Simona Giunta
Marche Polytechnic University
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Featured researches published by Simona Giunta.
Palaeogeography, Palaeoclimatology, Palaeoecology | 2003
Simona Giunta; Alessandra Negri; Caterina Morigi; Lucilla Capotondi; N Combourieu-Nebout; Kay-Christian Emeis; Francesca Sangiorgi; L Vigliotti
A very detailed environmental history of the last deglaciation and the Holocene is recorded in a high sedimentation rate core collected in the Southern Adriatic Sea (Core AD91-17). The stratigraphic framework, based on radiocarbon dating (14C AMS) and the oxygen isotope record, allows recognition of the paleoceanographic changes of the last 16 200 years. Fluctuations within the coccolithophorid assemblage identify five intervals that can be correlated to major changes in the planktonic foraminifera records. Recognition of the same zonation in the eastern Mediterranean Sea suggests that they are truly basin-wide ecozones rather than local events. Interpretation of the paleoceanographic meaning of these coccolithophorid ecozones, together with planktonic and benthic foraminifera, dinocyst, pollen, magnetic parameters, oxygen isotopes and alkenone unsaturation indexes, outlines fluctuations related to different paleoclimatic phases. In particular, from 16 200 to about 11 670 yr BPnc all proxies register cold conditions with a well-ventilated sea bottom. A gradual sea-surface temperature (SST) increase characterized the period between 11 670 and 10 800 yr BPnc, followed by a slight cooling coincident with the beginning of the Younger Dryas. Between 8650 and 6560 yr BPnc, corresponding to sapropel S1 formation, all proxies register a transition to warmer climate. Sea-surface productivity reached maximum values, while evidence for development of low salinity superficial waters and of a deep chlorophyll maximum is observed. The multi-proxy analysis suggests the presence of at least three phases in the S1 sapropel itself. The first part of the sapropel is characterized by high nutrient availability, warm stratified waters and severe bottom anoxia. Between 7650 and 7500 yr BPnc, corresponding to an interruption of the sapropel, we observe a rapid reoxygenation at the seafloor when SST warmed. Just after the sapropel interruption, and particularly between 7400 and 7250 yr BPnc, a slight climatic deterioration, an increase of salinity and a decrease of runoff are observed. At the top part of the sapropel, eutrophic environments, a well-stratified euphotic zone and dysoxic conditions at the bottom are identified. From 6560 to 5080 yr BPnc, conditions became more oligotrophic and SST reached a maximum, while a slight increase of superficial water salinity may suggest the end of stratified waters and the beginning of water column mixing. Finally, between 5080 and 2240 yr BPnc all proxies indicate warm and normal salinity waters. The bottom environment returned to normal oxygenated conditions.
Palaeogeography, Palaeoclimatology, Palaeoecology | 2003
M. S. Principato; Simona Giunta; Cesare Corselli; Alessandra Negri
Planktonic foraminiferal and calcareous nannofossil assemblages of three box-cores from the western–central part of the Mediterranean Ridge area were investigated and correlated. In particular we focused on the most significant faunal and floral signals recorded before, during and after sapropel S1 deposition. The interval preceding S1 is characterised by an increasing trend of the two planktonic foraminiferal species, Globorotalia inflata and Truncorotalia truncatulinoides, that are usually related to a well developed cold and deep mixed layer. This change is supported also by the rarity of warm water coccolithophorid species and by the presence of the deep dwelling species Florisphaera profunda. The beginning of S1 is marked by the disappearance of G. inflata and T. truncatulinoides and by the significant increase in abundance of Globigerinoides ruber, especially the rosea variety usually considered indicative of warmer conditions. Warm water species increase also within the coccolithophorid assemblage, while the upwelling species Reticulofenestra spp. suddenly decreases and remains low across the whole sapropel interval. The sedimentary expression of the end of anoxia is the upper boundary of the oxidised level observed above S1 in the three box-cores. Across this boundary we detect a small but well defined increase of Braarudosphaera bigelowii, the decrease of warm water coccolithophorid species and the increase of Reticulofenestra spp. This boundary is marked also by the reoccurrence of the planktonic foraminiferal species G. inflata and Neogloboquadrina pachyderma dextral and by an evident decrease of G. ruber var. rosea, indicating the end of the Holocene Climatic Optimum and the beginning of a cold and wet phase, probably corresponding to the Atlantic–Subboreal continental transition.
