A quantitative analysis of calcareous nannofossils and planktonic foraminifera assemblages and geochemical studies were carried out on core C18 (40j00V55UN, 15j09V22UE), recovered near Cape Palinuro (southern Tyrrhenian Sea, Italy). Four radiocarbon ages place the core in the time interval 32–0 ky BP. Coccolithus pelagicus, Gephyrocapsa caribbeanica and Gephyrocapsa mu¨llerae dominated the coccolith assemblages during the glacial period, while foraminifera assemblages show high percentages of Turborotalita quinqueloba and Globorotalia scitula. Calcidiscus leptoporus and Gephyrocapsa oceanica seem to be controlled by nutrient availability; moreover, low percentages of iron seem to influence the distribution of G. oceanica. Low nutrient availability seems to overlap the climatic signal in the distribution of Syracosphaera pulchra. An increase in Umbilicosphaera sibogae and Rhabdosphaera claviger, the occurrence of tropical taxa and an increase in sub tropical and temperate species, among the planktonic foraminifera, characterise the Holocene assemblages. During this period, Globorotalia truncatulinoides reached its highest percentages, testifying to the onset of deep winter convection and vertical mixing that characterise the modern Tyrrhenian Sea.
L'analisi quantitativa dei nannofossili calcarei e delle associazioni a foraminiferi planctonici e studi geochimici sono stati effettuate su C18 core (40j00V55UN, 15j09V22UE), recuperato nei pressi di Capo Palinuro (Tirreno meridionale, Italia). Quattro datazioni radiocarbonio hanno posto il core nell'intervallo di tempo 32-0 ky BP. Coccolithus pelagicus, Gephyrocapsa caribbeanica e Gephyrocapsa mu ¨ llerae dominano le associazioni durante il periodo glaciale, mentre le associazioni a foraminiferi mostrano alte percentuali di Turborotalita quinqueloba e Globorotalia scitula. Calcidiscus leptoporus e Gephyrocapsa oceanica sembrano essere controllato da disponibilità di nutrienti, inoltre, basse percentuali di ferro sembrano influenzare la distribuzione di G. oceanica. Bassa disponibilità di nutrienti sembra sovrapporsi al segnale climatico nella distribuzione di Syracosphaera pulchra. un aumento di Umbilicosphaera sibogae e Rhabdosphaera claviger, il verificarsi di taxa tropicali e un aumento del sub specie tropicali e temperate, tra i foraminiferi planctonici, caratterizzano le associazioni dell'Olocene. Durante questo periodo, Globorotalia truncatulinoides ha raggiunto le sue più alte percentuali, che testimoniano l'inizio della convezione profonda e verticale che caratterizzano il Mar Tirreno attualmente.
(2004)a. Reconstruction of the Holocene palaeoenvironmental and palaeoceanographic evolution in the north-western sector of the Magellan Strait, on the basis of calcareous nannofossil, textural and geochemical data
AMORE F;
2004-01-01
Abstract
A quantitative analysis of calcareous nannofossils and planktonic foraminifera assemblages and geochemical studies were carried out on core C18 (40j00V55UN, 15j09V22UE), recovered near Cape Palinuro (southern Tyrrhenian Sea, Italy). Four radiocarbon ages place the core in the time interval 32–0 ky BP. Coccolithus pelagicus, Gephyrocapsa caribbeanica and Gephyrocapsa mu¨llerae dominated the coccolith assemblages during the glacial period, while foraminifera assemblages show high percentages of Turborotalita quinqueloba and Globorotalia scitula. Calcidiscus leptoporus and Gephyrocapsa oceanica seem to be controlled by nutrient availability; moreover, low percentages of iron seem to influence the distribution of G. oceanica. Low nutrient availability seems to overlap the climatic signal in the distribution of Syracosphaera pulchra. An increase in Umbilicosphaera sibogae and Rhabdosphaera claviger, the occurrence of tropical taxa and an increase in sub tropical and temperate species, among the planktonic foraminifera, characterise the Holocene assemblages. During this period, Globorotalia truncatulinoides reached its highest percentages, testifying to the onset of deep winter convection and vertical mixing that characterise the modern Tyrrhenian Sea.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
