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New constraints on the occurrence of Y-3 Upper Pleistocene tephra marker layer in the Tyrrhenian Sea
No full textABSTRACT: Munno R. & Petrosino P., New constraints on the occurrence of Y-3 Upper Pleistocene tephra layer in the Tyrrhenian Sea.
(IT ISSN 0394 – 3356, 2004).
A widespread tephra layer, other than the well known Y-5, has been identified in the Upper Pleistocene marine succession in the
Tyrrhenian Sea. Two investigated gravity cores showed, in fact, the presence of two companion pyroclastic tephra layers, separated by
a varying thickness of pelagic sediments. The pyroclastic layers are mainly made up of pumice fragments and glass shards together
with few K-feldspars and clino-pyroxene crystals. Both layers are alcali-trachytic in composition, even though a sharp difference emerges
in the K/Na ratio that characterizes the two glasses. 14C dating of foraminiferous shells embedded in the clay layers directly
underlying the most recent tephra gave an age of about 26 ka. An accurate review of literature regarding tephrostratigraphy in the
Mediterranean area made it possible to correlate the older one to the Y-5 marker layer, joined to the Campanian Ignimbrite eruption, a
paroxystic event in the Campi Flegrei area. The younger layer has been correlated with the Y-3 marker layer and probably represents
another huge pyroclastic flow event from the Campanian area, whose products have not yet been distinguished in the field from those
of typical Campanian Ignimbrite. This work clearly identifies the layer Y-3, firstly recorded by Keller et al. (1978), as the result of a specific
volcanic event different from the Campanian Ignimbrite (marker layer Y-5), defines its mineralogical and chemical composition
together with its relative age offering an useful support for paleoclimatic and paleoenvinromental reconstruction of the sedimentation in
the Tyrrhenian area.
RIASSUNTO: Munno R. & Petrosino P., Caratterizzazione di Y-3, un tefra per il Pleistocene superiore nel Mar Tirreno. (IT ISSN 0394 –
3356, 2004).
Nella successione marina del Pleistocene Superiore, nel basso Tirreno, è stato identificato e caratterizzato un livello di tefra diverso
dall'Y-5, che è il livello marker in genere associato con la grossa eruzione dell' Ignimbrite Campana. Molti gravity cores analizzati hanno
infatti mostrato la presenza di una doppietta di livelli piroclastici, separati da uno spessore variabile di sedimenti pelagici. I livelli di tefra
sono entrambi costituiti da frammenti di pomici e shard vetrose con una minima percentuale di cristalli di k-feldspato e clinopirosseno.
Entrambi i livelli mostrano un chimismo alcalitrachitico, ma sono caratterizzati da una netta differenza nel rapporto K/Na. Datazioni 14C
ottenute su gusci di foraminiferi prelevati all'interno dell'argilla alla base del tefra più recente hanno fornito un'età di circa 26 ka. Una
revisione accurata della letteratura riguardante la tefrostratigrafia nell'area mediterranea ha permesso di correlare il più antico con il
marker Y-5, che rimanda all'eruzione dell'Ignimbrite Campana, un evento parossistico proveniente dall'area flegrea. Il livello più recente
è stato correlato con il marker Y-3 e, probabilmente, rappresenta un altro evento di rilievo dell'area campana, i cui prodotti, sul campo,
non sono stati ancora distinti da quelli dell'Ignimbrite Campana. Il lavoro identifica in maniera definitiva il livello Y-3, individuato per la
prima volta da Keller et al. (1978), come il risultato di un evento specifico diverso dall'Ignimbrite Campana (marker layer Y-5), ne definisce
la composizione mineralogica e chimica, l'età relativa e, mappandone la distribuzione, offre un utile supporto per la ricostruzione
paleoclimatica e paleoambientale della sedimentazione nell'area mediterranea
The late Quaternary tephrostratigraphical record of the San Gregorio Magno Basin (southern Italy)
No full textTwenty-one primary pyroclastic layers were found embedded in the lacustrine sediments of the San Gregorio Magno basin (Southern Apennine). These sand-sized layers were characterized by a noticeable juvenile fragments content and by a sharp basal contact with the underlying clay and silt sediments. The tephra layers have been correlated with terrestrial counterparts reporting to well known eruptive events of the Campanian volcanic area, or with reference layer from deep sea sediment cores and from Monticchio maar sequence. The investigation of the San Gregorio Magno tephra layers made it possible to deduce that lacustrine sedimentation at San Gregorio Magno basin began before 170 ky B.P. and lasted at least until the Neapolitan Yellow Tuff emplacement, occurred about 15 ky B.P. Through the results of tephra layers analysis the fluctuating sedimentation rate of the basin was pointed out. Finally, the presented correlation between lacustrine and marine sequences represents a step forward to the reconstruction of the late Quaternary tephrostratotype for southern Italy
Mineralogy and geochemistry of the low potassium series of the Campania Volcanics (South Italy).
No full textIL VESUVIO IERI, OGGI, DOMANI. STAMPATO A CURA DELLASSESSORATO ALLURBANISTICA DELLA REGIONE CAMPANIA
No full textCD-ROM VERSIONE MULTIMEDIALE CON AGGIUNTE DEL LIBRO IL VESUVIO IERI, OGGI, DOMANI
No full textCDRom contenente la versione in .html del libro "Il Vesuvio ieri, oggi, domani
Sr isotope geochemistry of megacrysts from Continental Rift and converging plate margin in alkaline volcanism South Italy.
No full textA late Middle Pleistocene climatic cycle in southern Italy inferred from pollen analysis and tephrostratigraphy of the Acerno lacustrine succession.
No full textThe Acerno lacustrine basin is a tectonic palaeolake formed during the Middle Pleistocene. Pollen analysis and tephrostratigraphy performed on the lacustrine succession (about 100 m thick) allowed the vegetation history to be reconstructed and correlated with OIS 9 and 8 on the basis of the presence of the Lower WTT (297 ka) marker level
Evolution of the Late Quaternary San Gregorio Magno tectono-karstic basin (southern Italy) inferred from geomorphological, tephrostratigraphical and paleoecological analyses: tectonic implications
No full textThe Pantano di San Gregorio Magno is a 4.7km2 large tectono-karstic basin located in the axial belt of the Southern Apennines, an area affected by intense seismicity. The basin was formed in the Middle Pleistocene and is presently undissected. It is filled by lacustrine sediments (clays, silts and pyroclastic sands) passing laterally into alluvial fan deposits. Geomorphological investigations were integrated with tephrostratigraphical, palynological and palaeoecological analyses of a 61m thick core (not reaching the bedrock). The multiproxy analysis of the S. Gregorio Magno record shows that, over the last 200k yr, the basin hosted a freshwater lake with an oscillating level. Age constraints provided by the tephrostratigraphic record allowed estimation of the sedimentation rate, which varied strongly through time. Evolution of the basin resulted from the complex combination of tectonic subsidence, karst processes and changing amounts of sedimentary inputs. The latter was influenced by allogenic contributions related both to primary and reworked volcanoclastic inputs and was climate-driven. The overall evidence, which indicates that in the long-term the accumulation rate substantially counterbalanced the accommodation space created by faulting, suggests that the basin evolution was also modulated by changing subsidence rates
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