The relationship between Carboniferous Limestone insoluble residues and soils on limestone pavements in North Wales

Seven limestone pavements across North Wales were selected for geochemical analysis. The pavements represented a wide variety of locations and cover. At each location a limestone dint and soil from an adjacent gryke were sampled for analysis. Limestone insoluble residue and gryke infilling were analysed for seven elements, Cu, Zn, Pb, Mn, Ni, Sr and Mg, using atomic absorption spectroscopy. The absence of certain elements in the immediate limestone bedrock seems to confirm the claim by some authors that the majority of the insoluble residue in grykes is introduced from outside the area. Glaciation or periglacial aeolian transport/deposition is often cited as the mechanism. Whereas that cannot be ruled out in these areas, an additional source is postulated. Heavy metal smelting began in earnest in North Wales during the late 16th century, and airborne contaminants were reteased from this process. The levels of heavy metals in the soil samples suggest that this may have been an additional source.