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Southon, J.
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- PublicationRestrictedVolcanism and deformation since 12,000 years at the Campi Flegrei caldera Italy(1999)
; ; ; ; ; ; ; ; ;Di Vito, M. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Isaia, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Orsi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Southon, J.; Lawrence LiÍermore National Laboratory, LiÍermore, CA, USA ;de Vita, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;D’Antonio, M.; Dipartimento di Geofisica e Vulcanologia, Largo San Marcellino 10, 80138 Naples, Italy ;Pappalardo, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Piochi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; ; ; ; ; ; ; The Campi Flegrei caldera is a restless, nested structure resulting from two major collapses related to the Campanian Ignimbrite 37,000 years BP. and the Neapolitan Yellow Tuff 12,000 years BP. eruptions, respectively. Detailed stratigraphical, structural, volcanological and 14C AMS. geochronological studies, devoted to the reconstruction of the volcanic and deformational history of the Campi Flegrei caldera in the past 12,000 years have been carried out. The results of these studies show that in this time span, intense both volcanic and volcano-tectonic activity was confined inside the Neapolitan Yellow Tuff caldera. Volcanism was concentrated in epochs of intense activity, alternating to periods of quiescence. The I epoch lasted from 12,000 to 9500 years BP giving rise to 34 explosive eruptions, each every 70 years on average. During the II epoch, dated between 8600 and 8200 years BP, six explosive eruptions took place at an average interval of 65 years. The III epoch lasted from 4800 to 3800 years BP and produced 16 explosive and four effusive eruptions which followed each other at mean intervals of 50 years. Eruption vents of the I epoch were located mostly along the marginal faults of the Neapolitan Yellow Tuff caldera, while those of the II epoch aligned on the northeastern sector of this margin. During the III epoch volcanism was confined in the northeastern sector of the Neapolitan Yellow Tuff caldera floor. The caldera floor is disjointed in blocks with variable vertical movements by fault and fracture systems mainly trending NE–SW and NW–SE. The still active resurgence of the caldera floor began soon after its collapse. Onset of both II and III epoch of activity coincides with increase in resurgence rate of La Starza marine terrace, the most uplifted part of the resurgent block.172 11 - PublicationRestrictedThe Agnano–Monte Spina eruption 4100 years BP/ in the restless Campi Flegrei caldera Italy(1999)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;de Vita, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Orsi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Civetta, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Carandente, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;D’Antonio, M.; Dipartimento di Geofisica e Vulcanologia, L. go San Marcellino, 10-80138 Naples, Italy ;Deino, A.; Institute of Human Origin, Berkeley, CA, USA ;di Cesare, T.; Dipartimento di Geofisica e Vulcanologia, L. go San Marcellino, 10-80138 Naples, Italy ;Di Vito, M. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Fisher, R.V.; Department of Geological Sciences, UniÍersity of California, Santa Barbara, CA, USA ;Isaia, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Marotta, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Necco, A.; Dipartimento di Geofisica e Vulcanologia, L. go San Marcellino, 10-80138 Naples, Italy ;Ort, M.; Department of EnÍironmental Sciences and Geology, Northern Arizona UniÍersity, Flagstaff, AZ, USA ;Pappalardo, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Piochi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Southon, J.; LiÍermore National Laboratory, LiÍermore, CA, USA; ; ; ; ; ; ; ; ; ; ; ; ; ; ; 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 reserved285 20