Saltmarsh development from fen: Analysis of late Holocene deposits from north-central Fenland, U.K.

Abstract

Abstract Lithostratigraphic studies in north-central Fenland reveal the occurrence of a silty clay unit separating fen peat deposits from saltmarsh clayey silt deposits. Lithological and organic carbon data show gradual transitions from the underlying fen and to the overlying saltmarsh palaeoenvironments. Magnetic susceptibility data indicate pedogenic alteration of the deposits substantiated by percentage carbonate carbon data. Palynological data reveal a development from Betula carr to saltmarsh via an intermediate environment with pollen and spores derived from both seaward and landward facies. Analysis and interpretation suggest that the silty clay unit was deposited in a brackish open water habitat as a result of freshwater and tidal ponding behind the saltmarsh. The evidence suggest the existence of a previously unrecorded successional environment between coastal reedswamp and saltmarsh facies. This environment occurred in broad, shallow gradient coastal settings during periods of rapid saltmarsh growth. No modern comparable environment exists due to the effect of drainage and sea defence schemes. Comparison is made with other sites within Fenland.