Trace-element fingerprinting of the 69–36 ka Colli Albani eruptive units: A preliminary dataset for archaeological and tephra studies in central-southern Italy

Abstract

Trace element compositions determined by ICP-MS have been acquired for six eruptive units from the most recent explosive activity of the Colli Albani Volcanic District, central Italy, documented at the Albano maar by seven eruptive units dated at ~69 ka (Albano 1–3) and ~41 ka through ~36 ka (Albano 4–7). Ratios of selected immobile trace elements (e.g. Zr/Y vs Nb/Y) have been used to build an original reference dataset of 15 samples for discriminating the six main units of the Albano maar eruptive succession, albeit it has to be considered preliminary since scarcity of outcrops and incomplete occurrence of these eruptive units hindered the acquisition of a larger dataset. In order to test its applicability, we have used it as an integrative tool to identify a weathered tephra layer (CIS-1) which has been here dated by 40Ar/39Ar method at 70 ± 2 ka, previously attributed to an undefined Albano unit, occurring in the stratified Paleolithic site of Cava Muracci. The new 40Ar/39Ar and trace element data, alongside the previous major element composition, indicate that tephra CIS-1 correlates with Albano 3 (~69 ka). The results of this study, besides providing a chronological constraint for a local archaeological site, demonstrate how trace element discrimination diagrams combined with other tephrochronological constraints can provide a useful indication for tephrostratigraphic purposes. Although more reference data are needed to test the full soundness of the trace element ratios for fingerprinting individual Albano units, the results also support this method as a new promising tool for the development and application of the tephrochronology, which would offer the great advantage to be potentially applied even to strongly altered and unsuitable volcanic deposits.