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A thick lithic gravel-sand bed buried deep inside Santorini caldera, and its possible relationship to caldera flooding. IODP Expedition 398 Hellenic Arc Volcanic Field

Tim Druitt 1, Sarah Beethe2, Natasha Keeley3, Charlie Wallace4, Abigail Metcalfe1, Katharina Pank5, Jonas Preine6, Sofia Della Sala4, David Pyle4, Ralf Gertisser3, Steffen Kutterolf5, Olga Koukousioura7, Paraskevi Polymenakou8, and IODP Expedition 398 scientists

  • Affiliations: 1University Clermont-Auvergne, Laboratoire Magmas et Volcans, Clermont-Ferrand, France; 2College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, USA; 3School of Life Sciences, Keele University, Keele, UK; 4Department of Earth Sciences, University of Oxford, Oxford, UK; 5GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany; 6Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole MA, USA; 7School of Geology, Aristotle University of Thessaloniki, Thessaloniki, Greece; 8Institute of Marine Biology, Biotechnology and Aquaculture, Hellenic Centre for Marine Research, Heraklion, Greece 

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 60

  • Programme No: 3.11.20

  • Theme 3 > Session 11

Abstract

The post-collapse histories of ignimbrite calderas, and the onsets of new caldera cycles, are often masked by thick intracaldera fills. IODP Expedition 398 deep-drilled the fill of the marine Santorini caldera, penetrating up to 125 m below the sea floor, and terminating just above the seismically imaged acoustic 'basement' interpreted as intracaldera tuff from the 3.6 ka Minoan eruption. Drilling took place at four drill sites, two in the southern caldera basin and two in the northern basin, the deepest penetration being attained in the south (Site U1595). The lowermost unit penetrated is a pumiceous sand overlain by highly oxidized scoria (Unit L5). This is overlain by up to 35 m of lithic gravels that grade upwards into lithic sands (Unit L4). Tephra layers from the nascent intracaldera Kameni Volcano are vaguely defined in the upper levels of the L4 sands, but become better defined upwards, forming an ~8 m thick layer of stacked tephra layers (Unit L3). This is directly overlain by a 30 m thick pumice layer from the 726 CE eruption of Kameni volcano (Unit L2), then in turn by tephra from historical Kameni eruptions (Unit L1). In this presentation, we characterize the layer of gravels and sands between 100 and 65 m below the sea floor (Unit 4), both sedimentologically and petrologically. Along with biostratigraphic, paleo-botanic, and seismic stratigraphy constraints, we test the hypothesis of Nomikou et al. (2016) that Santorini caldera underwent catastrophic flooding following the Minoan eruption, and if so when.