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A 37-Meter Record of Paleoclimatological Events from Stable Isotope Data on Continental Molluscs in Valle di Castiglione, Near Rome, Italy
No full textEvolución biológica y climática de la Región Pampeana durante los últimos 5 millones de años. Un ensayo de correlación con el Mediterráneo occidental
No full textComposicion isotopicas de los fosiles de gasteropodos continentales de la provincia de de Buenos Aires. Indicacion paleoclimaticas
No full textAlgunos datos de la composicion isotopicas de las costras carbonatadas de los acantillado marinos entre Mar del Plata y Miramar
No full textStable isotope on the last 30 ka molluscan fauna from Pampa grassland, Bonaerense region, Argentina
No full textFossil and living shells of terrestrial and freshwater molluscs collected from various sites in the Bonaerense and Patagonia regions of Argentina were analysed for their stable isotope content as a possible tool for palaeoclimatic and palaeoenvironmental reconstruction. The oxygen isotope composition of calcareous shell from fleshwater samples was interpreted in terms of a change in moisture condition and the related evaporative effect on surficial bodies of water, linked to a climatic shift. The carbon isotope composition mainly records changes in biological productivity. Interpretation of the isotopic composition of the land snail carbonate is more complex and worldwide data from living shells have been used to decipher to some extent the palaeoenvironmental record contained in their isotopic composition. Overall, the interpretations deduced from isotopic data of land snails as well as from nearby freshwater molluscs are quite comparable. The isotopic data suggest that arid conditions occurred between 35 and 15 ka B.P. and warmer conditions around 35-25 ka B.P. A shift toward a new phase comparable with the present meteorological and climatic situation probably began around 9 ka B.P. and it was linked to some short but severe climatic fluctuations, thus suggesting that high climatic stress characterised this period. Moreover, a trend toward slightly arid conditions is suggested by isotopic data, possibly sometimes after 5 ka. The differences arising from the geographical location and the short duration of each single series studied still hamper an extensive interpretation of the isotopic data
Stable isotope data on continental molluscs from Valle di Castiglione, near Rome, Italy. 37 m record of palaeoclimatological events
No full textNew stable isotope analyses on molluscan shells from a long core drilled in the crater lake of Valle di Castiglione, near Rome, extended the investigated portion of the core to 37 m. The succession of delta(18)O parts per thousand values in the core interval 37-2.3 m ranges from -2.8 to +6.9 parts per thousand with only six samples below 0 parts per thousand((PDB)). These results point to arid climatic phases coupled with the high measured delta(18)O values of the biogenic carbonate. In contrast, depleted (18)O samples correspond to wet climatic periods, in agreement with a strong evaporative control on the lake water isotopic composition. The (13)C content of the shells shows sharp changes controlled by the dissolved inorganic carbon isotope budget. Isotopic data suggest that the whole body of water behaved as a closed system, thus resembling lacustrine systems located in arid and semiarid regions where hydrological control dominates the geochemical parameters
Escenario de la evolución climatica entre la Región Pampeana y el area del Mediterráneo occidental durante el Cuaternatio
No full textZanchetta G., Leone G., Fallick A.E., Oxygen isotope composition of living land snail shells: data from Italy
No full textStable isotope record in mollusca and pedogenic carbonate from Late Pliocene soils of Central Italy
No full textThe Late Pliocene (younger than 2.5 Ma) alluvial fan succession of Toppetti Quarry, near Todi, Umbria, Central Italy, includes many palaeosols. Pedogenic carbonate concretions and mollusc remains were separated from 73 palaeosols collected along 150 m of exposure and analysed for their oxygen and carbon stable isotope content. delta C-13 and delta O-18 of the pedogenic carbonate and land snail shells suggest that no dramatic change in local climate took place. Values of the pedogenic carbonates are similar to other data reported for the Mediterranean region. delta O-18 data suggest a mean annual temperature and/or delta O-18 similar to modern climatic conditions. Carbon isotope data from both land snails and pedogenic carbonate are consistent with a prevailing type C-3 vegetation. A mixture of forest and C-3 grassland, sustained by a mean annual precipitation between 300 and 1000 mn, mainly in the cool periods of the year, seems to be the most likely scenario. The limited variation shown by the isotope composition of the biogenic and inorganically precipitated carbonate indicates that the environmental variations are referable mainly to change of humidity rather than temperatur
Oxygen isotope composition of living land snail shells: data from Italy
No full textSixty-seven shells of living land snails were selected from 31 different localities across Italy to investigate the relationships between their oxygen isotopic composition (δ18Os) and the mean value of local rainfall (δ18Op). Despite the difficulty for some localities to correctly estimate the oxygen isotopic composition of local rainfall, a good relationship was found. This indicates that the oxygen isotopic composition of environmental water used by the snails is, in Italy, strictly related to that of the local meteoric precipitation. However, the relationship found is substantially different from that previous established for central Europe, indicating that regional climatic conditions are important in defining the final isotopic composition of land snail shells. Moreover, these equations may not hold for different climatic conditions existing during, for instance, glacial and interglacial periods. The data also show that isotopic differences among species are relatively narrow and that they may depend on ecological factors (i.e., style of life) rather than any clearly identifiable different vital offset
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