Bulk organic δ13C and C/N ratios as palaeosalinity indicators within a Scottish isolation basin

Microfossils in isolation basin sediments are frequently used to reconstruct sea-level change, but preservation problems and non-analogue situations can limit their usefulness. Here we investigate the potential of stable carbon isotopes (delta C-13) and C/N ratios from bulk organic matter, as an alternative proxy of salinity within isolation basin sediments from a basin in northwest Scotland. Within the Holocene sediment delta C-13 and C/N are determined largely by the mean weighted values of the predominant source of the organic material. Analysis of modern materials and comparison with the diatom record shows that the marine parts of the sequence are dominated by high delta C-13 and variable C/N. In the fresh water sequences the organic material is a mixture of both freshwater aquatic and terrestrial plant input that have relatively low delta C-13 and high C/N. The application of delta C-13 and C/N ratios in the studied basin in general follow the environmental change recorded by the diatoms and shows the potential of bulk organic matter in the investigation of salinity change in isolation basins. Copyright (c) 2005 John Wiley & Sons, Ltd.