Paleontology (including both invertebrate paleontology and palynology) is the natural complement to the use of structure and stratigraphy in oil exploration. The decision to use it or not is fundamentally economic as is the decision to use structure (seismic) or stratigraphy. However, the changing pattern of exploration makes the use of fossils increasingly appropriate. Fossils can be used to supply evidence of time correlation and original environmental conditions that is independent of the data obtained from the rocks themselves. It is also being found that fossils themselves in many instances provide the trapping mechanism.

Fusulines are the only fossil group with a long history of application in the Mid-Continent, but many other microfossils are now becoming more useful as their study matures. There is no universally applicable fossil group because no organism was ever able to survive everywhere, but each System and many environments contain organic remains especially suitable to use therein. Thus, competence in several fossil groups is necessary to cope with normal exploration problems. Multiple competence also assures that for most subsurface problems enough usable fossils will be available to provide answers. The increased sophistication of lithostratigraphy and production techniques has made coring more commonplace. This makes available the whole range of macrofossils, which are especially valuable ecause in many cases their significance already is understood.

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