对浅水三角洲的一点认识

Discussion on the shallow water delta

以岩心和测井资料为基础,结合前人研究成果,对浅水三角洲的沉积动力、分类、相带划分进行深入探讨,认为浅水三角洲以河流作用为主,而波浪及湖平面频繁波动过程产生的冲刷—回流作用较小,但仍对沉积物有不同程度的改造;浅水三角洲应该限定为毯式结构特征的浅水型三角洲,吉尔伯特型浅水三角洲应归入深水三角洲中;分类上,按供源体系应将浅水三角洲分为浅水曲流河三角洲、浅水辫状河三角洲及浅水扇三角洲。对高邮凹陷北斜坡垛一段早期泥岩颜色、沉积构造、垂向结构等进行分析,发现其发育浅水辫状河三角洲,沉积特征更接近陆上河流相,而与典型三角洲沉积特征差别较大,这是因为浅水三角洲的沉积动力以河流作用为主,并以此为例阐述了浅水三角洲的识别特征。

Based on core and logging data, and combined with the results of previous studies, sedimentary dynamics, classification and facies division of shallow water delta were discussed in depth. It is considered that fluviatile action dominated on the shallow water delta while the influence of erosion-backwash action came of wave and frequent fluctuations in lake level was lesser but still had different degrees of transformation on sediments. Shallow delta should be defined as blanket structural, while Gilbert type delta should be classified into deep water delta. According to the source system, shallow water delta should be divided into shallow water meander delta, shallow water braid river delta and shallow water fan delta. By analysis of mudstone color, sedimentary structure and vertical structure at early stage of Duo-1 segment of North slope in Gaoyou depression, it is found that shallow water braid river delta developed in Duo-1 segment. The sedimentary characteristics were closer to subaerial fluvial phase while had larger differ-ence with typical delta sedimentary characteristics. This is because, for shallow water deltas, effects of rivers are the main sedimen-tary dynamics. Meanwhile, based on this example, identifying characteristics of shallow water delta was elaborated.