Glass geochemistry and ages of Middle Pleistocene (130–770 ka) pyroclastic deposits from the Aegean Arc: Towards a refined tephrostratigraphy for the Eastern Mediterranean region

• Applicant: Dr. Polina Vakhrameeva, Ph.D.
• Subject Area: Geology ; Mineralogy, Petrology and Geochemistry
• Term: from 2021 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 468398523

Tephra layers, i.e., pyroclastic material produced by volcanic eruptions and preserved in sedimentary archives, provide an invaluable tool for precise correlation and dating of past climate and environmental changes that are documented in these archives. The successful application of the method to distal locations (i.e., hundreds to thousands kilometers far from volcanic sources) requires detailed knowledge of the chemical compositions and ages of proximal (i.e., near-source) tephra deposits to which data from distal tephra layers can be compared. In the Eastern Mediterranean region, many distal tephra layers known from marine and terrestrial archives cannot yet be identified and used for correlation and dating purposes because their volcanic sources in Italy, Greece and Turkey have remained insufficiently studied. This is particularly true for tephras that were erupted during the Middle Pleistocene (c. 130–770 ka). The chemical compositions of Middle Pleistocene tephras, e.g., those from the climate archives of Tenaghi Philippon (NE Greece) and ODP Site 964 (Ionian Sea), suggest that many of them originate from volcanic sources in Greece and specifically from the South Aegean Volcanic Arc (SAVA).The here proposed project aims to comprehensively characterize ages and chemical compositions of proximal pyroclastic deposits in the SAVA. Specifically, the study will focus on several Aegean Arc volcanic centers that were active during the Middle Pleistocene such as Kos, Methana and Milos. First, major- and trace-element analyses (EPMA, LA-ICP-MS, SIMS) of single volcanic glass particles will be carried out to identify diagnostic differences in chemical compositions of these volcanic sources and their individual eruptions. Second, high-precision ages of Aegean Arc tephra deposits will be determined using radioisotopic dating techniques (Ar-Ar, U-Th-Pb, (U-Th)/He).Ultimately, the generated dataset for the Middle Pleistocene of the SAVA will be used (i) to link the near-source tephra deposits with their distal equivalents from marine and terrestrial climate archives; (ii) to identify tephra deposits that are widespread, well-dated and compositionally distinctive, and thus can be used as key tephra markers; and (iii) to build a refined tephrostratigraphy for the Middle Pleistocene in the Eastern Mediterranean region. Such a tephrostratigraphy is essential for constructing robust and precise age models for Eastern Mediterranean paleoclimate records and their direct comparisons.

• DFG Programme: Research Grants