珠江口盆地NSQ2陆架边缘三角洲的识别标志及沉积模式

Identification marks and depositional model of the shelf-margin delta from NSQ2 of the Pearl River Mouth basin,China

陆架边缘三角洲是根据相对海平面变化进行分类的一种三角洲类型,是指发育于大陆架边缘、越过大陆坡折向陆坡延伸的三角洲。借助岩心资料、测井曲线和地震剖面等资料,对珠江口盆地NSQ2低位域的沉积物进行了分析,认为此时存在陆架边缘三角洲。因为从地震剖面上可见前积体越过陆架坡折继续向盆地进积,形成向海和向陆减薄的楔形体;从岩心上可见砂泥岩交互的三角洲前缘前端的滑塌体和以浊积水道沉积为主的重力流沉积;在测井曲线上,可见典型的漏斗形,为三角洲前缘河口坝-远沙坝序列及块状箱形重力流水道;在平面上,其砂厚图主要呈弓形或新月形状。综合这些特征认为NSQ2低位时期发育陆架边缘三角洲,并且总结了该地区的稳定的陆架边缘三角洲沉积模式。

Shelf-margin delta is a new type of delta classified by the relative sea level change. It means that the delta develops on the shelf-margin, passes the shelf break and extends to the slope. The authors analyse the sediments in the LST of NSQ2 in the Pearl River Mouth basin and consider that there exists a shelf-margin delta based on the cores, well logs and seismic data. People can see that foresets progress toward the basin, forming a thinning wedge towards to the land and the basin in the seismic section, the slumps with the sandstone-mudstone interbeds on the front end in the front of delta and gravity flow deposits mainly consisting of turbidity channel deposits in cores, the typical funnel-shaped and box-like gravity flow channels indicating mouth bars and far sand bars in GR curves, and the arcuate or crescent sand isopach map in a plan. All of these indicate a shelf-margin delta exists in the LST of NSQ2. Also, a stable shelf-margin delta model is summarized.