Facies, architecture and genetic controls of carbonate ramp aprons development

Cool-water Carbonate Ramp Aprons (CRA) are depositional systems in which skeletal sand and gravel are redistributed basinwards on a ramp, off a shallow carbonate platform by tractive currents as a result of flow funnelling in between topographic highs. These deposits are different and should not be confused with the carbonate apron models proposed by of Mullins and Cook (1986) who describe either carbonate deep water turbiditic systems accumulated at the base of the slope or talus cones formed at the margins of carbonate build ups. A key example of CRA facies assemblages is represented by the Early Pleistocene, Favignana Calcarenite where bimodal depositional processes, occurring in a water depth range estimated between 5 and 80 m, typical of this depositional environment, resulted in the accumulation of distinct and alternating sedimentary packages: a low- energy sedimentary assemblage formed by typical subaqueous dunes consisting of tabular cross bedded grainstones and packstones often bioturbated is coupled with a heterogeneous facies assemblage where, coarse-grain filled erosional depressions, largely variable in size, formed by downslope confined flows generating elongated scours are associated with low- angle cross bedded grainstones formed in supercritical conditions (backset bedded, antidunes etc). Based on outcrop examination and 2D seismic line interpretation CRA deposits have a triangular shape which form a series of coalescent fans forming an overall apron connecting the shallow carbonate platform/ inner ramp setting (factory) to the deeper basin through a steep ramp. The seismic data in particular allow the deciphering of the internal architecture and understanding the modality of progradation and aggradation and lateral shift of these sedimentary bodies. In the sedimentary record the carbonate ramp aprons develops a wedge-like geometry composed by discrete superposed and laterally stacked lenticular bodies often separated by erosional surfaces marked by reflector discontinuities. The frequency of erosional/reactivation surfaces attest for frequent high-energy events which, in the basis of sedimentary facies present in outcrops, demonstrate the important role plaid by high-energy storms and possibly tsunamis in building these deposits. Similarly to what has been described for the Favignana Calcarenites, CRA deposits can represent an important part of ancient sedimentary record of intrashelf carbonate successions such as the Oligocene/Miocene carbonate successions in the Gulf of Venezuela. There, well-sorted calcarenite drift deposits forming similar well-sorted calcarenite drift apron-shaped deposits, similar to the ones described in Favignana are visible in the topographic lows, next to steep platform margins

SEDIMENTARY DYNAMICS OF THE MARETTIMO CONTINENTAL SHELF AND MARETTIMO CHANNEL (EGADI ISLANDS – WESTERN MEDITERRANEAN): ANALYSIS OF DEPOSITIONAL AND EROSIONAL FEATURES.

Sedimentary dynamics of the Marettimo continental shelf and Marettimo Channel (Egadi Island – Western Mediterranean), have been unveiled based on the erosive and depositional features observed at the seafloor. Different morphologic features were recognized through side scan sonar, multibeam and high-resolution seismics, acquired in the framework of national Research Projects (CARG, GebecSud, MaGIC) carried out by the Department of Earth and Marine Science (former Department of Geology and Geodesy) of the University of Palermo. Sediment samples have been also collected and analyzed. The Egadi Islands are part of the NW Sicilian offshore, and belong to the mountain chain that connects the Sicilian chain to the Maghrebides one. The Marettimo Island represents an isolated portion of the Egadi continental shelf and is separated from the rest of the archipelago by the Marettimo Channel. Previous studies allowed to recognize different kind of sedimentary structures along the seafloor. Lo Iacono and Guillén (2008) described extensive field of subaqueous dunes (Ashley, 1990) along the Marettimo inner shelf, forming on gravelly and pebbly sediments and related to strong storm events (H:5.5 m, T: 12 s). Larger dunes have been observed in the north-western sector of the inner shelf with wavelengths ranging from 1 to 2.5 m, heights between 15 cm and 30 cm and extending laterally for hundreds of meters. Moreover in the north-eastern sector of the inner shelf, sorted bedforms have been detected at a depth of 40 m: they are characterized by a width varying between 15 m and 50 m and a length that reaches hundreds of meters. In the south-eastern sector of the Marettimo outer shelf, Colantoni et al. (1993) map two groups of sedimentary structures. In the same area, Lo Iacono (2004) recognized two-dimensional and three-dimensional subaqueous dunes. 2D dunes are found at depths between 60 and 90 m and show a wavelength variable between 15 and 50 m. 3D dunes, which are found at a depth of 80 m, are characterized by a wavelength of 30 m and a lateral extent of 50 m. Morphological evidences of a strong hydrodynamic regime come also from the morphobathymetric analysis of the Marettimo Channel, that is a 24 km long submarine valley oriented NNW-SSE, with a depth ranging from a minimum of 180 m to a maximum of 370 m and a width from 2 km to 14 km. Inside the channel, south of its narrowest point, a 180 m deep bathymetric threshold separates two areas, which deepens towards opposite directions: north-west and south. The flanks of the sector that deepens towards the NW are affected by mass-wasting features (Lo Iacono et al., 2007). The western flank of the channel, which delimits the Marettimo continental shelf, is carved by gullies, making the shelf-edge very uneven. Gullies develop to a maximum depth of 280 m and have a length of 250 m and a width of 50 m. At the bottom of the channel a linear incision 20 m deep, 400 m wide and almost 3 km long, is probably generated by erosive bottom currents. On the whole, the morpho-sedimentary structures here described reveal a strong hydrodynamic regime. The morphological and textural features of the bedforms observed on the Marettimo inner continental shelf suggest the occurrence of sporadic medium to strong storm events coming from western sectors. The morphological characteristics of the Marettimo Channel reveal the occurrence of strong bottom currents probably related to the severe interchange of water masses between the Tyrrhenian Sea and the Sicily Channel. References: Ashley, G., 1990. Journal of Sedim. Petrology 60, 160–172. Colantoni, P., Ligi, M., Morsiani, M.P., Penitenti, D., 1993. UNESCO Reports in Mar. Science 58, 93–98. Lo Iacono, C., 2004. Università di Napoli ‘‘Federico II,’’ Naples, Italy. Ph.D. Thesis, 150pp... Lo Iacono, C., Catalano, R., Agate, M., 2007. VI Conv. FIST GeoItalia, Rimini (Italy), 12-14 Sept. Lo Iacono C., Guillén J., 2008. Continental Shelf Research 28, 245–256

