Relative Age Dating Using Fossils
Now that you have looked at 'relative' age dating using a family tree, you will next look at a similar set of data using fossils retrieved from Ocean Drilling Program (ODP) cores of sediment from the Marion Plateau, part of the Great Barrier Reef of Australia. You will analyze a range chart and find the important fossil events used in this part of the geologic section to determine the age of the cores. Using a variety of reference material, you will assign ages to these fossil events. Finally, you will examine the stratigraphy of the cores to look for discontinuities and other features by constructing an age-depth plot of the data.
Just as the 'government' recorded the yearly existence
of each member of your family, marine sediments record the existence of
species through time. The analogy is that a single species of fossil has
a range of existence through geologic time just like an individual has
a range of existence through a shorter period of time. Reconstructing
the actual evolutionary ranges of different fossil species through time
and comparing them to each other is like comparing the life ranges of
the relatives in your family tree. Once you know their age ranges relative
to each other, you can put relative age dates on records (either government
files, or in the case of fossils, sediment cores), arrange them in order
of oldest to youngest, and determine if there is any missing time (in
either the government records or the sediment cores).
