Type of bedding shown by sedimentary deposit when particles become
progressively finer from bottom to top.
Graded bedding is caused by the differential settling by size
and weight of suspended particles in water. Graded bedding can be used to
tell which are the oldest and youngest rocks in a sedimentary sequence because
the larger, older grains are at the base of the bed. (This is known as younging
direction or bedding tops).