Estimation of grain size variability with micro X-ray fluorescence in laminated lacustrine sediments, Cape Bounty, Canadian High Arctic

Finely laminated sediment cores from two Arctic lakes were investigated using the Itrax (TM) Core Scanner that provides micro X-ray fluorescence (mu-XRF) measurements with a spatial resolution of 100 mu m. We compared these chemical measurements with standard geochemical methods using, at the macroscopic scale, inductively coupled plasma-atomic emission spectrometry (ICP-AES) and, at the microscopic scale, energy dispersive spectroscopy (EDS). We also investigated the relationship between the chemical profiles and the grain size of sediments at macro-scale using laser particle-size analysis, and at microscopic scale, using thin section image analysis techniques. Results show a link between grain size and the relative abundance of several elements. Silicon and zirconium are associated with very coarse silt and sand deposits, K and Fe with clay-rich layers, and Ti with silty facies. Four sedimentary facies are characterised based on sedimentary structure and texture, and interpreted in terms of known seasonal hydroclimatic processes. We show that is possible to identify these sedimentary facies using mu-XRF element abundance or ratio variations. The K/Ti ratio is the best marker of the upper varve boundary, and it might be used for varve identification and counting of Cape Bounty sediments in future. More generally, this study demonstrates new applications for paleohydrological reconstructions from laminated sediments.