南海北部白云凹陷早中新世东部沉积体系研究
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摘要
基于白云凹陷东部钻井、岩芯和地震资料,通过地震属性分析、地震相分析及钻井岩芯分析,证实了白云凹陷在23.8～21 Ma之间除存在北部物源外还存在来自东沙隆起的东部物源体系,从而扩大了白云凹陷深水碎屑岩沉积研究领域。通过层序地层学研究和沉积相分析,建立了东部沉积体系沉积及演化模式:该体系在低位域形成海底扇沉积;水进域形成碳酸盐岩和硅质碎屑岩混合沉积;高位体系域主要发育高位三角洲沉积,其主要受相对海平面变化及物源供给控制。
Based on a large amount of drill,core and seismic data from the eastern Baiyun Sag,by the analysis of seismic attributes,seismic facices as well as drilling sedimentary facies,it is proved that in Baiyun Sag there is not only the north provenance but also the eastern depositional system which is derived from the Dongsha Uplift in early Miocene,and this discovery will lead to the expansion of the exploration scope for the deepwater clastic deposits of Baiyun Sag. The Eastern Depositional System is mainly developed in SQ23.8,with the bottom boundary SB23.8.Previous studies reported that the "Baiyun Movement" occurred in 23.8 Ma B.P.results in tremendous changes of Baiyun sag,causing the thermal subsidence of the sag,making the shelf neritic environment transform into slope deepwater environment,and SB23.8 is the interface of the shelf break belt migrating from the south of Baiyun sag to north.In 23.8 Ma B.P.the relative sea level fell to the lowest,which made the Panyu Low Uplift in the north and the Dongsha Uplift in the east be in a state of exposure.The formers' study has confirmed that the Panyu Low Uplift provides debris for the deep water of Baiyun sag,and then,whether the Dongsha Uplift which was also exposed in SQ23.8 can serve as the provenance for Baiyun sag is the breakthrough point of this paper. The erosion area of Dongsha uplift during early Miocene is about 20 000 km2,which is close to Baiyun sag,and considering such a great erosion area the uplift should provide materials for Baiyun sag.Besides,on the image of 3D seismic RMS amplitude slices present an abnormally high amplitude in the east of Baiyun sag,and the graph of sandstone/strata contour of SQ23.8 also presents high values in the east.In addition,on seismic,a wedge-shaped progradational reflection configuration with the direction from Dongsha Uplift to Baiyun sag in SQ23.8 is developed.Therefore,according to the above analysis,it is concluded that the Dongsha Uplift is one of the provenances of Baiyun sag during the period of SQ23.8 deposition. On seismic,the deposits characterized by wedge-shaped progradational reflection configuration are interpreted as the deposits of deltas for their developed location,and the deposits in front characterized by high-amplitude,good continuity,progradational reflection on the trend seismic profile,a hummocky bidirectional progradation configuration on the cross profile,are interpreted as the submarine fan.Through observation of the core it is found that the carbonate content is fairly high in the core of SQ23.8,indicating that the sediments come from Dongsha Uplift,because during the period of SQ23.8 deposition,only Dongsha Uplift developed carbonate,also,again confriming the viewpoint that Dongsha Uplift is the provenance of Baiyun sag.Besides,a variety of gravity flow sedimentary structures are found in the core,such as normal graded bedding,Bouma sequence and slump-deformation bedding and so on,indicating a kind of gravity flow deposits in bathyal environment.The sediments of the core are identified as submarine fan deposits. Based on the sequence division result by integrating well and seismic data,SQ23.8 can be divided into three system tracts: LST,TST and HST.Combining the sequence stratigraphic analysis and the study of the sedimentary facies,the sedimentary and evolution model of the eastern sedimentary system has been established.In this depositional system,the lowstand system tracts(LST) are represented by submarine fans,and the trangressive system tracts(TST) are dominated by the mixed deposits of clastic and carbonate rock,while in the highstand system tracts(HST) the deltaic deposits are well developed.The deposits and sedimentary model are mainly controlled by the change of relative sea level and material supply.
Based on a large amount of drill,core and seismic data from the eastern Baiyun Sag,by the analysis of seismic attributes,seismic facices as well as drilling sedimentary facies,it is proved that in Baiyun Sag there is not only the north provenance but also the eastern depositional system which is derived from the Dongsha Uplift in early Miocene,and this discovery will lead to the expansion of the exploration scope for the deepwater clastic deposits of Baiyun Sag. The Eastern Depositional System is mainly developed in SQ23.8,with the bottom boundary SB23.8.Previous studies reported that the "Baiyun Movement" occurred in 23.8 Ma B.P.results in tremendous changes of Baiyun sag,causing the thermal subsidence of the sag,making the shelf neritic environment transform into slope deepwater environment,and SB23.8 is the interface of the shelf break belt migrating from the south of Baiyun sag to north.In 23.8 Ma B.P.the relative sea level fell to the lowest,which made the Panyu Low Uplift in the north and the Dongsha Uplift in the east be in a state of exposure.The formers' study has confirmed that the Panyu Low Uplift provides debris for the deep water of Baiyun sag,and then,whether the Dongsha Uplift which was also exposed in SQ23.8 can serve as the provenance for Baiyun sag is the breakthrough point of this paper. The erosion area of Dongsha uplift during early Miocene is about 20 000 km2,which is close to Baiyun sag,and considering such a great erosion area the uplift should provide materials for Baiyun sag.Besides,on the image of 3D seismic RMS amplitude slices present an abnormally high amplitude in the east of Baiyun sag,and the graph of sandstone/strata contour of SQ23.8 also presents high values in the east.In addition,on seismic,a wedge-shaped progradational reflection configuration with the direction from Dongsha Uplift to Baiyun sag in SQ23.8 is developed.Therefore,according to the above analysis,it is concluded that the Dongsha Uplift is one of the provenances of Baiyun sag during the period of SQ23.8 deposition. On seismic,the deposits characterized by wedge-shaped progradational reflection configuration are interpreted as the deposits of deltas for their developed location,and the deposits in front characterized by high-amplitude,good continuity,progradational reflection on the trend seismic profile,a hummocky bidirectional progradation configuration on the cross profile,are interpreted as the submarine fan.Through observation of the core it is found that the carbonate content is fairly high in the core of SQ23.8,indicating that the sediments come from Dongsha Uplift,because during the period of SQ23.8 deposition,only Dongsha Uplift developed carbonate,also,again confriming the viewpoint that Dongsha Uplift is the provenance of Baiyun sag.Besides,a variety of gravity flow sedimentary structures are found in the core,such as normal graded bedding,Bouma sequence and slump-deformation bedding and so on,indicating a kind of gravity flow deposits in bathyal environment.The sediments of the core are identified as submarine fan deposits. Based on the sequence division result by integrating well and seismic data,SQ23.8 can be divided into three system tracts: LST,TST and HST.Combining the sequence stratigraphic analysis and the study of the sedimentary facies,the sedimentary and evolution model of the eastern sedimentary system has been established.In this depositional system,the lowstand system tracts(LST) are represented by submarine fans,and the trangressive system tracts(TST) are dominated by the mixed deposits of clastic and carbonate rock,while in the highstand system tracts(HST) the deltaic deposits are well developed.The deposits and sedimentary model are mainly controlled by the change of relative sea level and material supply.
引文
1庞雄,陈长民,施和生,等.相对海平面变化与南海珠江深水扇的响应[J].地学前缘,2005,12(3):167-177[Pang Xiong,ChenChangmin,Shi Hesheng,et al.Response between relative sea-levelchange and the Pearl River deep-water fan system in the South ChinaSea[J].Earth Science Frontiers,2005,12(3):167-177]
2彭大钧,庞雄,陈长民,等.从浅水陆架走向深水陆坡-南海深水扇系统的研究[J].沉积学报,2005,23(1):1-11[Peng Dajun,Pang Xiong,Chen Changmin,et al.From shallow-water shelf to deep-water slope:the research of deepwater fan systems in South China Sea[J].Acta Sedimentologica Sinica,2005,23(1):1-11]
3郑晓东,朱明,何敏,等.珠江口盆地白云凹陷荔湾深水扇砂体分布预测[J].石油勘探与开发,2007,34(5):529-533[Zheng Xia-odong,Zhu Ming,He Min,et al.Prediction of Liwan deep submarinefan sandbody distribution,Baiyun Sag,Pearl River Mouth Basin[J].Petroleum Exploration and Development,2007,34(5):529-53]
4陈长民,施和生,许仕策,等.珠江口盆地(东部)第三系油气藏形成条件[M].北京:科学出版社,2003:1-121[Chen Changmin,Shi Hesheng,Xu Shice,et al.The Conditions of Hydrocarbon Accu-mulation of the Tertiary Petroleum System in the Pearl River Mouth Ba-sin[M].Beijing:Science Press,2003:1-121]
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6朱伟林,张功成,高乐.南海北部大陆边缘盆地油气地质特征与勘探方向[J].石油学报,2008,19(1):1-9[Zhu Weilin,ZhangGongcheng,Gao Le.Geological characteristics and exploration objec-tives of hydrocarbons in the northern continental margin basin of SouthChina Sea[J].Acta Petrolei Sinica,2008,19(1):1-9]
7邵磊,李献华,汪品先,等.南海渐新世以来构造演化的沉积记录——ODPll48站深海沉积物中的证据[J].地球科学进展,2004,19(4):539-544[Shao Lei,Li Xianhua,Wang Pinxian,et al.Sedi-mentary record of the tectonic evolution of the South China Sea sincethe Oligocene:evidence from deep sea sediments of ODP site 1148[J].Advance in Earth Sciences,2004,19(4):539-544]
8庞雄,陈长民,邵磊,等.白云运动:南海北部渐新统-中新统重大地质事件及其意义[J].地质论评,2007,53(2):145-152[PangXiong,Chen Changmin,Shao Lei,et al.Baiyun movement:a greattectonic event on the Oligocene-Miocene boundary in the northern SouthChina Sea and its implications[J].Geological Review,2007,53(2):145-152]
9彭大钧,陈长民,庞雄,等.南海珠江口盆地深水扇系统的发现[J].石油学报,2004,25(5):17-23[Peng Dajun,Chen Changmin,Pang Xiong,et al.Discovery of deep-water fan system in South ChinaSea[J].Acta Petrolei Sinica,2004,25(1):17-23]
10张兴阳,罗顺社,何幼斌.沉积物重力流深水牵引流沉积组合鲍玛序列多解性探讨[J].江汉石油学院学报,2001,23(1):1-5[Zhang Xingyang,Luo Shunshe,He Youbin.Deposit assemblage ofgravity flow and traction current in deep water:a study of the multipleinterpretation of the Bouma sequence[J].Journal of Jianghan Petrole-um Institute,2001,23(1):1-5]
11 Middleton G V,Hampton M A.Turbidites and Deep-Water Sedimen-tation[M].United States:Pacific Section SEPM Publication,1973
12刘宝珺.沉积岩石学[M].北京:地质出版社,1980:497[LiuBaojun.Sedimentology[M].Beijing:Geological Publishing House,1980:497]
13 Mount J F.Mixing of siliciclast and carbonate sediments in shallowshelf environments[J].Geology,1984,12(2):432-435
14 Mount J F.Mixed siliciclastic and carbonate sediments:a proposedfirst-order textural and compositional classification[J].Sedimentolo-gy,1985,32(3):435-442
15 Armstrong A K.Carboniferous carbonate depositional models,prelim-iary lithofacies and paleotectonics maps,Arctic Alaska[J].AAPGBulletin,1974,58(4):621-645
