Radiocarbon Dates for Lava Flows and Pyroclastic Deposits on São Miguel, Azores

Moore, Richard B.; Rubin, Meyer

doi:10.1017/s0033822200013278

Cited by 45 publications

(51 citation statements)

References 7 publications

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“…The products of this eruption were dated at 0.840 + 0.060 ka BP (Moore & Rubin 1991). P17 is the only deposit that covers Pico das Camarinhas and its dating confirms the stratigraphy, namely, that little time elapsed between the eruption of these two eruptive events.…”

Section: Flank Eruptionsmentioning

confidence: 63%

“…The stratigraphic system proposed for the volcano by Moore is based on the identification of an eruptive sequence formed by pyroclastic flows (locally welded), fall and surge deposits, named the 'outflow deposit', which he considered to be linked to caldera formation c. 22 ka ago. This age was set by taking into account the carbon dating of charcoal found in deposits located two palaeosols above the 'outflow deposit', which gave an age of 21.160 + 0.180 ka BP (Moore & Rubin 1991). This does not agree with the absolute dating established in Queiroz (1997).…”

Section: Genesis Of the Calderamentioning

confidence: 96%

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Chapter 7 Eruptive history and evolution of Sete Cidades Volcano, São Miguel Island, Azores

Queiroz

Gaspar

Guest

et al. 2015

Memoirs

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Sete Cidades is an active central volcano on the western part of São Miguel. The geological record reveals that subaerial activity started more than 250 ka ago. Stratigraphic units defined for Sete Cidades deposits reflect major events in the history of the volcano and are organized into two main groups: the Inferior Group and the Superior Group. Caldera formation resulted from three major paroxysmal events that occurred at about 36, 29 and 16 ka ago. Analysis of the eruptive history of Sete Cidades shows that effusive or moderately explosive eruptions, of Hawaiian and/or Strombolian styles, were located on the slopes of the central volcano. Conversely, trachytic explosive activity is mostly centred inside the caldera involving, in a first stage, predominantly Plinian and sub-Plinian phenomena, changing about 5 ka ago to a dominant hydromagmatic style. Trachytic effusive eruptions are represented by domes and associated lava flows that crop out in the inner caldera walls and on the western slopes of the volcano. Offshore submarine activity is represented by the historic Surtseyan eruptions of 1638 and 1811. In the last 5 ka Sete Cidades was the most active central volcano in the Azores with 17 explosive eruptions predominantly with hydromagmatic character. Scoria conesThese are the most common volcanic edifices on Sete Cidades massif and were formed as a result of the accumulation of basaltic † Deceased 19 May 2012.

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Section: Flank Eruptionsmentioning

confidence: 63%

Section: Genesis Of the Calderamentioning

confidence: 96%

Chapter 7 Eruptive history and evolution of Sete Cidades Volcano, São Miguel Island, Azores

Queiroz

Gaspar

Guest

et al. 2015

Memoirs

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“…(e.g. Moore and Rubin 1991;Wallenstein 1999;Pensa et al 2015), but its age is generally reported as ~5 ka. Although the deposit is not genetically related to Furnas, it is well known and easily identified and, in the absence of well-exposed deposits relating to the second caldera-forming event at Furnas (~12,000 14 C y B.P.…”

Section: Furnas Eruptive Historymentioning

confidence: 99%

Temporal evolution of a post-caldera, mildly peralkaline magmatic system: Furnas volcano, São Miguel, Azores

Jeffery

Gertisser

O’Driscoll

et al. 2016

Contrib Mineral Petrol

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This is considered to take place in a density-stratified reservoir, with alkali basalt magmas at the base and hydrous trachytes forming an upper cap or cupola. The presence of this reservoir at shallow crustal depths beneath the caldera likely inhibits the ascent and subsequent eruption of mafic magmas, generating a compositional Daly Gap. Rare syenitic ejecta represent in situ crystallisation of trachytic magmas in the thermal boundary zone at the top of the reservoir. Trachytic enclaves within these syenites, in addition to banded pumices and ubiquitous clinopyroxene antecrysts in the UFG pumice falls, provide evidence for mingling/mixing processes within the magmatic system. Despite relatively uniform major element compositions, systematic trace element variations within individual eruptions highlight the importance of fractional crystallisation during late-stage evolution of the trachytes. This is facilitated by the accumulation of water and the development of mild peralkalinity, which contribute to low pre-eruptive melt viscosities and efficient crystal settling. Compositional zoning patterns between individual eruptions cannot be accounted for by periodic tapping of a single magma batch undergoing fractional crystallisation. Instead, up to four individual cycles are recognised, in which a zoned cap of eruptible trachytic magma, formed at the top of the reservoir, was erupted in one or more eruptions and was re-established via intermittent replenishment and subsequent fractional crystallisation. Keywords Furnas volcano · Peralkaline trachyte · Fractional crystallisation · Zoned magma reservoir · Post-caldera volcanismAbstract Furnas is one of three active central volcanoes on São Miguel Island, Azores, and is considered to be one of the most hazardous in the archipelago. In this study, the pre-eruptive magma plumbing system of the 10 young (<5 ka), intra-caldera, sub-Plinian, trachytic eruptions of the Upper Furnas Group (UFG) is investigated via whole rock major and trace element geochemistry, mineral chemistry, thermobarometry, and petrogenetic modelling. The main aim of this work is to elucidate the petrogenesis of the Furnas trachytes, constrain the P-TfO 2 conditions under which they evolve, and investigate the temporal evolution of the magma plumbing system. Results indicate that the trachytes are derived predominantly from extended fractional crystallisation of alkali basalt parental magmas, at depths between ~3 and 4 km.Communicated by Jochen Hoefs. Electronic supplementary materialThe online version of this article

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“…Previous detailed geological mapping and radiocarbon dating provide an excellent guide to eruption chronology on São Miguel (Booth et al, 1978;Moore, 1990; Moore and Rubin, 1991). Only the most easterly vol- Table 1.…”

Section: Geological Background and Sampling Strategymentioning

confidence: 99%