1,721,069 research outputs found
Provenance characteristic and modifications by transport processes of Palygorskite in wet and dry aerosols in Western Mediterranean
No full textSuitable facies for ichnofossil preservation: example from the Pleistocene coastal deposits of Sardinia (Italy)
No full textIn Sardinia, Quaternary deposits are mostly represented by beach deposits and cross-bedded aeolian sands attributed to the middle Pleistocene. These are followed by conglomerate beach deposits corresponding to the MIS 5.5 sea level high stand, and by cross-bedded aeolian sands which bear reddish paleosols. Tracks and trackways, belonging to the ichnogenus Bifidipes Demathieu, Ginsburg, Guerin & Truc, 1984, produced by “Praemegaceros” cazioti (Depéret, 1897) have been recently discovered in Pleistocene deposits cropping out along the northern and western coast of Sardinia (Fanelli et al, 2007). The “Praemegaceros” cazioti is an endemic middle size deer of Sardinia which lived in the island from the middle Pleistocene until the early Holocene (Palombo, 2005). This work focuses on Porto Paglia coastal area (south-west Sardinia), where Quaternary deposits are exposed along a high cliff for several kilometres, and where several thousand of tracks are well preserved. The Porto Paglia deposits are composed of different dune generation deposited during middle to early Pleistocene (Orru & Ulzega, 1986). The aim of our study was to identify the environment most conducive to the preservation of tracks and show the significance of “Praemegaceros” cazioti footprints for paleoenviromental reconstruction. The paleoenviromental reconstruction was achieved through sedimentological study: faces analysis, depositional geometry and petrographic observations. The results of this study allow us to describe two broad systems one retrogradational and one progradational. The deposits are separated by erosion/abrasive surfaces with which periods of retrogradation and progradation are expressed. By using these surfaces we can identify three sedimentary cycles corresponding to transgressive-regressive phases during the Pleistocene. The retrogradation deposits, which formed during the transgressive periods, are represented by a system of beach-sand bar-lagoon and associated foredune deposits. Intense slope erosion during sea level fall led to a system of sandy delta-fans and conglomerate fans deposits. The most suitable environment for track preservation is the lagoon. These, were subject to water level oscillations and desiccation. Abundant tracks are also present in the distal portions of sandy bars, where moist, coherent sediments are present in the backshore and relatively poorly in dune deposits. In contrast, footprints are not preserved in the coarse grained progradational deposits
Characterization of Palygorskite in dust of desertic provenance in aerosols, Sardinia, Western Mediterranean
No full textPalygorskite aggregated grains occur in aerosol dust samples in western Mediterranean Sea. Morphology and texture of palygorskite grains was characterized analytical using SEM with attached X-ray energy dispersive system. Palygorskite occurs as rounded aggregate grains (wind-shaped), as interwoven fibrous mats forming fine laminae, and as porefilling and pore-bridging cements that commonly coat detrital grains and occur among them. The results show distinct and characteristic textures of palygorskite in dry (aerosol in air) and wet (precipitation) deposition. The main sources of this clay mineral are the dry rivers, lake beds, salt lakes, and argillaceous bed-rocks in northwestern Africa. Air mass trajectories calculation independently indicate two different source area
Weathering of Pb-Zn mine tailings in PH buffered environment
No full textThe Ingurtosu Pb-Zn mine in south-western Sardinia, exhibits three main weathering processes: 1) oxidation without acidification derived from Pb and Zn sulphides; 2) oxidation with acidification derived from Fe sulphides; 3) pH buffering due to Ca and Mg carbonate dissolution. These weathering processes are followed by adsorption of metals on iron oxyhydroxides and precipitation of hydrated sulphates (sometimes carbonates). Nearly all iron sulphides and carbonate (siderite, ankerite) grains, have alteration rims made up of iron oxyhydroxides (goethite), where Zn, Cu and Pb are adsorbed after sulphide oxidation. Moreover, the occurrence of slightly weathered clay minerals confirms the low pH values are never reached. -from Author
Regime, dynamics and balance on the coast between Punta di li francesi and Capo Testa - northern sardinia
No full textComprehensive geomorphological and sedimentological mapping and applications for coastal management: Porto Pino, SW Sardinia, western Mediterranean
No full text
Morpho-sedimentology of a Mediterranean microtidal embayed wave dominated beach system and related inner shelf with Posidonia oceanica meadows: the SE Sardinian coast
Full text linkThis article presents a morpho-sedimentological map of a Mediterranean embayed microtidal wave-dominated beach system and related inner shelf. The study area is located between Capo Boi and the Torre de su Fenugu sector, and focuses on Solanas beach in SE Sardinia. All of the collected data were processed to draw a main 1:7,000 scale map, which shows the general characteristics of the entire area, including its hydrodynamic, morphological, and sedimentological features (distribution of siliciclastic and biogenic/bioclastic sediments), rocky outcrops, beach rocks, and marine phanerogam meadow coverage (mainly Posidonia oceanica). Several secondary maps such as routes and paths, side-scan sonar photomosaic interpretations, and sedimentary facies have also been included. In addition to its scientific value, the map can be an important tool for beach management purposes
Microbioerosion on the shells of recent foraminifers in polluted shallow water environment
No full textInvestigation on recent benthic foraminifers used as bioindicators for monitoring coastal pollution revealed that phototrophic bacterial colonies infest the surfaces of the calcareous benthic foraminifers. Many traces of microborers have been observed in foraminiferal shells coming from shallow waters in an industriai polluted coast. Samples were collected in the end of July 2006. Sampling depths ranged from the intertidal to two meters; water temperature were about 27°C to 31°C and salinity values of about 37 g/I. Preliminary results from SEM pictures have allowed to recognize the following ichnotaxa: Fasciculus acinosus Glaub related to the modern cyanobacterial species Hyella balani Lehmann, Orthogonun sp., which biological identity of its producers is unknown, and Scolecia filosa Radtke related to modern cyanobacterium Plectonema terebrans Bornet & Flahanet. Geochemical analysis performed on sediments show that the investigated industriai area is contaminated mainly by heavy metals (Fe, Mn, Pb, Zn, Cd). Increasing pollution results in low species diversity and population density, associated with an increase in tolerant or opportunistic species. In this contaminated environment aberrant foraminiferal tests were frequently found. Microanalysis reveals that deformed specimens locally contain high level of heavy metals. This suggests that heavy metals pollution may represent a particular microenvironment able for developing microbial communities. In fact the unpolluted coastal areas near the studied sites at the same batimetry don't show bioerosion traces; higher species diversity and population density than polluted areas and very scarce deformed forms were found
- …
