Scientific dating techniques
The scholar most associated with the rules of stratigraphy (or law of superposition) is probably the geologist Charles Lyell.
The basis for stratigraphy seems quite intuitive today, but its applications were no less than earth-shattering to archaeological theory.
Sometimes, scientists already know the age of the fossil because fossils of the same species have been found elsewhere and it has been possible to establish accurately from those when the dinosaur lived.
Geologists call this the principle of lateral continuity.
By measuring the ratio of the radio isotope to non-radioactive carbon, the amount of carbon-14 decay can be worked out, thereby giving an age for the specimen in question.
But that assumes that the amount of carbon-14 in the atmosphere was constant — any variation would speed up or slow down the clock.
The second method is called absolute dating and is done by analysing the amount of radioactive decay in the minerals of the rocks.
But even he “realized that there probably would be variation”, says Christopher Bronk Ramsey, a geochronologist at the University of Oxford, UK, who led the latest work, published today in Science.This is because new sediments are always laid down on top of sediments that have already been deposited.So, when looking at the history of a cliff face, it is important to read the story it tells from the bottom layer up. Climate records from a Japanese lake are set to improve the accuracy of the dating technique, which could help to shed light on archaeological mysteries such as why Neanderthals became extinct.Carbon dating is used to work out the age of organic material — in effect, any living thing.
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Various geologic, atmospheric and solar processes can influence atmospheric carbon-14 levels.