Miocene-Pliocene shortening, extension, and mafic magmatism support small-scale lithospheric foundering in the central Andes, NW Argentina

Lithospheric foundering may be a fundamental phenomenon in diverse tectonic settings and has been shown to affect surface deformation, subsidence, and uplift. In the central Andes, lithospheric removal has been proposed to have acted at the scale of the whole orogenic system, at a smaller scale, and cyclically. Although geophysical and geochemical data have led workers to infer lithospheric foundering beneath the central Andes, there is no consensus on the timing, magnitude, and location of such foundering events. New field mapping, sedimentology, and ⁴⁰Ar/³⁹Ar and U-Pb geochronology from the Puna Plateau in NW Argentina document the timing and spatial distribution of basaltic magmatism, contraction, and basin formation, and subsequent extension, all of which are predicted results of small-scale lithospheric drips. Our data are consistent with the formation of at least two small-scale (50-100 km) foundering events, alternating between the northern and southern Puna Plateau. Such "driplets" could be common in cordilleran systems and other plateaus and can contribute to significant recycling of lithosphere without causing extensive exhumation and surface uplift.