The biogeochemistry and pedogeochemistry of the West Hercules area, Rosebery, western Tasmania

Sixteen plant species were sampled over a known pedogeochemical anomaly at West Hercules, Rosebery. This orientation survey was conducted to assess the potential of biogeochemical surveys in the West Coast-type rainforests. Three species were subsequently re-sampled in order to determine the most sensitive plant organ for biogeochemical prospecting. Both a detailed pilot survey and an independent trial survey proved that young Nothofagus cunninghamii leaves accurately and precisely reflected the soil-lead concentrations. The primary plant-ash data can be enhanced with the use of selected elemental ratios. A litter survey down five cut grid lines showed that plant-litter has great potential for reflecting elemental concentrations in the soil. Thirty soil pits were dug and sampled every ten centimetres, both on and off the pedogeochemical anomaly. The samples came from areas with potential copper, lead and zinc mineralization and analyses have been restricted to these elements and potential scavengers. Chemical analyses for carbon, Cu, Pb, Zn, Ni, Fe and Mn revealed a distinct vertical and horizontal distribution that could be explained by changes in Eh/pH environment and presence of \metal scavengers\". A sequential analysis of the soils indicated which elements were distributed over which soil phases. Copper was sorbed in the clay while lead and zinc were occluded in the iron and manganese oxides. The organic matter present in the soil complexed iron manganese lead and zinc. The geochemical pedological and topographic data indicated that the pedogeochemical anomaly at West Hercules was a hydromorphic anomaly formed by seepage of groundwater from the upslope Hercules Host Rocks."