Chromaticity characteristics of the Last Glacial sediments in Houtian section of Nanchang city and its paleoenvironmental significance

Chroma is one of the important indicators of paleoenvironment reconstruction, and is often used for paleoclimate reconstruction of the loess plateau, but its research in the Quaternary sediments in subtropical humid regions is rare and its significance is unclear. The sedimentary profile of Houtian sandy land on the south bank of Poyang Lake was selected as the research object and the chromaticity test was carried out. Combining with the results of optically stimulated luminescence (OSL), the chromaticity parameters were compared with other climatic proxies, and the paleoclimate changes during MIS2-MIS4 were discussed. Results show that the chromaticity parameter curves have large fluctuations in the vertical direction of the profile, showing multiple cold-warm oscillations from dry-cold → warm-wet → dry-cold. Among them, the peak sections of the L^* (brightness) value curve are mainly concentrated in the dune sand layers of HT6, HT4, and HT1, indicating that the MIS4 stage, MIS3b stage, and early MIS2 stage, respectively, are dry and cold climate environment. The peak sections of the a^*(redness), b^* (yellowness), C^* (saturation), and h^* (hue) value curves are mainly concentrated in the sandy palaeosol layers of HT5, HT3, and HT2, representing the MIS3c stage, MIS3a stage and late MIS2 stage respectively, are warm and humid climate environment. The chromaticity index better reveals the characteristics of climate change in the Houtian area, and reflect the climate evolution pattern in the area affected by alternating winter monsoon and summer monsoon during the last glacial period.