Products of neptunian eruptions

摘要: A common pyroclastic facies in subaqueous volcanic successions comprises massive to graded, very thick (several tens of meters), laterally extensive kilometers) beds nonwelded pumice lapilli with volumes ranging cubic kilometers. This may be overlain by laminated ash or bimodal and giant (>1 m) clasts, underlain coarse lithic breccia. The association is inferred the typical product sustained magmatic volatile–driven explosive eruptions from vents at water depths ~1300–200 m. We propose term “neptunian” for such their products. eruption column rapidly mixes surrounding water, cools, increases density, collapses, while remaining under water. Lithic clasts that are too heavy entrained deposited close source, forming a neptunian Pumice waterlogged form dominant component collapsing eruption-fed, water-supported density currents (neptunian currents). Hot, buoyant, continue rise reach surface before being settling, along temporarily suspended ash, suspension deposits. Eruption magnitude, fragmentation mechanisms, juvenile pyroclast characteristics, especially vesicularity, similar Plinian-style eruptions, but behavior differs primarily because contrasting physical properties ambient fluid (water versus air).