Abstract:

In this article，the control of astronomical periods on the basal-level cycles，as well as methods of the identification of astronomical periods and the division of cyclic sequence by discrete wavelet transformation and spectrum analysis are probed.Stratigraphic basal level cycles are controlled by internal and external dynamic geologic actions resulted from celestial body movement and are consistent with astronomical periods.Cyclic sequences are the response of basal level cyclic movements.Discrete wavelet transformation and spectrum analysis technique are used in signal decomposing，reconstructing and filtering.Fourier transform technique is used in spectrum analysis of DWT detail components to confirm the master frequencies and the ratios.The relationship between sedimentary and astronomical cycles is ascertained according to the consistent relationship between master frequency ratios and astronomical frequency ratios.The geologic age of sedimentary cycles are defined by the absolute geologic age.The results indicate that periods of sedimentary cycles divided on the basis of detail components are twice of astronomical periods and can be divided into two cyclic sequences.Boundary surfaces and flooding faces of cyclic sequences locate at switch points of formation stacking pattern.The research shows that the division of stratigraphy sequence can be carried out reasonably and effectively with discrete wavelet transformation and spectrum analysis technique on the ground of the astronomical cycles.

Key words: astronomical period, basal-level cycle, discrete wavelet, spectrum analysis, Yanchang formation