Understanding the vertical distributions of organic carbon (OC) is crucial for predicting and simulating the influences of soil units on the terrestrial carbon cycle. The OC in the fine earth fraction was calculated for the soil units Anthrosols, Cambisols, Fluvisols, Leptosols, and Regosols in the municipality of Ponte de Lima, Portugal, at depths of 0–30 cm, 0–100 cm, 0–200 cm, and 0–2590 cm. In the study area, over 40% of the OC is concentrated in the Regosol unit, followed by the Anthrosols with over 23% OC at all depths, and the Leptosols with over 22% OC at all depths. The soil units Cambisols and Fluvisols have a lower representation in the territory, with values below 1.5% and 6.5% respectively at all depths. The obtained results contribute to assessing the potential of the soil units present in the municipality to sequester CO2, promoting the development of carbon inventories and analyzing the distribution of OC through accurate and reliable estimates of current C reserves as an essential tool for analyzing and modeling the effects of different factors involved in the potential of soil OC sequestration. [ABSTRACT FROM AUTHOR]