Abstract:

On the basis of oil and gas exploration and geological data of the Bohai sea, we carried out the apatite fission track dating of the core, the interpretation of the seismic profiles, and the analysis of sedimentarytectonic characteristics and tectonic evolution of the Liaodong Bay Depression; the study suggested that there were three tectonic uplift and erosion events in the Liaodong Bay Depression in the Cenozoic, which occurred in the late Mioceneearly Pliocene (corresponding peak age of 57 Ma), in the end of Dongying period in the Oligoceneearly Miocene (corresponding peak age of 1822 Ma and 2426 Ma), and in the end of the third period of the Shahejie in the Eocene (corresponding peak age of 3640 Ma), respectively. These tectonic uplift events were different in different places: the events that happened in the southern part are earlier and stronger than in the northern part. In the Eocene, there was a big depression containing very thick sediment in the east of the study area. But after depositing, the third section of the Shahejie was reformed by faultcutting, and the Liaodong Uplift was formed and eroded strongly, so that the structure of “a rise in between two sags” was formed in the larger depression. The transformation process is relevant to the changes in activity feature and intensity of TanLu Fault; it may cause the difference in uplift characteristics and in the strength of later transformation between east and west in the Liaodong Bay Depression. The change in tectonic pattern of the Liaodong Bay Depression was related to regional dynamic environment and background closely. These three tectonic uplift events have profound impacts on East China. So our study is helpful in further improving and enhancing the entire understanding of Cenozoic basins in eastern China and offshore, and provides basic data and scientific basis for the study of regional dynamic environment and background, petroleum exploration and resource evaluation in East China.

Key words: Liaodong Bay Depression, distinct uplift, fission track, tectonic evolution, TanLu Fault