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

J Sevink,R.L Van Hall,C.C Bakels,M.W Dee

doi:10.1016/j.quageo.2021.101154

J Sevink, R.L Van Hall + Show 2 more

Open Access

https://doi.org/10.1016/j.quageo.2021.101154

Copy DOI

Abstract

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 14 C 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 14 C 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 14 C dates. • Reduced post-tephra sediment accumulation visible in pollen density profiles. • F in distal Avellino tephra possibly toxic for contemporary marshy ecosystems.

Highlights

The Avellino eruption of the Somma-Vesuvius counts among the major Holocene eruptions in the Central Mediterranean and resulted in ‘Pompeii type’ sites close to the volcano, where the Avellino tephra covers an exceptionally well conserved Early Bronze Age landscape
Apart from wellknown factors such as the old wood/inbuilt age effect and bio turbation, we looked closer into the sampling error connected with dating plant macro remains from layers that formed in environments with low accumulation rates
The resulting sampling error can be assessed by combining the accumulation rate and thickness of the layer sampled

Summary

Introduction

The Avellino eruption of the Somma-Vesuvius counts among the major Holocene eruptions in the Central Mediterranean (see Zanchetta et al, 2011) and resulted in ‘Pompeii type’ sites close to the volcano, where the Avellino tephra covers an exceptionally well conserved Early Bronze Age landscape (see e.g. Albore Livadie, 1999; Vanzetti et al, 2019). These sites were discovered shortly before the end of the 20th century (Albore Livadie et al, 1998) and gave rise to numerous exca vations These allowed for a deep insight into the contemporary prehistoric cultures and their land use The relevance of this eruption for paleoclimatic archives lies in the wide distribution of its tephra and the associated possibilities for long distance correlation. It is enhanced by its specific chemical and mineralogical signature that al lows for its easy recognition (see Zanchetta et al, 2011 and 2019). This is exemplified by identification of the Avellino tephra in well known cores from locations as far apart as Lago d’Accesa, in Tuscany (Magny et al, 2007), Lago Grande di Monticchio, in Basilicate (Wulf et al, 2004), Lake Veliko jezero, in Croatia (Razum et al, 2020), Lake Ohrid and Lake Shkodra, both in Albania and Montenegro (Wagner et al, 2008; Sulpizio et al, 2010; respectively), and the Sea of Marmara, in Turkey (Çagatay et al, 2015)

Methods

Results

Conclusion