Marine tephrochronology and Quaternary explosive volcanism in the Lesser Antilles arc.

Document Type

Article

Date of Original Version

1-1-1981

Abstract

Explosive volcanism in the Lesser Antilles arc has been tackled by combined tephrochronologic studies of land deposits and 100 deep-sea piston cores from the adjacent Atlantic and Grenada Basins. Volcanic production in the arc during the late Quaternary has been estimated from deep-sea core data for a 105yr period as 527km3 (285km3 DRE), with the majority of this material (445km3) deposited in the marine environment. Marine tephra deposits are principally of two types: ash-fall layers and a variety of subaqueous pyroclastic gravity flow deposits. Ash-fall layers and associated air-borne dispersed ash represent about 1/3 of total production. They have been deposited almost exclusively in the Atlantic E of the arc and their dispersal is entirely controlled by westerly high-altitude winds. A variety of pyroclastic sediment gravity flow deposits account for approx 2/3 of the volcanic production. Most important are deposits which form as a result of the entry of ignimbrites directly into the sea during major eruptions. They have travelled up to 250km from source along the back-arc basin and form massive, poorly graded deposits up to 5m thick. Pyroclastic gravity flow deposits occur predominantly in the Grenada Basin, W of the arc and their distribution is aided by the steep (9o) slopes of the W arc flank. Microprobe analyses of glass shards in tephra deposits from the deep-sea and land show that rhyodacites are the dominant products of volcanism in this arc.-Authors

Publication Title, e.g., Journal

Tephra studies. Proc NATO ASI 'Tephra studies as a tool in Quaternary research', Iceland, 1980

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