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  • 1
    Publication Date: 2017-04-04
    Description: The identification and characterisation of high-frequency climatic changes during the Holocene requires natural archives with precise and accurate chronological control, which is usually difficult to achieve using only 14C chronologies. The presence of time-spaced tephra beds in Quaternary Mediterranean successions represents an additional, independent tool for dating and correlating different sedimentary archives. These tephra layers are potentially useful for resolving long-standing issues in paleoclimatology and can help towards correlating terrestrial and marine paleoclimate archives. Known major tephras of regional extent derive from central and southern Italy, the Hellenic Arc, and from Anatolia. A striking feature of major Holocene tephra deposition events in the Mediterranean is that they are clustered rather than randomly distributed in time. Several tephra layers occurred at the time of the S1 sapropel formation between c. 8.4 and 9.0 ka BP (Mercato, Gabellotto-Fiumebianco/E1, Cappadocia) and other important tephra layers (Avellino, Agnano Monte Spina, ‘Khabur’ and Santorini/Thera) occurred during the during the second and third millennia bc, marking an important and complex phase of environmental changes during the mid- to late-Holocene climatic transition. There is great potential in using cryptotephra to overlap geographically Italian volcanic ashes with those originating from the Aegean and Anatolia, in order to connect regional tephrochronologies between the central and eastern Mediterranean.
    Description: In press
    Description: (21)
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: JCR Journal
    Description: reserved
    Keywords: Holocene ; Mediterranean basin ; paleoclimate ; tephrochronology ; tephrostratigraphy ; 03. Hydrosphere::03.01. General::03.01.03. Global climate models ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 210 (1991), S. 191-201 
    ISSN: 1573-5117
    Keywords: methane ; methanogenesis ; meromictic lake ; Antarctica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Methane occurred in the monimolimnion, at depths greater than 11 m, of an antarctic meromictic lake, Ace Lake (depth 24.7 m). Although the water of the lake was of approximate marine salinity, bottom waters were depleted in sulfate (less than 1 mmol 1−1). The temperature of the bottom waters of the lake were constantly between 1 °C and 2 °C. Rates of methanogenesis from 14C-labelled precursors (bicarbonate, formate and acetate) were determined in time course experiments with the detection of 14CH4 produced by a gas chromatography-gas proportional counting system. Rates of 14CH4 production were difficult to determine as the reactions were always near our limit of detection. Reliable determinations of rates of methanogenesis at some depths using some precursors were obtained, the fastest rate being 2.5 µmol kg−1 day−1 at depth 20 m. Assuming constant rates of methanogenesis with time, this would equate to a turnover of methane in the lake every two years. The slow rate of methanogenesis suggests that the methanogens in Ace Lake may be working at well below their optimum temperature although definitive statements regarding the presence of psychrophilic methanogens in this antarctic lake must await isolation attempts or longer field studies using alternative methodologies.
    Type of Medium: Electronic Resource
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