## 4 Results
### Facies Model  
Utilizing grain size distribution and water depth, a facies distribution model is created along and across the Fraser River Delta, covering all simulated steps (Figure 4 and Table 2). In the delta plain (above zero sea level), the percentage of sand distribution is selected as the main facies controlling grain size, due to the overall sandy nature of the modern delta. Shale-rich zones are defined as having less than 20% sand, while sandy zones are defined as more than 25% sand (Table 2). In the subaqueous portion, the boundary between the delta front and prodelta is selected as 150 m, to simulate the real delta boundary [22]. Sand percentage progressively reduces from the delta plain to the prodelta; thus, 20% sand is selected to differentiate facies in the delta front, and 15% sand in the prodelta (Table 2).  
The results show that in S1 the upper delta plain is represented by sandy deposits, while the middle and lower delta plain is predominantly silty deposits (Figure 4A). The delta front shows almost uniform shale-rich deposits, and the prodelta is dominated by silt- and shale-rich deposits (Figure 4A). S2 shows a significant change, especially in the delta plain (Figure 4B). The upper and middle delta plain show sand-dominated deposits, while the lower delta plain shows silty deposits and, to a lesser extent, shale-rich deposits (Figure 4B). The vast majority of the delta front is characterized by shale-rich deposits, but local sand-rich deposits are present in the northern delta front (close to Vancouver) and the Boundary Bay delta (Figure 4B). The prodelta is represented by shale-rich deposits in both the Strait of Georgia and Boundary Bay delta (Figure 4B). S3 allows us to predict possible changes in facies distribution in the future. S3 shows that in 5000 years, the majority of the delta plain will be sand-rich, with local silty deposits at the edge of today's delta plain-delta front boundary and at the Boundary Bay delta (Figure 4C). Similarly, the delta front will also be dominated by sand-rich deposits. The distal portion of the delta front will be shale-rich (Figure 4C). The prodelta in S3 will remain shale-rich, but a local silt-rich deposition will develop in the south delta front (close to Point Roberts) (Figure 4C). Boundary Bay seems to be filled with shale-rich deposits; however, it is clear that these sediments would be  
Figure 4: (**A–C**) Spatial facies distribution plots at the end of each time step, interpreted based on grain size percentage and bathymetric data (Table 2).  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Facies** & \multicolumn{2}{c}{**Bathymetry (m)**} & \multicolumn{2}{c}{**Sand (\%)**} & \multicolumn{2}{c}{**Shale (\%)**} \\ \hline  & **Min.** & **Max.** & **Min.** & **Max.** & **Min.** & **Max.** \\ \hline Sandy delta plain & \(-164\) & \(0\) & \(25\) & \(38.2\) & - & - \\ \hline Silty delta plain & \(-164\) & \(0\) & \(20\) & \(25\) & - & - \\ \hline Shale-rich delta plain & \(-164\) & \(0\) & \(0\) & \(20\) & - & - \\ \hline Sandy delta front & \(0\) & \(150\) & \(20\) & - & - & - \\ \hline Shaley delta front & \(0\) & \(150\) & \(0\) & \(20\) & - & - \\ \hline Silty prodelta & \(150\) & \(400\) & \(15\) & \(36.6\) & \(0\) & \(50\) \\ \hline Prodelta shale & \(150\) & \(400\) & - & - & \(50\) & \(74.7\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Grain size and bathymetric parameters utilized to interpret facies distribution.  
dispersed southward if the outer edge of the model was bigger. Therefore, the subaqueous Boundary Bay delta deposition is ignored in S3. Unfortunately, accurate paleobathymetric data covering the south of Boundary Bay is not available to extend the model southward.