Tectonic control on the evolution of the fluvial systems of the Vinchina Formation (Miocene), Northwestern Argentina.

LIMARINO, C., TRIPALDI, A., MARENSSI, S. A., NET, L. I., RE, G. Y CASELLI, A. T.

The Sedimentary and Tectonic Evolution of Cenozoic Andean Foreland Basins,

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Lugar: New York; Año: 2001; p. 751 - 762

The Miocene Vinchina Formation accumulated in a large foreland basin related to the uplift of the Andes Mountains. This 5100 m thick unit was mostly deposited in fluvial environments but short episodes of eolian and lacustrine sedimentation also occurred. Low angle intraformational unconformities and dramatic facies changes define three depositional sequences. Sequence 1 (S1) is composed of sandstones and mudstones deposited in anastomosing river systems during a period of tectonic quiescence. Sequence 2 (S2), formed by conglomerates and sandstones with scarce intercalations of mudstones, rests on a low angle erosional surface and represents deposition in fluvial braided systems. S2 probably result of progradation of clastic wedges after an episode of uplift of the fold-thrust belt. Sequence 3 (S3), dominated by sandstones, mudstones and sparse intraformational conglomerates, was deposited in ephemeral braided and meandering rivers governed by a complex balance between subsidence and supply. Fluvial styles in the Vinchina Formation allowed the recognition of three major stages in the foreland basin evolution. During the underfilled stage (S1), high subsidence rates favoured the development of axial anastomosing rivers with well preserved floodplain sediments. Early postectonic sedimentation marks initial overfilled conditions (S2), characterized by high sediment supply and progradation of clastic wedges as braided rivers deposits. Finally, more advanced overfilled conditions (S3) were reached when sediment supply matched subsidence giving birth to ephemeral braided and meandering systems.