CONICET | Buscador de Institutos y Recursos Humanos

Late Carboniferous stratigraphy of Bolivia records a carbonate setting in the north, yielding to a complex array of tectonically- and glacially-influenced siliciclastics in the south and east. The Macharetí and Mandiyutí groups of southern Bolivia record glacially influenced deposition in the Chaco-Tarija Basin during the Late Paleozoic ice ages. Palynological analysis of diamictites and shales confirms a Pennsylvanian age for the glacial units. The Macharetí and Mandiyutí groups consist of repeating sequences of fluviodeltaic sands and glacial diamictites. Each group varies greatly in thickness, bound by significant unconformities at their bases. New stratigraphic sections show significant lateral changes in the Macharetí and Mandiyutí groups across the Chaco-Tarija Basin. Deposition of these units within paleovalleys ranges from 0 to 1800 m, with measured sections varying in thickness from 84 m to 1800 m. Lateral variability of both facies and thickness of the Macharetí and Mandiyutí groups reflects the tectonics, glaciation, and paleolatitude changes occurring during their deposition. Fieldwork was completed in summer 2007, 2008, and 2009 in southern and central Bolivia. Several sections have been measured, drafted, and correlated. In addition, samples have been taken of the diamictites and shales for palynology and of the sandstones for provenance. Basin-wide correlation of sections will be presented here.