**2. Distributive fluvial deposition**

the lateral migration of the channels. People can explain the interaction of the allogenetic controls (accommodation space and sediment supply) which have controlled the formation the fluvial sequence. Many authors have put forward their respective models [1–15]. But till now, there is still not a widely accepted model as a passive continental margin model of

36 Seismic and Sequence Stratigraphy and Integrated Stratigraphy - New Insights and Contributions

Fluvial deposits are among the best understandable depositional systems. However, the associated sequence stratigraphy application in fluvial systems is one of the most challenging topic, especially when the river sediments are isolated or away from the shorelines and the sea, such as the overfilled continental sedimentary basins which have only the continental strata record preserved, or in the case that the data availability is limited to the continental basin. In the latter case, all efforts should be made to expand the range of observation scale, if possible, to study the relationships between the rivers and the age of the coastal and marine systems. However, the modern stratigraphy is enough in order to provide a genetic stratigraphic analysis of the stratigraphic record, from the scale of a single depositional system to

All siliciclastic detritus is transported by fluvial system from some point. Debris is eroded from mountain source area and is carried into basins, forming alluvial fans, coastal plains, deltas, fan deltas, as well as fluvial deposition itself. Recognizing fluvial depositional settings and reconstructing local fluvial styles are the main works of a sedimentologist. Three conventional examples [16] of fluvial styles are shown in **Figure 1**, while there may be some other

Taking the Wenliu Area as an example, this chapter aims at addressing researches about

**Figure 1.** (a) A model for a meandering river, based on the South Saskatchewan River, Canada [17]; (b) a model for a sandy-braided river, based on the South Saskatchewan River, Canada [17]; (c) a model for an anastomosed river in a

humid environment. Based on the work of Smith and Smith [18] in Banff National Park Canada.

sequence stratigraphy.

the scale of the whole basin [16].

types beside the conventional ones [19].

another type of river.

The new river type we are going to propose is a kind of river that resembles distributive fluvial system (DFS) very much. DFS was firstly raised by Weissmann et al. [20]. Weissmann et al. have discussed that many aggradational depositional systems are dominated by distributive landscapes in both subaerial and subaqueous settings. The term "distributary fluvial systems" (DFS) addressed a key question in the earth sciences, i.e., that the most of the current fluvial facies models have a limited relevance in the interpretation of the ancient deposits.

Weismann et al. [20] also pointed out that many of the DFSs have been impacted by significant Quaternary climatic fluctuations and the deposits will represent the Quaternary sedimentary features of the history. From the regional to the local scale, the distributive fluvial systems display characteristics including: (1) deposition in the alluvial system becomes diving into the basin, (2) the radiation pattern of channels from a vertex, (3) a broadly fan-shaped deposit that is convex upward across the DFS and concave upward down-fan, and (4) an intersection point above which the alluvial system is held in an incised valley and below which it spreads out across an active depositional lobe (if the river is presently incised into its DFS). The observed DFS geometry and graphic style in these different basins are very different. In the open DFSs, the river is not confined in a valley, nor is able to transfer on the surface of DFS. The tearing process is dominated by node tearing near the DFS vertex or intersection. These rivers seem to have significant differences from the valley, because the floodplain material can be easily deposited and saved in the open fan. The DFS rivers observed in many sedimentary basins are now wholly or partially cut into the DFS. The incision takes two main forms: (1) incision of the proximal DFS controlled by sediment supply and discharge control due to climate change [21, 22, 23] or tectonic tilting [21, 22], or (2) incision driven by basic level decline (whether is the ocean, lakes, or by river capture) [24].
