1,721,034 research outputs found
Review about sea level oscillations during the last hemi cycle and tectonic stability of coastal sectors [Rassegna dello stato dell'arte sulle ricerche delle variazioni del livello del mare relativoe all'ultimo semiciclo climatico e sul concetto di stabilita' tettonica]
No full textThis paper summarizes the major contributions to understanding the sea-level oscillations during the last climatic hemicycle. More than seventy fundamental publications are reviewed bearing on the dynamics of eustatic processes and on the tectonic and isostatic behaviour of coastal sectors. The critical analysis of methodologies and results yielded by different reserchers has allowed to propose a new correlation scheme for sea-level data in different parts of the world. The improvement in datation techniques and the theoretical modelling of both glacio-eustatic variations and isostatic rebounds of coastal sectors to deglaciation, have been pivotal in sea-level researches during the 70 and '80. During the last decade, the refinement of radiodating techniques has prompted the correlation of sea-level data from different parts of the world. The available data set has grown from coral reefs and morpho-depositional units such as marine terraces and transitional coastal deposits, to include oxygen-isotopic analysis of deep-sea muds, their relationships with changes of ice volumes, datation of submerged speleothems and marin biogenic overgrowths. Comparative analysis of data on relative sea-level changes in different coastal sectors has pointed out the need for evaluating the tectonic and isostatic behaviour of the investigated coastal sectors. Based on the results of our research and the review of existing literature, a new reference marker is proposed in order to allow data correlation from different coastal sectors on the ground of their tectonic and isostatic stability. Such marker is represented by the eustatic sea level related to the substage 5e. The "relative eustatic variation" during the late Pleistocene-Holocene is here defined as the sea-level change caused by water volume variation induced by climatic variation relative to the present-day sea level. Such change is deduced from geological-geomorphological indicators such as terraces and notches found in coastal areas which are proved to be stable since the "Eutyrrhenian". The rate of vertical uplift for these areas must be below 0.016 m/ka, equal to about 2 m in the last 125 ka. The difficulty in constructing previsionai eustatic models is finally discussed in the light of the complexity of the process itself and of the concurrence of anthropic activity. This problem can be only alleviated by the availability of a greater number of data from tectonicvally stable area
Sea level curve and paleoclimatic determination from speleothems [L'uso degli speleotemi per ricostruzioni paleoclimatiche e variazioni del livello del mare]
No full textIn the frame of discussion on speleothem sedimento-logy we introduce a particular subclass of speleothemes undergoing accretion both in the continental (subaerial dripstones) and marine (marine organic overgrowth) environments, and describes the chemical-phisycal aspects of speleotheme growth. Hus allows a correct use of this speleothem subclass in paleoclimatic and eustatic investigation. Applications and limits of the most common datation techniques (U/Th,14C) to the chronological reconstructions of sea level oscillations are outlined. The significance of speleothemes wide marine overgrowth as paleoclimatic indicators through the analysis of variations in oxygen and carbon isotopie rations is also discussed (δ;18O e δ13C). The integrations of informations deriving from continental and submerged speleothem allow detailed paleoenvironmental reconscrutions to be made. Durin glacial-interglacial oscillations, an encrease of δ;18O indicate cooling, and marine organogenic overgrowth on speleothemes allows the precise detection of submsion timing
Vermetid reefs in the Mediterranean Sea as archives of sea-level and surface temperature changes
Full text linkVermetid reefs are among the most important bioconstructions in the Mediterranean Sea, with a distribution restricted to the warmest part of the basin. Their structure, and vertical and geographical distribution make them good biological indicators of changes in sea level and sea-surface temperature over the last two millennia
Variazioni del livello marino ed evoluzioni della costa toscana in epoca storica: opportunità di porti e approdi
No full textImplementazione del Marine Reservoir Correction Database lungo le coste italiane.
No full textConvegno Nazionale per le Scienze del Mare "Quali Mari Italiani?" organizzato dal CoNISMa - Lecce, 4/8 Novembre 2008
The non-tropical coral Cladocora caespitosa as the new climate archive for the Mediterranean: high-resolution (~weekly) trace element systematics
No full textHigh-resolution (similar to weekly) laser ablation ICP-MS trace element analyses (B, Sr, U, Mg, Ba) are reported for the scleractinian coral Cladocora caespitosa, collected from the Northern Adriatic Sea. Geochemical ratios (Sr/Ca, B/Ca, Mg/Ca, U/Ca, Ba/Ca) were measured in a 38-mm long (similar to 10 years' growth) external coralline portion (wall region) and generally exhibit a close relationship with the in situ measured (weekly-fortnightly) data on sea surface temperature (SST), available for the last 6 years. In particular, B/Ca ratios tuned to fine-scale variations in SST show a high degree of correlation (r = -0.856, n = 136) with SST, and indicate that coral calcification only occurs above a minimum temperature threshold of 14-16 degrees C. In addition, the ranges of trace element variability are larger than those typically recorded in tropical corals, consistent with the large seasonal variations in SST of the Adriatic. This study thus demonstrates the feasibility of extracting and exploiting high-resolution geochemical records from non-tropical corals such as C. caespitosa as a proxy for SST
Petrographic and Geochemical Analysis of a Non-Tropical Mediterranean Coral (Cladocora Caespitosa): Implications for its use as a Palaeoclimatic Proxy
No full textLi/Ca ratios in the Mediterranean non-tropical coral Cladocora caespitosa as a potential paleothermometer
No full textHeavy metal concentration in the skeletal aragonite of the zooxanthellate Mediterranean coral (Cladocora caespitosa): studying the potential for monitoring man-induced pollution
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