facies

Facies refer to the characteristic features of a rock or sediment that reflect its environment of formation. They include aspects like texture, composition, and appearance, which help geologists identify where and how the rock or sediment was formed. For example, a sandy, shallow-water facies indicates a coast or beach environment, while a deep-sea facies might consist of fine mud or clay. Recognizing facies allows geologists to interpret past environments and understand Earth's history, such as ancient climates, water depths, and biological activity.