The dating and correlation of an eastern Mediterranean lake sediment sequence: a 46–4 ka tephrostratigraphy for Ioannina (NW Greece)

Abstract

Terrestrial archives from the Mediterranean have been crucial to expanding our understanding of past environmental variability on a range of timescales. Dating Quaternary sequences in the Mediterranean is, however, often challenging, and age models often have large chronological uncertainties. Tephra deposits can provide crucial age control for detailed environmental reconstructions on sub-centennial timescales. Here, tephra analysis is undertaken for the first time on a sediment core (I-08) from Lake Ioannina, northwest Greece, for the interval spanning 46-4 ka BP. Detailed visible and 'crypto-' tephra analysis identifies deposits associated with explosive volcanism at Italian volcanic sources, including Campi Flegrei, Pantelleria, and the Aeolian Islands. We identify two visible tephra layers, the Campanian Ignimbrite (CI/Y-5; ca. 39.8 ka BP) and Pantelleria Green Tuff (PGT/Y-6; ca. 45.7 ka), as well as the Holocene Vallone del Gabellotto cryptotephra marker (VG/E-1; ca. 8.3 ka BP). Evidence for repeated remobilisation and redeposition of CI tephra material is outlined, and the potential mechanisms and effects of sediment reworking in lake environments are examined. Bayesian modelling, which incorporates the new tephra ages with earlier radiocarbon dates, extends the I-08 core chronology back to ca. 46 ka BP, facilitating direct correlation of the Ioannina sequence to others in the Mediterranean region.

Identification of the Campanian Ignimbrite in the Dead Sea and consequent time-transgressive hydroclimatic shifts in the Eastern Mediterranean

“…The distinct major and minor chemical compositions of these shards are consistent with the CI eruption from Campi Flegrei, Italy (Fig. 3) and seen in proximal [20] and distal occurrences [23,24] . The DS_137.51 shards show a large composition scatter, incorporating the different eruption phases of the CI eruption (Plinian and pyroclastic density currents, PDC) [19] .…”

“…This mass transport of sediment carried a large amount of reworked CI shards, from the catchment of the lake into the deep basin [37] . Several other records have also witnessed similar remobilisation of CI shards after the initial deposition [23,24] , associated with degrading climate conditions.…”

“…The geochemical signature of glass shards from the DS record can be con dently correlated to the CI based on major, minor and trace element analysis. The glasses incorporate the bimodal composition seen at the proximal deposits of the eruption [19,20] as well as in distal records [23,24] (Fig. 3).…”

“…3). Many other distally located records also show volcanic glasses with similar chemical compositions [18,24,27] . By using single glass trace element analysis on the two shards from DS_137.498 and ve shards from DS_137.51, further evidence is provided that these shards are from the CI eruption, rather than the multiple smaller pre-CI eruptions seen at a limited number of proximal outcrops [41] and distal records [26,43] located in the northern Mediterranean (Fig.…”

“…The ash from this eruption was dispersed over 2000-3000 km across eastern Europe and the northern-central Mediterranean region [18] (Fig. 1), deposited as visible and cryptotephra (non-visible) layers in numerous sedimentary archives in proximal [19,20] , distal marine [21,22] , terrestrial [23,24] and archaeological sequences [18,25] and has been extensively geochemically characterised. The CI is stratigraphically identi ed in many Mediterranean palaeoclimatic records to have occurred 700-800 years after a climatic downturn to colder and drier conditions in the Mediterranean region [21,[26][27][28] , coinciding with the North Atlantic ice surge of Heinrich Event 4 (HE4) 29 .…”