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

Author(s)

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

Affiliation

^[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

• Document type: Journal article
• Source: BRAZILIAN JOURNAL OF GEOLOGY; v. 51, n. 2 2021-05-14.

Abstract

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)

• FAPESP's process: 14/13937-3 - Comparative analysis of modern fluvial systems and the rock record: outcrop-scale analogue modelling for the palaeoenvironmental interpretation of fluvial deposits
• Grantee: Maurício Guerreiro Martinho dos Santos
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 14/06889-2 - Paleohydrological changes, chronology of events and sediment dynamics in the quaternary of the Pantanal Wetland
• Grantee: Mario Luis Assine
• Support Opportunities: Research Program on Global Climate Change - Regular Grants