## 4 Results
### Distribution of the Channels and Related Depositional Elements  
During the early Late Miocene (sequence S1), a NE-SW-oriented depression was developed in the middle portion of the study area (Figure 7A), which measures 30-40 km in width and 200-400 ms TWT in depth (Figures 4 and 7A). The depression can be divided into western and eastern portions by a local topographic high in between (Figure 7A). The eastern one contained relatively thick infillings (Figure 4D). The two portions merged into a depression with the disappearance of the local topographic high (Figure 7A). The topographic depressions on both sides of the uplift zone were characterized by the development of U-shaped channels (Figure 4D). The western channel had a larger length and higher sinuosity than the eastern counterpart (Figure 7A). During the middle Late Miocene (sequence S2), along with the pre-existing depression zone that was gradually filled and the negative topography became weak, five NE-SW-oriented channels were developed in the study area (Figure 7B). The two channels in the eastern and western portions were relatively large, with widths of 6-15 km and depths of 100-150 ms TWT, while the three channels in the middle portion were relatively small, with widths of 3-5 km and depths of \(\sim\)100 ms TWT (Figures 4 and 7B). All the channels were U-shaped in cross sections and were filled by low-to-moderate amplitude and variable-continuity reflections (Figure 4). During the late Late Miocene (sequence S3), four NE-SW-oriented channels were persistently developed in the study area (Figure 7C). In comparison to the channels in sequence S2, the western channel migrated westward, with channel width increasing to about 11-20 km, while the eastern channel decreased in width to about 5-12 km (Figures 4 and 7C). Meanwhile, the middle two channels remained small, with widths increasing to 4-10 km and depths decreasing to \(\sim\)50 ms TWT (Figures 4D and 7C). These channels displayed U-shaped cross sections and were primarily filled by low-to-moderate amplitude, high-continuity, and divergent reflections (Figure 4D). During the Early Pliocene (sequence S4), the channel system underwent a significant change. An E-W-oriented V-shaped channel was formed in the northern region, measuring 2-7 km in width and 200-400 ms TWT in depth (Figures 4D and 7D). Levees were developed on both sides of the upper reach of the channel, with the left-hand levees being higher than the right-hand counterparts (Figure 4), i.e., the thickness of the left-hand levee was 40-110 ms TWT, while the right-hand levee was 10-50 ms TWT (Figure 6D). Sediment waves were mainly distributed on the left-hand side of the lower reach of the channel (Figure 7D), with wavelengths of 1-2 km and wave heights of 10-15 ms TWT (Figure 4D). Meanwhile, a NEE-SWW-oriented V-shaped channel was developed in the southern region, with a width of 5-15 km and a depth of 400 ms TWT (Figures 4 and 7D). Similarly, the channel displayed preferential development of the left-hand levees (Figures 4 and 7D). In addition, three inherited channels were developed in the middle portion of the study area during this period. These channels were characterized by U-shaped external forms, with widths of 4-9 km and depths of 20-40 ms TWT (Figure 4D), ultimately converging northward into the lower reach of the northern channel (Figure 7D). During the Late Pliocene (sequence S5), the distribution of the channels was similar to that in the Early Pliocene (Figure 7D-E). The northern and southern V-shaped channels developed levees on both sides, with thicknesses ranging from 40 to 130 ms TWT (Figure 4). The left-hand levees were overall higher than the right-hand counterparts (Figures 4 and 6E). Note that a sediment wave field was also developed on the left-hand side of the lower reach of the northern channel with wavelengths of 0.5-3.4 km and wave heights of 5-10 ms TWT (Figure 4D).