Holocene climate changes in the central Mediterranean as recorded by lake-level fluctuations at Lake Accesa (Tuscany,Italy) |
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| Institution: | 1. College of Environment and Resources, Inner Mongolia University, Huhhot 010021, China;2. Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China;1. Dipartimento di Scienze Chimiche e Geologiche, Università di Cagliari, Via Trentino 51, 02127 Cagliari, Italy;2. Dipartimento di Storia, Scienze dell''Uomo e della Formazione, Università di Sassari, Via Zanfarino, 62, 07100 Sassari, Italy;3. Dipartimento di Biologia Ambientale, Sapienza Università di Roma, Piazzale Aldo Moro 5, 00185 Roma, Italy;4. Université P. Valéry Montpellier 3, CNRS ASM UMR 5140, Montpellier, France;1. School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK;2. Geochronology and Tracers Facility, NERC Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK;3. Basin and Reservoir Studies Group, Department of Earth Science, University of Bergen, Allegaten 41, 5020 Bergen, Norway |
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| Abstract: | This paper presents a high-resolution lake-level record for the Holocene at Lake Accesa (Tuscany, north-central Italy) based on a range of sedimentological techniques validated in previous studies, with a chronology derived from 43 radiocarbon dates and four tephra layers. It gives evidence of centennial-scale fluctuations with major highstands at ca 11 500, 11 100, 10 200, 9400, 8200, 7300, 6200, 5700–5200, 4850, 4200, 3400, 2600, 1200 and 400 cal BP. Except for the Early Holocene until ca 10 500 cal BP, this pattern of hydrological changes appears to be in agreement with the regional pattern established for west-central Europe. Correlations with the Preboreal oscillation and the 8.2 ka event as well as with the atmospheric 14C residual series suggest that lake-level fluctuations developed at Accesa in response to (1) final steps of the deglaciation in the North Atlantic area and (2) variations in solar activity. For the period after 4500 cal BP, correlations with other palaeohydrological records from central Italy indicate that lake-level changes reconstructed at Accesa were mainly driven by climatic variations while anthropic activities and local geomorphological factors only played a secondary role. The Accesa lake-level record also highlights millennial-scale variations with a maximal lowstand at ca 9200–7700 cal BP contemporaneous with Sapropel event 1 in the Mediterranean. It was followed by generally higher lake-level conditions. This appears to be the opposite of that observed in Sicily (southern Italy) where a lake-level maximum developed at ca 9000–8200 cal BP and was followed by a general trend towards aridification. These opposite patterns were interpreted as contrasting hydrological responses to orbitally induced changes in summer insolation. This interpretation has to be tested by further lake-level studies in the central Mediterranean region. Finally, correlations between major lowstands and periods of maximal representation of Quercus ilex point to convergences between climate oscillations and Holocene vegetation history in the Accesa region. However, the maximal representation of Abies during the first half of the Holocene, including a time window where lake level reached a minimal level, suggests a more subtle impact of seasonality processes. |
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