Study of marine sedimentary deposits along Ecuador and southern Colombia through land-sea correlations of volcanic ash: a powerful tool to improve dating of past major earthquakes - Université Clermont Auvergne Accéder directement au contenu
Poster De Conférence Année : 2022

Study of marine sedimentary deposits along Ecuador and southern Colombia through land-sea correlations of volcanic ash: a powerful tool to improve dating of past major earthquakes

Mathilde Bablon
Marianne Saillard
Gueorgui Ratzov
  • Fonction : Auteur
François Michaud
  • Fonction : Auteur
  • PersonId : 1127172
Jean Yves Collot
  • Fonction : Auteur
  • PersonId : 1127173
Jean-Noël Proust
S. Migeon
Pablo Samaniego
François Nauret
Jean-Luc Devidal
François Orange
  • Fonction : Auteur
  • PersonId : 1076966
Céline C. Liorzou

Résumé

Along active margins, large magnitude earthquakes induce submarine slope instabilities, generating turbidite deposits and debris flows. These catastrophic events are recorded in the stratigraphy from the slope basins to the subduction trench. These sedimentary records provide a unique opportunity to time-extend local seismic catalogs, and their analysis is a strong tool to study the age, source and frequency of large past earthquakes. However, one of the main challenges is accurately dating the deposits, especially in settings where few datable foraminifers are available (below the Carbonate Compensation Depths, in low primary productivity environments, within sequences with poorly preserved hemipelagic sediments between erosive turbidites, etc…). In such cases, volcanic ash emitted during the largest eruptions represent robust stratigraphic markers distributed over thousands of square kilometers, which can provide valuable temporal constraints. Marine sediment cores collected during the Amadeus and Atacames oceanographic cruises (R/V L’Atalante; Collot et al., 2005; Michaud et al., 2015) reveal numerous turbidite deposits, which could be a consequence of earthquakes that occurred along the Ecuadorian margin during the Holocene. The knowledge of such events is essential to better assess the present and future seismic hazards, as well as their potentially destructive impact on marine and coastal environments. Silty to sandy turbidite layers are encountered at the mouth of the Esmeraldas and Patia Canyons, in northern Ecuador, whereas fine-grained turbidites are present at the Ecuadorian trench and in slope basins between Punta Galera and the Gulf of Guayaquil. Turbidite sequences are interbedded with volcanic ash and hemipelagic layers. In this study, we provide new 14C ages performed on planktonic foraminifera present in hemipelagic layers to constrain the age of turbidite sequences. We also characterized the lithofacies and geochemistry of distal volcanic ash fallouts, and we propose a first land-sea correlation of these deposits to identify their source. We show that products from at least eight explosive eruptions of Guagua Pichincha, Atacazo-Ninahuilca, Cotopaxi, and Cerro Machín volcanoes occurring between ~1.0 and 8.6 Ma are recorded in marine sediments. Correlation of ash layers between marine sedimentary cores allows us to provide time constraints to cores that contains turbidite sequences but cannot be dated using the radiocarbon method. Our multidisciplinary approach is innovative in this region and aims to be developed both offshore and onland to participate to a better evaluation of seismic and volcanic hazards in Ecuador.
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Dates et versions

hal-03942942 , version 1 (17-01-2023)

Identifiants

  • HAL Id : hal-03942942 , version 1

Citer

Mathilde Bablon, Marianne Saillard, Gueorgui Ratzov, François Michaud, Jean Yves Collot, et al.. Study of marine sedimentary deposits along Ecuador and southern Colombia through land-sea correlations of volcanic ash: a powerful tool to improve dating of past major earthquakes. 4th Assembly of the Latin American and Caribbean Seismological Commission (LACSC), Oct 2022, Quito, Ecuador. ⟨hal-03942942⟩
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