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.