Last ated: July 1, References. This article was co-authored by our trained team of editors and researchers who validated it for accuracy and comprehensiveness. This article has been viewed 5, times. Learn more Dating fossils is an interesting and enlightening process.
Learn more Dating fossils is an interesting and enlightening process.
It is a technical process that is usually undertaken by experts. The relative dating method allows you to discover whether a fossil is older or younger than another fossil or rock and the absolute dating method uses chemical testing to estimate the age of the fossils. Please help us continue to provide you with our trusted how-to guides and videos for free by whitelisting wikiHow on your ad blocker.
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Method 1 of All rights reserved. This image may not be used by other entities without the express written consent of wikiHow, Inc. Use the carbon dating method if the fossil is less than 75, years old. This method only works on young fossils as carbon decays quicker than other minerals.
FOSSILS: how fossils are dated
If no traces of carbon are found in a fossil, this indicates that it is older thanyears. Use an accelerator mass spectrometer to measure the amount of carbon in the fossil. Fossils need to be clean in order for carbon dating to be accurate.
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Apply the fission tracking method. Uranium is found in many different rocks and fossils.
The uranium content can cause fissures in the fossil surface. The greater the number of fissures in a rock, the older the fossil is likely to be.
Measure the amount of argon in the surrounding rocks. Volcanic rocks can be dated by measuring the amount of argon in them. Each time a volcano erupts a new layer of ash and rock is deposited. Fossils are found in between these layers and thus can be estimated to be a similar age to the rocks that they around. Test the amount of argon using a thermal ionization mass spectrometer.
Analyze the amino acid racemization. The extent of amino racemization in a fossils can be used estimate its age. The older a fossil is, the more that the amino acids will have racemized.
Heat fragments of the fossils in water and then hydrolyze the fragments in 6M hydrochloric acid. For example if you have a fossil trilobite and it was found in the Wheeler Formation.
Jun 12, Another common method, uranium-lead dating, relies on the radioactive decay of uranium and can be used to date rocks containing the oldest known fossils .
The Wheeler Formation has been previously dated to approximately million year old, so we know the trilobite is also about million years old.
Scientists can use certain types of fossils referred to as index fossils to assist in relative dating via correlation. Index fossils are fossils that are known to only occur within a very specific age range.
Typically commonly occurring fossils that had a widespread geographic distribution such as brachiopods, trilobites, and ammonites work best as index fossils. If the fossil you are trying to date occurs alongside one of these index fossils, then the fossil you are dating must fall into the age range of the index fossil. Sometimes multiple index fossils can be used.
Unlike relative dating methods, absolute dating methods provide chronological estimates of the age of certain geological materials associated with fossils, and even direct age measurements of the. Absolute dating is used to determine a precise age of a fossil by using radiometric dating to measure the decay of isotopes, either within the fossil or more often the rocks associated with it. Relative Dating The majority of the time fossils are dated using relative dating techniques. Using relative dating the fossil is compared to something. Sep 14, Use the carbon dating method if the fossil is less than 75, years old. This method only works on young fossils as carbon decays quicker than other minerals. If no traces of carbon are found in a fossil, this indicates that it is older than , years%(8).
In a hypothetical example, a rock formation contains fossils of a type of brachiopod known to occur between and million years. The same rock formation also contains a type of trilobite that was known to live to million years ago. Since the rock formation contains both types of fossils the ago of the rock formation must be in the overlapping date range of to million years. Studying the layers of rock or strata can also be useful. Layers of rock are deposited sequentially.
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If a layer of rock containing the fossil is higher up in the sequence that another layer, you know that layer must be younger in age. This can often be complicated by the fact that geological forces can cause faulting and tilting of rocks. Absolute Dating Absolute dating is used to determine a precise age of a rock or fossil through radiometric dating methods. This uses radioactive minerals that occur in rocks and fossils almost like a geological clock.
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So, often layers of volcanic rocks above and below the layers containing fossils can be dated to provide a date range for the fossil containing rocks. The atoms in some chemical elements have different forms, called isotopes.
These isotopes break down at a constant rate over time through radioactive decay. By measuring the ratio of the amount of the original parent isotope to the amount of the daughter isotopes that it breaks down into an age can be determined. We define the rate of this radioactive decay in half-lives. If a radioactive isotope is said to have a half-life of 5, years that means after 5, years exactly half of it will have decayed from the parent isotope into the daughter isotopes.
Then after another 5, years half of the remaining parent isotope will have decayed. While people are most familiar with carbon dating, carbon dating is rarely applicable to fossils.
Best method for dating fossils
Carbon, the radioactive isotope of carbon used in carbon dating has a half-life of years, so it decays too fast. It can only be used to date fossils younger than about 75, years.
Potassium on the other hand has a half like of 1.