Bank and Ditch Patterning
Bank and ditch features manifest in the phosphate record as linear bands of relatively high and low phosphate content (Yerkes et al. 2007: 866). This is a result of organic debris collecting in ditches, and the inability of organic debris to remain fixed to banks. The material that contributes to the increase in phosphate content in ditches may not necessarily be a result of human activity, although it is most common. It is possible that once a ditch was constructed it began to fill with naturally deposited material. This patterning, however, is still considered to be of anthropogenic origin because it results from the presence of a ditch.
Band and ditch patterning was confirmed by Yerkes et al. (2007) at an Early Copper Age settlement site in Hungary. Excavated earthwork enclosures, which surrounded the site, were identifiable in the phosphate patterning as areas of elevated phosphate levels in the ditches and depressed levels over the banks (Yerkes et al. 2007: 866).
Pattern Maps and Interpretations
Bank and ditch patterning over the defendable earthwork complex on Dungurrough
The defendable banks and ditches on the Dungurrough promontory fort, Achill Island, are visible as linear patterning with several indications of low phosphate content in bank areas and increased phosphate content in ditch areas (Figure 7). A set of three banks and ditches are discernable on the isthmus of the Dungurrough promontory. The central ditch is much deeper and more protected than the other ditches and is where the highest increase of phosphate levels within the defendable complex is located. The phosphate concentrations within the defendable complex are most likely representative of organic debris in the depressions of the defendable ditches.