摘要:
下扬子陆区苏北盆地在结晶基岩形态、性质、分布面积等方面与海区南黄海盆地具有显著区别;前者印支面基岩地质图NEE向窄条带状展布的构造线方向支持不对称对冲构造运动的观点,与后者主体构造线方向呈宽缓近EW向不同;由于位于传统观点划分的南黄海盆地中央隆起区,下扬子区磁异常主体与上、中扬子区四川盆地及江汉盆地磁异常主体相当,钻井和二维地震资料解释发现,该区赋存厚度超过5 000 m的前中生代沉积,三叠系青龙组碳酸盐岩与新近系直接不整合接触;由此认为,下扬子区传统中央隆起区为前中生界巨大沉积坳陷区,表明海域南黄海盆地具有与中、上扬子区更为近似油气地质构造条件。但是,由于滩海区至今存在地震资料采集巨大空白带,使原本已经十分复杂的地质构造特征研究及其海陆域盆地对比研究更加困难和难以实现。笔者根据重力特别是高精度航磁资料,在江苏沿海与南黄海海域之间解释发现了一条NW向深大断裂带—陈家港断裂带,首次证实下扬子区海陆域盆地被构造分割,二者地层、沉积和构造特征海陆有别是不争的事实。
Abstract:
The Subei Basin, land part of the Lower Yangtze region, has significant difference in the morphology, properties and distribution pattern of crystalline bedrocks with the South Yellow Sea Basin, offshore part of the Lower Yangtze Region. On the Indo-China-surface geological map, the NEE tectonic lines consisting of narrow strips support the assumption of asymmetric ramp tectonic movement, while in the offshore side, the tectonic lines are dominated by those in nearly EW direction. According to the traditional point of view, the central uplift of the South Yellow Sea Basin, where the magnetic anomalies of the lower Yangtze region is well developed, is equivalent to the magnetic anomaly bodies of the Sichuan and the Jianghan Basins on the upper and middle Yangtze respectively. 2D seismic data has revealed a thick sequence of Pre-Mesozoic deposits which is more than 5,000 meters thick, indicating that the central uplifting area of the traditional Lower Yangtze region was a huge depression before Mesozoic and the offshore part of the South Yellow Sea Basin which is similar with the upper and middle Yangtze Regions. However, owing to the seismic blank in the coastal shallow water, the comparative study of the land and sea part basins faces difficulties. Based on gravity and high precision aeromagnetic data, the authors discovered a NW-trending deep fault-the Chenjiagang fault zone between the coastal Jiangsu and South Yellow Sea, and for the first time confirmed that the land and sea parts of the South Yellow Sea Basin was tectonically faulted. As the results, both stratigraphy, depositional and tectonic characteristics on the two sides of the fault are different.
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