Chapter 3
Geologic Time
Chapter Outline:
I.
Stratigraphic Correlation Techniques
a. Lithostratigraphy
b. Biostratigraphy
c. Chemostratigraphy
d. Sequence Stratigraphy
e. Other Correlation Techniques
II.
The Geologic Time Scale
a. Chronostratigraphy
Key Terms:
Relative Age Dating
Numerical Age Dating
Stratigraphy
Correlation
Lithostratigraphy
Formation
Biostratigraphy
Biozone (or Zone)
Chemostratigraphy
Isotopic Excursions
Sequence Stratigraphy
Unconformities
Disconformities
Eustatic
The Geologic Time Scale
GSSP (Global Boundary Stratotype Section and Point)
Chronostratigraphic Units
System Period
Parent Isotope
Daughter Isotope
In-Class Activities:
Instructor Notes for In-Class Activity 1
Title:
Unconformities: Pages torn out of the book of geologic time.
Time:
5-10 minutes prep; 40 – 50 minutes in class (or can assign research between class periods)
Materials:
Internet required. Print instruction sheets as handouts.
Handouts:
Instruction sheet including questions to be answered and relevant websites.
http://www.uwsp.edu/geo/faculty/hefferan/geol106/class2/unconformities.htm
http://www.cliffsnotes.com/WileyCDA/CliffsReviewTopic/Unconformities.topicArticleId9605,articleId-9497.html
http://comp.uark.edu/~sboss/siccar.jpg
http://www.uh.edu/~jbutler/physical/grandcanyon.gif
http://web.uct.ac.za/depts/geolsci/geoteach/images/Resources/botha3.jpg
Procedures:
Have students review the section “Sequence Stratigraphy” in the textbook. Students will
find the answers to the following questions by using the textbook and the following
websites as references.
http://www.uwsp.edu/geo/faculty/hefferan/geol106/class2/unconformities.htm
http://www.cliffsnotes.com/WileyCDA/CliffsReviewTopic/Unconformities.topicArticleId9605,articleId-9497.html
Have the students, in groups of 3-4, carefully examine the photo in
http://comp.uark.edu/~sboss/siccar.jpg All of the rocks shown in this photo are
sedimentary rocks.
1) What type of unconformity is the person in the photo pointing to?
2) Describe the sequence of events that must have occurred to produce the rocks
shown in this photo.
Next have the students examine the diagram in
http://www.uh.edu/~jbutler/physical/grandcanyon.gif
3) What types of unconformities are represented in the diagram?
4) Which of the five unconformities shown in the diagram is the oldest? Which of the
principles of relative dating allowed for you to obtain your answer?
5) Is the granite or the schist older, how do you know this?
Lastly have the students examine the following photograph
http://web.uct.ac.za/depts/geolsci/geoteach/images/Resources/botha3.jpg
Make sure that they are aware that the lower whiter rock is an igneous rock called diorite,
and that the brownish rocks on the top are horizontal sedimentary layers.
6) What type of unconformity is shown in this photography?
7) Describe the sequence of events that led to the formation of the rocks shown in this
photo.
After answering these questions, students should discuss the geological significance of
unconformities, and review the methodology for differentiating between nonconformities,
angular unconformities, and disconformities.
Student
Instructions: See above.
Specific
Suggestions:
Objectives:
Sometime later in the semester the instructor should show the students actual examples of
unconformities in the field.
Students should be able to:
Evaluate the geologic significance of unconformities.
Recognize the processes that would result in the formation of unconformities.
Differentiate between the three kinds of unconformities.
In-Class Activity 1: Handout
The purpose of this exercise is for your group (3-4 students) to discuss and understand the importance of
Unconformities in the rock record. Upon completing this exercise you should be able to determine the
Sequence of geologic events that leads to the formation of unconformities. You should be able to
Differentiate between the three types of unconformities; nonconformities, disconformities, and angular
Unconformities.
The sequence stratigraphy section of your textbook will serve as a useful reference in answering the following
questions. Also, the following websites are also useful references.
http://www.uwsp.edu/geo/faculty/hefferan/geol106/class2/unconformities.htm
http://www.cliffsnotes.com/WileyCDA/CliffsReviewTopic/Unconformities.topicArticleId-9605,articleId-9497.html
First, carefully examine the photo in http://comp.uark.edu/~sboss/siccar.jpg All of the rocks shown in this
photo are sedimentary rocks.
1) What type of unconformity is the person in the photo pointing to?
2) Describe the sequence of events that must have occurred to produce the rocks shown in this photo.
Next, carefully examine the diagram in http://www.uh.edu/~jbutler/physical/grandcanyon.gif
3) What types of unconformities are represents in the diagram?
4) Which of the five unconformities shown in the diagram is the oldest? Which of the principles of
relative dating allowed for you to obtain your answer?
