Trans-European ash plumes from the largest explosive volcanic eruptions: A tephra record from the East European Plain

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One of the prerequisites of predicting future giant eruptions is the understanding of sizes and recurrence times of past similar events. The size of known explosive eruptions, however, is often poorly constrained as the majority of estimates are based solely on proximal deposits and do not consider voluminous veils of distal ash. Many ash plumes were dispersed by prevailing westerly winds towards the East European plain where tephra findings are ubiquitous and often associated with archaeological layers. In spite of importance of these tephra findings for the paleovolcanological, paleoclimate and archaeological research, those have never been studied with modern analytical tools. Tephra from only one locality, a cluster of Paleolithic sites of Kostenki-Borschevo (Middle Don River, Russia), was geochemically characterized and linked to the famous ~40 ka Campanian Ignimbrite eruption (Italy). About a hundred of other tephra sites dispersed in south Russian steppe from Penza and Tambov cities in the north to the Caucasus Mountains in the south remain unidentified and undated. Most of the tephras occur in tens of meters thick loess sequences, while a few tephras were found also in caves in the course of archaeological excavations. These tephras are likely derived from Mediterranean, Carpathian, Turkish, North Iranian and Caucasian eruptions and - once geochemically analyzed - could inform about earlier unknown volcanic events, their magnitudes and compositions of parent magma. In addition, geochemically fingerprinted and dated tephra layers provide an excellent tool for precise correlation and dating of disparate paleoenvironmental and archaeological archives. We propose a collaborative regional study of visible tephra layers in south Russia, which will include field work for tephra and sediments sampling, characterization of paleogeographic and paleoenviromental conditions of tephra deposition, and subsequent geochemical analysis (EMPA, LA-ICP-MS, TIMS) and dating (Ar-Ar, U/Pb, (U-Th)/He) of the tephras. The project team includes volcanologists and geochemists from Germany and Russia who have extensive experience in cooperative tephra studies, as well as young Russian paleogeographers and geomorphologists with an expertise in paleoenvironmental research in south Russia. We believe that joint efforts will permit us to (i) decipher a long-anticipated tephra record from southern Russia, (ii) delineate distribution of tephras from different sources, and (iii) estimate the ages and magnitudes of parent eruptions. The identified tephra layers will be integrated into the European tephra framework and contribute to the integration of the Russian paleoenvironmental data into the all-European context.