Late Cenozoic tectonism, caldera and plateau formation in the central Andes

RILLER, U.; I. PETRINOVIC; J. RAMELOW; J. GRESKOWIAK; M. STRECKER; O. ONCKEN

EARTH AND PLANETARY SCIENCE LETTERS

Año: 2001 vol. 188 p. 299 - 311

0012-821X

The evolution of Andean volcanism including the formation of late Miocene to Recent collapse calderas on the Punaplateau is generally interpreted in terms of the kinematic framework of the Nazca and South American Plates. Wepresent evidence that caldera dynamics and associated ignimbrite volcanism are genetically linked to the activity of firstorderNW^SE-striking zones of left-lateral transtension on the local and regional scales. Consequently, ages of collapsecalderas indicate activity of these fault zones which initiated at about 10 Ma on the Puna plateau. The onset of suchfaulting points to a change in the deformation regime from dominantly vertical thickening to orogen-parallel stretchingupon reaching maximum crustal thickness and critical surface elevation. Horizontal magma sheets that formed at midcrustallevel possibly due to heat advection by volume increase of asthenospheric mantle below thickened crust weretapped by sub-vertical faults. This accounts well for the observed tectono-magmatic phenomena at surface. It followsthat formation of collapse calderas and eruption of voluminous ignimbrites appear to be related to the mechanicalevolution of the Andean plateau rather than to changes in the geometry of the Wadati^Benioff zone or plate boundarykinematics.