| The continuous Chinese paleosol-loess sequences, which are traditionally regarded as good records of paleoclimatic changes, provided insights into past long-term climatic changes thus are widely used to indicate paleoclmatic conditions and paleoenvironmental evolution. With the development of paleoclimate and paleoenvironment to higher resolution, study of loess provides important evidences for the global climatic evolution, abrupt oscillations, climatic change regularities on millennial, centennial scale. So many scientists devote themselves to the research of climatic unstability, in order to clarify the dynamic mechanism and provide useful information for the prediction of climatic evolution and calamity.However, the research into paleoclimatic evolution must based on different sections in different areas. Then, we can distill useful environmental information by combining analysis of integrated indicators. As a result, the efforts to study past high-resolution climatic varibilities are challenged on ideal sections. In the study of different temporal scales, the researchers pay no attention to paleoenvironmental evolution since 30 ka BP. By contrast, they are willing to throw themselves into early-late Pleistocene or even the whole Quaternary. We know, to the survival and development of Human being, of important is the period since 30ka BP in the course of which many high-frequency and rapid climatic oscillations occurred including three Heinrich events, Younger Dryas event, and the last glacial maximum. The area studied (103°00′N, 36°00′E) is in the center of Gansu Province at 1600 to 2450 m altitude. Mean annual temperature in study area is 5-9℃. Precipitation averages approximately 300 mm per year, about 75% of which falls between June and September. The low precipitation and arid climate have led to sparse vegetation and bad entironment. Hongzuisi section is located on the second terrace of secondary tributary of the Yellow River. It is characterized by a series of lacustrine peat and clay layer. The sedimentation is successive and stable. It is an ideal section for the study on the climate change in the past 30 ka of Lanzhou area. The Hongzuisi section was 17.74 m thick. 902 samples of organic carbon isotope, CaCO3 content, granularity were collected at 2 cm intervals. In some special part, the samples were collected at 1 cm intervals. We tested the organic carbon isotope in Finnigan MAT251 mass spectrometer. Results were reported relative to the V-PDB standard. Measure precision of organic carbon isotope during the study was less than 0.2‰. We calculated CaCO3 content based on the volume of CO2 which was produced from interaction between samples and standard acid.Analytical precision was <2%. In order to testify the validity of result, we also test the carbonate carbon isotope, oxygen isotope together with granularity. Chronological data were obtained by 14C dating of 5 samples from 2.4, 3.05, 3.95, 6.75 and 9.75 m in Hongzuisi section respectively. We use R/S anslysis, functional spectral analysis and wavelet analysis to infer the persistency and periodicity of paleoenvironment in Hongzuisi section since about 30 ka. As a part and parcel of nonlinear theory, the rescaled range analysis (R/S analysis), proposed by Harold E. Hurst in 1965, play an important role in paleoclimatic evolution. In this paper, the rescaled range analysis was used to analyze the pale climatic evolution of Hongzuisi section in Lanzhou area on the basis of the materials of organic carbon isotope, CaCO3 content, granularity, carbonate carbon isotope and oxygen isotope. According to R/S analysis, the feature of organic carbon isotope and carbonate oxygen isotope can indicate temperature change, the CaCO3 content and carbonate carbon isotope can show the precipitation in some degree. While the granularity represent the synthetical information. The result also indicates that this method is very useful to study the durative of climatic change. Based on the results, we can conclude that the trend of paleocl...
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