东海陆架盆地西湖凹陷渐-中新世异常反射体的特征与成因
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摘要
通过对东海陆架盆地西湖凹陷反射地震剖面的详细解释,结合该区域地质背景、构造演化历史和反射地震剖面及其重磁曲线的对比分析结果,对发现的一类处于渐-中新世不整合面的异常反射体的成因进行了分析,探讨了其演化过程。结果表明,发现的21个异常反射体总体分布状况是南部多、北部少,个体之间相互孤立存在,大小基本一致,内部孔隙发育,其密度大于新生代沉积层而小于中生代基底岩石。由此认为,这些异常反射体是渐-中新世在地表处形成的火成岩体,在部分遭受风化剥蚀后被沉积层所覆盖。由于这些火成岩体的周围断层发育,孔隙度较高,且形成时期早于该区域的生烃高峰期,故推测这些异常反射体中可能富集大量油气资源。同时认为,东海陆架结构在该过渡期具有较大的不稳定性。
Twenty-one anomalous reflectors on Oligocene and Miocene transition in Xihu Depression,East China Sea Basin were found by detailed explaining seismic information.The formation cause and evolutionary process of the anomalous reflectors with the geological background was analyzed and discussed,and the comparison with the gravity and magnetic data was also carried.The results showed that these anomalous reflectors in south Xihu Depression are more than in north and distribute individually,they have a great porosity and the same size basically,their densities are higher than those in Cenozoic sediment and lower than those in Mesozoic rocks,their reflectance signatures on seismic profile are changing from bottom like igneous rock to up like sediment.In order to reasonably explain anomalous reflectors,this paper inferred that the anomalous reflectors were Miocene igneous rock,and then covered by sediment after weathered and denuded in the surface.By analyzing the evolution of the anomalous reflectors,it was suggested that there is a number of oil and gas in them,and indicated the continental shelf in East China Sea is instability in the Oligocene and Miocene transition period.
Twenty-one anomalous reflectors on Oligocene and Miocene transition in Xihu Depression,East China Sea Basin were found by detailed explaining seismic information.The formation cause and evolutionary process of the anomalous reflectors with the geological background was analyzed and discussed,and the comparison with the gravity and magnetic data was also carried.The results showed that these anomalous reflectors in south Xihu Depression are more than in north and distribute individually,they have a great porosity and the same size basically,their densities are higher than those in Cenozoic sediment and lower than those in Mesozoic rocks,their reflectance signatures on seismic profile are changing from bottom like igneous rock to up like sediment.In order to reasonably explain anomalous reflectors,this paper inferred that the anomalous reflectors were Miocene igneous rock,and then covered by sediment after weathered and denuded in the surface.By analyzing the evolution of the anomalous reflectors,it was suggested that there is a number of oil and gas in them,and indicated the continental shelf in East China Sea is instability in the Oligocene and Miocene transition period.
引文
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[3]龚建明,陈国威.西湖凹陷东部断阶带火成岩的分布特征[J].中国海上油气(地质),1995,1:13-17.
[4]LI C F,ZHOU Z,GE H,et al.Correlations between erosionsand relative uplifts from the central inversion zone of the Xihu De-pression,East China Sea Basin.Terrestrial[J].Atmospheric andOceanic Sciences,2007,18(4):757-776.
[5]LI Q,JIAN Z,LI B.Oligocene-Miocene planktonic foraminiferbiostratigraphy,Site 1148,northern South China Sea[J].PRELL W L,WANG P,BLUM P,et al.Proc ODP,Sci Re-sults,2004,184:1-26.
[6]高德章,赵金海,薄玉玲,等.东海重磁地震综合探测剖面研究[J].地球物理学报,2004,47(5):853-861.
[7]江为为,宋海斌,郝天珧,等.东海陆架盆地及其周边海域地质、地球物理场特征[J].地球物理学进展,2001,16(2):18-27.
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[9]胡惠娟,陶国保.东海西湖凹陷第三纪岩浆活动与油气聚集的关系[J].海洋地质译丛,1997,3:13-19.
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