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

Document Type


Date of Original Version



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