Chemical dating techniques
Several dating methods exist, depending on different criteria and techniques, and some very well known examples of disciplines using such techniques are, for example, history, archaeology, geology, paleontology, astronomy and even forensic science, since in the latter it is sometimes necessary to investigate the moment in the past in which the death of a cadaver occurred.Relative dating methods are unable to determine the absolute age of an object or event, but can determine the impossibility of a particular event happening before or after another event of which the absolute date is well known.Absolute dating provides a numerical age or range in contrast with relative dating which places events in order without any measure of the age between events.In archaeology, absolute dating is usually based on the physical, chemical, and life properties of the materials of artifacts, buildings, or other items that have been modified by humans and by historical associations with materials with known dates (coins and written history).Historians, for example, know that Shakespeare's play Henry V was not written before 1587 because Shakespeare's primary source for writing his play was the second edition of Raphael Holinshed's Chronicles, not published until 1587.Thus, 1587 is the post quem dating of Shakespeare's play Henry V.Different methods have their own limitations, especially with regard to the age range they can measure and the substances they can date.A common problem with any dating method is that a sample may be contaminated with older or younger material and give a false age.
Particular isotopes are suitable for different applications due to the type of atoms present in the mineral or other material and its approximate age.
For example, techniques based on isotopes with half lives in the thousands of years, such as Carbon-14, cannot be used to date materials that have ages on the order of billions of years, as the detectable amounts of the radioactive atoms and their decayed daughter isotopes will be too small to measure within the uncertainty of the instruments.
One of the most widely used and well-known absolute dating techniques is carbon-14 (or radiocarbon) dating, which is used to date organic remains.
This problem is now reduced by the careful collection of samples, rigorous crosschecking and the use of newer techniques that can date minute samples.
Volcanic rocks – such as tuff and basalt – can be used in dating because they are formed at a particular moment in time, during an eruption.