Simulation of sedimentary filling process of confined and unconfined canyons: taking the Area M of Qiongdongnan Basin as an example

The changes in the sand-mud ratio and sediment-filling rate in underwater canyon directly affect the geomorphic characteristics of the canyon. Taking the Central Canyon in the Area M of the Qiongdongnan Basin as an example, based on 1 000 km² of three-dimensional seismic data, the canyon types formed in seven periods in the area were recognized and classified. Software Fluent was used to simulate the characteristics of the filling process under the conditions of different sand-mud ratios in single- and dual-sourced scenarios. Results show that the canyons that formed in the early stage (T50-T30) are confined canyons, and the those formed in the late stage (T29_1-T29) are unconfined canyons. The channels developed in the confined canyons have strong meandering ability, the superposition of multi-stage channels is obvious, and channel complexes are mostly developed; however, in the unconfined canyons, channels developed are mainly transversely migrated, and then slowly diffused into an open area and formed lobe complexes. The simulation and study of the canyon-filling processes increased the accuracy of identification of sedimentary units in the canyons, and provided a theoretical basis for the efficiency and the optimization of exploration target areas.