Assemblage Zone

A grouping of fossils that are found to occur together in a sample. Can be autochthonous or allochthonous. Generally used interchangeably with the term biofacies. Assemblage zones are usually environmentally controlled and are useful only in local correlation. In a given sample, such as one collected over a thirty-foot interval, several biofacies may be grouped together; the sample is identified by the oldest biofacies, a characteristic fossil or an index fossil.