Discovery of cryptotephra at Middle–Upper Paleolithic sites Arma Veirana and Riparo Bombrini, Italy: a new link for broader geographic correlations

Chemical characterization of cryptotephra is critical for temporally linking archaeological sites across vast geographic areas. Here, we describe cryptotephra investigations of two Middle to Upper Paleolithic sites from northwest Italy, Arma Veirana and Riparo Bombrini. Cryptotephra are present as small (<100 micron) rhyolitic glass shards at both sites, with geochemical signatures rare for volcanoes in the Mediterranean region. Arma Veirana contains two chemical distinct shard types. One cryptotephra bearing deposit (population one) from Arma Veirana contains shards of a high silica rhyolite (>75 wt. %) with low FeO (<1 wt. %) and a K2O/Na2O >1 and the second deposit (population two) contains a high silica rhyolite (>75 wt. %) but with high FeO (2.33-2.65 wt. %). Trace element analysis of population one (P1) by LA-ICP-MS show depletions in Ba, Sr, Eu and light rare-earth elements (LREE) and an enrichment in Th, U, Pb and heavy rare-earth elements (HREE). Population two (P2) shards are enriched in LREE and relatively depleted in HREE and Eu. Shards at Riparo Bombrini (population three) are also a high silica rhyolite (>75 wt. %) with low FeO (<1 wt. %). Trace element analyses are very similar to P1 at Arma Veirana. These results suggest that shards from population one (P1) at Arma Veirana correlate with population three (P3) at Riparo Bombrini, providing a link between deposits at both sites. Geochemical characteristics suggest three possible sources for P1 and P3; the 37.7 ka E-11 tephra related to eruptions on Lipari Island, the Acigol volcanic field in Turkey and the Miocene Kirka-Phrigian caldera in Turkey. Based on archaeological and geochemical evidence, we suggest that 37.7 ka E-11 tephra is the best match to P1 and P3. This study highlights how cryptotephra can benefit archaeology, even without a source eruption determined, by providing a distinct link between Arma Veirana and Riparo Bombrini as well as other deposits throughout the Mediterranean.