Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 10

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  Sicily
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
1
EN
The Sicily island is rich in high quality rock raw materials and has a long historical culture in natural stone production. The resources of limestone, marble, sandstone and basalt in Sicily are huge and exploited for many centuries. Its biggest city centers and historical monuments are adorned with locally quarried marble, limestone and lava stone from the Etna volcano. Exploring the raw materials potential was closely related to the development of first Sicily inhabitants who initially used available natural stones adapting them for their basic needs. The art of using stones - in the field of building structure improvement, and the use of impressive rock varieties in sculpture and art decoration were developed by ancient Greeks, Romans, and later Arabs and Normans who invaded this island. In many Sicilian cities it is possible to trace new objects growing on the older buildings, which are characterized by the invader cultures or new trends in construction. Material culture of stone applied in Sicilian construction and architecture was developed with the emerging styles. For the construction of these historical buildings, a local stone on the island has been used.
EN
Neptunian sills at Rocca Busambra, a fragment of the Trapanese/Saccense Domain in western Sicily, host the most abundant ammonite and gastropod fauna which has ever been recorded from the Jurassic of the western Tethys. The fauna is dominated by parautochthonous organisms which were swept into the sills by gentle transport. Ammonites are characterized by perfect preservation and small size, a feature which is due to the predominance of microconchs but also of stunting. The most complete sill is 0.7 m thick and could be separated into 17 levels which range in age from the early Toarcian into the late Kimmeridgian, thus representing the most extreme case of palaeontologically and depositionally documented stratigraphic condensation in Earth history. The unique feature of the Rocca Busambra sills is due to the interaction of three processes: extreme stratigraphic condensation on the sea floor, weak tectonic fracturing of the host rock and repeated reopening on top of already existing sills. Contrasting percentages of gastropods in individual levels reflect sea-level oscillations which correspond to long known low- and highstands during the Jurassic of the western Tethys. Comparisons with other ammonite-bearing sill faunas reveal several similarities, but represent only short-timed phases of tectonic pulses and deposition.
EN
The Sicilian Thrust System (STS) is a south-verging (Africa-verging) fold-and-thrust belt including a Mesozoic-Paleogene sedimentary sequence. This thrust stack owes its origin to the deformation of pre-orogenic strata deposited in different palaeogeographic domains belonging to passive margins of the African plate. The STS was deformed during the Neogene, following the closure of the Tethys Ocean and the continental collision between the Sardo-Corso Block and the north Africa margins. The thrust pile was detached from the underlying basement during the Miocene-Pleistocene. The regional-scale structural setting recognized allows us to reconstruct the tectonic evolution of the STS as follows: I - piggy-back thrusting from the Late Oligocene to the Langhian, inducing the building of the Inner Sicilian Chain (ISC); II - piggy-back thrusting from the Langhian to the Tortonian, inducing the formation of the Middle Sicilian Chain (MSC); III - generalized extensional deformation in the chain-foredeep-foreland system from the Tortonian to the Early Pliocene; IV-a new onset of piggy-back thrusting after the Early Pliocene allowed the building of the Outer Sicilian Chain and out-of-sequence thrusting in the previously developed ISC and MSC.
EN
A GIS+analysis was carried out in a test basin of southern Sicily, the Magazzolo River basin, in order to assess susceptibility conditions to gully erosion phenomena. The linear density of ephemeral and permanent gullies computed within each class of nine environmental variables was used to generate a gully erosion susceptibility map for the area. A validation procedure carried out in order to test the reliability of the adopted method highlighted a clear correlation between the occurrence of gullies and the computed susceptibility levels.
EN
Ephemeral gullies (EGs) are channels of different sizes refilled by tillage equipment normally used on farms. In this paper, the data-set collected from 1995 to 2007 in a wheat--ultivated area in Raddusa (Sicily, Italy), having a surface of almost 80 ha, were used to analyze the morphological characteristics of EGs. The measurements show an high temporal variability in EG characteristics. The EG measurements and the rill erosion measurements carried out in 15 plots located in the experimental "Sparacia" area (Sicily), demonstrated that a morphological similarity condition exists between rills and ephemeral gullies. The occurrence of step-pool structures in an EG occurring in the observation period in the same place allows to conclude that, in the considered environment, an ephemeral channel, such an EG, similarly to a stream, tends to reach a step-pool morphology as the structure that maximises its stability.
