Sedimentology and geochronology of aeolian deposits on the Middle Negro River, northern Amazon, Brazil

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Abstract
Fields of sandy paleodunes have been identified in Brazil, Colombia, Venezuela, and Guyana north of the South American continent. In this study, geochronological data obtained by optically stimulated luminescence (OSL) for paleodunes in the Middle Rio Negro region (Brazil) allowed the identification of two stages of dune deposition: the older from 169.74 ± 1.01 ka to 124.38 ± 0.91 ka and the younger from 18.89 ± 0.88 ka to 14.75 ± 0.77 ka. The older interval is the first reported in the Amazon; no correlated sediment has been documented. In contrast, the more recent depositional interval correlates to the interval of paleodune fields of the region called “dry corridor” in the Late Pleistocene–Holocene. In this study, we associated the genesis of paleodunes with the reworking of alluvial deposits from the Negro and Demini rivers, driven by river seasonality during the Pleistocene–Holocene, as evidenced by characteristic microtextural data.

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