Depositional Environments Depositional environment refers to conditions under which sediment accumulates. Different sediment accumulates in different environments because the size of the sediment depends on strength of the current transporting it.
Geologists recognize many different environements.
Youngest sedimentary rock, exposed on the rim of the Canyon is the Kaibab Limestone. It represents the deposits of a Bahama-like reef area. Canyon formed as a consequence of river erosion. Note that it's not the water itself that does the grinding, but rather is the sand being carried by the water. Note that this process happens more vigorously during a flood, when the volume, velocity, and turbulence of the water is much greater.