Oldest
_______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ Youngest Determining Absolute Ages by Radiometric Dating
You can only use radioactive dating on igneous rock (exception: 14
C dating which can be used on formerly living material, but this has a short time range). This is because radioactive dating determines how long ago that mineral was formed. It tells you when the volcanic
rock formed. In particular, it tells you when the crystals within the volcanic rock formed, but this is about the same as the age of the whole volcanic rock itself. You cannot use this method for dating sediments or sedimentary rock directly because sediments are derived from a wide range of source rocks, each of which has a different age. So one part of the sedimentary rock might yield a radioactive age of 3 billion years, another part gives 2 million years, and yet another gives 100,000 years. To determine the ages of sedimentary rocks (and hence of the fossils within them), you need to find volcanic rocks just above and/or below the sedimentary rocks of interest. 1.
List the relative ages of the geological features labeled on the diagram above: Oldest
_______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ Youngest
3. Consult the diagram above. If the Zoroaster Granite (a kind of volcanic rock) were dated and found to be 2 billion years old and the igneous sill F were dated at 1.5 billion years old, what could you say about the absolute ages of the following:
