Characterising the nature, evolution and origin of detachment fault in central depression belt, Qiongdongnan Basin of South China Sea: evidence from seismic reflection data
-
摘要: 以区域地质、地震、钻井、测井资料为基础,通过对琼东南盆地深水区新近采集的2D长电缆剖面、3D地震剖面地层和地质构造的精细解释,并运用断裂活动性定量分析技术和回剥技术,重新落实了2号断裂带的几何学特征以及运动学演化,分析了该断裂对琼东南盆地深水区中央坳陷带结构构造的控制作用.研究表明,晚始新世时期,琼东南盆地受区域NW向拉张应力场的影响,2号断裂带开始发育,主要表现为多个早期NE向小型断陷盆地的控盆边界断裂,呈现出不连续分布和区段式活动特征.渐新世时期,伴随着南海扩张,区域应力场由NW-SE向拉张转变为SN向拉张,先前不连续的小断裂沿走向上延展并相互连接、合并,现今所见的2号断裂带主体发育成型,表现为由乐东东段-陵水弧形断裂、松南宝岛弧形断裂组成的大型断裂带,二者之间呈左阶斜列展布,剖面上呈铲式形态,向下延伸变缓,并沿Moho面滑脱而形成大型拆离断层.与拆离断层的活动相伴,在其上盘发育了大型滚动背斜,构成了琼东南盆地南部隆起区的主体构造,在滚动背斜中可见早期的一系列小断陷被卷入褶皱.2号断裂带延伸到长昌凹陷则转变为多个斜列式排列的小断裂,并逐渐消失,总体上与控制长昌凹陷南侧的北倾正断层带呈相向叠合式过渡转换.由西向东中央坳陷带表现出地堑、半地堑交替排列变化的结构特征.中中新世以后,2号断裂活动明显减弱,断裂系统对盆地沉积充填影响微弱,2号断裂隐伏活动控制了盆地中部和东部加积式陆坡的发育.在区域上,琼东南盆地中央坳陷带处于南海西北次海盆“V”型尖端向西延伸的区段,其主要活动时期与西北次海盆的发育时期一致,加之松南宝岛凹陷和长昌凹陷之间发育来自于Moho面之下的岩浆侵位和喷发,显示其与南海扩张早期之间的密切联系.因此,本项研究不仅有助于阐明琼东南盆地深水区盆地结构构造特征及其演化,而且可为陆缘伸展与洋盆扩张相统一模式的建立提供地质构造依据.Abstract: Using regional geological, newly acquired 2D and 3D seismic, drilling and well log data, especially 2D long cable seismic profiles, the structure and stratigraphy in the deep-water area of Qiongdongnan Basin are interpreted. The geometry of No.2 fault system is also re-defined, which is an important fault in the central depression belt of the deep-water area in the Qiongdongnan Basin by employing the quantitative analysis techniques of fault activity and backstripping. Furthermore, the dynamical evolution of the No.2 fault system and its controls on the central depression belt are analyzed. This study indicates that the Qiongdongnan Basin was strongly influenced by the NW-trending tensile stress field during the Late Eocene. At this time, No.2 fault system initiated and was characterized by several discontinuous fault segments, which controlled a series small NE-trending fault basins. During the Oligocene, the regional extensional stress field changed from NW-SE to SN with the oceanic spreading of South China Sea, the early small faults started to grow along their strikes, eventually connected and merged as the listric shape of the No.2 fault system as observed today. No.2 fault detaches along the crustal Moho surface in the deep domain of the seismic profiles as a large-scale detachment fault. A large-scale rollover anticline formed in hanging wall of the detachment fault. There are a series of small fault basins in both limbs of the rollover anticline, showing that the early small basins were involved into fold deformation of the rollover anticline. Structurally, from west to east, the central depression belt is characterized by alternatively arranged graben and half-graben. The central depression belt of the Qiongdongnan Basin lies at the extension zone of the tip of the V-shaped northwestern ocean sub-basin of the South China Sea, its activity period is the same as the development period of the northwestern ocean sub-basin, furthermore the emplacement and eruption of magma that originated from the mantle below the Moho surface occurred at the region between Songnan-Baodao and Changchang sags, from east to west with the early-stage spreading of the South China Sea. Therefore, this study not only helps in depicting the structural features and evolution of the deep-water basin in the Qiongdongnan Basin, but also provides the geological and structural evidence for establishing a unified model of continental margin extension and oceanic spreading.
-
Key words:
- Qiongdongnan Basin /
- No.2 fault /
- detachment fault /
- central depression belt
-
Clift P, Lin J, Barckhausen U. 2002. Evidence of low flexural rigidity and low viscosity lower continental crust during continental breakup in the South China Sea. Marine and Petroleum Geology, 19(8): 951-970 Kusznir N J, Hunsdale R, Roberts A M, et al. 2005. Timing and magnitude of depth-dependent lithosphere stretching on the southern Lofoten and northern Vøring continental margins offshore mid-Norway: implications for subsidence and hydrocarbon maturation at volcanic rifted margins. Geological Society, London, Petroleum Geology Conference series. Geological Society of London, 6: 767-783 Kusznir N J, Karner G D. 2007. Continental lithospheric thinning and breakup in response to upwelling divergent mantle flow: application to the Woodlark, Newfoundland and Iberia margins. Geological Society of London, Special Publications, 282(1): 389-419 Lavier L L, Manatschal G. 2006. A mechanism to thin the continental lithosphere at magma-poor margins. Nature, 440(7082): 324-328 Lei Chao, Ren Jianye, Tong Dianjun. 2013. Geodynamics of the oceancontinent transition zone, northern margin of the South China Sea: implications for the opening of the South China Sea. Chinese Journal of Geophysics (in Chinese), 56(4): 1287-1299 Masini E, Manatschal G, Mohn G. 2013. The Alpine Tethys rifted margins: Reconciling old and new ideas to understand the stratigraphic architecture of magma-poor rifted margins. Sedimentology, 60(1): 174-196 Mohn G, Manatschal G, Beltrando M, et al. 2012. Necking of continental crust in magma-poor rifted margins: Evidence from the fossil Alpine Tethys margins. Tectonics, 31(1): doi: 10.1029/2011TC002961 Pang Xiong, Chen Changmin, Peng Dajun, et al. 2007. Pearl River Deep-water Fan System and Petroleum in South China Sea (in Chinese). Beijing: Science Press Peron-Pinvidic G, Manatschal G. 2009. The final rifting evolution at deep magma-poor passive margins from Iberia-Newfoundland: A new point of view. Int J Earth Sci, 98(7): 1581-1597 Ren Jianye, Lei Chao. 2011. Tectonic stratigraphic framework of Yinggehai-Qiongdongnan Basins and its implication for tectonic province division in South China Sea. Chinese Journal of Geophysics (in Chinese), 54(12): 3303-3314 Reston T, McDermott K. 2014. An assessment of the cause of the ‘extension discrepancy' with reference to the west Galicia margin. Basin Research, 26(1): 135-153 Tong Dianjun, Ren Jianye, Lei Chao, et al. 2009. Lithosphere stretching model of deep water in Qiongdongnan basin, northern continental margin of South China Sea, and controlling of the postrift subsidence. Earth Sci J China Univ Geosci (in Chinese), 34(6): 963-973 Wang Pinxian, Li Qianyu. 2009. The South China Sea—Paleoceanography and Sedimentology. Netherlands: Springer Wang Zhenfeng, Li Xushen, Sun Zhipeng, et al. 2011. Hydrocarbon accumulation conditions and exploration potential in the deepwater region, Qiongdongnan basin. China Offshore Oil and Gas (in Chinese), 23(1): 7-13 Zhang Jian, Wang Jiyang. 2000. Deep geodynamic characteristics of tectonic spreading in continental margin of the northern South China Sea. Science in China (Series D) (in Chinese), 30(6): 561- 567 -
点击查看大图
计量
- 文章访问数: 1851
- HTML全文浏览量: 40
- PDF下载量: 2197
- 被引次数: 0
下载:
