Multi-criteria analysis for mapping susceptibility to iron formation caves development in the Gandarela mountain range (MG), southeast Brazil.
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2021
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In tropical regions, abundant in iron-rich geological materials, caves that are genetically and
geographically associated with exploitable mineral deposits may develop. These caves have
speleological relevance and are environmentally and legally protected in Brazil. Thus, for
better planning of exploitation and environmental licensing, it is necessary to study the genesis
and development of the iron formation caves seeking to preserve them without impeding the
advancement of mining. This subject is complex, rarely studied, and few are the knowledges
on alternatives to predict the occurrence of these caves. This gap justifies the development
of research and products capable of assisting decision-makers, planners, and competent
authorities in supporting the definition of target sites for speleological prospecting in the field.
In this study, the prediction of the factors involved in the development of iron formation caves
was evaluated producing a map of susceptibility in a GIS environment using fuzzy logic and an
analytical hierarchic process (AHP). Therefore, the variables: iron oxide ratio, slope gradient,
normalised difference vegetation index (NDVI), plan curvature, profile curvature, lineament
intensity, and height above the nearest drainage (HAND) were selected. These variables
were obtained by processing of geospatial data from a region of the Gandarela Range (Minas
Gerais, Brazil). The fuzzy logic and AHP techniques were applied, and for the validation of
the results, a previously surveyed cave inventory was used. The results showed satisfactory
performance of the map produced in predicting areas favourable to the occurrence of iron
formation caves, presenting an area under the receiver operating characteristic (ROC) curve
of approximately 0.85, which indicates a high prediction rate and validates the proposed
method. Such results demonstrate that this susceptibility map was reliable and that the set
of criteria and weights used were suitable for mapping areas favorable for speleological
prospecting.
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Susceptibility map, Analytical hierarchy process, Fuzzy logic
Citação
NOLA, I. T. de S.; BACELLAR, L. de A. P. Multi-criteria analysis for mapping susceptibility to iron formation caves development in the Gandarela mountain range (MG), southeast Brazil. International Journal of Speleology, Tampa, v. 50, p. 173-187, maio 2021. Disponível em: <https://digitalcommons.usf.edu/ijs/vol50/iss2/5/>. Acesso em: 29 abr. 2022.