Publication Date:
2020-12-17
Description:
The Agnano–Monte Spina tephra AMST , dated at 4100 years BP by Arr Ar and C AMS techniques, is the product
of the highest-magnitude eruption in the Campi Flegrei caldera CFc. during its last epoch of activity 4800–3800 years BP..
The sequence alternates magmatic and phreatomagmatic pyroclastic-fallout, -flow and -surge beds and bedsets. Two main
pumice-fallout deposits with variable easterly-to-northeasterly dispersal axes are about 10 cm thick at 42 km from the vent
area. High particle concentration pyroclastic currents were confined to the caldera depression; lower concentration flows
overtopped the morphological boundary of the caldera and traveled at least 15 km over the surrounding plain. The unit is
subdivided into six members, named A through F in stratigraphic sequence, based upon their sedimentological characteristics.
Isopachs and isopleths maps suggest a vent location in the Agnano plain. A volcano-tectonic collapse begun during
the course of the eruption, took place along the faults of the northeastern sector of the resurgent block within the CFc, and
generated the Agnano plain. The early erupted trachytic magma had a homogeneous alkali–trachytic composition, whereas
later-erupted magma shows small-scale hetereogeneities. Trace elements and Sr-isotope compositions, indicate that two
isotopically distinct magmas, one alkali–trachytic and the other trachytic, were tapped and partially mixed during the
eruption. The small volume 1.2 km3 DRE. of erupted magma and the structural position of the vent suggest that the
eruption was fed by a dyke intruded along a normal fault in the sector of the resurgent block under a tensional stress regime.
q1999 Elsevier Science B.V. All rights reserved
Description:
Published
Description:
269–301
Description:
1V. Storia e struttura dei sistemi vulcanici
Description:
JCR Journal
Description:
restricted
Keywords:
Agnano–Monte Spina tephra
;
Campi Flegrei caldera
;
magma
;
pyroclastic-fallout; pumice
;
04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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