Analysis of High-frequency Sedimentary Cycle Superposition Type in Quantou Formation in Dongling Area of Songliao Basin

Key words: 
• Fischer plots /
• high-frequency depositional cycles /
• gamma ray well logging /
• Quantou Formation /
• Dongling area

Abstract: According to calculative cycle thickness by the natural gamma logging curve, using Fischer plots to identify the high-frequency sedimentary cycle Superposition type, trying to proclaim the relation between GR logs reflective fluctuation of clay content and climate cycle.  Choosing well SN109 natural gamma logging curve which possess clearly top and bottom and continuous layers in Dongling area of Songliao Basin as experimental data. Using the extreme point method, 1 166 high-frequency depositional cycles can be identified. The thickness of these cycles change form 0.125 m to 2.75 m, the average  is 0.62 m. According to Fischer plots, the estimation of the average period of high-frequency depositional cycles is 17.2 ka, the average period of medium-frequency depositional cycles is between 86.1~103.3 ka, the average period of low-frequency depositional cycles is between 305~416 ka, corresponding with 19~24 ka of the precession of equinox, 85~140 ka of the short eccentricity, and 350~400 ka of the long eccentricity of Milankovitch cycles,  respectively. It is suggested that the production of lacustrine depositional cycles of Quantou Formation was controlled by the Milankovitch cycles.