Morphology and geochemistry of soils formed on colluviated weathered bedrock: Case studies from unglaciated upland slopes in west-central Yukon

Soil morphology and geochemistry were studied at three mineral properties (gold; lead-zinc; copper-gold) in the unglaciated terrain of west-central Yukon. The purpose of this work was to describe soil and parent material properties, and to assess the effects of soil development and slope processes on element distribution in soils derived primarily from colluvium and weathered bedrock. At each property, soils were examined on slopes with opposing aspects. These results provide baseline pedological and soil-geomorphological descriptions for the Klondike Plateau, which will assist future biophysical mapping and contribute to our understanding of landscape evolution. Results pertaining to soil geochemistry provide landscape related guidelines for mineral exploration. For example, the stratigraphic distribution of loess within soil profiles is described according to slope aspect. This allows the explorationist to design sampling procedures that are more likely to detect geochemical anomalies in the underlying bedrock. Soil geochemical variations in colluvium are shown to reflect upslope variations in bedrock lithology. Results of the soil particle size fraction geochemistry indicate that for base metal elements such as copper, lead and zinc, the -80 mesh component was generally the most responsive in either the B or C horizon. For gold, the -80 mesh fraction worked well in the B horizon, whereas the -230 mesh contained the highest concentration in the C horizon.