6
Content available remote New data on the Jurassic evolution of the Panormide Carbonate Platform (Sicily)
EN
The Jurassic of the Panormide Carbonate Platform records several discontinuity surfaces reflecting a complex sedimentary dynamics at a time of general extension in the western Tethyan realm. Previous studies documented subaerial exposure with karst bauxites between Upper Triassic and Upper Jurassic in the internal sector of the platform. On the contrary, at same time the marginal sectors of the platform record Rosso Ammonitico type sedimentation and the subsequent progradation of a new, Upper Jurassic platform. Latest sedimentological and stratigraphical studies added new data on these discontinuity surfaces in the Palermo Mountains. The succession of Mt. Castellaccio is characterized by Upper Triassic peritidal dolostones crosscut by various generations of neptunian dykes filled by pelagic limestones with crinoids, brachiopods, ammonites and filaments (Pliensbachian to Middle Jurassic). They are covered by red sediments rich in ferric ooids and lithoclasts enclosed in a red, argillaceous matrix. Petrographics and X-ray analyses have confirmed the presence of boehmite, kaolinite and hematite in these rocks, on the basis of which they may be qualified as low-grade bauxites. Above, with an angular unconformity, there follow Kimmeridgian loferitic limestones interbedded to bioclastic grainstone/packstone with Clypeina sulcata (Alth). At Punta Raisi, a stratigraphically equivalent, but sedimentologically different succession has been studied. The Upper Triassic peritidal dolostones are overlain by Lower Jurassic cyclic peritidal limestone with very poor microfauna. It is repeatedly interrupted by yellow to browinsh paleosoil levels. The top of this succession is red-coloured and is marked by a complex dissolution surface, with pinnacles and grooves. It is capped by a thick Fe-Mn crust with Foraminifera, small ammonites and filaments [Bajocian-Callovian(?)]. Based on preliminary petrographical and geochemical analyses a brief subaerial event may be hypothesized. However, the very same petrographic analyses revealed the effects of undoubtedly submarine bioerosion (action of sponge, fungi and bacteria), too. So even if we accept the idea of a transient subaerial phase, a strong submarine overprint during subsequent drowning, possibly contributing to the development of the pinnacle-and-groove topography can not be excluded, either. The Fe-Mn-crust is overlain by pelagic sediments displaying a coarsening upward trend and gradually passing into bioclastic grainstones/packstones with abundant carbonate platform elements (Kimmeridgian). This work is intended to add new arguments to the stratigraphic evolution and, consequently, to the subsidence history of the Panormide Carbonate Platform. Results are as follows: * evidence for an Early Jurassic shallow water depositional environment; * restriction of the size of the hiatus between Lower and Middle Jurassic; * verification of the presence of a submarine dissolution surface analogous to that of the Trapanese Platform; * increase of the areal extension of bauxites on the Panormide Platform; * confimation of the synchroneity of the re-establishment of the shallow-water carbonate sedimentation during the Late Jurassic. This data moreover allow a better paleogeographic reconstruction and a key to understand the combined effects of sea-level changes, tectonics and thermal (?)updoming at the time of an overall extensional regime.
EN
The Sciacca area, in Southwestern Sicily, belongs to the external zone of the Neogene Maghrebian thrust and fold belt. Two different groups of south-verging thrust sheets crop out in this area: the so called "Saccense" units that consist of thick Mesocenozoic neritic and pelagic platform carbonates; the "Sicanian" units made of Permian to Cenozoic deeper-water sediments. The tectonic boundary between Saccense and Sicanian units runs NW-SE from Monte Genuardo to Caltabellotta. This boundary is orthogonal to the main thrust fronts and nearly parallel to the direction of thrust propagation. Thrust-top-basin deposits of Pliocene age obscure the tectonic relationships along this alignment leaving different solutions open for its structural interpretation and for the palinspastic restorations between platform and basin-derived units. Recent sedimentological and stratigraphical studies focused in this zone document the presence of Upper Triassic reef limestones in the Saccense units (Pizzo Telegrafo unit), close to the tectonic alignment. The macro and microfacies analysis reveal a typical Dachstein-type reef composition of these deposits. As consequence they can be interpreted as markers of platform edges facing high-energy, open marine basins. The collected data are thus consistent with the presence of a Late Triassic platform-basin transition close to the present-day tectonic boundary. An intense Jurassic paleotectonic activity along this margin is proved by in situ brecciation and the presence of large polyphase neptunian dykes crosscutting the reef deposits and the overlying Lower Jurassic platform limestones (Inici Formation). The dykes are filled up by Middle to Upper Jurassic Rosso Ammonitico type condensed limestones. Basaltic pillow lavas occur as thick wedges intercalated to the Jurassic pelagic limestones. They indicate repeated episodes of (trans)tensional stresses along the paleomargin. An anomalous thin Cretaceous to Miocene sedimentary cover (Scaglia type calcilutites and glauconitic sandstones) is punctuated by deep erosional truncations and megabreccias. These sediments fill up later generations of neptunian dykes confirming the paleotectonic activity in this zone throughout the Jurassic-Miocene times. In the Sicanian basinal units flanking the tectonic alignment the influence of the platform paleomargin is recorded by extensive Lower Jurassic carbonate aprons interbedded to cherty calcilutites. Upper Triassic reef-derived elements are common constituents of these clastics as recently documented at Campofiorito and Monte Triona. Looking at the present day structural relationships in the studied area we can conclude that the Triassic/Jurassic paleomargin has played an important role as major transpressional dextral escape during the Neogene Sicanian mountain building.
