Download Lab #32: Using Fossils to Determine Relative and Absolute Ages

Lab #32: Using Fossils to Determine Relative and Absolute Ages
Objective: 1. Interpret the history and determine the ages of the rock
illustrated.
Background: Geologic time is divided into units, based on the presence or
absence of certain forms of life. Before the record of past life began to
appear in the rocks, many billions of years had passed. With the beginning
of the Paleozoic Era, hard parts of animals began to be preserved in
certain rocks. Abundant Paleozoic fossils have allowed geologists to
construct a far more detailed time scale for this era compared to the
previous era, the Precambrian. Every organism is associated with a
particular environment, so the fossil record provides invaluable information
for the learning of ancient environments. Some of our record is based on
plants although they are not preserved as often as animal hard parts such
as shells, teeth, or even skeletons.
Prelab Questions:
1. Write the four eras of Earth”s history in order from oldest to
youngest.
2. When did the Paleozoic era begin? When did it end?
3. What are the three “ages” of the Paleozoic Era?
Procedure
1. Set up a legend and color code for the block diagram illustration. Record
the legend in Data Table 54-1.
3. Cut out, fold and tape the diagram to form a geologic map and four
cross sections.
4. Be sure to paste your block diagram into your lab notebook.
Data and Observations
Color
Rock Layers
Layer A
Layer B
Layer C
Layer D
Questions and Conclusions
1. During what period did the dike intrude into the rock sequence?
2. What is the probable age of the oldest layer shown? Explain.
3. What is the probable age of the youngest layers shown? Explain.
4. Is the dike older or younger than Layer E? How can you tell?
5. Write a summary of the geologic history of this area. Name the periods
of geologic time involved.