Fossil succession relative dating
When geologists study layers of rocks, they get a glimpse of the past.Determining the precise way that sedimentary rocks have layered throughout time gives them insight into how natural events have occurred.These periods were based on the fossil record, much of it documented by Smith.“The Geologic Timescale is the Principle of Fossil Succession at its best,” says Jaelyn Eberle.Curator of vertebrate paleontology and assistant professor of geology at the University of Colorado-Boulder, Eberle teaches her students about how the divisions within the geologic timescale are all based on fossil turnovers in the rock record—periods when species of plants and animals went extinct or originated.As an example of how they are used, radiometric dates from geologically simple, fossiliferous Cretaceous rocks in western North America are compared to the geological time scale.To get to that point, there is also a historical discussion and description of non-radiometric dating methods.Geochronologists do not claim that radiometric dating is foolproof (no scientific method is), but it does work reliably for most samples.
Relative dating not only determines which layers are older or younger, but also gives insight into the paleoenvironments that formed the particular sequence of rock.
Though radiometric dating offers a modern way to date rocks, the principles of stratigraphy remain a tried and true way to learn about rock layers.
Stratigraphy, or the scientific study of rock layers, includes relative dating.
The example used here contrasts sharply with the way conventional scientific dating methods are characterized by some critics (for example, refer to discussion in "Common Creationist Criticisms of Mainstream Dating Methods" in the Age of the Earth FAQ and Isochron Dating FAQ).
A common form of criticism is to cite geologically complicated situations where the application of radiometric dating is very challenging.
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Before radiometric dating enabled geologists to apply absolute dates to rocks, she explains, dating rock layers relative to each other based on their fossils was the best method available.