The dataset comprises biochemical measurements of salt marsh soil, and samples from fields on former salt marsh, taken using a soil corer. Sampling was conducted at three restored salt marshes and six accidentally breached sites on the Essex coast, UK, providing a chronosequence from 16 to 114 years since restoration of tidal flow. Natural salt marsh at all sites were also sampled, along with adjacent fields on former salt marsh (where access permitted). All salt marsh sampling took place in October 2011. Field sample sites were sampled between July 2010 and April 2017. This data was collected as part of the NERC Centre for Ecology & Hydrology's Multi-functional land-use options project (C03463) in order to determine the trajectory and timescale of habitat recovery, and provide empirically-based predictions of changes in the rate of carbon sequestration over time following saltmarsh restoration. Data is also represented for fields on former saltmarsh to give a 'before' time point to be able to calculate these changes. Full details about this dataset can be found at https://doi.org/10.5285/0b1faab4-3539-457f-9169-b0b1fbd59bc2