The dataset comprises physical and biogeochemical measurements of saltmarsh soils from across 42 UK saltmarshes. The data provides a quantitative measure of soil dry bulk density and inorganic concentration across soil substrate and marsh types. Between 2018 and 2021, 58 wide diameter gouge cores (60 mm in diameter) were collected to facilitate the calculation of inorganic carbon burial rates in saltmarsh soils. Sites were chosen to represent contrasting habitat 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. Full details about this dataset can be found at https://doi.org/10.5285/31b32e4d-6385-4ded-84aa-67f9daf8f82d