Relations between elemental content in till, mineralogy of till and bedrock mineralogy in the province of Småland, southern Sweden

Abstract

Information on soil mineralogy is essential for weathering rate calculations. Quantitative mineralogical analyses are expensive and time-consuming, and thus indirect methods of determining the mineralogical composition are important, for example estimating the composition based on the elemental content in till (total concentrations), or based on information about the underlying bedrock. The mineralogical composition and the elemental content in till were analysed in two areas in southern Sweden, at 10 sites in each area. There were significant differences between the areas regarding both elemental content and optically determined mineralogy. The content of calcium was significantly higher in one area, 5ESV, and there were tendencies in this direction also for magnesium and iron. The potassium content was significantly higher in the other area, 6FNV. The variation in soil chemistry between the areas can be explained by higher contents of the minerals biotite, hornblende and epidote in the first area (5ESV) and higher contents of K-feldspar in the second (6FNV). Normative mineralogy was determined based on the elemental content. A comparison between the normative mineralogy and the optically determined mineralogy showed great similarities which indicates that there is good potential for using elemental content for estimating the mineralogical composition. The difference in till composition between the areas could not be explained by the underlying bedrock, which indicates that the information available on the bedrock is not sufficient for estimation of the till mineralogical composition.