Michigan Rocks



Learning Goals

Instructional Sequence



Michigan Fossils

 Lesson Number: 6

Main Ideas & Objectives:
MI-5 – Fossils are a record of the existence of past life (plants and animals) that once lived on the earth. Fossils are different ages.
MI-6 - Fossils are used to determine the relative age of rock and understand the history of the earth.
MI-7 – The geologic history of Michigan can be told in part by the fossil evidence found in sedimentary rocks.

O-6– Use fossiliferous outcrop data to locate areas of similar geologic age in Michigan.
O-7– Use fossils to identify the age of rocks.
O-8– Use information from the MI Fossil Poster and the Fossiliferous Outcrops of Michigan Map to identify fossils sieved from earth material and determine possible locations for where the Earth material might have been excavated.

Grade Levels:
Grades 4-8. Students in lower grades (4,5) will need additional support for activity 6.3 . Activities 6.1, 6.2, and 6.4 could be used in grade 3.

Lesson Purpose:
In this lesson, students use the geologic time line containing the fossiliferous outcrops found in Michigan (recorded by geologic age) to find a pattern of sedimentary rock ages in the Lower Peninsula and eastern portion of the Upper Peninsula. Students will sieve fossil-laden earth material collected in Michigan, identify the fossils in this sedimentary rock, use information provided from the MI Fossil Poster to learn about the age of the fossils and apply the technique of relative age dating of rock using fossil evidence. This lesson is an inquiry lesson that involves students in the application of geologic data that is used to map the location of similar age rock strata, recognize the pattern of sedimentary rock in Michigan and apply relative age dating of earth material using fossil evidence.

 Activity Description:

6.1 -Michigan Fossils – Teacher leads a whole-class discussion about fossils. Students share fossil-finding stories in small groups.

6.2 - Fossiliferous outcrops in Michigan - Teacher leads a whole-class introduction to the map of Michigan counties and the Fossiliferous Outcrop Geologic Timeline.

6.3 - Color County Map of Michigan - Using the information on the Fossiliferous Outcrop Geologic Timeline, students color the counties on a Michigan map that have outcrops of similar aged fossils. Students look for patterns of similar aged fossil-laden rock in Michigan .

6.4 - Students sieve the Michigan Earth materials containing fossils and separate the fossils from the rock.

6.5 - Referencing their Michigan Fossil Chart, students will suggest areas in Michigan where the Earth material may have been extracted. They will also clean, identify the specimen and “card” their fossil, recording information about that specimen on the fossil card provided.

Background Information:

Fossils are the remains or traces of once living things, both plants and animals, that are preserved from the geologic past. Fossils can be found in rocks, glacial ice, ancient tar pits and amber. Fossils are formed in several ways; Fossils can be the actual preservation of an animal, the preservation of the shape of the organism (a mold or cast of the organism) or trace fossils (indications that an organism was once on Earth) such as dinosaur tracks, trails left by animals, burrows of animals or coprolites (fossilized feces of animals). Each organism is evidence of the life that existed during that geologic time period. Only a small fraction of past life has been preserved as fossils. To become a fossil, organisms must be buried by sediment before they are eaten or body tissues decompose. Body parts of organisms that are hard (shells, bones, and teeth) are more likely to become a fossil in the rock record.

Fossils are used to help determine the relative age of Earth materials. The type of fossil found in rock helps determine how old that rock layer is compared to other rock layers. To match rocks of the same age, geologists rely on index fossils. These fossils are found in many places, but are found only in rocks deposited during a short span of geologic time. The presence of these fossils in sedimentary rocks provides a method of matching rocks of the same age. Fossils can be used to determine the age of sedimentary rock layers by correlating the age of the fossil to the age of the rock.

Rock layers can be found on the surface of the Earth. These exposures are called outcrops. If the outcrops contain fossils, these areas are called fossiliferous outcrops. Geologists learn a great deal about the physical environment of a past geologic time by studying the organisms found in these outcrops. Fossils provide evidence of ancient environments, they show that living organisms have changed over geologic time and they are used to correlate rocks in one location to those in another.

Materials Needed:

Optional Resources

 Detailed Procedure:

 Activity 6.1 Michigan Fossils

  1. Lead a whole class discussion about fossils. Questions to ask include
    • What is a fossil? Evidence of past life preserved in a rock
    • Are fossils found in Michigan ? Yes. Michigan even has a state fossil of a coral called Hexagonaria (Petosky stone).
    • What evidence do you have that fossils are present in Michigan ? Student answers may vary. One big piece of evidence is the presence of Petosky stones, which are really fossilized coral.
  2. Have a student recorder take class notes.
  3. In small group (2-3 students), have students exchange stories about their experiences finding fossils. Students should include details about the types of fossils they found and where they found the fossils.

Activity 6.2 Fossiliferous outcrops in Michigan

  1. Lead a whole class discussion of fossiliferous outcrops. Questions to ask include
  2. What is a fossiliferous outcrop? Bedrock that contains fossils exposed at the surface of the Earth.
  3. What would an outcrop look like? Student answers will vary. Usually, outcrops look like cliffs or large areas of the ground covered by one large rock.
  4. Did you find your fossil in an outcrop?
  5. Distribute the Fossiliferous Outcrop in Michigan Geologic Time Line and explain it using the overhead. Features to point out include:
    • Divisions of Michigan into counties.
    • Counties in Michigan with fossiliferous outcrops correlated with certain geologic ages (this data indicates the age of the outcrop material).
    • Review Geologic Time if necessary
Eon Era Period Epoch

Date mya (Millions of Years Ago)

