One of the most frequent questions a Palaeobotanist or Palaeontologist hears concerns the method for dating sediments containing fossil plants and animals. Present knowledge is based on a long series of efforts to date the ages of various rocks. At the present time, the best absolute dating involves the use of naturally occurring radioactive isotopes contained in various minerals that make up a rock. It was demonstrated that there are radioactive isotopes of certain elements that decay at a constant rate irrespective of heat, pressure and any other factor in the environment. Radioactive isotopes like U , U , Thorium , K 40 , C 14 have been used in making ace determination. U and Th are found most frequently in an igneous rock while K 40 and C 14 are components of some sedimentary rocks.
Carbon dating is used to determine the age of biological artifacts up to 50, years old. This technique is widely used on recent artifacts, but educators and students alike should note that this technique will not work on older fossils like those of the dinosaurs alleged to be millions of years old. This technique is not restricted to bones; it can also be used on cloth, wood and plant fibers. Carbon dating has been used successfully on the Dead Sea Scrolls, Minoan ruins and tombs of the pharaohs among other things. Carbon is a radioactive isotope of carbon.
Assumptions of Radiometric Dating
As we learned in the previous lesson, index fossils and superposition are effective methods of determining the relative age of objects. In other words, you can use superposition to tell you that one rock layer is older than another. To accomplish this, scientists use a variety of evidence, from tree rings to the amounts of radioactive materials in a rock.
Asked by Wiki User. Sedimentary rock is composed of the weathered remains of a variety of rocks of all ages. It would therefore only be possible to date specific components of a sample, none of which would equate to the age of the sedimentary rock as a unit.