Mapping contemporary magnetic mineral concentrations in peat soils using fine-resolution digital terrain data

Abstract

Small-scale spatial variability in the concentration of magnetic minerals in peat soils has been explained by differences in the deposition and interception of magnetic minerals at the soil surface and the retention of magnetic minerals within the soil. Each of these processes is controlled by topographic conditions. Recent advances in the field of digital terrain analysis and the availability of fine-resolution digital elevation models means that the relationship between the concentration of magnetic minerals in peat soils and topography can be explored using quantitative methods. Alport Moor is an ombrotrophic peat moorland in the Peak District National Park, UK. 24 peat cores were collected from Alport Moor covering an area of 0.1 km 2. Each core was analysed for mass specific magnetic susceptibility. Three topographic attributes (topographic wetness index, difference from mean elevation and elevation as a percentage of elevation range) were extracted from a high resolution LiDAR digital elevation model of Alport Moor. Stepwise multiple regression analyses show that topographic wetness index and difference from mean elevation are excellent predictors of variation in peak magnetic susceptibility and total magnetic susceptibility inventories for peat soils of this upland area. The results demonstrate that the contemporary concentration of magnetic minerals in the peat soils of Alport Moor is controlled by micro- and local-scale variations in water table position. The results also suggest that the contemporary level of magnetic minerals in the peat soils of Alport Moor is controlled by the retention of such particles in the soil environment. Differences in the deposition and interception of magnetic minerals play a secondary role in controlling magnetic mineral concentrations. Spatial maps of magnetic susceptibility reveal that peat soils adjacent to gully edges at Alport Moor have the highest concentration of magnetic minerals. The mapping approach used in this study could be applied to other peatland environments.