摘要：The nature of sedimentation and sediment accumulation rates in Sepetiba Bay, Brazil were interpreted from grainsizepatterns, natural radiochemical distributions and seismic stratigraphy. The grain-size analyses showed progressiveupward fining of sediment in cores, and a higher percentage of clay in surficial deposits in 1996 than observed during aprevious spatial survey in the 1970s. Based on 210Pb geochronology, accumulation rates range from 0.37 cm yr-1 to 2.0 cmyr-1 for the last hundred years. In contrast, seismic stratigraphy indicates a range from 0.01 to 0.17 cm yr-1 over the last7000 years. Particularly high accumulation rates are found in the northeast part of the bay, and, as a consequence of thesehigh rates, the shoreline in the northern part of the bay prograded approximately 400 m in the last 100 years. An apparentincrease in accumulation rates and a tendency for deposits to fine upward over the last ~ 100 years are attributed tohuman disturbance and soil erosion inland, which have been accelerated with economic development since the late 1970s.
