@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 = "27 abr. 2024"
}