Fossils in Context: creating your own fossiliferous 'limestone'
This material was originally developed as part of the
Carleton College Teaching Activity Collection through its collaboration with the SERC Pedagogic Service.
Summary
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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Context
Audience
200-level Paleobiology course for undergraduates (geology, biology and non-majors)
Skills and concepts that students must have mastered
none
How the activity is situated in the course
One to four lab exercises, depending on how elaborate I want to get.
Goals
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.
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.Teaching materials and tips
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Supporting references/URLs
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