Coastal Sedimentation in a Tropical Barrier-Island System During the Past Century in Sepetiba Bay, Brazil

• Autor(a) principal: Borges, Heloisa Vargas
• Data de Publicação: 2016
• Outros Autores: Nittrouer, Charles A.
• Tipo de documento: Artigo
• Idioma: por
• Título da fonte: Anuário do Instituto de Geociências (Online)
• Texto Completo: https://revistas.ufrj.br/index.php/aigeo/article/view/6994
• topic: 210Pb geochronology; Sedimentation; Sepetiba Bay; Seismic stratigraphy; Geocronologia do 210Pb; Sedimentação; Baía de Sepetiba; Estratigrafia sísmica.

The nature of sedimentation and sediment accumulation rates in Sepetiba Bay, Brazil were interpreted from grainsize patterns, natural radiochemical distributions and seismic stratigraphy. The grain-size analyses showed progressive upward fining of sediment in cores, and a higher percentage of clay in surficial deposits in 1996 than observed during a previous spatial survey in the 1970s. Based on 210Pb geochronology, accumulation rates range from 0.37 cm yr-1 to 2.0 cm yr-1 for the last hundred years. In contrast, seismic stratigraphy indicates a range from 0.01 to 0.17 cm yr-1 over the last 7000 years. Particularly high accumulation rates are found in the northeast part of the bay, and, as a consequence of these high rates, the shoreline in the northern part of the bay prograded approximately 400 m in the last 100 years. An apparent increase in accumulation rates and a tendency for deposits to fine upward over the last ~ 100 years are attributed to human disturbance and soil erosion inland, which have been accelerated with economic development since the late 1970s.