洪积层

例句：

1. 1.The river has carved a deep erosional valley in the alluvialfan of the Yellow River.
   黄河的冲积扇上形成了一条深深的侵蚀峡谷。
2. 2.The geological survey team used a high-resolution satellite image to map the sedimentary layers of the region.
   地质调查队使用高分辨率卫星图像来绘制该地区的沉积层。
3. 3. The study revealed that the thicknessof the alluvial fan varied greatlyacross different sections of the river.
   研究显示，河流不同段落的冲积扇厚度差异很大。