CHARACTERISTICS AND ORIGIN OF TRANSVERSE ACCOMMODATION ZONES IN THE DONGPU SUBBASIN,BOHAI GULF BASIN, AND THEIR ROLE IN REGIONAL SEGMENTATION

Through an analysis of the distribution of vertical displacements along the strike of the boundary faults in the Dongpu subbasin in various phases,the authors deduce the growth process of these faults.He thinks that the complex fault system originated from connection of individual fault segments during their growth,each of which controls a half-graben.On that basis,accommodation zones and structures are recognized and distinguished.An accommodation zone consists of several regularly arranged accommodation structures,while the latter formed by overlapping of two fault terminations or separate growth of various segments of a large fault.Two transverse zones are developed in the Dongpu subbasin,each of which comprises several types of accommodation structure.They strike nearly perpendicularly to the strike of the Dongpu subbasin and occur as discontinuous transverse rises between half-grabens,which control the north-south segmentation of the subbasin and separate the subbasin into the north,central and south along-strike areas,each of which has its own structural,sedimentary and petroleum geological characteristics.The along-strike heterogeneous extension is the dominant factor for forming the transverse accommodation zones and the fault segmentation is the direct cause for their formation.Transverse accommodation zones exert great influence on the structure,sedimentation and hydrocarbon distribution of the subbasin.