Lithic-rich and lithic-poor ignimbrites and their basal deposits. Sovana and Sorano formations (Latera caldera, Italy)
| Autor: | Greg A. Valentine, Claudia Fletcher, Danilo M. Palladino, Kailey DiemKaye |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
010504 meteorology & atmospheric sciences
pyroclastic flow ignimbrite pyroclastic surge caldera multiphase flow Geochemistry Pyroclastic rock 010502 geochemistry & geophysics 01 natural sciences Lapilli Head (geology) Traction (geology) Geochemistry and Petrology Pyroclastic surge Clastic rock Pumice Caldera Geology 0105 earth and related environmental sciences |
| Popis: | Conceptual models explaining the characteristics of ignimbrites and their basal deposits have mainly focused on variations in particle concentration and speed of the parent pyroclastic currents. Here, we focus on the effects of relative proportions of clasts that are well coupled to the carrier gas phase and those that are poorly coupled, i.e., the proportions of fine and/or low-density clasts compared to coarse and/or dense clasts. We document facies and macroscopic clast populations of two ignimbrite-producing eruptive sequences of similar volume and composition, both erupted from Latera caldera (central Italy). The Sovana ignimbrite has 1–15 vol% dense lithic clasts and locally up to 70 vol% in lithic-rich domains. It preserves evidence of emplacement of multiple overlapping flow units with local internal channeling. The ignimbrite is underlain by two basal deposits: (1) a radially distributed, 20–80-cm-thick vitric tuff referred to as BUS (basal unit Sovana) that thins gradually with distance and shows evidence of emplacement by lateral currents; and (2) a fines-depleted, lenticular, massive lapilli tuff, up to 20 cm thick, with abundant lithic clasts. The Sorano ignimbrite, in contrast, has |
| Databáze: | OpenAIRE |
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