Base surge deposits,eruption history,and depositional processes of a wet phreatomagmatic volcano in Central Anatolia (Cora Maar) |
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| Institution: | 1. Dipartimento di Scienze della Terra e Geoambientali, via Orabona 4, 70125, Bari, Italy;2. IDPA-CNR, via Mario Bianco 9, Milan, Italy;3. Instituto de Geología, Fac. Ingeniería UASLP, Dr. M. Nava No 5, Zona Universitaria 78240, San Luis Potosí, Mexico;1. Department of Geological Engineering, Middle East Technical University, 06800 Ankara, Turkey;2. Department of Geological Engineering, Muğla University, 48100 Turkey;3. Isotope Geosciences Unit, SUERC, East Kilbride, G75 0QF, UK;1. School of the Environment, Washington State University, PO Box 642812, Pullman WA 99164-2812, USA;2. Geological Sciences, University of Idaho, 875 Perimeter Drive, Moscow, ID 83844, USA;1. MTA-ELTE Volcanology Research Group, Pázmány Péter sétány 1/C, H-1117 Budapest, Hungary;2. Vulcano Research Group, Department of Mineralogy, Geochemistry and Petrology, University of Szeged, Egyetem utca 2, H-6722 Szeged, Hungary;3. Department of Petrology and Geochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/C, H-1117 Budapest, Hungary;4. Volcanic Risk Solutions, Massey University, Private Bag 11 222, Palmerston North, New Zealand;5. Department of Lithospheric Research, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria;1. Volcanic Risk Solutions, Massey University, Private Bag 11 222, Palmerston North, New Zealand;2. School of Environment, The University of Auckland, Auckland, New Zealand |
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| Abstract: | Cora Maar is a Quaternary volcano located to the 20 km northwest of Mount Erciyes, the largest of the 19 polygenetic volcanic complexes of the Cappadocian Volcanic Province in central Anatolia. Cora Maar is a typical example of a maar-diatreme volcano with a nearly circular crater with a mean diameter of c.1.2 km, and a well-bedded base surge-dominated maar rim tephra sequence up to 40 m in thickness. Having a diameter/depth ratio (D/d) of 12, Cora is a relatively “mature” maar compared to recent maar craters in the world.Cora crater is excavated within the andesitic lava flows of Quaternary age. The tephra sequence is not indurated, and consists of juvenile clasts up to 70 cm, non-juvenile clasts up to 130 cm, accretionary lapilli up to 1.2 cm in diameter, and ash to lapilli-sized tephra. Base surge layers display well-developed antidune structures indicating the direction of the transport. Both progressive and regressive dune structures are present within the tephra sequence. Wavelength values increase with increasing wave height, and with large wavelength and height values. Cora tephra display similarities to Taal and Laacher See base surge deposits. Impact sags and small channel structures are also common. Lateral and vertical facies changes are observed for the dune bedded and planar bedsets.According to granulometric analyses, Cora Maar tephra samples display a bimodal distribution with a wide range of Mdφ values, characteristic for the surge deposits. Very poorly sorted, bimodal ash deposits generally vary from coarse tail to fine tail grading depending on the grain size distribution while very poorly sorted lapilli and block-rich deposits display a positive skewness due to fine tail grading. |
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