Data report: component and grain size analysis of visible tephra layers, Cores 1H through 6H, Holes U1396A and U1396B, southwest Montserrat: Expedition 340

Abstract

Integrated Ocean Drilling Program Expedition 340 recovered up to 138 m of continuous core from Site U1396, 55 km southwest of Montserrat. The recovered section contains >180 visible tephra layers dating to ~4.5 Ma. Of these, the uppermost 70 tephra layers date to 2.5 Ma, covering the period of known subaerial volcanism on Montserrat. Each tephra sample underwent component analysis through point counting and grain size analysis with a Malvern Mastersizer 2000 particle size analyzer. Component analysis shows that the tephras are dominated by grains consisting of glass shards and crystals. A small number of samples from within Core 340-U1396A-6H contained scoria. Grain size analysis showed that most tephras consist of fine to medium sand and are poorly to moderately sorted.