Comparative analysis of Meso-Cenozoic tectonic evolutions of the Jiyang and Linqing depressions and Luxi area

Abstract：Analyses of six balanced seismic sections or forward tectonic models across the Jiyang and Linqing depressions and Luxi area show that the extension rate in the region in the Paleocene, especially in the early Paleocene, was greatly higher than that in the Mesozoic, the extension rate for the Jiyang depression being higher than that for the Linqing depression and the extension rate for the Luxi area lowest. The development of the proto basin of the Dongying and Huimin subbasins in the Jiyang depression broadly went through five phases. In the Mesozoic the amount of extension in the east was markedly large than that in the west, and strong erosion occurred in the east during the Late Cretaceous. From the above, it is inferred that： this was related to the rifting along the Tanlu fault in the Mesozoic, and rifting was intense in the east and tectonic inversion was also strong at the end of the Cretaceous. The amounts of extension of the Dongying and Huimin subbasins were close during the deposition of the Four Member of the Shahejie Formation and Kongdian Formation. They belong to strike-slip pull-apart sedimentary subbasins. After the deposition of the Third Member of the Shahejie Formation, differential development again occurred in the east and west parts: the amount of extension in the east was noticeably larger than that in the west. The whole of Meso-Cenozoic witnessed strong vertical rifting and inversion, and in a plan view movement similar to a seesawing movement was manifest. Located in the transitional place of strong rifting, the Linqing subbasin had well-developed transitional structure and thus a downfaulted lake basin was unable to develop steadily; so the hydrocarbon-forming conditions were poor.