莺歌海盆地坡折带特征及其对沉积体系的控制

Patterns of Slope-Break Zone and Their Depositional Models in the Yinggehai Basin

坡折带是层序样式划分的重要依据 .大量地震剖面的精细解剖表明 ,莺歌海盆地坡折带可划分为构造坡折带和沉积坡折带 ,进而将层序构成样式划分为四类 ,即挠曲坡折型、断裂坡折型 (生长断裂型 )、沉积坡折型 (陆架陆坡型 ,相当于Ⅰ类层序 )和缓坡型 .不同类型层序样式控制不同低位体的空间分布 .挠曲坡折、断裂坡折和沉积坡折控制了各三级层序中斜坡扇和盆底扇的分布 ,而缓坡控制强制性海退型低位三角洲的分布 .详细的构造研究表明 ,莺歌海盆地裂后期边缘断裂 ,如①号断裂和莺东断裂在不同时期不同部位仍表现出程度不同的活动性 .正是由于这些断层的活动性及其在空间上的差异性 。

The slope-break is thought to be an important criterion to distinguish the patterns of sequences. In the Yinggehai basin, the slope-break can be classified into two types: structural and sedimentary slope-break zones, which can be divided further into four patterns, that are bend slope-break, fault slope-break (growing fault), sedimentary slope-break (shelf/slope-break) and gentle slope types. Different patterns of sequences control different distributions of lowstand sandstones. The bend slope-break, fault slope-break and sedimentary slope-break restrict the distribution of slope fans and basin floor fans in the third-order sequences, and the gentle slope-break limits the distribution of lowstand deltas which were formed in the course of restricted sea-level decrease. The results of tectonic researches show that the marginal faults, such as the No.1 fault and the Yingdong fault, still are active during the post-rifting stage, which controlled the formation of slope-break in this basin.