valley train

A valley train is a geological deposit of glaciofluvial sand and gravel that extends along the floor of a valley. These deposits are formed by meltwater streams flowing from glaciers. As glacial streams carry debris, they lose velocity beyond the ice margin, causing them to deposit some of their load. This process chokes the stream channel with sediments, forcing the stream to shift course and create braided channels separated by sand and gravel bars.12

In mountainous regions where valleys are deep enough, these deposits form elongate, planar features known as valley trains. If the ice margin stabilizes during glacial retreat, a new valley train can form inside a previous one, creating terraces that can help reconstruct past ice margin positions.2