Interpreting paleoenvironments from fossils could be regarded as more of an art than a science. Or perhaps more correctly as a detective story. The evidence and clues will be there but it is how they are put together to form the conclusion that can be the tricky part. We know that certain fossils live(d) in certain environments. Surely if the life habitat maps of each species/genus/group in a particular sample are overlain it will show us the most likely environment of deposition?
Such an assumption might be true if we could be sure that all the fossils present in any one sample should in fact be there. The surprising thing is that many fossils in a sample are not “supposed” to be there at all. Some may be there through direct contamination because our sampling methods may be inadequate or samples may be contaminated by mechanical processes (see the section on Operational Biostratigraphy and “caving”). Others may be in a sample because of the geological process known as “reworking”, where older fossils have become incorporated in to younger sediments because they have been eroded out of older strata. Another consideration might be that the organism that results in our fossil may have died in one place, but has become a fossil somewhere far removed from its natural habitat (see below).
It is the role of the biostratigrapher to take such matters under consideration. On the upside, even fossils that are not “supposed” to be in a particular sample can also provide us with useful information. Let’s take the simplest option first and assume that all our fossils in a sample are there “honestly”. How do we as geologists use fossils to interpret paleoenvironments?