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Zhornyak, L. V.
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Zhornyak, L. V.
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- PublicationRestrictedStratigraphic evidence for a “pluvial phase” between ca 8200–7100 ka from Renella cave (Central Italy)(2011-02)
; ; ; ; ; ; ; ; ; ;Zhornyak, L. V.; Dipartimento di Scienze della Terra, University of Pisa, Pisa, Italy ;Zanchetta, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Drysdale, R. N.; Department of Resource Management and Geography, University of Melbourne, Victoria 3010, Australia ;Hellstrom, J. C.; School of Earth Sciences, University of Melbourne, Victoria 3010, Australia ;Isola, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Regattieri, A.; Dipartimento di Scienze della Terra, University of Pisa, Pisa, Italy ;Piccini, L.; Dipartimento di Scienze della Terra, University of Firenze, Firenze, Italy ;Baneschi, I.; Istituto di Geoscienze e Georisorse, CNR Pisa, Italy ;Couchoud, I.; Laboratoire EDYTEM, UFR CISM, Université de Savoie, 73376 Le Bourget du Lac, France; ; ; ; ; ; ; ; A stratigraphic and chronological study of the upper level of Renella Cave (Apuan Alps, Central Italy) reveals that two episodes of flowstone accumulation bracket a thick clastic layer deposited between ca 8.2 and 7.1 ka. This layer, which represents a period of enhanced cave flooding, is substantially in phase with an interval of depleted oxygen isotope values previously recorded in a stalagmite from nearby Corchia Cave, interpreted to have resulted from an increase in local precipitation. These data confirm that during this period of time the region experienced relatively wetter conditions, including an increase in high-magnitude events capable of invading the higher passages of Renella Cave. The timing of the clastic phase occurred when the Eastern Mediterranean experienced deposition of sapropel layer S1, which is thought to reflect the stagnation of sea water produced largely by enhanced flood activity along the Nile in response to increased monsoon intensity in northern equatorial Africa. Recent estimates suggest that S1 may have lasted from ca 10.8 to ca 6.1 ka cal BP. Combined evidence from Renella and Corchia Cave indicates that the period corresponding to the wettest phase in the Apuan Alps was much shorter than this, and suggests that there is no straightforward connection between increased advection of water vapour from the Atlantic between 8.2 and 7.1 ka, as recorded in the Corchia and Renella records, and monsoon-driven enhancement of Nile discharge and S1 deposition in the eastern Mediterranean.178 26 - PublicationOpen AccessA mid-Holocene stalagmite multiproxy record from southern Siberia (Krasnoyarsk, Russia) linked to the Siberian High patternsA multiproxy record from a stalagmite collected from Torgashinskaya Cave (Southern Siberia, Russia) and growing between ca. 6 and 3.8 ka shows evidence for regional climatic changes occurring at ca. 5 ka. Interpretation of stable isotope ratios (δ18O and δ13C) and fluorescence data (intensity and wavelength of the emitted fluorescence) suggests that the interval between ca. 5 and 4.2 ka was generally warmer and drier than the interval between ca. 6 and 5 ka. The observed bipartitioning of the climate, attributable to the so-called ‘middlelate Holocene transition’, has a striking similarity to changes in K+ and Na+ concentration of Greenland ice cores (taken as indicators of the strength of the Siberian High and Icelandic Low, respectively), in the abundance of hematite-stained grains in subpolar North Atlantic sediments and, to lesser extent, in the summer Asian monsoon intensity deduced by δ18O from Chinese speleothems. In particular, the δ18O record at Torgashinskaya Cave can be interpreted as mostly driven by temperature changes. Besides several episodes of drift towards higher temperatures, it also strongly suggests the presence of short cooling events centered at 4.1+0.08/-0.07, 4.85+0.05/-0.06, 5.1+0.09/-0.09, 5.3+0.08/-0.07 and 5.8+0.12/-0.13 ka. Notably, the last three such events are in very good correspondence with spikes in the K+ and Na+ concentration of Greenland ice cores. Instead, the cooling around 4.1 ka could be the local response to the 4.2 event, a cold/dry episode identified in several records in the Northern Hemisphere. This suggests that δ18O of speleothem calcite from this area could be a useful proxy for defining the evolution of the Siberian High and its effect on the wider regional climate.
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