Chemical analysis of ash layers in ODP Leg 104 holes ...
Numerous fresh ash layers comprise about 0.3% by volume of Neogene to Holocene sediments drilled at Leg 104 Sites 642 and 643 (Vøring Plateau, North Atlantic). Median grain sizes of the ashes are about 100 /µm and maximum grain sizes range up to 1200 µm. Rhyolitic pumice shards dominate, with minor...
| Main Authors: | , , |
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| Format: | Article in Journal/Newspaper |
| Language: | English |
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PANGAEA
1989
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| Subjects: | |
| Online Access: | https://dx.doi.org/10.1594/pangaea.736965 https://doi.pangaea.de/10.1594/PANGAEA.736965 |
| Summary: | Numerous fresh ash layers comprise about 0.3% by volume of Neogene to Holocene sediments drilled at Leg 104 Sites 642 and 643 (Vøring Plateau, North Atlantic). Median grain sizes of the ashes are about 100 /µm and maximum grain sizes range up to 1200 µm. Rhyolitic pumice shards dominate, with minor bubble wall shards. Basaltic shards are poorly vesicular and blocky or round. Phenocrystic plagioclase, zircon, and clinopyroxene occur in the rhyolitic, plagioclase, and clinopyroxene phenocrysts and basaltic lithics in the basaltic tephra. Quartz, amphibole, clinozoisite, and rutile are interpreted as xenocrysts. All ash layers are well-sorted and represent distal fallout from major explosive eruptions. Most ashes are rhyolitic (high-K and low-K) in composition, some are bimodal (tholeiitic and rhyolitic). Early Miocene tephra is dominantly basaltic.Iceland is inferred to be the likely source region for most ashes. Late Miocene high-K rhyolites may have originated from the K-rich Jan Mayen magmatic province. One ... : Supplement to: Bitschene, Peter Rene; Schmincke, Hans-Ulrich; Viereck-Götte, Lothar (1989): Cenozoic ash layers on the Vøring Plateau (ODP Leg 104). In: Eldholm, O; Thiede, J; Taylor, E; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 104, 357-366 ... |
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