Sedimentary features and sedimentary evolution of the shelf-margin delta in late Oligocene of southeast Baiyun sag
Wang Siqi;Zhang Zhongtao;Lin Changsong;Qin Chenggang;Xing Zuochang;School of Energy,China University of Geosciences(Beijing);Institute of Shenzhen Branch Company of China National Offshore Petroleum Corporation;School of Marine and Ocean,China University of Geosciences(Beijing);
We established the third-order sequence stratigraphic framework and revealed the structures and geomorphology of a large-scale shelf-margin delta in the deep-water area of the late Oligocene Baiyun sag,based on an integrated analysis of cores,well-logs and three dimensional seismic data.Result shows:Seven third-order sequences are recognized in Zhuhai and the lower Zhujiang formation of the sag,three stages of shelf-margin deltas were revealed in contain distribute in the upper part of ZHSQ5,ZHSQ6and ZHJSQ1,respectively.The shelf-margin delta of the ZHSQ5period was small and mudrich,with the pre-delta was 300 mthick and an oblique progradation configuration in the front-delta.The shelf-margin delta in the ZHSQ6period was wide lateral distribution about 5km,S-shape progradation in seismic data,a thinning phenomenon in the foreset body toward the basin,and some small-scale slump bodies in the distal slope of the pre-delta.The shelf-margin delta in the ZHJSQ1period inherited the depositional characteristics of that in of ZHJSQ1period,but with some larger slump turbidite fan in the fore-slope.The delta was deposited in a paleo-water depth about 600m,with the calculated front slope angle 4°~7°.It indicates a deep-water shelf-edge environment.The relative sea-level changed and sediment supply co-controlled the formation time and scale of the shelf-margin delta,and the syn-depositional faults controlled its morphology and location.The barrier bar,distributary channel and turbiditic sand in the shelf delta are potential reservoir.
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