Absolute dating techniques listed
Originally fossils only provided us with relative ages because, although early paleontologists understood biological succession, they did not know the absolute ages of the different organisms.It was only in the early part of the 20th century, when isotopic dating methods were first applied, that it became possible to discover the absolute ages of the rocks containing fossils.
Isotopic dating of rocks, or the minerals in them, is based on the fact that we know the decay rates of certain unstable isotopes of elements and that these rates have been constant over geological time.
Once these age relations were worked out, another principle fell into place - the principle of fossil succession.
We discuss the 7 principles of stratigraphy first and then see how these apply to fossils.
Principle of Uniformitarianism The principle of Uniformitarianism was postulated by James Hutton (1726-1797) who examined rocks in Scotland and noted that features like mudcracks, ripple marks, graded bedding, etc.
where the same features that could be seen forming in modern environments.
One good example is granite, which normally has some potassium feldspar (Figure 8.15).