crude oil

Water that has remained in an aquifer for a long timespan, usually thousands or millions of years.

A fossil formed when an animal, plant, or other organism dies, its flesh decays and bones deteriorate due to chemical reactions; minerals gradually enter into the cavity, resulting in a cast, which is in the general form of the original organism.

Any fuel derived from hydrocarbon deposits such as coal, petroleum, natural gas and, to some extent, peat; these fuels are non-renewable, and their burning generates the greenhouse gas carbon dioxide.

Any ancient remains of a plant or animal that lived during a specific geological period and that can be used to date the containing rocks.

(paleontology) A type of fossil reflecting the reworking of sediments and hard substrates by organisms, rather than the physical remains of the organism itself. This includes structures such as burrows, trails, impressions, coprolites and borings.

(evolutionary theory) Any species discovered first as a fossil and believed extinct, but which is later found living; an organism that has remained unchanged over geological periods.

plural of fossil record

The collective record of biological development that is reflected in the fossilized remains of organisms through geological history. / The record of preserved evidence for a single species or taxon.

plural of fossil fuel