A massive body of rock characterised by its age, lithological structure, conditions of formation (depositional environment) and other features that distinguishes it from adjacent rocks
Depositional facies may consist of one or few lithofacies spread through its body
For example, a river bed may have a corse-grain lithofacies at the central deep channel where water is fast and fine-grain lithofacies on the shallow sides where water is slow.
See Also
Petroleum Industry / Upstream / Subsurface E&P Disciplines / Petroleum Geology