什么是 Facies association and facies succession？

A facies association is a group of facies that occur together and were deposited in one environment, such as channel sand, levee silt and floodplain mud with roots. A facies succession is a vertical sequence of facies in which some property changes progressively upward; in a fining-upward succession the grain size decreases upward, in a coarsening-upward succession it increases.