The occurrence of fossil bearing material depends on environmental factors before and after the time of preservation. After death, the first preserving factor is a rapid burial in water bodies or terrestrial sediment which would help in preserving the specimen. These rocks types are usually termed clastic rock, and are further subdivided into fine, medium and coarse grained material. While fossil's can be found in all grain typed, more detailed specimens are found in the fine grained material. A second type of burial is the non-clastic rock, form where the rock is made up of the precipitation of compacted fossil material, types of rock include limestone and coal. The third fossil bearing material is the evaporates, which precipitate out of concentrated dissolved salts to form nodular deposits, examples include rock salt and phosphate concentrations. The evaporates are usually associated with gastropod, algae, vertebrate, and trace fossils.
