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A 25 myr chronostratigraphy of ignimbrites in south Peru; implications for the volcanic history of the Central Andes

Jean-Claude Thouret, Brian R. Jicha, Jean-Louis Paquette and Evren H. Cubukcu
A 25 myr chronostratigraphy of ignimbrites in south Peru; implications for the volcanic history of the Central Andes
Journal of the Geological Society of London (September 2016) 173 (5): 734-756

Abstract

With an area exceeding 25 000 km (super 2) and volumes c. 5000 km (super 3) , south Peru hosts the Andes' second largest Neogene ignimbrite field. We document the extent, stratigraphy and chronology of 12 ignimbrite sheets in the Rio Ocona-Cotahuasi-Maran and Colca deep canyons. Based on 74 (super 40) Ar/ (super 39) Ar and U/Pb age determinations, ignimbrite-forming episodes span 25 myr. Prior to 9 Ma, eight large-volume ignimbrites were produced every 2.4 myr. After 9 Ma, average lulls between small- to moderate-volume ignimbrites decreased to 0.85 myr. The refined volcanic stratigraphy reveals three main features. (1) Larger volume ignimbrites were emplaced by punctuated flare-ups between 25 and 9 Ma during uplift of the Western Cordillera. (2) Numerous smaller ignimbrites were emplaced after 9 Ma as the ignimbrite production rate decreased threefold. This decrease may be due to the declining crustal melting rate, decreasing plate convergence rate after 9 Ma, or more magma stagnation in the shallow crust, which promoted the growth of composite cones. (3) Growth of two volcanic arcs has added twice as much volume (c. 53 km (super 3) Ma (super -1) ) to the Rio Ocona-Cotahuasi-Maran volcanic field than the ignimbrites after 2.27 Ma. Estimated linear arc magma output has, however, decreased twofold (0.15 - 0.08 km (super 3) km (super -1) Ma (super -1) ) from the Early Quaternary to the Pleistocene-Holocene.Supplementary materials: Supplementary text, tables 1-3 and figures 1-4 are available at http://doi.org/10.6084/m9.figshare.c.3147100


ISSN: 0016-7649
EISSN: 2041-479X
Coden: JGSLAS
Serial Title: Journal of the Geological Society of London
Serial Volume: 173
Serial Issue: 5
Title: A 25 myr chronostratigraphy of ignimbrites in south Peru; implications for the volcanic history of the Central Andes
Affiliation: Universite Blaise Pascal, Laboratoire Magmas et Volcans, Aubiere, France
Pages: 734-756
Published: 201609
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 80
Accession Number: 2016-085256
Categories: StratigraphyIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., strat. cols., 2 tables, geol. sketch maps
S16°30'00" - S15°00'00", W74°00'00" - W72°30'00"
Secondary Affiliation: University of Wisconsin at Madison, USA, United StatesHacettepe University, TUR, Turkey
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201641
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