This data set consists of environmental and geochemical information obtained from samples of 27 sediment cores collected from the vegetated shoreline of three lakes in Finland (Kallavesi, Vesijärvi and Oulujärvi). The sampling campaign occurred in August 2023. From the sediment samples, we measured wet and dry weights, grain size, organic matter content and total organic carbon, that were used to study sedimentary organic carbon stocks and their drivers.