How are fossils found

Methods of age determination

stratigraphy

Not only the location with its geological features is decisive, the location of the find within a certain rock layer is also important in order to determine the age precisely. Experts can also use the sequence of the rock layers to determine their age.

The age of the fossil always corresponds to the age of the bedding rock layer. However, counterfeiters who take advantage of this approach also know this. Replicated alleged relics are actually always embedded in the old original rock in order to give a real impression.

Index fossils

Another feature for determining the age of the fossils are so-called index fossils. Guide fossils can be embedded in the rock near interesting finds and thus allow a chronological classification.

Index fossils include both animals and plants that can be safely assigned to a certain age. Key fossils are, for example, so-called ammonites, cephalopods with a snail shell that lived for a period of 350 million years and became extinct in the Cretaceous period.

Magnetic field and radiometric age determination

The earth's magnetic field and the radioactive decay of isotopes also help to determine the age of fossils, especially in the case of very old finds. Since the earth's magnetic field reverses its polarity over and over again, the alignment of ferrous minerals in the rock can provide information about its age. In addition, all rock formations consist of a combination of chemical elements.

These can exist in different isotopes, which decay in a precisely defined time. With the radiometric age determination, the experts can measure the amount of radioactive isotopes still present and thus infer the age of the find.

Slowly decaying isotopes allow the age of very old finds to be determined. Rapidly decaying isotopes, on the other hand, are used to date finds that are less than 100,000 years old.