GEOTECTONIC FEATURES OF THE MARINE MESOZOIC-PALEOZOIC ON THE LAOSHAN UPLIFT OF THE SOUTH YELLOW SEA BASIN

The South Yellow Sea Basin is located in the northeast of the lower Yangtze platform and the active region to the east of Tanlu faults zone. It is a multi-cycle superimposed basin consisting of the marine Mesozoic-Paleozoic basin overlaid by the continental Mesozoic-Cenozoic basin on the basis of the Presiniancratonic basement. In recent years, high quality deep reflections have been obtained from the seismic profiles passing through the Laoshan Uplift. It is found that the continuous Mesozoic and Paleozoic is more than 4~5 km in thickness. Because of the insufficient exploration for marine Mesozoic-Paleozoic, the oil and gas exploration in the area is restricted. Based on the seismic data, combined with drilling data from its adjacent areas as well as regional geological data, we studied the Mesozoic-Paleozoic geotectonic characteristics of the Laoshan Uplift. The results show that there are two marine structural layers on the Laoshan Uplift, separated by a mudstone detachment zone of Lower Silurian, i.e. the Gaojiabian Formation. This area experienced the evolutionary stages of the formation of basement, the development of craton, the stable platform, the uplift and erosion, and the continental orogeny. The upper structural layer is relatively complex, where thrust folds and imbricate thrust faults are developed. It lies unconformablyupon the lower structural layer. The fracture development of this area is weak.There are two main groups of fractures. Faults developed along E-W direction are relatively large, and those developed in N-E direction are subordinate.