Geochemical characterization of mid-distal Nisyros tephra on Datca peninsula (southwestern Anatolia)

We present new distal records of tephra deposits that overly the Kos ignimbrite in seven locations of Datca peninsula. Tephra in one of these locations were previously associated with Nisyros Kyra sub-unit based only on the field characteristics. We use different proxies such as field observations, petrography, mineral, glass, and whole-rock chemistry in order to characterize and correlate the previously and recently identified pumice fall deposits on Datca. The total thickness of the fall deposit reaches to 3.5 m. The size of the pumice clasts is generally within the range of lapilli, and they have vitrophyric texture consisting mainly of plagioclase (andesine to labradorite) with scarce clinopyroxene (diopside to augite), olivine (Fo(48-50)), amphibole (magnesio-hastingsite), and biotite crystals. Amphibole is a ubiquitous phenocryst in all Datca tephra units and used as a criterion for the correlation. Glass major element analyses by EMPA reveal two different groups with andesitic and dacitic compositions. Difference in silica content (up to ca. 4 wt%) detected in the same specimen also designates the heterogeneity in pumice glass. This heterogeneity in glass composition is also supported by the frequent occurrence of banded pumice clasts in Datca tephra. Whole-rock composition of the pumice is mainly andesitic with calc-alkaline affinity. Multi-element patterns on primitive-mantle normalized diagram display typical arc-magmatism signature (i.e. depletion in Nb, Ta, Ti, and P).