Learning Experience 2

Stratigraphy and evolution: Using fossils to tell “deep time” Participants/students will learn about the earliest concepts of telling time in rocks using fossils: relative age dating using the various flora and fauna present. This allows for the construction of a relative geologic time scale, namely, one that is not tied to absolute ages. An exploration of Lyell’s early application of relative age dating and his influence on Darwin’s theory of evolution as developed on the Beagle will be included. The concept of “deep time” will be explored through the fossil record of the earliest forms of life.

Time Frame - 1 hour

Materials

• Cards representing various fossil assemblages from a stratigraphic section

Procedure

1. Presenter/teacher will discuss the historical development of relative age dating using fossils by William Smith and Charles Lyell and how Lyell's book on the Principles of Geology influenced Darwin's thinking during his voyage on the Beagle.
2. Participants/students will be given cards representing faunal fossil assemblages from various stratigraphic sections.  Starting with the information that sample J represents the youngest sample (i.e., from the top of the composite stratigraphic section), teachers will arrange the cards in order from the oldest sample at the base and the youngest sample at the top.
3. Presenter will introduce the fossil record in general and discuss some of the earliest fossilized assemblages of organisms.
4. Teachers will have a visual field trip to one of the most spectacular outcrops showing the earliest fossils: The Burgess Shale in Canada.

Formative Assessment

The presenter/teacher may ask the following questions while participants/students are doing this exercise:

1. What type of relative dating technique (i.e., what theories or hypotheses were invoked) was used to formulate this composite section? 
2. Is there only one solution to the arrangement?
3. What could have happened if you were not given the information that sample J was the youngest sample?
4. If you did not know which sample was the youngest, i.e., you didn't know if the stratigraphic section you were sampling was overturned or not, how could you use information from the outcrop to determine the correct sequence of the stratigraphic section?

Presenter/teacher may give a solution set to the stratigraphic order of the various sections studied by the teachers. The presenter will also check that all the participants/students have their sections in the proper stratigraphic order.