Plio-Pleistocene geological evolution of the northern Sicily continental margin (southern Tyrrhenian Sea): new insights from high-resolution, multi-electrode sparker profiles

High-resolution seismic profiles were acquired in the north Sicily offshore region with an innovative, multi-tip sparker array which lacks ringing and has a base frequency around 600 Hz. The new data, combined with published data, suggest that intra-slope and extensional basins formed as a consequence of the late Miocene (?)–early Pliocene shortening and thrusting, and the middle (?)–late Pliocene continental rifting affecting the internal side of the Sicilian-Maghrebian chain. Early (?) Pleistocene to Holocene high-amplitude and high-frequency sea-level changes resulted in repeated sub-aerial exposure and flooding of the shelf, and the deposition of cyclically arranged hemipelagic and shelf sediments. An uplift of the shelf could explain the non-preservation of the transgressive and of the lowstand wedge systems tracts in the oldest sequences

STRATIGRAPHIC AND STRUCTURAL ANALYSIS OF A HIGH RESOLUTION SEISMIC SURVEY PERFORMED IN THE BAY OF AUGUSTA (SE SICILY)

The Bay of Augusta is located along the NE margin of the Hyblean Plateau (SE Sicily). In this area a mostly bioclastic and terrigenous Quaternary succession outcrops. This area recorded a constant regional uplift rate of <1 mm/yr during the Late Pleistocene and recurrent, strong (up to 7.0 Md) historical earthquakes. Data for this study come from a recent nearshore geophysical survey performed by URS Corporation Ltd with the aim to evaluate the potential for seismic hazard. The collected data consist of: 1) a high resolution seismic survey (sparker source and sub-bottom profiling); 2) five soil borings to characterize and obtain age dates for shallow subsea sediments. Four main seismic units have been recognized inside the sedimentary infill: • Unit D is the oldest, seawards dipping, unit overlying the acoustic basement. Upwards this unit is bounded by a rough, erosional truncation (horizon H4). • Unit C shows sub-horizontal reflectors with variable seismic attributes, forming a prominent angular unconformity above H4; in the proximal sector of the Augusta Bay they lie seaward dipping. This unit shows valuable thickness change across the Bay and is bounded upwards by a very rough erosional truncation (horizon H3). • Unit B shows planar parallel reflectors with good lateral continuity. Its thickness change and it is very thin along the slope of the morphostructural highs formed by uplift of units D and C. Upwards it is bounded by a very prominent erosional truncation (H2 horizon). • Unit A is imaged by sub-horizontal, continuous reflectors, alternating with intervals of transparent seismic facies. The reflectors onlap the H2 horizon and, in a few places, display prograding geometry. On the collected samples biochronological and radiometric age-dating has been performed. The cores drilled the unit A and the uppermost part of the unit B, where the sediments have revealed absolute age > 50 kA. Two main groups of faults, referred to as the northwest and the southwest fault zones, are separated by a central zone where no evident fault planes have been imaged by seismic data. The faults in both groups strike from N30W to N52W and are also inferred to be steeply dipping. The faults pertaining to northwestern cluster show a very little offset, < 15 m. These faults have displaced mostly seismic unit C and have controlled two, NW-SE trending little structural lows in the central and in the northernmost sectors of the investigated area. These restricted basins have been filled by B and A seismic units deposits that don’t appear displaced by the fault cluster. The southeastern fault zone is long less than 700 m and show an offset of 1 to 5 m. These faults displaced the horizons of seismic Unit C in a sector where this unit outcrops at the sea bottom or it is draped by a very thin veneer of Unit A sediments. The faults pertaining to the northwestern zone post-date Unit C but they appear older than Units B and A.Radiocarbon age-dating have demonstrated that the most recent horizons involved in the northwestern fault zone displacement is > 50 kA. As concern the southeastern fault zone, results coming from radiocarbon age dating don’t have sufficient resolution to correlate deposits to seismic horizons involved in tectonic deformation. Nevertheless, there the seismic unit A also appears slightly involved by the latest faults activity. The analysis of the Bay of Augusta seismic grid has shown that very recent tectonic features have displaced the Late Quaternary sedimentary infill; interpretation of our results could better constrain the neotectonic setting of an area characterized by high seismic hazard

