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Deep sea volcaniclastic deposits at the foot of Walvis Ridge seamounts (South Atlantic) and Ulleungdo Island (East Sea/Sea of Japan) reveal complex subaqueous to subaerial explosive volcanism in intraplate settings

David M. Buchs1; Deniz Cukur2; Duncan Muir1; and Expedition 391 Scientist

  • Affiliations: 1School of Earth and Environmental Sciences, Cardiff University, UK; 2 Marine Geology and Energy Division, Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon, Republic of Korea 

  • Presentation type: Poster

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

  • Poster Board Number: 75

  • Programme No: 6.2.11

  • Theme 6 > Session 2

Abstract

Volcaniclastic deposits at the foot of large intraplate oceanic volcanoes are commonly associated with erosion and reworking of volcanic products from shallow-marine to subaerial environments and can also be a direct product of subaerial explosive volcanism. However, primary volcaniclastic deposits resulting from subaqueous explosive volcanism could also occur in deeper marine environments, but there remains very limited evidence for them. New lithological and geochemical observations stemming from rotary coring of the lower flanks of Walvis Ridge seamounts during IODP Expedition 391 and piston coring of the seafloor close to Ulleungdo Island and Anyongbok seamount in the East Sea (Sea of Japan) document varied modes of subaerial to subaqueous volcanic activity. On the flank of Walvis Ridge seamounts, Upper Cretaceous to Palaeocene primary volcanogenic turbidites were encountered interbedded with lavas close to 4 km water depth. These deposits were emplaced during the island stage of the seamounts and document coeval effusive and explosive volcanism in both subaerial and deeper marine conditions. In the East Sea, Quaternary pumiceous mass transport deposits and tephra layers found below 2 km water depth reveal important tephra reworking on the flank of Ulleungdo Island during Plinian eruptions and, probably, recurring regional dispersals of pumice rafts. Geochemical and tephrochonological constraints suggest subaqueous pumice formation close to 500 m water depth at Anyongbok seamount. Together, new deep-sea observations from the South Atlantic and the East Sea outline complex subaerial to subaqueous volcanic processes and effects in intraplate settings, with yet unclear tsunamogenic implications.