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@Article{RossettiVaGrCoTaYe:2017:ImLaHo,
               author = "Rossetti, Dilce de F{\'a}tima and Valeriano, M{\'a}rcio de 
                         Morisson and Gribel, R. and Cohen, M. C. L. and Tatumi, Sonia H. 
                         and Yeed, M.",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de 
                         Pesquisas da Amaz{\^o}nia (INPA)} and {Universidade Federal do 
                         Par{\'a} (UFPA)} and {Universidade Federal de S{\~a}o Paulo 
                         (UNIFESP)} and {Universidade Federal de S{\~a}o Paulo 
                         (UNIFESP)}",
                title = "The imprint of Late Holocene tectonic reactivation on a megafan 
                         landscape in the northern Amazonian wetlands",
              journal = "Geomorphology",
                 year = "2017",
               volume = "295",
                pages = "406--418",
                month = "Oct.",
             keywords = "Megafan paleolandorm, Northern Amazonia, Neotectonics, Late 
                         Holocene.",
             abstract = "The modern Amazonian ecosystem outcomes from the complex interplay 
                         of different factors performed over the geological history, with 
                         tectonics being long speculated as perhaps a fundamental one. 
                         Nevertheless, areas where tectonic activity can be fully 
                         characterized are still scarce in view of the large dimension of 
                         this region. In this work, we investigate the signature of 
                         neotectonics in one megafan paleolandform that typifies a large 
                         sector of the Negro-Branco basin in northern Amazonia. The 
                         approach joined regional morphostructural descriptions of the 
                         Viru{\'a} megafan surface and the acquisition of topographic, 
                         sedimentological, and chronological data focusing on the central 
                         sector of the megafan. The results revealed an abundance of rivers 
                         that form dendritic, subdendritic, and trellis patterns. These 
                         rivers also have numerous straight segments, orthogonal junctions, 
                         and orthogonal shifts in courses. Structural lineaments, defined 
                         by straight channels and also straight lake margins, are aligned 
                         along the NW-SE and NE-SW directions that are coincidental with 
                         the main regional structural pattern in Amazonia. This study also 
                         led to recognize two large areas of lower topography in the 
                         south-central part of the megafan that consist of rectangular 
                         depressions parallel to the morphostructural lineaments. A 
                         sedimentological survey indicated that cores extracted external to 
                         the largest depression have only distributary channel and overbank 
                         sand sheet megafan deposits. Optically stimulated luminescence 
                         (OSL) ages ranged from 17.5  2.0 to 46.9  3.4 ky and radiocarbon 
                         ages ranged from 5.95.7 to 20.119.6 cal ky BP. In contrast, cores 
                         extracted within the depression consisted of fluvial deposits 
                         younger than 2.11.9 cal ky BP that increased in thickness toward 
                         the central part of the depression. We propose that the studied 
                         megafan was affected by tectonic reactivation until at least a 
                         couple thousand years ago. Tectonics would have produced subsiding 
                         areas more prone to flooding than adjacent terrains, which 
                         constituted sites for renewed deposition of fluvial sediments 
                         reworked from the megafan surface following its abandonment. A 
                         comparison of our data with those from other Amazonian areas with 
                         similar records of late Holocene tectonics suggests a landscape 
                         imprinted by faulting, probably of strike-slip motion. This 
                         finding increases the record of neotectonic activity in the 
                         Amazonian wetlands and may be useful in studies aiming at 
                         discussing the origin and extension of late Holocene deformation 
                         in the South American intraplate. In addition, we present a 
                         megafan with an unusual development in a cratonic region under the 
                         combined effect of climate and tectonics.",
                  doi = "10.1016/j.geomorph.2017.07.026",
                  url = "http://dx.doi.org/10.1016/j.geomorph.2017.07.026",
                 issn = "0169-555X",
             language = "en",
           targetfile = "rossetti_imprint.pdf",
        urlaccessdate = "30 nov. 2020"
}


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