Speleothems dating method

speleothems dating method

How are speleothems dated?

Speleothems, despite their uniform mineralogy (calcite, less commonly aragonite), occur in a great variety of forms, dimensions, and colors, and any of these can be dated by U-series methods provided their age is within the dating limit of the particular method.

How old are speleothems in caves?

Entering a cave decorated with various sorts of speleothems commonly prompts questions about the age of these formations. It is intuitive to suggest that tall stalagmites or thick flowstone took a long time to form, but until the middle of the 20th century no method existed which allowed the quantitative determination of how old speleothems are.

Why sample broken speleothems from a cave?

Many dripstone caves contain abundant broken speleothems, locally reworked by a cave stream. Sampling such fragments is clearly easier to justify than removing in situ stalagmites and still provides valuable insights into the history of a cave or the regional paleoclimate.

What is the uranium-thorium dating method?

The dating method of choice for speleothems, known as the uranium-thorium (U-Th), or 230 Th method, belongs to the family of uranium-series methods and was first applied to speleothems in the early 1970s, although its physical principles were known since the beginning of the 20th century.

What are the prerequisites for the dating of speleothems?

As with any dating method a fundamental prerequisite is the lack of post-depositional alteration, that is, no gain or loss of isotopes within the decay chain of interest. Using state-of-the-art instrumentation this method allows dating speleothems between essentially zero and ca. 600,000 years before present.

How do scientists date the layers of a speleothem?

Scientists can date the layers in the speleothem by measuring how much uranium, a radioactive element, has decayed. Uranium from the surrounding bedrock seeps into the water and forms a carbonate that becomes part of each layer of the speleothem as it forms.

What do 14 C dates of speleothems mean?

In short, 14 C dates of speleothems provide only a rough estimate of their formation age and samples older than ca. 50,000 years cannot be dated using this method.

How old are speleothems in caves?

Entering a cave decorated with various sorts of speleothems commonly prompts questions about the age of these formations. It is intuitive to suggest that tall stalagmites or thick flowstone took a long time to form, but until the middle of the 20th century no method existed which allowed the quantitative determination of how old speleothems are.

What is uranium dating and how does it work?

Uranium dating is the oldest method of isotopic dating in which we can determine the age of organic materials using the radioactive chemical element Uranium. There are three different types of this technique: Uranium-Uranium method, Uranium-Thorium method and Uranium-Lead method.

What is uranium/thorium dating?

The method is used for samples that can retain Uranium and Thorium, such as carbonate sediments, bones and teeth. Ages between 1000 and 300,000 years have been reported. Augustinus, P.C., Short, S.A. and Heijnis, H. 1997. Uranium/Thorium dating of ferricretes from mid- to late Pleistocene glacial sediments, western Tasmania, Australia.

What is a uranium and thorium sample?

The method is used for samples that can retain Uranium and Thorium, such as carbonate sediments, bones and teeth. Ages between 1000 and 300,000 years have been reported.

What is the half life of carbon-14 in uranium dating?

For carbon-14, the half-life is about 5730 years. This technique is very important in forensic investigations, in determining the age of fossils, etc. What is Uranium Dating? Uranium dating is the oldest method of isotopic dating in which we can determine the age of organic materials using the radioactive chemical element Uranium.

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