Skip to Main Content
Book Chapter

Multiple styles and scales of lithospheric foundering beneath the Puna Plateau, central Andes

By
Susan L. Beck
Susan L. Beck
Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, Arizona 85721, USA
Search for other works by this author on:
George Zandt
George Zandt
Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, Arizona 85721, USA
Search for other works by this author on:
Kevin M. Ward
Kevin M. Ward
Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, Arizona 85721, USA
Search for other works by this author on:
Alissa Scire
Alissa Scire
Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, Arizona 85721, USA
Search for other works by this author on:
Published:
January 01, 2015

Lithospheric foundering or delamination has been long recognized as an important process in the formation of the Andes, but the scale, timing, and surface uplift consequences remain controversial. We use recently completed ambient noise tomography and finite-frequency P-wave tomography results and other geologic and geophysical information to identify two ~200-km-diameter regions of piecemeal delamination in the Puna region between 21°S and 27°S. One location in the northern Puna Plateau is centered under the 11–1 Ma large-volume silicic Altiplano-Puna volcanic center, and the other in the southern Puna Plateau is centered approximately between the Arizaro Basin and 6–2 Ma Cerro Galan volcanic field. The foundering in the northern location has progressed to the point where the main thermal anomaly resides in the middle and upper crust, and the surface volcanic flare-up and mantle thermal anomalies are both in a waning stage. In the southern location, the main thermal anomaly is still in its waxing stage in the lower crust and upper mantle, and the foundering mantle material is imaged in the mantle wedge.

The differing patterns of back-arc volcanism in the two foundering centers suggest different styles and timing of delamination, with the foundering process coming to completion earlier in the north than in the south. Based on plate-motion reconstructions, the NE-SW–aligned Juan Fernandez Ridge swept southward through this area starting about ca. 14 Ma in the north and ca. 10 Ma in the south. Although we do not think the passage of the Juan Fernandez Ridge initiated foundering, it played an important role in facilitating delamination by increasing interplate coupling, and weakening and perhaps hydrating the upper plate, and its passage allowed the delaminated material to sink into the expanding space of the mantle wedge. Another important factor in this evolution is the upper-plate lithospheric strength variations inherited from the different geologic basements underlying the northern and southern Puna regions. As the larger-scale delamination progressed, leaving behind thin lithosphere and a mantle wedge with a mixture of continental lithospheric fragments and hot asthenosphere, smaller secondary Rayleigh-Taylor instabilities occurred beneath the southern Puna Plateau, influencing basin development, and subsequent melting of this “drip” material was the source of the ensuing low-volume mafic volcanism.

You do not currently have access to this article.

Figures & Tables

Contents

GSA Memoirs

Geodynamics of a Cordilleran Orogenic System: The Central Andes of Argentina and Northern Chile

Peter G. DeCelles
Peter G. DeCelles
Department of Geosciences, University of Arizona, Tucson, Arizona, USA
Search for other works by this author on:
Mihai N. Ducea
Mihai N. Ducea
Department of Geosciences, University of Arizona, Tucson, Arizona, USA, and Universitatea Bucuresti, Facultatea de Geologie Geofizica, Strada N. Balcescu Nr 1, Bucuresti, Romania
Search for other works by this author on:
Barbara Carrapa
Barbara Carrapa
Department of Geosciences, University of Arizona, Tucson, Arizona, USA
Search for other works by this author on:
Paul A. Kapp
Paul A. Kapp
Department of Geosciences, University of Arizona, Tucson, Arizona, USA
Search for other works by this author on:
Geological Society of America
Volume
212
ISBN print:
9780813712123
Publication date:
January 01, 2015

References

Related

Citing Books via

Related Articles
Related Book Content
Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal