Fossil Dating - How Does the Geologic Column Date Fossils?
How does fossil dating work? The earth's crust consists of many layers of sedimentary rock (called "strata"). Evolutionary geologists assume that each layer represents an epoch of time, typically millions of years. This is a secondary assumption based upon the primary assumption of Uniformitarianism - the assumption that current geologic processes, occurring at the same rates observed today, in the same manner, account for all of Earth's geological features. Thus, it assumes that geological processes are essentially unchanged today from those of the unobservable past, and that there have been no cataclysmic events in earth's history.
These layers of sedimentary rock contain billions of fossil remains. Some fossils are unique to certain layers. The layers are arbitrarily arranged into a specific order (not necessarily the order in which they are found). This order reflects the assumption of biologic evolution. The creatures supposed to have evolved first are considered to be the oldest and are thus placed at the bottom of the column of layers. The creatures that are thought to have evolved relatively recently are higher up and so on. This arbitrary arrangement of sedimentary layers is called the "geologic column." A variety of fossils from each layer of strata have been chosen to be "index fossils."
Fossil Dating – The Assumptions
Evolutionists assume the age of an index fossil by the stage of evolutionary history the fossil is thought to be in. They guess how long it would take for one kind of life to evolve into another kind of life and date the fossils and rocks accordingly. The rocks are dated by the index fossils, while the remainder of the fossils found in the rock layer are dated by the rocks. Many critics reject the use of fossils to date rock layers and rock layers to date fossils on the grounds of circular reasoning.