The geoscience department weekly seminar presents:

Speaker: Dr. Alexander Tye

Topic: Formation of the Salarde Antofalladepression, PunaPlateau, Argentina by transient extension: an effect of lithospheric foundering

Although removal of negatively-buoyant lithosphere via foundering is thought to strongly affect the tectonic evolution of orogens, the effects of foundering on orogenic deformation and the geologic record remain relatively poorly constrained. New field observations, mapping, and geochronology from the southern Punaplateau, Argentina, reveal a complex late Cenozoic evolution of upper crustal deformation coeval with a foundering event hypothesized from geophysical and geochemical evidence. Our observations suggest that the Antofalladepression, an enigmatic, linear basin 125 km long, was formed by localized, syn-convergent extension beginning during Miocene time. Deformation of the southern Punaplateau was spatially heterogeneous, with coeval extension and shortening in different areas. The inferred spatial heterogeneity in deformation is inconsistent with a causal mechanism that would affect the entire orogen, such as slowing plate convergence, but is consistent with the heterogeneous effects of lithospheric foundering observed in numerical models.