STRUCTURAL PATTERN AND EVOLUTION OF THE MESOZOIC STRATA IN THE BOHAI BAY BASIN RANGE: A CASE FROM SOUTHERN SHORE OF MIDDLE RANGE OF THE HUANGHUA DEPRESSION

Bohai Bay basin range is located at the center of a Mesozoic plateau in eastern North China craton in Mesozoic. Its structural evolution is a key problem to understand process from formation to collapse of this plateau. Moreover, these Mesozoic strata are important oil-gas exploration objectives in eastern China in recent years. However, structural pattern and evolution of this region are not clear up to the present. The south shore of Huanghua depression is not only an important and new oil-gas exploration area for Mesozoic buried hill in the Dagang exploration area, but also is located at spatial and temperal switch site of Mesozoic-Cenozoic structural patterns of the Bohai Bay basin. Therefore, the study area is of important implication for research. A large number of seismic profiles were interpreted to analyze distribution rule of relic Mesozoic strata. Furthermore, we subdivided the structural units in the study area and discussed its Mesozoic structural evolution. Taking Yang'erzhuang fault as a border, we divided the study area into a northwest region and a southeast region. Structures in the former is more complex than in the latter. The northwest region inherited EW Indosinian structural pattern,and also experienced slip and compression during the early and middle Yanshan movement.Then strike-slip and intense slip-break structures occurred during Yanshan movement and Cenozoic. The Yang'erzhuang fault is a strike-slip fault system which evolved from Indosinian period and then experienced compression and strike slipping in middle Yanshan movement, and went through dextral slipping during Yanshan movement and Cenozoic. These processes indicate that the Yang'erzhuang fault controls the structural pattern and evolution of Mesozoic strata in this area. In summery, structural evolution in the study area is an epitome of tectonic evolution of the Bohai Bay basin.