A thin, fines-poor, and lithic- and crystal-rich layer locally present, from proximal to distal areas, at the base of the pyroclastic density current deposits of the Campanian Ignimbrite eruption (39 ka), sourced from Campi Flegrei (Italy), is interpreted as a ground layer (GL). It has an average lithic and crystal content of 57 and 25 wt%, respectively. The GL rests on a paleosol or an early fall deposit and is capped by a stratified ash deposit. It is bounded by erosion surfaces and its thickness does not change systematically from the source. The occurrences of GL in places separated from the source by a stretch of sea and the angular to sub-angular shape of the lithic clasts are consistent with deposition from a dilute current. The presence of the GL up to 971 m above sea level and beyond 1400–1500-m-high mountain ridges, allows estimation of the thickness of the PDC as having been at least 1.5 km. To investigate the parameters influencing the transport and emplacement mechanisms that produced the GL, we use field and sedimentological data (grain size and componentry), from samples collected between 30 and 70 km from the source. The progressive decrease in maximum lithic clast and median grain-size with distance from the vent and increasing altitude corresponds to lateral and vertical grading of lithic clasts within the current. The coarser clasts moved toward the basal part of the current, settling in more proximal areas and at low altitude. Farther from the vent (45–50 km), the lower part of the pyroclastic current impacted against the reliefs surrounding the Campanian Plain, causing the emplacement of coarser and more poorly sorted deposits on slopes oriented toward the source.

The ground layer of the Campanian Ignimbrite: an example of deposition from a dilute pyroclastic density current / Scarpati, Claudio; Sparice, Domenico; Perrotta, Annamaria. - In: BULLETIN OF VOLCANOLOGY. - ISSN 0258-8900. - 77:11(2015), pp. 1-10. [10.1007/s00445-015-0985-0]

The ground layer of the Campanian Ignimbrite: an example of deposition from a dilute pyroclastic density current

SCARPATI, CLAUDIO;SPARICE, DOMENICO;PERROTTA, ANNAMARIA
2015

Abstract

A thin, fines-poor, and lithic- and crystal-rich layer locally present, from proximal to distal areas, at the base of the pyroclastic density current deposits of the Campanian Ignimbrite eruption (39 ka), sourced from Campi Flegrei (Italy), is interpreted as a ground layer (GL). It has an average lithic and crystal content of 57 and 25 wt%, respectively. The GL rests on a paleosol or an early fall deposit and is capped by a stratified ash deposit. It is bounded by erosion surfaces and its thickness does not change systematically from the source. The occurrences of GL in places separated from the source by a stretch of sea and the angular to sub-angular shape of the lithic clasts are consistent with deposition from a dilute current. The presence of the GL up to 971 m above sea level and beyond 1400–1500-m-high mountain ridges, allows estimation of the thickness of the PDC as having been at least 1.5 km. To investigate the parameters influencing the transport and emplacement mechanisms that produced the GL, we use field and sedimentological data (grain size and componentry), from samples collected between 30 and 70 km from the source. The progressive decrease in maximum lithic clast and median grain-size with distance from the vent and increasing altitude corresponds to lateral and vertical grading of lithic clasts within the current. The coarser clasts moved toward the basal part of the current, settling in more proximal areas and at low altitude. Farther from the vent (45–50 km), the lower part of the pyroclastic current impacted against the reliefs surrounding the Campanian Plain, causing the emplacement of coarser and more poorly sorted deposits on slopes oriented toward the source.
2015
The ground layer of the Campanian Ignimbrite: an example of deposition from a dilute pyroclastic density current / Scarpati, Claudio; Sparice, Domenico; Perrotta, Annamaria. - In: BULLETIN OF VOLCANOLOGY. - ISSN 0258-8900. - 77:11(2015), pp. 1-10. [10.1007/s00445-015-0985-0]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11588/636542
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