] Dipartimento Scienze della Terra, Università della Basilicata

Lucente Claudio [email protected] Regione Emilia Romagna Servizio Tecnico Corrado Bacini Enza, Panaro e Secchia, Modena Lugli Stefano [email protected] Dipartimento di Scienze della Terra, Università di Modena e Reggio Emilia

Manzi Vinicio [email protected] Dipartimento di Scienze della Terra, Università di Parma Marchetti Dori Simona [email protected] Dipartimento di Scienze della Terra, Università di Modena e Reggio Emilia

Martire Luca [email protected] Dipartimento Scienze della Terra, Università di Torino

119 Mele Mauro [email protected] Dipartimento Scienze della Terra, Università di Milano Milli Salvatore [email protected] Dipartimento di Scienze della Terra, Università di Roma La Sapienza

Mienert Juergen [email protected]; Department of Geology, University of Tromsø Norway Monegato Giovanni [email protected] Dipartimento di Geologia, Paleontologia e Geofisica, Università di Padova

Morigi Caterina [email protected] Dipartimento di Scienze del Mare Università Politecnica delle Marche Natalicchio Marcello [email protected] CNR - IGG Istituto di Geoscienze e Georisorse di Torino

Negri Alessandra [email protected] Dipartimento di Scienze del Mare, Università Politecnica delle Marche Onofrio Vincenzo [email protected] Dipartimento di Geologia e Geofisica, Università di Bari

Ortolani Franco [email protected] Dipartimento di Pianificazione e Scienza del Territorio, Università di Napoli Pagliuca Silvana [email protected] CNR ISAFoM di Napoli

Pandolfi Luca [email protected] Dipartimento di Scienze della Terra, Università di Pisa Panieri Giuliana [email protected] Dipartimento di Scienze della Terra e Geologico-Ambientali, Università di Bologna

Parisi Serena [email protected] Dipartimento Scienze della Terra, Università della Basilicata Parlagreco Luca [email protected] ICRAM di Roma

Pascucci Vincenzo [email protected] Istituto di Scienze Geologico-Mineralogiche, Università di Sassari Perotti Elena [email protected] Dipartimento Scienze della Terra, Università di Torino

Perri Francesco [email protected] Dipartimento Scienze della Terra, Università della Basilicata Perrotta Sonia [email protected] Istituto di Geologia, Università di Urbino

Petrucci Fabrizia [email protected] Gruppo GAMPS Badia a Settimo, Firenze

Piovan Silvia [email protected] Dipartimento di Geografia, Università di Padova

Roveri Marco [email protected] Dipartimento di Scienze della Terra, Università di Parma Russo Franco [email protected] Dipartimento di Scienze della Terra, Università della Calabria

Sabato Luisa [email protected] Dipartimento di Geologia e Geofisica, Università di Bari Sampalmieri Gianluca [email protected] Dipartimento di Scienze Geologich,e Università di Roma tre

Sandrelli Fabio [email protected] Dipartimento di Scienze della Terra, Università di Siena

120 Sarti Giovanni [email protected] Dipartimento di Scienze della Terra, Università di Pisa Simone Lucia [email protected] Dipartimento di Scienze della Terra, Università di Napoli

Smith Mike [email protected]

Sonnino Maurizio [email protected] Dipartimento di Scienze della Terra, Università della Calabria

Spalluto Luigi [email protected] Dipartimento di Geologia e Geofisica, Università di Bari Stanzione Olivier [email protected] Dipartimento di Scienze della Terra, Università di Roma La Sapienza

Tinivella Umberta [email protected] OGS - Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Trieste Teruggi Liliana [email protected] Dipartimento di Ingegneria Civile, Università di Firenze

Tinterri Roberto [email protected] Dipartimento di Scienze della Terra, Università di Parma Trenkwalder Stefania [email protected] CNR - IGG Istituto di Geoscienze e Georisorse di Torino

Tropeano Marcello [email protected] Dipartimento di Geologia e Geofisica, Università di Bari Varrone Dario [email protected] CNR - IGG Istituto di Geoscienze e Georisorse di Torino

Zecchin Massimo [email protected] Istituto Nazionale di Oceanografia e di Geofisica Sperimentale OGS di Trieste Zembo Irene [email protected] Dipartimento Scienze della Terra, Università di Milano

121