Radiocarbon dating distal tephra from the Early Bronze Age Avellino eruption (EU-5) in the coastal basins of southern Lazio (Italy): Uncertainties, results, and implications for dating distal tephra

• Published in: Quaternary geochronology 2021-04, Vol.63, p.101154, Article 101154
• Main Authors: Sevink, J., Bakels, C.C., van Hall, R.L., Dee, M.W.
• Format: Article
• Language: English
• Subjects: Avellino eruption; Bayesian analysis; Central Italy; Radiocarbon dating; Sampling error; Tephra toxicity; Tephrochronology
• ISSN: 1871-1014; 1878-0350
• DOI: 10.1016/j.quageo.2021.101154

Distal tephra from the major Somma-Vesuvius Avellino (AV) eruption is widespread in the coastal basins of Southern Lazio (Central Italy). Dated to 1995 ± 10 cal yr BC in 2011, later on doubts arose about the reliability of this frequently cited age. This led to a major effort to date AV tephra holding sections, based on a thorough methodological approach. Various aspects were studied to identify sections yielding reliable 14C ages, including bioturbation, inbuilt age, and variable sediment accumulation rate. Lowered rates upon deposition of tephra, particularly in anoxic marshy environments and attributed to toxic F contents, showed up as sharp increases in pollen density. The ‘sampling error’ was quantified for specific sedimentary environments and derived from coring data and published data on accumulation rates for similar Central Mediterranean sites. Next, two Bayesian analyses were performed, a traditional using the full set of samples and a novel, based on samples that were deemed as suitable (no bioturbation, inbuilt age, etc.) and of which the age was corrected for the sampling error. The age obtained by the novel analysis had the smallest range (1909–1868 cal yr BC), differs about a century, and is virtually identical to the ages published by Passariello et al. (2009) and Alessandri (2019). The earlier found age (2011) is ascribed to a statistical coincidence. The results solve a long debate on the age of the AV eruption, which is the youngest of the three major eruptions in the Central Mediterranean Bronze Age. Ages of the other two, the Agnano Mt Spina (Phlegrean) and FL eruption (Etna), are still uncertain and disputed. This study illustrates the need for a thorough approach in 14C dating tephra holding sediment archives in the Central Mediterranean, and employed a methodology that can be applied in such approach. Attention is called for potentially toxic fluorine concentrations in Campanian tephra, which may have had a serious impact on the contemporary environment and induced chronological hiatuses, but hitherto were not reported for the early tephra. •New date Avellino eruption ends controversy about its age: c. 1890 cal BCE.•Sample error quantified and applied in Bayesian analysis of 14C dates.•Reduced post-tephra sediment accumulation visible in pollen density profiles.•F in distal Avellino tephra possibly toxic for contemporary marshy ecosystems.