1,721,044 research outputs found
Benthic foraminiferal assemblages from Messinian deposits (western Sardinia, Italy): Preliminary report
No full textMicropalaeontological analyses of benthic foraminiferal assemblages were carried out on stratigraphic sections from the Late Miocene of Sinis Peninsula (Capo San Marco, western Sardinia, Mediterranean Sea). Biotic index values and the relative abundance of the most abundant foraminiferal species have been used for a palaeoenvironmental reconstruction. The palaeoenvironmental significance of foraminiferal assemblages indicates a shallower trend from an upper bathyal-circalittoral environment to coastal lagoon facies that are characterized by variable salinity and some fluvial run-off episodes during the pre-Messinian Salinity Crisis stage. After a subaerial exposure, a siliciclastic carbonate platform developed at the start of the Messinian Salinity Crisis. The re-establishment of marine conditions during the Upper Messinian is marked by fossiliferous marly limestone and sandy marls (cfr. Terminal Carbonate Complex) bearing microfaunas (benthic foraminifera, ostracods, rare planktonic taxa) and macrofauna intercalated in siliciclastic fluvial deposits. During the Messinian stages, the paleoecological conditions in the Sinis Basin were intermittently suitable for sustaining marine biotas, indicating that this basin was not uninterruptedly desiccated
Comprehensive geomorphological and sedimentological mapping and applications for coastal management: Porto Pino, SW Sardinia, western Mediterranean
No full textPalynological analysis of the Early Neolithic site at Sa Punta (central-western Sardinia, Italy)
No full text5PC - The fossil plant record of Sardinia. Field Guidebook of the 9th EPPC, Sardinia 1-4 Sept. 2014
No full textThe excursion will touch some of the sections where to collect plant fossil remains of Carboniferous, Permian and Jurassic deposits. To gather a fossil plant collection from the Miocene lacustrine sections is today very difficult because the artificial lake for water supply, such as the Omodeo Lake, has submerged the “Fossil Forest of Zuri” with its silicified trunks 12-15 m high and more than a meter in diameter and, furthermore, the stratigraphy of fill Miocene lacustrine basins is at present, for the most, hidden by the development of intensively cultivated fields. New findings of fossil plants are actually retrieved when canals for water distribution have been excavated in the interested areas. The “Foresta Fossile” of the Perfugas-Martin basin, and the “Foresta Fossile of Zuri” that are protected by a severe regional and national laws are, ironically, self-endangered
Il Neolitico antico terminale di Sa Punta - Marceddì (Terralba, OR)
No full textThe definition of the Early to Middle Neolithic transition in Sardinia is mainly grounded in few excavated sites, both in caves and in rock shelters. This paper aims at presenting the evolution process of later cardial ware facies, using the preliminary results from the ongoing excavations in the open-air coastal site of Sa Punta, along the southern part of the Gulf of Oristano (central-west Sardinia). Delimited by recent buildings the remaining archaeological surface showed an original Early Neolithic dwelling structure, possibly having either a barrier or a drainage function. Pottery and lithics analysis led us to place the phase of frequentation at the end of the 6th millennium cal BC, according to the available radiocarbon dates. A whole interpretation of the site function is here proposed based on paleofaunistic and palynological data
Microbial borings in benthic foraminifera from an heavy metal polluted coastal area (Portovesme, southwestern Sardinia)
No full textA monitoring survey from coastal environments facing the industrial area of Portoscuso-Portovesme (South-Western Sardinia, Italy) has revealed intense bioerosional processes in tests of benthic foraminifera collected in water less than 2m deep. Electron Microscopic investigation show that 1) microbial communities extensively infest foraminifera, 2) heavy metals fluxes (Zn, Pb, Cd) and carbonate dissolution are correlated and this correspond to decrease in foraminifera richness, low population density, biodiversity and to marked increase in abnormality and pyritisation of the tests. In addition, carbonate dissolution induced by euendoliths is selective depending on Mg content and morpho-structural types of foraminiferal taxa.
The bioerosional process on foraminiferal tests was analyzed via SEM (ESEM QUANTA 200, FEI, Hillsboro, Oregon, and partly with EVOLS15, ZEISS) at Cagliari University (Italy). The epoxy resin-casts of foraminifera were made at Erlangen University (Germany) in collaboration with M. Wisshak. To estimate quantitatively the impact of the microbial borings on the foraminifera and the selective bioerosion on high-Mg and low-Mg foraminiferal tests, 300 individuals were picked randomly from each sample on the fraction >63 μm and were observed with scanning electron microscope. A total of 1200 foraminifera was examined. As well as the bioerosional features on several morpho-structural taxa have been quantitatively calculated. The percentages of calcareous dissolution in foraminifera, distinguish between high-Mg and low-Mg tests, have been compared with heavy metals values, ph-pore waters and richness of specimens.
Scanning Electron Microscope images of the test surfaces and of epoxy resin-casts of foraminifera provide the recognition of microboring traces and cavities produced by phototrophic (cyanobacteria, chlorophyta) and heterotrophic (fungi) organisms. Comparing foraminiferal hosts belonging to diversified morpho-structural types with the bioerosional features, our data point out that the increase in heavy metal fluxes is clearly marked by an increase of microbial infestation, reaching a peak at the more polluted sites. Consistent carbonate dissolution differences occur between porcelanaceous imperforate and hyaline perforate groups. When comparing hyaline with porcelanaceous specimens for each sampling site, it was observed that the percentage of bioerosion in hyaline specimens increases from 19.9% to 59.7%, whereas in porcelanaceous tests bioerosion increases from 35.1% to 80.3%. An opposite behavior show the benthic foraminifera assemblages, which abruptly decrease increasing the heavy metal fluxes, while the percentage of the teratological increases (until 11%) in accordance with the increase of the pollutants. Our multiproxy analyses show that the affects of the biochemical dissolution are controlled, as well, by the chemical composition and ultramicrostructure of the foraminifera substrates and by the bioavailability of organic matter in their skeleton texture
Sedimentology, geomorphology and benthic habitats of a beach system of South Western Australia: implications for coastal management
Full text link- …
