Consequently, they can only be resolved in time slices that cut through the upper part of a trunk incised valley. The incised tributaries tend to be signi fi cantly shallower relative to their trunk counterparts. It is approximately 13.4 km long and has several orders of branches with dendritic patterns. The longest incised tributary feeds C2.15 and is designated as C2.16 (Fig. These are very small-scale incised channels that feed Class 1 and Class 2 incised valleys (Figs. Class 2 valley systems lack the internal heterogeneity that is documented in Class 1 systems, but Class 1 and Class 2 systems are hypothesized to be similar in the facies that are sandy in both types of systems. Also, Class 2 channel systems tend to have higher sinuosity, suggesting that they might have inherited the meander pattern from preincision fl uvial conditions. These valleys are comparable in their dimensions with the “ trunk incised valley ” re- ported by Posamentier (2001). Although Class 2 valleys resemble Class 1 valleys due to the presence of well-developed dendritic tributaries in both systems, Class 2 systems are signi fi cantly smaller (typically less than 4 km wide) than Class 1 systems. This class of fl uvial systems could be exempli fi ed by C2.10 and C2.15 (Figs. This may be explained by the fact that ZQ3 was drilled through the margin of the trunk valley C4.1 (Fig. However, the coarse interval, which is less than 6 m, is obviously thinner than expected. As indicated by shallow borehole ZQ3, which intersects trunk valley C4.1 and shows that the basal part of C4.1 consists primarily of sandy or pebbly deposits (Figs. These clustered channels are associated with the relatively coarse-grained deposits. Close-up images through the base of the lower portion of the valley fi ll indicate that the changes at the base of the incised valleys have very complex internal architectures, consisting of numerous small-scale channels, cutting across each other and displaying an overall braided pattern (Figs. Seismic time slices through the upper portion of the section reveal a homogeneous and fl at landscape, which is thought to correspond to the interval composed of muddy deposits (Figs. They have very low sinuosity and the most striking features are the presence of the dendritic subordinate tributaries along the valley margins (Figs. This type of fl uvial systems is typically more than 10 km in width and reaches 16 km at maximum. The best examples of Class 1 fl uvial systems contain the C2.1 and C4.1 (Figs. (Class 1 to Class 3) are incised in their nature while the latter three (Class 4 to Class 6) are not incised.
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