Geoelectric Subsurface Characterization in the Emerged Portion of the Barra Falsa Channel using the Ground Conductivity Meter (LIN-EM), Bojuru, RS, Brazil

• Published in: Geofísica internacional 2025-01, Vol.64 (1), p.1417-1435
• Main Authors: Rebés Lima, José Pedro, Stalliviere Corrêa, Iran Carlos, Weschenfelder, Jair, Fontoura Hansen, Marco Antonio, Sambaqui Gruber, Nelson Luis Sambaqui Gruber, Moreira, Cesar Augusto Moreira, Calixto Bortolin, Eduardo Calixto Bortolin
• Format: Article
• Language: English
• Subjects: coastal evolution; lin-em method; sea-level fluctuations; stratigraphy, paleochannels
• ISSN: 0016-7169; 2954-436X
• DOI: 10.22201/igeof.2954436xe.2025.64.1.1747

Geophysical investigation in the coastal region of the emerged portion of Barra Falsa, Bojuru, RS, Brazil, provided valuable information about the depositional evolution and paleoenvironmental changes that occurred during the Quaternary period. The combination of electromagnetic surveys, analysis of stratigraphic wells, 3.5 kHz reflection seismic and previous geological data allowed for a comprehensive characterization of sedimentary environments associated with sea-level fluctuations. Electromagnetic surveys using the LIN- EM method with the Geonics EM34TM system revealed different conductivity responses in the subsurface, which could be interpreted in relation to depositional events. Five depth intervals were identified and related to specific events, such as the closure of the Barra Falsa channel, estuarine infilling, and channel drowning during marine transgressions. Furthermore, the comparison of the results of electromagnetic surveys with data from stratigraphic wells allowed calibration of indirect data. This multidisciplinary approach highlights the importance of integrating geophysical and geological techniques to reconstruct coastal environment evolution over time. This study provides a detailed insight into paleoenvironmental and depositional changes on the coast of Bojuru, demonstrating how these techniques can significantly contribute to future research and the sustainable management of coastal areas. The knowledge gained here is essential for understanding the dynamics of coastal zones and the influences of sea-level variations in the Southern region of Brazil. La investigación geofísica en la región costera de la porción emergida de Barra Falsa, Bojuru, RS, Brasil, proporcionó información valiosa sobre la evolución deposicional y los cambios paleoambientales que ocurrieron durante el período Cuaternario. La combinación de estudios electromagnéticos, análisis de pozos estratigráficos, sísmica de reflexión de 3.5 kHz y datos geológicos previos permitió una caracterización integral de los entornos sedimentarios asociados con las fluctuaciones del nivel del mar. Los estudios electromagnéticos utilizando el método LIN-EM con el sistema Geonics EM34TM revelaron diferentes respuestas de conductividad en el subsuelo, que pudieron interpretarse en relación con eventos deposicionales. Se identificaron cinco intervalos de profundidad y se relacionaron con eventos específicos, como el cierre del canal Barra Falsa, el relleno estuarino y el ahogamiento d