Event beds in the northern Ecuadorian trench: characteristics, sources, recurrence, and paleoseismic significance
Abstract
This study investigates gravity-flow deposition in the supply-limited northern Ecuadorian margin to extend the paleoseismic record, using core and chirp dataset collected offshore the Esmeraldas and Pedernales segments. Event-bed architecture, benthic-foraminiferal and ichnological assemblages, and along-strike stratigraphy are integrated to reconstruct depositional processes and evaluate how margin morpho-structure and tectonic preconditioning control source-to-sink relationships, event-bed style, distribution, recurrence, and paleoseismic significance. Hemipelagic sediments are interbedded with single-pulsed (STu), multi-pulsed (MTu), amalgamated turbidites (ATu), volcaniclastic turbidites (VTu), and debrite-turbidite (DT) couplets. The internal architecture of MTu, ATu, and DT couplets reveals quasi-synchronous but temporally staggered flow pulses within a single composite event. In the northern zone, middle-bathyal-to-abyssal sources are routed through the Galera collision zone and Galera Fault, where landward-and steeply dipping structures favor larger, less frequent failures resulting in MTu-ATu and DT couplets. In the south, upper-to middle-bathyal sources are routed through gullies, where the seaward-dipping structures of the Atacames collision zone favor smaller, more frequent STu. Forty-five event beds deposited over ~5 kyr (AD 1897 to 3403 BC) include 8 margin-wide MTu-ATu and DT couplets with a mean recurrence interval of 577 (+240/-239) yr, consistent with an ~600-yr recurrence for Mw ≥ 8 earthquakes, and 29 basin-wide STu with multi-decadal recurrence intervals, consistent with Mw 7-7.5 earthquakes. Nine DT couplets in deeper chirp stratigraphy span ~17 kyr across the lowstand and highstand but absent during the intervening transgression. Sea level acted as a secondary modulator, while earthquakes remained the principal, though not exclusive, trigger. These findings demonstrate the paleoseismic value of supply-limited trenches when depositional processes and tectonic preconditioning are evaluated.
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BibTeX
@article{muthre2026event,
title = {{Event beds in the northern Ecuadorian trench: characteristics, sources, recurrence, and paleoseismic significance}},
author = {Mishelle Muthre and Jean-Noël Proust and Gueorgui Ratzov and Sébastien Migeon and Jean-Yves Collot and Miguel Gonzalez and Francois Michaud},
journal = {Quaternary Science Reviews},
year = {2026},
month = sep,
doi = {10.1016/j.quascirev.2026.110244},
url = {https://insu.hal.science/insu-05733487v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Event beds in the northern Ecuadorian trench: characteristics, sources, recurrence, and paleoseismic significance
AU - Mishelle Muthre
AU - Jean-Noël Proust
AU - Gueorgui Ratzov
AU - Sébastien Migeon
AU - Jean-Yves Collot
AU - Miguel Gonzalez
AU - Francois Michaud
PY - 2026
DA - 2026/09/01
JO - Quaternary Science Reviews
DO - 10.1016/j.quascirev.2026.110244
UR - https://insu.hal.science/insu-05733487v1
AB - This study investigates gravity-flow deposition in the supply-limited northern Ecuadorian margin to extend the paleoseismic record, using core and chirp dataset collected offshore the Esmeraldas and Pedernales segments. Event-bed architecture, benthic-foraminiferal and ichnological assemblages, and along-strike stratigraphy are integrated to reconstruct depositional processes and evaluate how margin morpho-structure and tectonic preconditioning control source-to-sink relationships, event-bed style, distribution, recurrence, and paleoseismic significance. Hemipelagic sediments are interbedded with single-pulsed (STu), multi-pulsed (MTu), amalgamated turbidites (ATu), volcaniclastic turbidites (VTu), and debrite-turbidite (DT) couplets. The internal architecture of MTu, ATu, and DT couplets reveals quasi-synchronous but temporally staggered flow pulses within a single composite event. In the northern zone, middle-bathyal-to-abyssal sources are routed through the Galera collision zone and Galera Fault, where landward-and steeply dipping structures favor larger, less frequent failures resulting in MTu-ATu and DT couplets. In the south, upper-to middle-bathyal sources are routed through gullies, where the seaward-dipping structures of the Atacames collision zone favor smaller, more frequent STu. Forty-five event beds deposited over ~5 kyr (AD 1897 to 3403 BC) include 8 margin-wide MTu-ATu and DT couplets with a mean recurrence interval of 577 (+240/-239) yr, consistent with an ~600-yr recurrence for Mw ≥ 8 earthquakes, and 29 basin-wide STu with multi-decadal recurrence intervals, consistent with Mw 7-7.5 earthquakes. Nine DT couplets in deeper chirp stratigraphy span ~17 kyr across the lowstand and highstand but absent during the intervening transgression. Sea level acted as a secondary modulator, while earthquakes remained the principal, though not exclusive, trigger. These findings demonstrate the paleoseismic value of supply-limited trenches when depositional processes and tectonic preconditioning are evaluated.
SN - 0277-3791
SN - 1873-457X
ER -