The Study Of Cyclic Stratigraphy Proxy Of Geophysics And Analysis Methods In Songliao Basin, Northeast China

In this paper, the author gives the cycle identification method for detecting the Milancovitch cycles from geophysical logging data. After a detailed discussion of the theory, using condition and using effect of the methods, the author develops a friendly interface and multiple functional cycle identification program system by rewriting formulas, programming independent modules.In the beginning of the paper, the author discuses the theory background of the Milancovitch, and puts forward three kinds of period identification methods based on the problem of cycle identification. The author systematically discusses the theories, using conditions and deficiency of the classical power spectrum analysis methods. Then, according to the advantages of the classical power spectrum analysis methods, which there are no spectrum information changed with time in the frequency domain, the author studies the characteristics, and the advantages and disadvantages of short time fourier transform, a time-frequency analysis method. The author discusses the wavelet transform analysis method which overcoming the disadvantages of the two above methods. In the paper, the author also gives the discussion of preprocessing methods, window-function selection methods and power spectrum analysis methods for unequally-spaced data.The author discusses the evidence and advantage of geophysical logging data. As the precondition of geological application, the author discusses firstly, how to identify the Milankovitch cycles from the geophysical logging data, then, studies the relationship between Milankovitch cycles and deposition rate. The author introduces in detail how to analysis the characteristics of deposition rate changed with time(or depth)and puts forward to the thought of transforming the depth profile to time profile by use of the deposition rate curves changed with time.In the paper, the author calculates the Milankovitch cycles of Qingshankou formation and the first part to second part of Nenjiang formation in Songliao basin by logging data of different wells. The result shows the Milankovitch cycles are recorded in all the wells. Using the Milankovitch cycles result, the author analyses the feature of deposition rate changed with time, extracts the specific cycle curves for stratigraphic division and comparison with high precision. The author also explores the method of calculating the continuous time of sedimentary strata, and calculates the continuous time of Qingshankou formation by mean of the logging data from Songke NO.1 well with good continuity and high precision. Comparing to the known information proves the correctness of the result. By counting the number of wavelength of the precession cycles, the author analyses the continuous time of event key bed from the first part of Qingshankou formation, which provides supported evidence that this event key bed is corresponding to the paleo-oceanic anoxic event near the boundary of Cenomanian-Turonian in Cretaceous.