Relationship between Paleotopography and Volumetric Change Rate of Lacustr ine Basin to the Sequence Structure

Key words: 
• lake level change /
• sequence, accommodation /
• accommodation variation rate /

Abstract: Through the comparison of the difference of sequence structure in Dongying depression and Dongpu dep ression, and the analysis of basin volume and topography of Dongying depression and Dongpu dep ression, it is considered that the paleotopography of basin, the ratio of the accommodation added to the total accommodation are nearly related to the sequence structure. During the sedimentation of the third member of Shahejie Formation, the variation rate of accommodation added and created by the third order cycle lake level fluctuation in Denying dep ression are nearly equal to the variation rate of accommodation added and created by the fourth order cycle lake level fluctuation in Dongpu depression. During the sedimentation of third member of Shahejie Formation, the basin volume ofDongying dep ression is very large and the slope is very steep, and the development of sequence is controlled by third order cycle lake level change, so the sequence is very thick. The sandbody thickness in the sequence is also big, and its distribution is very concentrative. During the sedimentation of the third member of Shahejie Formation, the basin volume ofDongpu depression is very small, the topography is very gentle, and the developmemt of sequence is controlled by fourth order cycle lake level change, so the thickness of its sequence is small, and the sandbody thickness in the sequence is small too. Its distribution is very wide and is not stable.