Thermoluminescence color image analysis of sediments from Lake Khuvsgul,Mongolia, and its potential to investigate paleoenvironmental change

Thermoluminescence color images (TLCIs) of lacustrine sediments from Lake Khuvsgul (Hovsgol), Mongolia, were taken with a digital camera, and the RGB information of each color pixel was converted into numerical information to plot a CIE chromaticity diagram. The number of pixels within one of five color zones was counted for statistical color analyses. A total of 163 samples were collected for the core depth of 2.10–59.49 m. Twelve images were investigated for each sample. The number of colored pixels (analogous to the emission intensity) varied along the core depth. The amount of HCl-soluble-material, i.e., calcium carbonates, shows similar fluctuations, and the colored pixel points on the CIE chromaticity diagram fell in the same region with those for calcium carbonates from the catchment area. These results indicate that the major source of luminescence is calcium carbonate. When TLCIs are investigated after grain size separation, a small number of pixels are found in the blue-purple region, separate from the main cluster of pixels in the CIE diagrams for only fine particles. Because aeolian dust is expected to be in fine-grained fractions, these distinctive luminescence emitters are possibly of aeolian origin. TLCI has a potential to extract information for aeolian dust in lake sediments.