Glass geochemistry and tephrostratigraphy of key tephra layers in and around Lake Van, Eastern Anatolian Volcanic Province (EAVP)

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中文题名安纳托利亚东部火山带(EAVP)瓦尔湖及周边地区关键火山灰层的玻璃化学特征及火山灰层序列分析
作者Rebecca J. Kearney1CA1;Jeremy Goff2;Victoria Smith3;Markus J. Schwab1;Yavuz Özdemir4;Özgür Karaoǧlu5;Matthew Thirlwall6;Dan N. Barfod7;Oona Appelt8;Christina Günter9;Jan Fietzke10;Nadine Pickarski11;Ina Neugebauer1;Rik Tjallingii1;Achim Brauer1,9
作者单位1Section Geomorphology, GFZ Helmholtz Centre for Geosciences, Telegrafenberg, Potsdam, Germany;2Independent Researcher;3School of Archaeology, Oxford University, Oxford, UK;4Department of Geological Engineering, Van-Yüzüncü Yil University, Van, Turkey;5Department of Geological Engineering, Eskişehir Osmangazi University, Eskişehir, Turkey;6Centre for Dynamic Earth and the Solar System (CeDESS), Department of Earth Sciences, Royal Holloway University of London, Egham, UK;7NEIF Argon Isotope Laboratory, SUERC, Glasgow, Scotland;8Section Chemistry and Physics of Earth Materials, GFZ Helmholtz Centre for Geosciences, Telegrafenberg, Potsdam, Germany;9Institute of Geosciences, University of Potsdam, Potsdam, Germany;10GEOMAR Kiel, Kiel, Germany;11Geological Survey of North Rhine-Westphalia, Krefeld, Germany
刊名Quaternary Science Reviews
2025
352
摘要
The volcanoes of Nemrut and Süphan in the Eastern Anatolian Volcanic Province (EAVP) are significant sources of volcanic ash (tephra), which are found in palaeoclimatic and archaeological records in the eastern Mediterranean region. However, there is sparse glass geochemistry and little known about the eruption history of these volcanoes, limiting their full tephrochronological potential. Here, we present detailed, comprehensive single-shard major, minor and trace elem geochemistry of tephra deposits sampled at new and previously studied proximal outcrops around Lake Van and fourteen visible tephra layers (V-layers) from the ICDP Ahlat Ridge (AR) core of Lake Van spanning 130 to 30 ka. The volcanic glass from the following proximal eruption units: Lower Trachytic Pumice (LT-P), Lower Trachytic Ignimbrite (LT-I), Middle Pumices, Upper Rhyolitic Pumice and Ignimbrite (UR-PI), Upper Trachytic Ignimbrite (UT-I), and the chosen V-layers were geochemically characterised. This new glass data allows new and revised previous chrono-stratigraphic correlations between the proximal units and several V-layers. Mixed rhyolitic and trachytic glasses of V-18a correlate to the UR-P and UR-I proximal tephra units, and to previously published data from the Middle Nemrut (M-NF)-O, M-NF-I, Tatvan Ignimbrite and AP-8 units. These are all from the same caldera forming eruption of Nemrut at ∼33 ka. Glasses of the older V-30 layer correlate to a Middle Pumice Unit and M-NF-R, and V-45 represents the ‘Çekmece Formation’. The trachytic glasses of V-51 correlate to LT-P, LT-I and the M-NF-Agglutinate unit erupted from Nemrut. The distinctive basaltic glasses from V-60 correlate to an eruption of İncekaya and V-64 is a newly identified eruption from the Süphan volcano. The older V-layers identified and analysed are from Nemrut based on comparing the new glass compositions to previously published whole-rock and glass data. This comparison indicates the V-75 pantelleritic tephra correlates to the dated AP-4 proximal unit. Each of these large eruptions are easily chemically differentiated using SiO2, FeOt, CaO and Al2O3. The integration of the proximal outcrops with the continuous, well-constrained Lake Van sedimentary medial record provides a detailed tephrostratigraphic record in a volcanic region where the proximal outcrop record is fragmented and confusing.

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