The dataset comprises of physical and biogeochemical measurements of saltmarsh soils from across 19 UK saltmarshes. The data provides a quantitative measure of soil dry bulk density, organic carbon content, nitrogen content, CN ratio, N/C ratio, δ13Corg and δ15N across varies substrate and marsh types. Between 2018 and 2021, 33 wide diameter gouge cores (60 mm in diameter) were collected as part of the Carbon Storage in Intertidal Environments (C-SIDE) project to facilitate the calculation of organic carbon burial rates in saltmarsh soils. Sites were chosen to represent contrasting habitats types in the UK, in particular sediment types, vegetation and sea level history. The work was carried out under the NERC programme - Carbon Storage in Intertidal Environment (C-SIDE), NERC grant reference NE/R010846/1.