The potential in fluvial geomorphology of a new mineral identification technology (QEM*SEM)

The mineralogical signatures of fluvial sediments can be used to identify source areas and the degree of mixing of sediments from different fluvial and non-fluvial sources. The potential use of these signatures has not been fully realised because of uncertainties that result from mineralogical change as a result of sorting and weathering and the considerable time and expense involved in conventional optical mineral identification. A new quantitative mineral identification system QEM*SEM (Quantitative Evaluation of Materials by Scanning Electron Microscope), using an image analysis system with energy dispersive spectrometry and back scatter electron responses to identify phases, has been employed to provide rapid and economic analysis of sediments; large numbers of grains are counted with a greater statistical reliability than was previously possible.Results from a survey at the Nepean River, NSW, delineate the maximum level of flooding in an environment where clearly defined flood deposits are not evident. The results suggest the flood levels to be higher than predicted from previous studies.