Abstract:

Eolian sediments from the Zeku profile (ZK) of the northeastern Tibetan Plateau as the object of the study. The chromaticity parameters a^*, b^*, L^* and the calculation of C^* and h^* of 169 samples were measured by CM-5 spectrophotometer, and the environmental evolution of the northeastern Tibetan Plateau since 9.4 ka was discussed based on the analysis of the variation characteristics of each chromaticity parameter of wind-formed sediments, supplemented with the indexes of magnetization rate, SC/D, SiO₂ and Fe₂O₃. The results shows that: (1) From the bottom to the top of the profile, the chromaticity parameters a^* and L^* are characterized by increasing first and then decreasing. (2) Chromaticity parameters can be used as effective proxies for reconstruction the paleoclimate on the northeastern Tibetan Plateau. The high values of a^* and L^* indicate the warm-wet environment, and the high values of h^* indicate the cold-dry environment. Chromaticity parameters indicate different environmental sensitivities, but they are sensitive to climate abrupt change, which can be used to judge the typical cold and warm events of climate abrupt change. (3) The environment in the northeastern Tibetan Plateau since 9.4 ka has shown a development situation from warm-wet to cold-dry, which can be divided into two major stages. During 9,480-4,290 a BP, the climate was temperatureandhumidity, showing fluctuations of warmer and wetter→warmer and wetter→warmer and wetter. After 4,290 a BP, the climate wascold and dry, the climate as a whole is cold and dry, showing a change of warm and dry→warm→cool→cold and dry.

Key words: chromatic parameter, environmental evolution, northeastern Tibetan Plateau