Explosive volcaniclastic sedimentation in the Comoros Archipelago over the past 1.5 Myr (western Indian Ocean)

A new chronostratigraphic framework for deep-sea volcaniclastic sedimentation in the Somali Basin provides key constraints on the timing, magnitude, and recurrence of explosive volcanism associated with the Comoros Archipelago over the past ~1.5 Myr. Multibeam bathymetry, high-resolution seismic reflection data, and seven sediment cores recovered north of the archipelago are combined to establish basin-scale correlations of volcaniclastic turbidites. Temporal control is achieved through tuning of oxygen isotope stratigraphies.Seismic–core correlations reveal multiple regionally extensive event deposits, with individual layers covering minimum areas ranging from ~20 km² to more than 130,000 km². Petrographic observations and geochemical analyses show that the turbidites are dominated by basaltic to trachybasaltic glass fragments (sideromelane and tachylite), consistent with a Comorian volcanic provenance. The large volumes, widespread dispersal, and sharp basal contacts of these deposits support direct syn-eruptive emplacement by eruption-fed sediment gravity flows, rather than post-eruptive remobilization. Such deposits require highly energetic explosive activity, consistent with Surtseyan to (sub-)Plinian eruptions capable of generating large quantities of pyroclastic material and transporting it hundreds of kilometers into the deep basin.The resulting chronostratigraphy documents recurrent phases of intensified volcaniclastic sedimentation at ~1.63–1.35 Ma, ~1.03–0.72 Ma, and ~0.40–0.13 Ma, indicating episodic but long-lived explosive volcanism in the Comoros region during the Quaternary. These findings highlight the Comoros Archipelago as a major center of explosive basaltic volcanism in the western Indian Ocean and underscore the importance of deep-marine sedimentary records for assessing the frequency, magnitude, and hazard potential of large-scale submarine eruptions.