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Fracture variability in basalts and its effect on river erosion: a case study in the Paraná Volcanic Province

Lima, Adalto Gonçalves ; Pelegrina, Marcos Aurelio ; Pontarolo, Murilo

Earth sciences research journal, 2021-03, Vol.25 (1), p.13-19 [Periódico revisado por pares]

Bogata: Universidad Nacional de Colombia

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  • Título:
    Fracture variability in basalts and its effect on river erosion: a case study in the Paraná Volcanic Province
  • Autor: Lima, Adalto Gonçalves ; Pelegrina, Marcos Aurelio ; Pontarolo, Murilo
  • Assuntos: Aircraft ; Axes (reference lines) ; Basalt ; Bedrock ; Channel flow ; Cooling ; Density ; Direction ; Fractures ; GEOSCIENCES, MULTIDISCIPLINARY ; Joints (timber) ; Photogrammetry ; Plucking ; Polls & surveys ; Remotely piloted aircraft ; Rivers ; Surveying ; Tectonics ; Variability
  • É parte de: Earth sciences research journal, 2021-03, Vol.25 (1), p.13-19
  • Descrição: The variation in the structural characteristics (cooling joints and tectonic fractures) of basaltic flows implies potential variability in the intensity of erosion by plucking. The erosive behavior of the rivers that sculpt these areas depends on their interaction with the diverse fracture systems. In view of this, we analyzed the effect of fracture variability in basalts on erosion in a bedrock river reach located in the Continental Volcanic Province of the Paraná Basin, southern Brazil. The 120-m-long reach is influenced somewhat by a possible fault that crosses it near one end. The fracture density and fracture direction were evaluated through field photogrammetry in seven sample areas distributed along the reach. The fracture direction and main erosion axes were also surveyed by remote piloted aircraft (RPA) aerial imaging. Tectonic fractures were identified in the field; they do not always appear in the survey of the sample areas but are evident in the RPA survey. The main erosion axes coincide with the principal fracture directions (tectonic fractures), which are disposed obliquely to the channel flow direction, making an average angle of 50°. The more abundant and multidirectional cooling joints act to control the plucking process and not to determine the erosion direction. The fracture density decreases with increasing distance from the fault crossing zone (from 9.62 to 3.73 m/m²), although the lower value is influenced by the presence of an amygdaloidal basalt zone. The higher fracture density favors more intense plucking.
  • Editor: Bogata: Universidad Nacional de Colombia
  • Idioma: Inglês;Português
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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