First integrated tephrochronological record for the last ∼190 kyr from the Fucino Quaternary lacustrine succession, central Italy

Abstract

We present the first integrated tephrochronological study (major and trace elemental glass composition, Sr and Nd isotope analyses, and 40Ar/39Ar dating) for the last one tenth (∼82 m) of the ∼900 m-thick Quaternary lacustrine succession of the Fucino Basin, the largest and probably only Central Apennine intermountain tectonic depression that hosts a continuous lacustrine succession documenting the Plio-Quaternary sedimentary history up to historical times. Major element glass compositions, determined using a wavelength-dispersive electron microprobe (WDS-EMPA), yielded the geochemical fingerprinting needed for a reliable identification of most of the 23 stratigraphically ordered tephra layers under investigation. These include tephra from Italian volcanoes such as Campi Flegrei, Etna, Colli Albani, Ischia, Vico, Sabatini, and undefined volcanic sources in the Neapolitan area and Latium region. The recognition of key Mediterranean marker tephra layers (e.g. X-5 and X-6) is supported by trace element data acquired by Laser Ablation Inductively Couple Plasma Mass Spectrometry (LA-ICP-MS). The Sr and Nd isotope compositions of selected layers where also determined for circumscribing the volcanic source of distal tephra and for supporting correlations with individual eruptive units. We also propose a new, more expeditious covariation diagram (CaO/FeOtot vs Cl) for identifying the volcanic source of trachytic to phonolitic and tephrytic to phonolitic tephra, that are the most common compositions of pyroclastic rocks from volcanoes of Campania and Latium regions. Finally, we present five new 40Ar/39Ar age determinations, including a new, analytically well-supported, and more precise 40Ar/39Ar age for the widespread Y-7 tephra, and the first 40Ar/39Ar age determinations for one tephra from the Sabatini volcanic district (∼126 ka) and one tephra from Neapolitan volcanic area (Campi Flegrei?; ∼159 ka). These newly dated tephra are widely dispersed (e.g. Monticchio, southern Italy, Adriatic Sea and Lake Ohrid, Macedonia-Abania) and have thus the potential to become important Mediterranean MIS 5 and MIS 6 tephrochronological markers. Altogether the new geochemical data and 40Ar/39Ar ages precisely constrain the chronology of the investigated Fucino succession spanning the last ∼190 ka. In light of these results and by considering that this sedimentary succession possibly extends back to ∼2 Ma, Fucino is likely to provide a very long, continuous tephrostratigraphic record for the Mediterranean area and become a key node in the dense network of tephra correlations of this region

A rare Mid-Würmian lithoid tuff in the Agro Pontino graben (Southern Lazio, Italy) and its identification as an Albano 5-7 related distal tephra deposit (41-36 kaBP): characteristics, provenance and palaeogeographical implications

“…Assuming that isotope equilibrium existed between clinopyroxenes and phlogopites, resulting from the contemporaneous crystallization of those mineral phases during a dominant magmatic fractionation process , the measured isotope ratios match with those reported for the <69 kaBP Colli Albano volcano , Giaccio et al 2007, Gaeta et al 2011, Giaccio et al 2013. In particular, the 87 Sr/ 86 ratio of 0.709584 ± 10 (Figure 7) approaches the values of Albano 1 (0.709385-0.7095), falls in the Albano 3 range (0.708477-0.70963), and perfectly overlaps the values of Albano 5-7 (0.709512-0.709675) , Giaccio et al 2007, 2017b. However, the Ricci tuff lacks olivine that instead is typically recovered in the Albano 1 (DU1 in Giaccio et al, 2007: when in distal position).…”

“…All together, the analyses show that the lithoid tuff originates from the Colli Albani volcano and may be a distal variant of the Albano 5-7 unit, more explicitly from the larger events during this eruptive phase: Albano 5 (DU3) or Albano 7 (DU4) from ~40 and ~36 kaBP, respectively [Giaccio et al 2013[Giaccio et al , 2017b. This would be in agreement with the statement by Gaeta et al [2011] that Colli Albani tephra with an age younger than 69 ka can be quite well discriminated from earlier tephra by their Sr-isotopic ratios.…”

“…Relevant eruptions include the late eruptive cycles from the Colli Albani volcano , Giaccio et al 2007, 2017b, and from the Campi Flegrei, in the form of the Campanian Ignimbrite [about 39.2 kaBP, De Vivo et al 2001 and references therein, 39.85 ± 0.14 kaBP, Giaccio et al 2017a] and the Neapolitan Yellow Tuff [about 14.9 kaBP, Deino et al 2004 and references therein]. Tephra from these various eruptions can be identified on the basis of their low K content and associated mineral chemistry [e.g., , and isotope geochemistry, in particular their 87 Sr/ 86 ratio, which is higher for the products from the Colli Albani volcano , Giaccio et al 2007, Gaeta et al 2011, Giaccio et al 2013, and their 143 Nd/ 144 ratio, which is slightly lower for the Campi Flegrei products [Pappalardo et al 2002, Arienzo et al 2010, Di Renzo et al 2011, Piochi et al 2014.…”

“…Freda et al [2006] refer to the younger second cycle eruptions of units 5-7 (c. 39 kaBP) as being more violent than the older eruptions (units 1-4). In the most recent publication by Giaccio et al [2017b], the Albano 5 and 7 are reported as the most energetic explosive episodes during the late stage, dating from ~40 and ~36 kaBP, respectively. very recently published a tentative study based on a preliminary data set of trace element compositions of whole rock samples from the various Albano units.…”

“…Because of its thickness and petrology, and the absence of significant soil formation and weathering in this tuff and overlying sediments, the tuff would probably originate from one of the latest eruptions of the Colli Albani and might be linked to the Mid-Wür-mian Peperino Albano eruptive cycle ], more recently described as the Albano 5-7 tephra by Giaccio et al [2013Giaccio et al [ , 2017b.…”