Two-mica rhyolitic tephra in the East Pisco Basin (Peru): new age and dispersion constraints for the eruptions of the Eastern Cordillera of Central Andes

Bosio, Giulia; Gioncada, Anna; Di Celma, Claudio; Villa, Igor Maria; Pichavant, Michel; Urbina, Mario; Bianucci, Giovanni (2020). Two-mica rhyolitic tephra in the East Pisco Basin (Peru): new age and dispersion constraints for the eruptions of the Eastern Cordillera of Central Andes. Bulletin of volcanology, 82(6), pp. 1-22. Springer-Verlag 10.1007/s00445-020-1373-y

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Two-mica—biotite and muscovite—volcanics are particularly rare in the geological record. One of the several dozen volcanic ash layers from Central Andes volcanoes found in the upper Miocene marine succession of the Pisco Formation (Ica Desert, Peru) contains juvenile biotite and muscovite, sillimanite/andalusite, feldspars, and rhyolitic glass. 39Ar–40Ar dating on biotite and muscovite concordantly constrain an age of 7.96 Ma for this two-mica ash layer. A second tephra in the Pisco Formation has a similar biotite composition and an age between 7.45 and 6.93 Ma. The peculiar mineral assemblage and the chemical composition of biotite indicate a strongly peraluminous composition of the erupted magmas and, together with the 39Ar–40Ar ages, suggest to consider a correlation of these ash layers to the eruptions of the Miocene Macusani (Peru) or Morococala (Bolivia) volcanic complexes in the Eastern Cordillera of Central Andes. The major and trace element composition of glass supports the correlation with Macusani. A prove- nance from Morococala seems less likely given the large distances involved. These results provide new data on the volcanic activity of the Eastern Cordillera revealing ash that dispersed to over 500 km to the west, in the forearc marine basins. This finding highlights that the exhumed forearc East Pisco Basin is highly promising as an archive of distal ash for the reconstruction of the volcanic activity of Central Andes during the Miocene silicic flare-ups.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Other Institutions > Emeriti, Faculty of Science
08 Faculty of Science > Institute of Geological Sciences
08 Faculty of Science > Institute of Geological Sciences > Isotope Geology

UniBE Contributor:

Villa, Igor Maria

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

0258-8900

Publisher:

Springer-Verlag

Funders:

[UNSPECIFIED] Ministero dell’Istruzione dell’Università e della Ricerca (Italy)

Language:

English

Submitter:

Igor Maria Villa-Toscani

Date Deposited:

15 Apr 2021 08:40

Last Modified:

15 Apr 2021 08:50

Publisher DOI:

10.1007/s00445-020-1373-y

Web of Science ID:

WOS:000533910700001

Uncontrolled Keywords:

Volcanic Chronostratigraphy, Tephrochronology

BORIS DOI:

URI:

https://boris.unibe.ch/id/eprint/153142

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