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Sources of some late Pleistocene and Holocene tephras found on Eastern Adriatic coast

Due to the proximity of active volcanic areas there is a great potential for research of distal tephrason the eastern Adriatic coast. Potential sources of tephras are found mainly in Italy. In recent studies, mainly Pleistocene tephras were found in terrestrial pedo- sedimentary sequences and loess deposits(Mikulčić Pavlaković et al. 2011, Wacha et al. 2011, Babić et al., 2012, 2013), mostly without the methodological determination of their source and potential age, except for findings and determination of the NYT (Neapolitan Yellow Tuff) in the Vela spilja on the Island of Korčula (Radić et al., 2007) and findings of Mercato eruption tephra in the sediment core from the Veliko jezero on Mljet (Jahns and Van Den Bogaard 1998). In total, 19 previously unknown tephra occurrences were found in marine and lake cores along the eastern Adriatic coast so far, mostly of Holocene age. In the Veliko jezero on the Mljet Island there are 10 tephra layers, glass shards from 9 of these were analyzed by microprobe for major element composition. The obtained results indicate that sources of eruptions are Campi Flegrei and Vesuvius. Four of the tephra layers from Mljet are linked with eruption events of known dates and an unknown eruption of Vesuvius has been discovered as well. The oldest identified eruption in Veliko jezero is NYT at some 14 900 cal yrs BP (420 cm core depth). The next identified is Mercato eruption at 8 900 cal yrs BP (at 250 cm depth) (Mele et al., 2010). The last identified eruption is Avellino 4 400 cal yrs BP (153 cm) (Wulf et al., 2012). The Avellino eruption is also attributed to the tephra finding directly above the depth of 153 cm and is interpreted as a reworked Avellino tephra. For other tephras there are some indications about affiliation to specific eruptions, but additional analysis of trace elements is required. With the data obtained and their combinations with the C-14 ages firm chronological model of development of Mljet's lakes has been established.bIn addition to tephra from Veliko jezero (Mljet I.), concentrations of the major elements were determined for tephras found in lake sediment cores of Baćinska jezera. In lake Sladinac at a depth of 261 cm Avellino eruption was found. Tephra from lake Podgora has not been linked to any eruption so far. In the marine core from the Pirovac bay (central Dalmatia), at a depth of 721 cm, NYT tephra was found. In addition to the late-Pleistocene and Holocene tephras described, some older tephras were found in Quaternary pedo-sedimentary sequences at Sovinje, on Pašman Island and Resnik, near Split (Central, Dalmatia). The 20 cm thick tephra deposit from Sovinje, due to devitrification of glass shards and contamination with surrounding sediment, was not analysed. Devitrification of volcanic glass shards from Resnik prevented analysis of major element data on them as well, rather than that, analysis of the major elements on the pyroxenes was made. Based on obtained data and OSL date above the layer, the tephra can be correlated with the POP-1 eruption (Giaccio et al., 2012, dated 92.4 ± 4.6 ka). The eruption of POP-1 is also described in the Italian part of the Adriatic (Bourne et al., 2015). Proximal equivalent of POP-1 eruption hasn’t been found yet, although based on the geochemistry of pyroxenes and the findings of Ce-Monazite there is a reasonable indication that the tephra comes from the Roman volcanic province.

Tephrostratigraphy, Pleistocene, Holocene, Eastern Adriatic, Mljet Island

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