Sediment transport in the Severn Estuary during the past 8000–9000 years

Abstract

The suspended sediment in the Bristol Channel contains abundant size-sorted Foraminifera with a mean size of ∼140 μ m. The dead foraminiferal assemblages from the subtidal channels and intertidal mudflats are made up partly of indigenous forms, showing a wide size range, and partly of transported forms, having a mean size of ∼140 μ m.It is therefore inferred that net transport of fine material is from the west (Celtic Sea and Bristol Channel) into the estuary. Samples from sixteen boreholes and pits in the Flandrian deposits on the east side of the stuary yield evidence of abundant transported Foraminifera, from which it is inferred that net landward transport of fine material has taken place throughout the past 8–9000 years. Further, the Foraminifera have been used to interpret the environments of deposition of the sediments. It is concluded that sedimentation up to marsh level occurred at different times in different parts of the estuary margin as at present and that there is no foraminiferal evidence supporting the idea of a widespread Romano-British transgression.