Types, Characteristics and Significance of Distributary Channel Systems
摘要: 研究总结了三角洲平原中五种主要类型的分流水道沉积特征、分形几何特征及其形成条件。所度量的河控、潮控和波控三角洲的五种主要分流水道体系的分维值变化范围为１.０４６至１.７６３。以分流水道类型或分流格式为基础，划分了相应五种常见的三角洲平原类型，并阐述了分流水道组合式及其演化与三角洲体制的关系。Abstract: Based on genesis, distributary channel systems (DCS) are subdivided into river and tide-dominated DCS. Taking into consideration the internal sedimentary architecture of channel fill and sand distribution patterns or geometric structure of drainage systems, the former is further divided into sinuous, branched and anastomostic systems, and the latter into tide-branched and tide-anastomostic DCS. Controlled by physical factors of environment, DCS reveal a certain characteristics of geometric structure and fractal geometry. Fractal dimensions of five types of DCS are calculated by means of fractal geometry. Results show that there is self-similarity in a distributary channel system, and fractal dimensions calculated vary from 1.046 to 1.763. In general the sinuous has simple geometric structure and low fractal dimension that is below 1.30; the anastomostic, the branched and the tide-anastomostic have complex geometric structures and high fractal dimensions that are above 1.40. Fractal dimension of the tide-branched is between above tow groups. In low delta plain, fractal dimensions of DCS are closely related to physical parameters of environment, especially to the gradient of offshore and average power of wave. Low fractal dimension corresponds to the great gradient of offshore and high average power of wave. Since characteristics of DCS reflect environmental parameter, types of deltaplains can be defined by types of DCS. The paper has defined five types of delta plains, including delta plains with sinuous, anastomostic, branched, tide-branched and tide-anastomostic distributaries. Delta plains of Rhone, Zhujiang and Mekong belong respectively to delta plain with sinuous, anastomostic and tide-branched distributaries. At least five types of combination modes of delta plains are found: type 1 delta plains with sinuous → anastomostic → branched distributaries; type 2 delta plains with sinuous → branched distributraries; type 3 delta plains with sinuous → tide-anastomostic distributaries; type4 delta plains with sinuous → tide-branched distributaries; type5 delta plains with single sinuous distributaries. Type1 is found in Permian Coal Measures of North Anhui. Mississippi delta plain is a typical example of type 2.
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