Abstract
Large volcanic eruptions are major geohazards, so identifying their frequency in the geologic record is critical for making predictions and hazard assessments. Following the discovery of a thick (18 cm) tephra layer in marine sediments from Integrated Ocean Drilling Program (IODP) Site U1396 between Montserrat and Guadeloupe in the Caribbean Sea, we document here how high-precision Pb isotopes, trace elements, and grain morphological analyses of the tephra can be used, together with volcanological models, to identify a large (Volcanic Explosivity Index ?6) Plinian eruption from Basse-Terre, Guadeloupe, at ca. 2.36 Ma. This previously unrecognized eruption is believed to be the largest documented volcanic event in this region since this time. We hypothesize that this large eruption was associated with the final stage in the evolution of an individual volcanic center, which has implications for prediction of geohazards in this setting.
Highlights
Reconstructing the history of island arc volcanoes is critical for determining their petrological evolution and potential geohazards, but such studies are difficult because erosion and later eruptions destroy and obscure the subaerial record of volcanoes, with much of the erupted material rapidly transported to the oceans (Le Friant et al, 2015)
While marine sediment cores can provide more complete histories of arc volcanism, this approach requires identification of the depositional mode of marine tephra layers and their precise origin from closely spaced and compositionally similar volcanoes. This problem is exemplified in the Lesser Antilles, Caribbean Sea, where volcanism has been active since ca. 40 Ma
SEDIMENT CORE OBSERVATIONS Tephra was likely delivered to Site U1396 from different sources, but prevailing wind directions and seafloor topography suggest, that these layers were predominantly from volcanoes on Montserrat and Guadeloupe
Summary
Reconstructing the history of island arc volcanoes is critical for determining their petrological evolution and potential geohazards, but such studies are difficult because erosion and later eruptions destroy and obscure the subaerial record of volcanoes, with much of the erupted material rapidly transported to the oceans (Le Friant et al, 2015). The present study uses geochemical, grain morphology, and volcanological techniques to identify the origin and magnitude of the eruption that generated the thickest tephra layer from Site U1396.
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