The attempt by sedimentary geologists to recognize the environment of deposition  of a sedimentary rock is called "facies analysis". A "facies" is a specific type of rock formed in a specific environment.  The approach of studying the sediments themselves is called "sedimentology", whereas the approach of studying the included fossils is a part of "paleoecology".

There are four main ways that the environmental preferences of a fossil species can be determined:

1. The fossil can be compared with a living relative whose preferences can be observed directly. This works reasonably well for younger rocks, such as Cenozoic ones, but with increasing age of rocks, the degree of relatedness between fossils and living species becomes less, and the inferences therefore more tenuous.

2. There may be a consistent association of the species with a specific type of sediment, the environment of deposition for which may be inferred from the sediment itself.

3. An individual fossil of the species might have been found which died in the act of doing something ecologically interesting. For instance, plesiosaurs (dinosaur relatives) are known to have produced live young (rather than to lay eggs) because the fossil of a female that died in the process of birth has been found.

4. The shape or structure of the animal's shell or skeleton might limit or dictate the way in which it lived, and we might therefore be able to determine its environment from the shape of its body. This type of study is called "functional morphology".

The following environmental section of this webpage is based primarily on functional morphology, though some of the inferences included have been determined or tested by the others as well.

You are given the choice below of working through a simple (and short) example of how bivalves and echinoids might be used to interpret a sedimentary environment and then proceeding to pages on the ancient environments (and their fossils) of southwestern Georgia or of proceeding directly to the environments.