Characterization of tephra layers recorded in marine sediments off Ecuador during the past 10 Ma, and implications on the regional geodynamics and volcanic hazard assessment - Archive ouverte HAL
Communication Dans Un Congrès Année : 2024

Characterization of tephra layers recorded in marine sediments off Ecuador during the past 10 Ma, and implications on the regional geodynamics and volcanic hazard assessment

Mathilde Bablon
Marianne Saillard
François Michaud
  • Fonction : Auteur
  • PersonId : 1127172
Pablo Samaniego
François Nauret
Jean-Luc Le Pennec
Gueorgui Ratzov
Ivan Vlastelic
  • Fonction : Auteur
  • PersonId : 1126843
Patricia Mothes

Résumé

The volcanism of the Northern Andes is characterized by an intense Plio-Quaternary activity, whose onshore deposits have covered older products associated with the early development of the arc. To improve our knowledge of the largest explosive eruptions that occurred in the Northern Andean arc since the Miocene, we analyzed tephra layers (morphology, mineralogy, major-trace element contents, Sr-Pb isotopy, 14C ages) recorded in marine sediments off Ecuador and Colombia. Along the margin, tephra recorded within shallow sediments were emitted during the Holocene. Identifying the volcanic source of distal tephra is challenging due to the large number of active volcanoes, and to size-dependent fractionation during atmospheric transport that modifies the mineral, chemical and even isotope composition of transported and settled tephra. We therefore developed a new isotopic method based on Pb isotopy, demonstrating that proximal and distal products define a single isotopic line in the 208Pb/206Pb-207Pb/206Pb space, whose equation is specific to each eruptive center. We then show that these isotopic lines are robust fingerprints of volcanic sources that do not depend on the age, mineral assemblage, and nature of the emitted products. Resulting land-sea correlations show that products of at least 12 explosive eruptions reached the Pacific Ocean since 8 kyr, and that such major events could have a major impact on current populations and infrastructures. In deep-sea sediments of the Panamá Basin, we identified 27 tephra layers emitted since the Early Pliocene. The long-term evolution of the geochemical composition of magmas, together with the recurrence of explosive eruptions, allow us to discuss the relationship between the regional geodynamics (i.e., subduction of a young aseismic ridge, slab morphology, crustal fault activity) and volcanic activity. In addition, we identified for the first time several Pleistocene rhyolitic tephra layers related to the activity of the Galápagos hotpot, revealing recent oceanic ridge-hotspot interaction.

Domaines

Volcanologie
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Dates et versions

hal-04699966 , version 1 (17-09-2024)

Identifiants

  • HAL Id : hal-04699966 , version 1

Citer

Mathilde Bablon, Marianne Saillard, François Michaud, Pablo Samaniego, François Nauret, et al.. Characterization of tephra layers recorded in marine sediments off Ecuador during the past 10 Ma, and implications on the regional geodynamics and volcanic hazard assessment. COT-INTIMATE-THM 2024 International Conference “Tephra: Chronology, Stratigraphy, Hazards, & Climate”, Sep 2024, Catania, Italy. ⟨hal-04699966⟩
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