Palaeogeography, Palaeoclimatology, Palaeoecology | 2003
Alessandra Negri; Caterina Morigi; Simona Giunta
We present the results of a micropaleontological study performed on the sapropel sequence associated with insolation cycle 180 from the Plio–Pleistocene Vrica sequence (Calabria, Italy). We performed a high-resolution study on the 3.38-m-thick layer c from a core drilled close to the classical outcrop section in which we analyze fluctuations in the abundance and composition of calcareous nannofossils and planktic and benthic foraminifera. Changes in the fossil assemblages reveal at least three major paleoenvironmental phases in layer c. The base of the sapropel contains an abrupt decrease in benthic fauna that continues through all of layer c. It also has an increase of the coccolithophorids species Coccolithus pelagicus. Planktic foraminifera show at the same depth a peak of the cold species Globorotalia scitula. These changes are followed by decreases in the carbonate preservation index and in abundances of Globigerinita glutinata, Globigerinita uvula and Neogloboquadrina pachyderma (sinistral), which suggest cold and highly productive upwelling waters. A short interval in the middle of the sapropel is characterized by low values of C. pelagicus, a fluctuating increase of Pseudoemiliania lacunosa and among the foraminifera an increase of Globigerinoides ruber together with the presence (although decreased) of G. glutinata, G. uvula and N. pachyderma (sinistral). We interpret these features as suggesting high seasonality with warm stratified and probably oligotrophic waters during summer and relatively cold conditions during winter. Finally, the topmost interval of the Vrica layer c exhibits the re-appearance of P. lacunosa together with abundant siliceous phytoplankton. Planktic microfauna show the disappearance of the cold species G. glutinata, G. uvula and N. pachyderma (sinistral). Thus this interval appears to be characterized by warmer temperature. The transition from the laminated to the massive sediment displays a sequence of events, including a decrease of the carbonate preservation index and peaks of Globorotalia inflata and G. scitula, suggesting again upwelling and mixing of the whole water column and, thus, transition to the oxygenated conditions characterizing the massive layer. Neither increased productivity nor stratification appear to characterize the whole sapropel interval, which is, however, always dysoxic.
Rivista Italiana di Paleontologia e Stratigrafia (Research In Paleontology and Stratigraphy) | 2001
Simona Giunta; Kay-Christian Emeis; Alessandra Negri
A detailed study has been performed on two eastern Mediterranean box cores (BC02 and BC06) and on a southern Adriatic piston core (AD91-17) on the alkenone unsaturation ratio, a molecular proxy for past sea surface temperatures. The aim was to identify climatic events of the last 16 Ky, with particular attention on the conditions during formation of sapropel S1. All three temperature curves lack evidence for cooling in the Younger Dryas stadial and warming in the Boelling/Alleroed interstadial events. Just prior to the sapropel S1 base, SST cooled and increased by about 5°C during the sapropel deposition interval. Within sapropel S1, SST show a marked warming followed by a clear cooling. In the topmost intervals of the cores SST are mostly constant, but a warming event is always observed. This warming phase may correspond to the Medieval climatic Optimum (in the AD91-17 core) and to the Roman Optimum (in the box cores).
Palaeogeography, Palaeoclimatology, Palaeoecology | 2007
Vinicio Manzi; Marco Roveri; Rocco Gennari; Adele Bertini; Ulderico Biffi; Simona Giunta; Silvia Maria Iaccarino; Luca Lanci; Stefano Lugli; Alessandra Negri; Angelo Riva; Massimo Rossi; Marco Taviani
Journal of Quaternary Science | 2003
Francesca Sangiorgi; Lucilla Capotondi; Nathalie Combourieu Nebout; Luigi Vigliotti; Henk Brinkhuis; Simona Giunta; André F. Lotter; Caterina Morigi; Alessandra Negri; Gert-Jan Reichart
Marine Micropaleontology | 2006
Tanja J. Kouwenhoven; Caterina Morigi; Alessandra Negri; Simona Giunta; Wout Krijgsman; Jean-Marie Rouchy
Marine Micropaleontology | 2007
Simona Giunta; Caterina Morigi; Alessandra Negri; François Guichard; Gilles Lericolais
Palaeogeography, Palaeoclimatology, Palaeoecology | 2006
Francesca Sangiorgi; Enrico Dinelli; P. Maffioli; Lucilla Capotondi; Simona Giunta; Caterina Morigi; M. S. Principato; Alessandra Negri; Kay-Christian Emeis; Cesare Corselli
Palaeogeography, Palaeoclimatology, Palaeoecology | 2006
Lucilla Capotondi; M. S. Principato; Caterina Morigi; Francesca Sangiorgi; P. Maffioli; Simona Giunta; Alessandra Negri; Cesare Corselli