Characteristics Of Synsedementary Faulting Of Neogene And Its Controls On Depositional Systems In Panyu Low Uplift

The Pearl River Mouth Basin is northern passive continental margin basin of South China Sea and Panyu low uplift is an important natural gas-bearing district of the Pearl River Mouth Basin.In this paper,guided by the theory and method of Sequence Stratigraphy,Seismic Geomorphology,sedimentology,Basin analysis and Conputer Medeling,and taking advantage of the rich seismic reflection data , core, well loggings and other geophysical and geological datum from oil field, Starting with the basin development of stratum and areal structural evolution, and based on developmental characteristics of third-grade interface, then establish third-grade Chrono-stratigraphic Sequence Framework of the research area. Zhujiang-Hanjiang Formation is divided into seven third-grade sequences, which are characterized with onlap or truncation unconformities and its relevant conformity surfaces.Combined with interpretation of trunk seismic cross-section and structural feature of the basin,the research area is plotted out 5 secondary structural units and expatiate the character of the tectonic framework.. During the Zhujiang-Hanjiang depositional stage there are chiefly two periods of faults with the fault trend of NW-NWW and EW predominant and en echelon arrangment and branching compound fabric can be seen on the surface , in vertical sections these faults mainly form parallel faulted terrace, pinnate, horsetail, combined Y-shaped fault assemblages etc. Through the analysis of the distribution, combination and character of the fault and Spatial distribution, we divide the synsedimentary faultings into 6 fault zones.We analyse numerically subsidence rate of the essential depositional stage in the research area by modeling tectonic subsidence curve. Subsidence rate in the south is higher than than in the north; The main subsiding stage is SQzj3 and SQhj2 as well as 3 subsidence episodes. The episodic change in tectonic subsidence rate controls the development of the important sets of reservoirs and cap rock assemblages in the area; Besides, it dominated by the movement of synsedimentary faultings.The results of palaeogeomorphic resuming and movement characteristic of the synsedmentary faultings show that sequence and depositional system were mainly controlled by the palaeohigh slope and the synsedimentary faulting slope break zone.HST and TST mainly distribute above slope-break zone and LST develops below slope-break zone. During faulting stage the northeast of area formed faulting slope-break zone and Fluvial delta and River braided delta mainly develops on the margin of slope-break zone and in the downdip direction,sedmenting a mass of delta front sand. faulting slope-break zone in the southeast and northeast、Sub-cut depression and riff valley control the distribution of lowstand systems tract wedge of the early sequence. The potential favorable zones comprise the southeastern lowstand systems tract delta sand body which is controlled by slope-break zone, stratigraphic traps which are developing in the onlap zone of sequence boundaries, and the updip pinch in palaeohigh slope and fault uplift-block structural traps in the middle .