VARIABILITY OF DEPOSITIONAL SETTING ALONG THE NORTH-WESTERN SICILY CONTINENTAL SHELF (ITALY) DURING LATE QUATERNARY: EFFECTS OF SEA LEVEL CHANGES AND TECTONIC EVOLUTION

The geological, geomorphological and sedimentological features of the north-western Sicily continental shelf are here illustrated with the aim to propose a geological model able to explain the Neogene-Quaternary evolution of the Sicilian continental margin in the context of the central Mediterranean region. Above the continental shelf and upper slope the sedimentary succession, showing along the different sectors of the margin considerably variable internal geometry and stratigraphic relationships with the underlying units, is interpreted as a IV order depositional sequence (Late Quaternary Depositional Sequence, LQDS) deposited during the last eustatic change (last 125 ky). The lower boundary of the LQDS is represented by a subaerial erosional surface formed during the last eustatic sea level fall ended in the LGM (20-18 ka). This unconformity lies above a seaward dipping Pleistocene succession whose depositional architecture is in turn controlled by Quaternary eustatic sea-level fluctuations. A dense dataset of morphobathymetric and high resolution seismic data allowed to recognize along the continental shelf to bathyal plain system different types of continental shelf with different stratigraphic and morphostructural settings, associated to both large-scale processes and specific factors related to more local control: a) predominantly rocky shelves, both accompanied by a moderate frontal sedimentary prism and with a structural edge, in the structural highs of the Monti di Palermo offshore and around the main rocky headlands (Capo San Vito, Monte Catalfano); b), depositional shelves, in the Castellammare, Palermo and Termini Imerese gulfs, both with a regular seaward deepening of the substrate and with a substrate uplift at the shelf break. We confirm that depositional sequences in this margin are the result of the interaction between sea level changes and sedimentation, but demonstrate that the tectonic activity has played a key role, not only in the creation of different types of continental shelves, but also to determine the different characters of each sequence in different areas. The general tectonic uplift during the Pleistocene, together with the episodic alternation of extensional and compressional events, often with strike-slip component, is responsible for the thickness and facies variation both onland, where residual Pleistocene marine deposits today outcrops, and in the continental shelf, where most of the depositional sequences developed and are now recognized. As well tectonic activity exerted a control on the geomorphological features (e.g. pockmarks and mounds) of the present day coastal areas and shelf-slope system, as well as for the submarine canyons and the mass failure processes

É possível ensinar a genética para alunos cegos?

O uso de modelos tridimensionais é uma estratégia que facilita ensinar temas considerados difíceis para muitos professores no ensino médio, mesmo para classes que não têm alunos com necessidades educacionais especiais. Tivemos como objetivo, portanto, desenvolver um modelo tátil que auxiliasse na compreensão da estrutura do DNA e de sua replicação. Para tanto, adaptamos os passos descritos por Miotto para a construção de modelos táteis. O resultado foi a construção da matriz e das estruturas básicas da molécula de DNA, em papelão coberto com diferentes texturas. As placas de acetato em alto relevo foram preparadas após a aprovação por um aluno cego, que informou que a escala e as texturas escolhidas possibilitaram a identificação da estrutura como um todo e de suas partes, que foram testadas e aprovadas por alunos cegos na sala de recursos de uma Escola Pública Estadual.Palavras-chave: Construtivismo. Linguagem da ciência e da sala de aula. Ensino de ciências. Educação especial. Genética.Teaching genetics to blind-students – is it possible?AbstractThe use of three-dimensional models is a strategy that facilitates teaching contents considered difficult for many high school teachers even in classes that do not have students with special educational needs. Our objective was to develop a tactile model that helps the understanding of the DNA structure and its replication. To achieve this, we adapted the steps proposed by Miotto for the production of tactile models. As a result, we constructed the matrix of the basic structures of the DNA molecule in cardboard covered with different textures. After approval by a blind student, who reported that the scale and textures chosen allowed identification of the structure as a whole and its parts, we prepared the high relief acetate plates. These were tested and approved by blind students in the “resource class” of a State Public School.Keywords: Constructivism. Science and classrooms language. Science education. Special education. Genetics

