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Morphological, textural and geochemical analysis of volcanic fallout trapped in proximal marine sequences: towards the identification of new submarine eruptions in Mayotte?

L.L. Baudry^1^ , E. Lebas1, K. Picòn Colmenares1,  M. Frey1,2, D. Benett1, G. Jouet3, C. Berthod1,4, L. Gurioli5, J-C Komorowski1, E. Médard5

  • Affiliations: 1 Université Paris-Cité, Institut de Physique du Globe de Paris, 75005 Paris, France; 2 Université Paris-Saclay, CNRS, GEOPS, 91405 Orsay, France; 3 Université Brest, CNRS, Ifremer, UMR6538 Geo-ocean, 92280 Plouzané, France; 4 Observatoire volcanologique et sismologique de Guadeloupe, Institut de Physique du Globe de Paris, Gourbeyre, France; 5 Université Clermont-Auvergne, CNRS, IRD, OPGC, Laboratoire Magma et Volcans, 63178 Aubière, France; ^^Now at Université d\'Orléans, Institut des Sciences de la Terre 

  • Presentation type: Talk

  • Presentation time: Tuesday 08:45 - 09:00, Room S150

  • Programme No: 3.13.2

  • Theme 3 > Session 13

Abstract

Volcanic eruptions pose significant risks to residents and infrastructures. Investigating past eruptions is hence crucial to assess them and develop effective response plans and monitoring systems. The Mahoran seismic crisis in May 2018 is an example of such event that affected an oceanic island and led to the creation of the REVOSIMA monitoring network offshore to follow Fani Maoré volcanic activity, responsible for this crisis. During MAYOBS15 and MAYOBS19 monitoring cruises, ~300 m of marine sediments were retrieved from the uppermost submarine slope at ~5 km from Petite-Terre. We conducted an in-depth and detailed investigation of tephra and cryptotephra present in one of the core (MAY15-CS02-S02) with the aim of identifying distinct volcanic events and distinguish primary ash layers from reworked deposits, and determine the aerial or submarine source of these events. This was made possible by careful observations and descriptions of each particle, aided by digital imaging. The quality of the correlation and comparisons between volcanic levels using these methods offered a new way of qualifying and quantifying the nature and proportion of particles. Geochemical analyses of major and trace elements confirmed a phonolitic nature and a submarine origin for the tephra and cryptotephra layers, with related sources situated in the Eastern Mayotte Volcanic Chain (EMVC). This meticulous work provides new, crucial information and constraints for refining Mayotte's eruptive history, and evaluate how submarine volcanism might evolve in this region. It also opens up new avenues for the observation and characterization of tephra and cryptotephra in marine environments.