5) Is the granite or the schist older, how do you know this?
Lastly, examine the following photograph:
http://web.uct.ac.za/depts/geolsci/geoteach/images/Resources/botha3.jpg
Note that the lower whiter rock is an igneous rock called diorite, and that the brownish rocks on the top are
horizontal sedimentary layers.
6) What type of unconformity is shown in this photography?
7) Describe the sequence of events that led to the formation of the rocks shown in this photo.
Neatly write your answers to these questions on notebook paper, submit these answers for your group.
These answers will be graded and handed back to you next week.
If time remains, students should discuss the geological significance of unconformities, and review the
methodology for differentiating between nonconformities, angular unconformities, and disconformities.
An understanding of these concepts will help you prepare for the next quiz and exam.
Instructor Notes for In-Class Activity 2
Title:
Absolute Dating: Finding out how long ago geologic events occurred.
Time:
5 – 10 Minutes prep; 40 – 60 minutes in class (or can assign research between class
periods)
Internet required. Print instruction sheets as handouts.
Materials:
Handouts:
Procedures:
A list of websites and questions to be answered. Students will find the following
websites particularly useful:
http://facweb.bhc.edu/academics/science/harwoodr/Geol101/Labs/radiometric/index.
htm
http://www.cartage.org.lb/en/themes/sciences/chemistry/NuclearChemistry/NuclearR
eactions/Radiometricdating/RadiometricDating%20.html
http://facstaff.gpc.edu/~pgore/geology/geo102/radio.htm
Hand out instruction sheets. Instruct the students use the “Geochronology” section in
Ch. 3 as a reference. In addition they can use the above three listed websites as
additional references. Have students work in groups of 3-4.
Ask students to go to
http://facstaff.gpc.edu/~pgore/geology/geo102/radiometric_dating_assignment.html
And print out the questions for this in class activity.
Using the references, the students should discuss the answers to the questions in the
print out, and write down their answers.
After all of the answers are completed, students should discuss the significance of
the term “half life”. The students should also discuss why Carbon-14 dating is not
useful in dating geologic events that occurred millions of years ago. The instructor
should emphasize that by having this discussion, students will be prepared for some
future quiz.
Tell the students that the lab will be graded, and that there will be a future quiz to test
the student’s knowledge of absolute dating.
Student
Instructions: See above
Specific
Suggestions:
Objectives:
The instructor will need to periodically check in on each group and ask specific
questions to check on their knowledge of the principles of absolute dating. If the
students are confused about a particular absolute dating problem, the instructor
should refer them to pages 81-82 of the textbook. The instructor should emphasize
the importance of understanding the definition of a “half-life”, and should ask the
students to think about why Carbon-14 dating is not useful for dating rocks millions
of years old in age. The instructor should not directly provide answers to the
questions, but should help guide the students to learning about the principles of
relative dating.
Students should be able to:
Apply and understand the definition of the term “half-life”
Understand the basics of how radiometric dating works.
Understand why geologists do not use Carbon-14 dating to determine the age of
rocks millions or billions of years old in age.
In-Class Activity 2: Handout
In the latter part of the 19th century Madame Curie place a rock with radioactive isotopes near some
photographic film in her desk. In the morning her husband Monsieur Pierre Curie discovered that the
film was developed. Both Madame and Monsieur determined that some invisible energy source must
have been emitted from the rock, they called this energy “radioactivity”. In 1905, Earnest Rutherford
reasoned that radioactive decay can be used to determine the absolute age of rocks. Today, we want
to gain a basic understanding of how radiometric (or absolute) dating works. In order to do this we
will need to understand the concept of “half-life”. By the end of this rock, you should also
understand why geologists do not use Carbon-14 radioactive dating to determine the age of rocks
millions or billions of years old in age.
First, go to http://facstaff.gpc.edu/~pgore/geology/geo102/radiometric_dating_assignment.html
Print out this page. During this exercise your group will answer the questions on this print out.
Use the “Geochronology” section of Ch. 3 in your textbook as a reference. Also, the following
Websites are also useful references
http://facweb.bhc.edu/academics/science/harwoodr/Geol101/Labs/radiometric/index.htm
http://www.cartage.org.lb/en/themes/sciences/chemistry/NuclearChemistry/NuclearReactions/Radiometricdating/RadiometricDating%20.html
http://facstaff.gpc.edu/~pgore/geology/geo102/radio.htm
Answer, the questions. After, completing the answers, hand them in to your instructor for grading.
Only one print out with the answers is needed for your group. If time remains, discuss as a group the
definition of the term “half-life”. Also, discuss the reason why geologists do not use Carbon-14 dating to
determine the age of rocks in millions or billions of years old in age. This will help you prepare for a
future quiz and test.