Subsidence in the Midst of Plateau Uplift: Neogene Evaporitic Basins of Northwest Argentina

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Sedimentary basins that form within magmatic arcs and plateaus are poorly understood. Basic questions include: Has there been any tectonic subsidence or just ponding of sediment? Is such tectonic subsidence due to magmatic movement, crustal thinning, thrust loading, or reactivation of pre-existing density anomalies? Observations and theoretical treatments of such basins are rare, in spite of extensive study of the genesis of sedimentary basins in other settings. Jordan will study Neogene and Quaternary intra- arc/intraplateau basins of the Central Andes mountain chain, in the Puna plateau of northwestern Argentina. Late Miocene to Recent depocenters accumulated 2000 to 5000 m of strata while the whole region was being uplifted. Potential clues to the causes of the basins include their coincidence with gravity highs and the fact that they are sediment-starved. Evaporite facies are volumetrically important, long-lived, and economically important. The work will document the paleogeography of the basins through the Miocene to Recent. Study of facies, contact relations between the basin fill and adjacent bedrock, provenance and paleocurrents will be complemented by absolute dating of intercalated ashes.