Ambiente e clima della Sicilia durante gli ultimi 20 mila anni

Environment and Climate in Sicily over the last 20, 000 years. (IT ISSN 0394-3356, 2010). A series of recent studies shed light on the central Mediterranean, and Sicily, climate and environment, starting from the last glacial maximum (about 20 ka cal BP). In the present paper, we examine most of these works, in order to unravel environmental changes of the past, mainly in terms of temperature, atmospheric pattern, precipitation, vegetation and faunal associations. The climate of the last glacial maximum was characterised by very low temperature and by repeated northerlies penetration, even during summer. Low precipitation values led to a steppe- or semisteppe-like vegetation pattern, dominated by herbs and shrubs. Episodes of climatic anomaly, characterised by lower temperature and strengthened wind activity, could have occurred during the Holocene, as testified by micropaleontological and geochemical investigations carried out on the southern Tyrrhenian Sea and in the northern Sicily Channel. In the terrestrial record, there is evidence of drought at 8.2 ka cal BP, from the isotopic composition of a stalagmite recovered near Palermo, and of prolonged drought intervals during the Little Ice Age in the Erice village (Trapani). The vegetation pattern shows the development of Mediterranean Maquis in coastal sites and deciduous forests in sub-montane and montane regions, approximately from the Holocene base. The human impact is the main factor that forced the present vegetation pattern, as a consequence of intensive land-use, which started about 2.7 ka cal BP, when Greek colonies were first established. Human activity is however superimposed on a natural trend towards aridity, with climatic forces still not fully understood

Fogli 609-596, Termini Imerese-Capo Plaia

Il Servizio Geologico Nazionale ha unificato i Fogli 609 "Termini Imerese" e 596 "Capo Plaia" in un unico Foglio denominato 609/596 "Termini Imerese-Capo Plaia" allo scopo di uniformare i rilievi e raccoglierne la descrizione in un unico volume delle Note Illustrative. Il Foglio 609/596 "Termini Imerese-Capo Plaia" della Carta Geologica d’Italia in scala 1:50.000 è stato realizzato nell’ambito del Progetto CARG con i fondi della Legge 67/88 - Legge 226/99 con una convenzione tra Servizio Geologico Nazionale ora ISPRA) e Regione Siciliana. Le aree ricadono interamente nella Provincia di Palermo, comprendono la fascia marina del Golfo di Termini Imerese fino al promontorio di Capo Plaia, la regione dei Monti di Termini Imerese e Trabia ad ovest e il settore occidentale del gruppo montuoso delle Madonie ad est. Tra questi rilievi si sviluppa un’ampio settore collinare inciso dai fiumi Torto e Imera settentrionale (o Fiume Grande)

Preservation of modern and MIS 5.5 erosional landforms and biological structures as sea level markers : a matter of luck?

The Mediterranean Basin is characterized by a significant variability in tectonic behaviour, ranging from subsidence to uplifting. However, those coastal areas considered to be tectonically stable show coastal landforms at elevations consistent with eustatic and isostatic sea level change models. In particular, geomorphological indicators—such as tidal notches or shore platforms—are often used to define the tectonic stability of the Mediterranean coasts. We present the results of swim surveys in nine rocky coastal sectors in the central Mediterranean Sea using the Geoswim approach. The entire route was covered in 22 days for a total distance of 158.5 km. All surveyed sites are considered to have been tectonically stable since the last interglacial (Marine Isotope Stage 5.5 [MIS 5.5]), because related sea level markers fit well with sea level rise models. The analysis of visual observations and punctual measurements highlighted that, with respect to the total length of surveyed coast, the occurrence of tidal notches, shore platforms, and other indicators accounts for 85% of the modern coastline, and only 1% of the MIS 5.5 equivalent. Therefore, only 1% of the surveyed coast showed the presence of fossil markers of paleo sea levels above the datum. This significant difference is mainly attributable to erosion processes that did not allow the preservation of the geomorphic evidence of past sea level stands. In the end, our research method showed that the feasibility of applying such markers to define long-term tectonic behaviour is much higher in areas where pre-modern indicators have not been erased, such as at sites with hard bedrock previously covered by post-MIS 5.5 continental deposits, e.g., Sardinia, the Egadi Islands, Ansedonia, Gaeta, and Circeo. In general, the chances of finding such preserved indicators are very low.peer-reviewe