Department of Geology

Georgia Perimeter College, Dunwoody Campus

Biostratigraphy, using the principle of faunal succession, is able to determine the age of specific assemblages of fossils by use of overlapping time ranges. The geological ranges are given for each of the genera listed for the various assemblages.

This lab exercise has 18 assemblages listed. You will only be completing the work for four (4) assemblages. You will be told which assemblages you will complete when you come to lab.

The fossil genera in these assemblages are listed in A Golden Guide to Fossils.

Complete these procedures (1-7) for each of the assemblages you are assigned to do.

1. Write out the taxonomy and geologic range for each of the genera listed for each of the assemblages. You will list the various heirarchy catagories that you learned for the various fossil groups. Do this by looking up each fossil genus in the Golden Guide to Fossils and find out its geologic range. Determine its taxonomy by reading the description of the genus and looking at the picture. For those genera that have the same taxonomy, all you have to do is list the various genera under the same hierarchy. (see example below)

   Example:

   Kingdom: Protoctista
   Phylum: Sarcodina
   Order: Foraminifera
   Genus: Triloculina, Geologic Range: Jurassic - Recent
   Genus: Uvigerina, Geologic Range: Eocene - Recent

   Note that for other genera, you may also be listing subphyla, classes, subclasses, and other taxonomic units.

2. Write the names of each of the genera in the biostratigraphic chart if you are using the blank charts. (The names have been completed for you if you printed out each individual assemblage charts).

3. Plot the range of each genus in the biostratigraphic chart.

   To plot the ranges, draw a line through the boxes (or shade in the boxes) that represent the geologic periods in which it lived.

   For some of the ranges, you will see Lower, Middle, or Upper before the period name (example: Lower Devonian). If so, note that the box on the chart for that period is divided into thirds. The bottom third represents Lower. The middle third represents Middle. The top third represents Upper. (See example below.)

   Devonian	Upper (Late)
   	Middle
   	Lower(Early)

   For the Paleogene, the box is divided vertically into three sections. They correspond to:

   Paleogene	Oligocene
   	Eocene
   	Paleocene

   For the Neogene, the box is divided vertically into four sections. They correspond to:

   Neogene	Holocene (Recent)
   	Pleistocene
   	Pliocene
   	Miocene

   Determine the age of each assemblage by plotting the ranges of each of the genera on the time charts. Find the time period(s) where all of the ranges overlap one another. This is the time at which all of them were alive simultaneously. In other words, to determine the age, you will want to find the smallest amount of time that all of the genera are found.

   Write the age of the assemblage at the top of the biostratigraphic chart.

   Place an astrict or star (*) by the one or two genera that are the best index fossils for the assemblage.
   In other words, note the one or two fossils that BEST serve to narrow down the range of the fossil assemblage and indicate the age of the assemblage as a whole (i.e., the time when they all coexisted). (For example, you may have one fossil whose range is ONLY Middle Silurian. That would be the best index fossil in that particular assemblage. Using only THAT fossil, you could pinpoint the age.) In some assemblages there are more than two genera that would best give the age of the assemblage.

   Answer any questions that may accompany the assemblage list.