Soils on the site comprise heavy clay with some peat, superimposed on glacial and estuarine gravel and mud deposits. In turn, these overlay Triassic dolomitic conglomerate in the west and Carboniferous Limestone in the east. "What is ‘special’ about the wildlife at Neddern Brook Wetlands, Caldicot SSSI?", Natural Resources Wales. Retrieved 20 February 2020
