Sediment accumulation in Sepetiba Bay (Brazil) during the Holocene: A reflex of the human influence

• Main Authors: Heloisa Vargas Borges, Charles A. Nittrouer
• Format: Article
• Language: English
• Published: Universidade do Estado do Rio de Janeiro 2017-03-01
• Series: Journal of Sedimentary Environments
• Online Access: http://www.e-publicacoes.uerj.br/index.php/jse/article/view/21868

The nature of sedimentation and sediment accumulation rates in Sepetiba Bay, Brazil were interpreted from grain-size 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.