Bulletin of Volcanology

, Volume 73, Issue 10, pp 1427–1454 | Cite as

A re-appraisal of the stratigraphy and volcanology of the Cerro Galán volcanic system, NW Argentina

  • Chris B. FolkesEmail author
  • Heather M. Wright
  • Raymond A. F. Cas
  • Shanaka L. de Silva
  • Chiara Lesti
  • Jose G. Viramonte
Research Article


From detailed fieldwork and biotite 40Ar/39Ar dating correlated with paleomagnetic analyses of lithic clasts, we present a revision of the stratigraphy, areal extent and volume estimates of ignimbrites in the Cerro Galán volcanic complex. We find evidence for nine distinct outflow ignimbrites, including two newly identified ignimbrites in the Toconquis Group (the Pitas and Vega Ignimbrites). Toconquis Group Ignimbrites (~5.60–4.51 Ma biotite ages) have been discovered to the southwest and north of the caldera, increasing their spatial extents from previous estimates. Previously thought to be contemporaneous, we distinguish the Real Grande Ignimbrite (4.68 ± 0.07 Ma biotite age) from the Cueva Negra Ignimbrite (3.77 ± 0.08 Ma biotite age). The form and collapse processes of the Cerro Galán caldera are also reassessed. Based on re-interpretation of the margins of the caldera, we find evidence for a fault-bounded trapdoor collapse hinged along a regional N-S fault on the eastern side of the caldera and accommodated on a N-S fault on the western caldera margin. The collapsed area defines a roughly isosceles trapezoid shape elongated E-W and with maximum dimensions 27 × 16 km. The Cerro Galán Ignimbrite (CGI; 2.08 ± 0.02 Ma sanidine age) outflow sheet extends to 40 km in all directions from the inferred structural margins, with a maximum runout distance of ~80 km to the north of the caldera. New deposit volume estimates confirm an increase in eruptive volume through time, wherein the Toconquis Group Ignimbrites increase in volume from the ~10 km3 Lower Merihuaca Ignimbrite to a maximum of ~390 km3 (Dense Rock Equivalent; DRE) with the Real Grande Ignimbrite. The climactic CGI has a revised volume of ~630 km3 (DRE), approximately two thirds of the commonly quoted value.


Cerro Galán 40Ar/39Ar Ignimbrite volumes Caldera collapse Trapdoor 



This research was funded by an Australian Research Council Discovery Program Grant DP0663560 to the research team led by R. Cas. We thank Monash University, Oregon State University, Universita di Roma Tre and Salta University for access to the various facilities required to undertake this research. J.G. Viramonte wishes to thank Agencia de Promoción Científica y Tecnologica, MINCyT, Argentina, Grant PICT BID-1728 OC/AR 38131. Journal reviews from Steve Sparks, Michael Ort and William McIntosh and suggestions from the editors for this special issue helped to improve this manuscript.

Supplementary material

445_2011_459_MOESM1_ESM.pdf (385 kb)
ESM1 (PDF 385 kb)


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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • Chris B. Folkes
    • 1
    Email author
  • Heather M. Wright
    • 1
    • 2
  • Raymond A. F. Cas
    • 1
  • Shanaka L. de Silva
    • 3
  • Chiara Lesti
    • 4
  • Jose G. Viramonte
    • 5
  1. 1.School of GeosciencesMonash UniversityVictoriaAustralia
  2. 2.US Geological Survey MS 910Menlo ParkUSA
  3. 3.Department of GeosciencesOregon State UniversityCorvallisUSA
  4. 4.Universitá Roma TreRomaItaly
  5. 5.Univesidad Nacional de SaltaInstituto GEONORTE and CONICETSaltaArgentina

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