Teach the Earth > Paleontology > Teaching Activities > Fossils in Context: creating your own fossiliferous 'limestone'

Fossils in Context: creating your own fossiliferous 'limestone'

Clint Cowan
Carleton College
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This activity was selected for the On the Cutting Edge Reviewed Teaching Collection

This activity has received positive reviews in a peer review process involving five review categories. The five categories included in the process are

  • Scientific Accuracy
  • Alignment of Learning Goals, Activities, and Assessments
  • Pedagogic Effectiveness
  • Robustness (usability and dependability of all components)
  • Completeness of the ActivitySheet web page

For more information about the peer review process itself, please see http://serc.carleton.edu/NAGTWorkshops/review.html.

This activity has benefited from input from faculty educators beyond the author through a review and suggestion process. This review took place as a part of a faculty professional development workshop where groups of faculty reviewed each others' activities and offered feedback and ideas for improvements. To learn more about the process On the Cutting Edge uses for activity review, see http://serc.carleton.edu/NAGTWorkshops/review.html.

This page first made public: Jun 4, 2009

This material was originally developed as part of the Carleton College Teaching Activity Collection
through its collaboration with the SERC Pedagogic Service.


Our museum collection is full of loose, individual, beautiful fossils of marine invertebrates. I try to get students to understand that most fossils they might actually find in the field are locked in rock, and they will need to identify them in cross-section. This can also be used as an elaborate taphonomy-environment lab.

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200-level Paleobiology course for undergraduates (geology, biology and non-majors)

Skills and concepts that students must have mastered


How the activity is situated in the course

One to four lab exercises, depending on how elaborate I want to get.


Content/concepts goals for this activity

Recognizing 3D shapes from 2D cuts through them.

Higher order thinking skills goals for this activity

Taphonomy and Paleoenvironmental reconstruction

Other skills goals for this activity

working in groups, working on a sustained topic for several weeks (optional) and researching environments.

Description of the activity/assignment

I order a lot of shells (online from SeaShellCity.com) and the students make their own limestones. We put the shells in portland cement (in large square ziploc containers); let them harden for a week, then cut them on the rock saw.
I have done this in a few ways.

Simple way for 3D reasoning: have students make a predictive sketch of what their limestone will look like cut. Then grade the accuracy of their prediction (award a prize).

Elaborate way for 3D reasoning, taphonomy and paleoenvironmental reconstruction: I sometimes provide the class with a carbonate shelf facies model (with a slide show from my own research), and have them work in teams, select an environment (from a map provided), research what benthos might live in that environment, then order shells of the calcareous ones, break those shells if necessary, and finally build a rock from the shells + portland cement. It really teaches taphonomy (especially comparing who lives in the environment vs. who makes it into the fossil record). Often, I then have the teams swap their rocks, and cut and interpret another team's rock.

Determining whether students have met the goals

I evaluate the degree of research on the benthos for the environment, and their interpretation of the other team's rock (I don't so much grade the actual rocks).

More information about assessment tools and techniques.

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