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Giraudi, C.
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- PublicationRestrictedConstraining the onset of the Holocene “Neoglacial” over the central Italy using tephra layers(2012-09)
; ; ; ; ; ;Zanchetta, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Giraudi, C.; ENEA, C.R. Saluggia, 13040 Vercelli, Italy ;Sulpizio, R.; CIRISIVU, c/o Dipartimento Geomineralogico, University of Bari, 70125, Bari, Italy ;Drysdale, R. N.; Department of Resource Management and Geography, University of Melbourne, Victoria 3010, Australia ;Sadori, L.; Dipartimento di Biologia Vegetale, Università “La Sapienza”, 00185 Roma, Italy; ; ; ; A study of six tephra layers discovered in different deposits between 1600 and 2700 m a.s.l. in the Apennine chain in central Italy allowed precise stratigraphic constraints on environmental and climatic changes between ca. 4.5 and 3.8 cal ka BP. Chemical analyses allowed the correlation of these tephra layers with the eruptions of Agnano Mt Spina (AMST) from Phlegrean Field and Avellino (AVT) from Somma–Vesuvius. Major environmental changes in the high mountains of the Central Apennines occurred just after the deposition of the AMST and predate the deposition of the AVT. At this time, renewed growth of the Calderone Glacier occurred, marking the onset of the Apennine “Neoglacial”. The presence of the AMST and AVT enabled us to make a precise, physical correlation with other archives in central Italy. Synchronization of records between sites showed that the period intervening the deposition of the AMST and AVT layers coincided with environmental changes that were not always exactly in phase. This highlights the fact that stratigraphic correlations using only radiocarbon chronologies (the most common method used for dating archives during the Holocene) could produce erroneous correlation of events, giving rise to oversimplified paleoclimatic reconstructions.443 99 - PublicationOpen AccessTiber delta CO2-CH4degassing: A possible hybrid, tectonically active Sediment-Hosted Geothermal System near Rome(2016)
; ; ; ; ; ; ;; ; ; ;Fiumicino town in the Tiber River delta, near Rome International Airport (Italy), is historically affected by large amounts of carbon dioxide (CO2) in the ground and gas eruptions triggered by shallow drilling. While it is known that CO2 originates from carbonate thermometamorphism and/or mantle degassing, the origin of methane (CH4) associated with CO2 is uncertain and the outgassing spatial distribution is unknown. Combining isotope gas geochemistry, soil gas, and structural-stratigraphic analyses, we provide evidence for a hybrid fluid source system, classifiable as Sediment-Hosted Geothermal System (SHGS), where biotic CH4 from sedimentary rocks is carried by deep geothermic CO2 through active segments of a half-graben. Molecular and isotopic composition of CH4 and concentration of heavier alkanes (ethane and propane), obtained fromgas vents and soil gas throughout the delta area, reveal that thermogenic CH4 (up to 3.7 vol% in soil gas; δ13CCH4: 37 to 40‰ VPDB-Vienna Peedee Belemnite, and δ2HCH4: 162 to 203‰VSMOW - Vienna Standard Mean Ocean Water in gas vents) prevails over possible microbial and abiotic components. The hydrocarbons likely result from known Meso-Cenozoic petroleum systems of the Latium Tyrrhenian coast. Overmaturation of source rocks or molecular fractionation induced by gas migration are likely responsible for increased C1/C2+ ratios. CO2 and CH4 soil gas anomalies are scattered along NW-SE and W-E alignments, which, based on borehole, geomorphologic, and structural-stratigraphic analyses, coincide with active faults of a half-graben that seems to have controlled the recent evolution of the Tiber delta. This SHGS can be a source of considerable greenhouse gas emissions to the atmosphere and hazards for humans and buildings.130 137