North American fossils. A list of where to find fossils in North America including geological formations as well as single sites. Fossils are the remains of living organisms that have been preserved through either permineralization, casts/molds, recrystallization, or other forms of mineralization. Dig sites such as these can be rich in fossils, yet some suggest we have only scratched the surface of the fossil record. The study of fossils is paleontology. Fossils are studied in relation to evolutionary theory as well as their comparison and relationships between taxa. The earliest fossils paleontologists have found are fossilized bacteria dating back billions of years.