According to data about the texture of the geological section

stratigraphy

hydrogeology

structural movement and sedimentation

and through restorationof palaeo-tectonics and synthetic analysis

the author suggests that in Pre-Jurassic

there was a great NE trend synclinorium

called the Cangxian-Tianjin syncli-norium

in the central-western part of the present Bohai Bay Basin.It spread along the Tianjin-Cangxian-Guantao zone

including the whole Cangxian Uplift

most ofthe Huanghua Depression and a part of the Jizhong Depression

Linqing Depression and Xingtai-Hengshui Uplift.During the Jura-Cretaceous

the synclinorium was remade and further developed as a result of shearing and compressing.However

from the Eocene

itbegan to break up under the tensil-shear stress and developed into uplifts alter-nated with depressions in the central-western part of the basin.The determination of the synclinorium is significant for the study of geological tectonics and further exploration of oil and gas in the region.