alluvial epoch

例句：

1. 1.The alluvial fan is a natural formation that forms in river valleys.
   冲积扇是河流谷地中自然形成的地貌。
2. 2.The alluvial deposits are rich in minerals and can be used for building materials.
   冲积沉积物富含矿物，可用于建筑材料。
3. 3.The alluvial deposits were formed over millions of years, and they are still visible today.
   冲积沉积物在数百万年形成至今，仍然可见。