Identification and division of high-frequency cycles based on Milakovitch theory：A case study on Miocene Sanya and Meishan Formations in Qiongdongnan Basin

Natural gamma data from the wells LS-33A,YC-35B and ST-36A in different structures of the Qiongdongnan Basin have been used for spectral analysis and continuous wavelet transform.In different wells,the Miocene Sanya and Meishan Formations are mainly dominated by the 404 ka and 95 ka eccentricity cycles.A high-resolution astronomical timescale of each formation is established based on the analysis of cycle filter and Milankovitch cycle curve which controls strata development.Finally,the sequence stratigraphy of high-frequency cycles in the Sanya and Meishan Formations is divided and correlated by using short eccentricity cycle curve as the reference curve for the fifth-order sequence units.The investigation provides a new effective approach to build the correlating framework of high-resolution sequence in the offshore basins.