How Ground Penetrating Radar helps to understand the Nhecolândia lakes landscape in the Brazilian Pantanal wetland

Autor(es)

Fabio Taioli ^[1] ; Mauricio Guerreiro Martinho dos Santos ^[2] ; Mario Luis Assine ^[3] ; Deborah Mendes ^[4]

Afiliação do(s) autor(es)

^[1] Universidade de São Paulo. Instituto de Energia e Ambiente - Brasil

^[2] Universidade Federal do ABC - Brasil

^[3] Universidade Estadual Paulista. Departamento de Geologia Aplicada - Brasil

^[4] Serviço Geológico do Brasil Ringgold Standard Institution - Brasil

• Tipo de documento: Artigo Científico
• Fonte: BRAZILIAN JOURNAL OF GEOLOGY; v. 51, n. 2 2021-05-14.

Resumo

Abstract The Pantanal wetland is an active sedimentary basin representing a relevant depositional setting for alluvial sedimentation studies. However, sedimentation homogeneity and the lack of outcrops makes sedimentary analysis more difficult. The Lower Nhecolândia is located at the Southern edge of the Taquari river megafan, whose genetic origin has been disputed as fluvial or eolian deposition. GPR analysis was used to characterize the subsurface stratigraphy and understand the region’s geomorphic evolution. The 100 MHz GPR provided continuous good quality sections up to a depth of 8 m. Two continuous reflections are disconformities that bound three depositional sequences characterized by distinct radar facies. The lower facies presents an upper erosional truncation followed by reflections presenting ∼1.5 m deep channelized forms and concave-up low amplitude reflections. The intermediate facies (∼4 m thick) presents a base with erosional truncation followed by concave-upward forms, ∼10 m wide, 1–3 m deep, separated by 1–2 m, and offlapping geometry. The upper facies has a flat base and thickness of 2–4 m, with parallel reflections; it shows a strong correlation between the radar facies and the forms preserved in the landscape, suggesting that channelized fluvial streams did not form them. The results obtained indicate that GPR use in the Pantanal is an important method to elucidate its geologic evolution. (AU)

• Processo FAPESP: 14/06889-2 - Mudanças paleo-hidrológicas, cronologia de eventos e dinâmica sedimentar no quaternário da Bacia do Pantanal
• Beneficiário: Mario Luis Assine
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Regular
• Processo FAPESP: 14/13937-3 - Análise comparativa entre depósitos de sistemas fluviais modernos e do registro geológico: desenvolvimento de modelos análogos em escala de afloramento para a interpretação paleoambiental de depósitos fluviais
• Beneficiário: Maurício Guerreiro Martinho dos Santos
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado