A Late Pleistocene–Holocene wetland megafan in the Brazilian Amazonia

Rossetti, Dilce de Fátima; Zani, Hiran; Cohen, Marcelo Cancela Lisboa; Cremon, Édipo Henrique

doi:10.1016/j.sedgeo.2012.09.015

Cited by 31 publications

(39 citation statements)

References 56 publications

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“…Main sedimentological characteristics of surface deposits at the Viruá megafan, with indication of the corresponding radiocarbon ages (modified fromRossetti et al, 2012b).…”

mentioning

confidence: 99%

The role of tectonics in the late Quaternary evolution of Brazil's Amazonian landscape

Rossetti

2014

Earth-Science Reviews

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“…Main sedimentological characteristics of surface deposits at the Viruá megafan, with indication of the corresponding radiocarbon ages (modified fromRossetti et al, 2012b).…”

mentioning

confidence: 99%

The role of tectonics in the late Quaternary evolution of Brazil's Amazonian landscape

Rossetti

2014

Earth-Science Reviews

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“…The area is characterized by sandy, nutrient poor and poorly-drained soils, that are developed on an extensive sedimentary lowland plain, derived from quartzite sands from the Içá geological formation (Rossetti et al 2012b;ICMBio 2014).…”

Section: Study Sitementioning

confidence: 99%

“…The monthly temperatures ranges from 20º-38ºC, the annual average is 24ºC (Rossetti et al 2012b). The average annual rainfall is about 2000 mm, the same for the state.…”

Section: Study Sitementioning

confidence: 99%

Xyridaceae of Viruá National Park, Roraima state, Brazil

et al. 2015

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A taxonomic treatment of the Xyridaceae in the Viruá National Park is presented. Located in Roraima state, northern Brazil, the park comprises a mosaic of lowland vegetation types, including forests, wetlands, and one of the largest continuous areas of campinarana in the Brazilian Amazon Basin. Xyridaceae are represented in the park by 20 species in the genera Abolboda and Xyris. Although the four species of Abolboda are widespread, most of the Xyris species (75%) are endemic to Amazonian open vegetation formations, such as campinaranas and savannas. This study was based on field, herbarium, and scanning electron microscopy research. The taxonomic treatment includes identification keys to the genera and species, morphological descriptions, SEM images of seeds for Xyris species, iconography, geographic distribution and comments on the ecology of the species. The poorly known Xyris connosepala is synonymized in Xyris guianensis.

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“…This was made possible mainly considering the geometry defined by the distribution of vegetation classes, such as shape, elongation, sinuosity, size, as well as pre-knowledge of the geomorphology from previous works undertaken in this region [19,28,29].…”

Section: Validation Of the Phytophysiognomic Mapmentioning

confidence: 99%

“…Such depositional systems are typical of areas of low topographic gradients having numerous avulsive channels and paleochannels (remnant of an inactive river) arranged into a distributary pattern [25][26][27]. Except for the Viruá megafan (e.g., [28,29]), located at the left margin of the Branco River (see location in Figure 1b), areas of open vegetation related with megafans in northern Amazonia remain to be characterized in more detail. The largest of these occurrences is associated with the Demini River, where two patches of open vegetation total ~4180 km 2 .…”

Section: Introductionmentioning

confidence: 99%

Classification of Vegetation over a Residual Megafan Landform in the Amazonian Lowland Based on Optical and SAR Imagery

2014

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Abstract:The origin of large areas dominated by pristine open vegetation that is in sharp contrast with surrounding dense forest within the Amazonian lowland has generally been related to past arid climates, but this is still an issue open for debate. In this paper, we characterize a large open vegetation patch over a residual megafan located in the northern Amazonia. The main goal was to investigate the relationship between this paleolandform and vegetation classes mapped based on the integration of optical and SAR data using the decision tree. Our remote sensing dataset includes PALSAR and TM/Landsat images. Five classes were identified: rainforest; flooded forest; wooded open vegetation; grassy-shrubby open vegetation; and water body. The output map resulting from the integration of PALSAR and TM/Landsat images showed an overall accuracy of 94%. Narrow, elongated and sinuous belts of forest within the open vegetation areas progressively bifurcate into others revealing paleochannels arranged into distributary pattern. Such characteristics, integrated with pre-existing geological information, led us to propose that the distribution of vegetation classes highlight a morphology attributed to a Quaternary megafan developed previous to the modern fluvial tributary system. The characterization of such megafan is important for reconstructing landscape changes associated with the evolution of the Amazon drainage basin.

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A Late Pleistocene–Holocene wetland megafan in the Brazilian Amazonia

Cited by 31 publications

References 56 publications

The role of tectonics in the late Quaternary evolution of Brazil's Amazonian landscape

The role of tectonics in the late Quaternary evolution of Brazil's Amazonian landscape

Xyridaceae of Viruá National Park, Roraima state, Brazil

Classification of Vegetation over a Residual Megafan Landform in the Amazonian Lowland Based on Optical and SAR Imagery

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