2彭大钧,庞雄,陈长民,等.从浅水陆架走向深水陆坡-南海深水扇系统的研究[J].沉积学报,2005,23(1):1-11[Peng Dajun,Pang Xiong,Chen Changmin,et al.From shallow-water shelf to deep-water slope:the research of deepwater fan systems in South China Sea[J].Acta Sedimentologica Sinica,2005,23(1):1-11]
3郑晓东,朱明,何敏,等.珠江口盆地白云凹陷荔湾深水扇砂体分布预测[J].石油勘探与开发,2007,34(5):529-533[Zheng Xia-odong,Zhu Ming,He Min,et al.Prediction of Liwan deep submarinefan sandbody distribution,Baiyun Sag,Pearl River Mouth Basin[J].Petroleum Exploration and Development,2007,34(5):529-53]
4陈长民,施和生,许仕策,等.珠江口盆地(东部)第三系油气藏形成条件[M].北京:科学出版社,2003:1-121[Chen Changmin,Shi Hesheng,Xu Shice,et al.The Conditions of Hydrocarbon Accu-mulation of the Tertiary Petroleum System in the Pearl River Mouth Ba-sin[M].Beijing:Science Press,2003:1-121]
5代一丁,庞雄.珠江口盆地珠二凹陷的石油地质特征[J].中国海上油气:地质,1999,13(3):169-180[Dai Yiding,Pang Xiong.Pe-troleum geological characteristics of ZhuⅡDepression,Pearl RiverMouth Basin[J].China Offshore Oil and Gas:Geology,1999,13(3):169-180]
6朱伟林,张功成,高乐.南海北部大陆边缘盆地油气地质特征与勘探方向[J].石油学报,2008,19(1):1-9[Zhu Weilin,ZhangGongcheng,Gao Le.Geological characteristics and exploration objec-tives of hydrocarbons in the northern continental margin basin of SouthChina Sea[J].Acta Petrolei Sinica,2008,19(1):1-9]
7邵磊,李献华,汪品先,等.南海渐新世以来构造演化的沉积记录——ODPll48站深海沉积物中的证据[J].地球科学进展,2004,19(4):539-544[Shao Lei,Li Xianhua,Wang Pinxian,et al.Sedi-mentary record of the tectonic evolution of the South China Sea sincethe Oligocene:evidence from deep sea sediments of ODP site 1148[J].Advance in Earth Sciences,2004,19(4):539-544]
8庞雄,陈长民,邵磊,等.白云运动:南海北部渐新统-中新统重大地质事件及其意义[J].地质论评,2007,53(2):145-152[PangXiong,Chen Changmin,Shao Lei,et al.Baiyun movement:a greattectonic event on the Oligocene-Miocene boundary in the northern SouthChina Sea and its implications[J].Geological Review,2007,53(2):145-152]
9彭大钧,陈长民,庞雄,等.南海珠江口盆地深水扇系统的发现[J].石油学报,2004,25(5):17-23[Peng Dajun,Chen Changmin,Pang Xiong,et al.Discovery of deep-water fan system in South ChinaSea[J].Acta Petrolei Sinica,2004,25(1):17-23]
10张兴阳,罗顺社,何幼斌.沉积物重力流深水牵引流沉积组合鲍玛序列多解性探讨[J].江汉石油学院学报,2001,23(1):1-5[Zhang Xingyang,Luo Shunshe,He Youbin.Deposit assemblage ofgravity flow and traction current in deep water:a study of the multipleinterpretation of the Bouma sequence[J].Journal of Jianghan Petrole-um Institute,2001,23(1):1-5]
11 Middleton G V,Hampton M A.Turbidites and Deep-Water Sedimen-tation[M].United States:Pacific Section SEPM Publication,1973
12刘宝珺.沉积岩石学[M].北京:地质出版社,1980:497[LiuBaojun.Sedimentology[M].Beijing:Geological Publishing House,1980:497]
13 Mount J F.Mixing of siliciclast and carbonate sediments in shallowshelf environments[J].Geology,1984,12(2):432-435
14 Mount J F.Mixed siliciclastic and carbonate sediments:a proposedfirst-order textural and compositional classification[J].Sedimentolo-gy,1985,32(3):435-442
15 Armstrong A K.Carboniferous carbonate depositional models,prelim-iary lithofacies and paleotectonics maps,Arctic Alaska[J].AAPGBulletin,1974,58(4):621-645
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