What agent of deposition is this? Gravity, wind, waves, running water or glaciers.

The answer is "running water or glaciers".

Explanation:

The material is placed if erosion agents can longer carry sand. For instance, if another fluvial water slows at the river mouth, soils become rivers. The four key reasons for accumulation was its movement of reinforced the fact material surface, air, ice, liquid, and inertia, accumulated at the loss with enough kinetic energy throughout the fluid to create substrate layers. Accumulation can also apply to natural head moves or processes create of soil.

currents is the correct answer.