Counties with Fossiliferous Outcrops of this Age
Phanerozoic Cenozoic Quaternary Holocene 0-0.1 No Known Outcrops
Pleistocene 0.1-2
Tertiary Neogene Pliocene 2-5
Miocene 5-24
Paleogene Oligocene 24-37
Eocene 37-58
Paleocene 58-66
Mesozoic Cretaceous   66-144
Jurassic 144-208 Ionia
Triassic 208-245 No Known Outcrops
Paleozoic Permian 245-286
Carboniferous Pennsylvanian 286-320 Calhoun, Clinton, Eaton, Ingham, Jackson, Saginaw, Shiawassea, Tuscola
Mississippian 320-360 Branch, Calhoun, Eaton, Huron, Jackson, Ottawa
Devonian 360-408 Alcona, Alpena, Antrim, Charlevoix, Emmet, Leelanau, Monroe, Prequeisle, St. Clair, Washtenaw, Wayne
Silurian 408-438 Chippewa, Delta, Luce, Mackinac, School Craft
Ordivician 138-505 Alger, Chippewa, Delta, Menominee
Cambrian 505-570 Dickinson
Proterozoic Precambrian 570-2,500 Dickinson, Iron, Marquette
Archean 2,500-3,800  
Hadean 3,800-4,600  


Activity 6.3 Color County Map of Michigan

  1. Beginning with the data given for the Precambrian age rock, have students locate each county listed and color each county Magenta on the map. Note: Some counties have outcrops of more than one age.
  2. Continue this process for all geologic time periods listed on the Geologic Time Line: Fossiliferous Outcrop Map of Michigan. The following colors should be used for the geologic ages:
  3. Period Color
    Jurassic Pink
    Pennsylvanian Yellow
    Mississippian Blue
    Devonian Green
    Silurian Purple
    Ordovician Red
    Cambrian Brown
    Precambrian Orange
  4. The completed map should look like this:
  5. In small groups, ask students to discuss and record all of the patterns shown by the plotting of this data on the map. Patterns students may see include:
    • Pre-Cambrian and Cambrian fossil outcrops occur only in the western Upper Peninsula .
    • Devonian fossil outcrops occur on the outer edges of the Lower Peninsula .
    • Pennsylvanian outcrops occur only in Mid-Michigan.
    • Jurassic fossil outcrops only occur in one county ( Ionia ).
  6. Discuss student thinking as a whole group. Explore with students what they were noticing about the patterns. Ask additional exploratory questions. Students should provide reasons for their answers. Potential exploratory questions are listed below. Have a student record all ideas.
    • Why do you think fossil outcrops are not found in every county? Most of Michigan is covered with glacial outwash and moraine deposits from the glaciers.
    • If there were fossil outcrops in the following counties, what age fossils do you think you would find and why? Emphasize that these answers are hypothesis.
      • Cheyboygan – Probably Devonian
      • Macomb – Probably Devonian
      • Montcalm – Maybe Jurassic?
      • Livingston – Maybe Mississippian? Maybe Pennsylvanian?
    • How could we find out what fossils would be in the bedrock in these areas?
      • We could drill through the glacial deposits to see what is there.
      • In the next activity, we will be using a geologic map of Michigan . There might be information on the maps that could help us answer the questions
    • Based on the age of the fossiliferous outcrops, in which counties are the rocks older? How do you know?
      • School Craft or Ionia? Schoolcraft (Silurian). Ionia is Jurassic .
      • Ingham or Monroe? Monroe (Devonian). Ingham is Pennsylvanian .
      • Chippewa or Iron? Iron (Pre-Cambrian). Chippewa is Silurian
    • Name another county that has fossiliferous outcrops of the same age as
      • Luce
      • Huron
      • Washtenaw

Activity 6.4 Sieving Fossils From Michigan Earth Materials

  1. Ask students to cover their desks with newspaper.
  2. Distribute sieves or colanders to teams of 3-4 students
  3. Explain and model the process of separating fossils from parent material using the sieves.
  4. Distribute one bag of fossiliferous Earth material to each team.
  5. Have students sieve the material, looking for fossils. Have students choose a fossil specimen and clean it with an old toothbrush.
  6. Return the remaining Earth materials to the original container.

Activity 6.5 Identifying and Carding Fossils

  1. Instruct students to identify their chosen fossil, using the information found on the Fossils of Michigan poster.
  2. Have students record all of the information requested on their Fossil Identification Card
  3. Allow students to glue fossil to the card and allow to dry.
  4. Ask students to use the information recorded on their Fossil Identification Card (Geologic Age of Fossil) and their colored map of Fossiliferous Outcrops of Michigan to suggest where in Michigan the Earth material containing their fossil may have been extracted. Have them share their thinking with their lab partner. Record all ideas. What evidence supports these idea? Construct as a class where these rocks and fossils are located in Michigan .
  5. Keep the completed Identification Cards as a classroom set until the end of the Michigan Rocks unit. These cards will be a useful reference in Lesson 7.

Management Details:

  1. Give all directions necessary to sieve the fossils from the Earth materials prior to beginning the student activity. Once engaged in collecting fossils, it is difficult to get the attention of students.
  2. Guide the “puddling” of glue on the Fossil Identification Cards – too little glue will not hold the fossils in place and too much glue will take a long time to dry and the glue may run during transport to the drying area.
  3. Have clean flat surfaces prepared to place the Fossil Identification Cards during glue drying.


Students can work in teams of two to sieve and identify fossils during Activity 6.4

Using this Activity:

  1. How does this activity match with your learning goals?
  2. What is the function of this activity?
  3. How will you identify student ideas about geologic time and use this activity to build on student ideas?
  4. How does this activity fit into the sequence of activities you are planning?
  5. How will you know if students are understanding the main ideas for this lesson?