MULTIVARIATE STATESTICS AND TIME SERIES ANALYSIS OF LACUSTRINE SEDIMENTS DURING PLEISTOCENE AT SOUTHERN MARGIN OF TIBETAN PLATEAU

The dramatic raise of the Tibetan plateau during the Pliocene has strongly controlled the global monsoon system. Lacustrine sediments of long living lakes at the southern fringe of the Tibetan plateau are good archives for palaeoenvironmental changes. We deal with three such lacustrine sections ie. Kashmir basin (Kashmir, India), Katmandu basin (Central Nepal) and Heqing basin (Yunnan, China). A 168 m-drill core of lacustrine sediments is recovered from the Heqing basin, Yunnan province, western China. Magnetic and nonmagnetic parameters were measured with an average interval of 10 cm. Carbon-14 dating at the top of the core and magnetostratigraphy (Blake event, B\M boundary) show that the core spans the last ~1Ma. Magnetic mineralogy is dominated by magnetite. Lithology and grain size analysis show that the core is quite homogeneous throughout. Results of Fourier analysis of susceptibility (c) and carbonate content show clear cyclicities. Wavelet analysis supports the results of Fourier analysis. A phase lag between parameters (c) and carbonate is observed. Different sliding windows show the change of the power spectrum and amplitudes all along the core. The results can be interpreted in terms of palaeoclimatic changes (e.g. topmost 50m behave differently than the lower part) and can be also used to improve the age frame by calibrating the spectra to Milankovitch cycles. Fuzzy cluster analysis of magnetic parameters, carbonate content and pollen shows a periodic grouping with division of the section into three different parts.