EN
The current knowledge of freshwater entomostracans from Sicily and some neighbouring central-Mediterranean countries is briefly reviewed. Data concerning different countries and different taxonomical groups are markedly inhomogeneous and often far from being representative of the real biota of the corresponding countries. This gap prevents a sound, biogeographical analysis of the freshwater microcrustacean fauna of the area. The major gaps that have to be filled are highlighted and the need for more surveys and monitoring is emphasised.
EN
North-Central Sicily represents an Apenninic-Maghrebian Chain sector, deriving from the Miocene- Pliocene deformation of different palaeogeographic domains-derived successions (carbonate platforms and pelagic basins), piled-up in ramp-flat and duplex style, and belonging during the Mesozoic-Tertiary to the Northern African Continental Margin. These domains are represented by outcropping basinal sedimentary successions (Imerese-Sicanian Basin), geometrically interposed between carbonate platform rock bodies: the Panormide (innermost) and the Hyblean-Pelagian Domains (more external). In this paper, using stratigraphic and structural data, we propose a new palaeogeographic model, in which the main differences from previous interpretations consist in the position of the Imerese Basin, here identified as the juncture between the Panormide Domain and the Sicanian Basin Auct., and the position of the Trapanese pelagic carbonate platform, considered as the juncture between the Hyblean-Pelagian Domain and the Sicanian Basin Auct. Tectono-sedimentary steps characterising the evolution of the Sicilian Miocene-Pliocene Foredeep illustrate the deformational history of the area. Two geological cross-sections depict the structural architecture of the tectonic edifice, characterised by different thrust sheets piled-up during the Miocene-Pleistocene time. The more external tectonic units are formed by elements deriving from the Plio-Pleistocene deformation of the northern margin of the Hyblean-Pelagian Domain. The "intermediate" tectonic units derive from the Miocene-Pliocene deformation of the Imerese- Sicanian Domain and the inner tectonic units are constituted by Panormide and Sicilide Domains-derived successions, deformed during the Miocene. A mostly neotectonics-related transcurrent faults reoriented the previous thrust sheets through NW-SE and W-E trending faults, producing large-scale positive flower structures which involved the geometrically deepest Hyblean-Pelagian substrate.
EN
Terravecchia Formation in the Scillato Basin is a good example of development of a post-tectonic basin. Practically continuous exposures across that basin give the rare possibility to observe the lateral distribution of lithofacies and gradual changes of sedimentary succession from an alluvial fan, fluvial plan to lacustrine and, eventually, to marine setting. The alluvial fan deposits are generally represented by polymictic, disorganised or crudely organised conglomerates representing mainly flow and debris flow deposits. The fluvial plain association is characterized generally by cross-bedded sandstones with streaks of conglomerates laid down within a channel bar system. Flood-plain deposits are subordinate. Sedimentary structures suggest deposition in a braided river. The fluvial plain association pass laterally to lacustrine/fluvial plain deposits represented by grey to pinkish mudstones with channelised sandstones. As an effect of subsidence the Scillato Basin was invaded by marine/brackish environment, and marly mudstones and siltstones with subordinate sandstones were deposited. That variability of sedimentary facies can be explained by vertical tectonic movements.
PL
Późnomioceńska formacja Terravecchia zachowana w basenie Scillato, stanowi dobry przykład rozwoju basenu posttektonicznego. Ciąg bardzo dobrych odsłonięć w poprzek basenu pozwolił na szczegółowe obserwacje rozkładu litofacji, struktur sedymentacyjnych oraz asocjacji facjalnych i ich wzajemnych związków. Wyróżnionych zostało kilka środowisk sedymentacyjnych, od stożka aluwialnego, przez rzekę roztokową po środowisko jeziorne i morskie. Osady stożka aluwialnego reprezentowane są przez czerwone i żółte, polimiktyczne zepieńce, o strukturach zarówno bezładnych jak i uporządkowanych, powstałe w wyniku działania prądów i spływów rumoszowych. Osady rzeki roztokowej to głównie przekątnie warstwowane piaskowce związane z różnego rodzaju łachami piaszczystymi. Mułowcowe osady równi zalewowych zachowały się tylko sporadycznie. Osady rzeczne przechodzą lateralnie w mułowcowe osady jeziorne z licznymi osadami kanałowymi w ich dolnej części. Pod koniec rozwoju basenu, w rezultacie subsydencji tektonicznej, nastąpiła ingresja morska i powyżej osadów rzeczno-jeziornych rozpoczęła się sedymentacja osadów brakiczno-morskich z poziomami fauny.
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.