The imprint of Late Holocene tectonic reactivation on a megafan landscape in the northern Amazonian wetlands
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 lar...
| Autor principal: | Rossetti, Dilce F. |
|---|---|
| Outros Autores: | Valeriano, M. M., Gribel, Rogério, Cohen, Marcelo Cancela Lisboa, Tatumi, Sônia Hatsue, Yee, Marcio |
| Grau: | Artigo |
| Idioma: | English |
| Publicado em: |
Geomorphology
2020
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| Acesso em linha: |
https://repositorio.inpa.gov.br/handle/1/17035 |
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oai:repositorio:1-17035 |
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oai:repositorio:1-17035 The imprint of Late Holocene tectonic reactivation on a megafan landscape in the northern Amazonian wetlands Rossetti, Dilce F. Valeriano, M. M. Gribel, Rogério Cohen, Marcelo Cancela Lisboa Tatumi, Sônia Hatsue Yee, Marcio Holocene Landform Landscape Lineament Morphostructure Neotectonics Paleoenvironment Wetland Amazonia 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 Viruá 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 5.9–5.7 to 20.1–19.6 cal ky BP. In contrast, cores extracted within the depression consisted of fluvial deposits younger than 2.1–1.9 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. © 2017 Elsevier B.V. 2020-06-15T21:38:18Z 2020-06-15T21:38:18Z 2017 Artigo https://repositorio.inpa.gov.br/handle/1/17035 10.1016/j.geomorph.2017.07.026 en Volume 295, Pags. 406-418 Restrito Geomorphology |
| institution |
Instituto Nacional de Pesquisas da Amazônia - Repositório Institucional |
| collection |
INPA-RI |
| language |
English |
| topic |
Holocene Landform Landscape Lineament Morphostructure Neotectonics Paleoenvironment Wetland Amazonia |
| spellingShingle |
Holocene Landform Landscape Lineament Morphostructure Neotectonics Paleoenvironment Wetland Amazonia Rossetti, Dilce F. The imprint of Late Holocene tectonic reactivation on a megafan landscape in the northern Amazonian wetlands |
| topic_facet |
Holocene Landform Landscape Lineament Morphostructure Neotectonics Paleoenvironment Wetland Amazonia |
| description |
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 Viruá 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 5.9–5.7 to 20.1–19.6 cal ky BP. In contrast, cores extracted within the depression consisted of fluvial deposits younger than 2.1–1.9 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. © 2017 Elsevier B.V. |
| format |
Artigo |
| author |
Rossetti, Dilce F. |
| author2 |
Valeriano, M. M. Gribel, Rogério Cohen, Marcelo Cancela Lisboa Tatumi, Sônia Hatsue Yee, Marcio |
| author2Str |
Valeriano, M. M. Gribel, Rogério Cohen, Marcelo Cancela Lisboa Tatumi, Sônia Hatsue Yee, Marcio |
| title |
The imprint of Late Holocene tectonic reactivation on a megafan landscape in the northern Amazonian wetlands |
| title_short |
The imprint of Late Holocene tectonic reactivation on a megafan landscape in the northern Amazonian wetlands |
| title_full |
The imprint of Late Holocene tectonic reactivation on a megafan landscape in the northern Amazonian wetlands |
| title_fullStr |
The imprint of Late Holocene tectonic reactivation on a megafan landscape in the northern Amazonian wetlands |
| title_full_unstemmed |
The imprint of Late Holocene tectonic reactivation on a megafan landscape in the northern Amazonian wetlands |
| title_sort |
imprint of late holocene tectonic reactivation on a megafan landscape in the northern amazonian wetlands |
| publisher |
Geomorphology |
| publishDate |
2020 |
| url |
https://repositorio.inpa.gov.br/handle/1/17035 |
| _version_ |
1787141066242129920 |
| score |
11.755432 |