The Proterozoic Fossil Record
Julie K. Bartley
Gustavus Adolphus College
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: May 25, 2009
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In this specimen-based activity, students examine microfossils and stromatolites and build an understanding of the Proterozoic paleontological record.
Introductory historical geology course or undergraduate paleontology course.
Skills and concepts that students must have mastered
Basic modes of fossilization; survey of sedimentary rock types; rules for sketching hand samples
How the activity is situated in the course
Second laboratory exercise in the "fossil record" portion of the historical geology lab; in a paleontology course, this activity would be combined with other pieces examining the microfossil record of the Proterozoic
Content/concepts goals for this activity
Conceptualization of an environment dominated by microorganisms (the Proterozoic), and particularly to understand the differences between the environment at a single time slice (e.g., seafloor at a point in time) vs. the geologic structure produced over time (e.g., accumulated layers of a stromatolite).
Higher order thinking skills goals for this activity
Analysis of spatial data: relationship between 2-D and 3-D structures. Evaluation of the importance of variables in producing observed structures.
Other skills goals for this activity
Writing: brief descriptions of observations, posing hypothesiss. Drawing: creating simple representations of complex rock structures.
Description of the activity/assignment
In this laboratory exercise (2 hours), students explore the Proterozoic fossil record by examining two samples of microfossils, preserved in chert) and numerous samples of stromatolites. The laboratory exercise coincides with lecture discussions on the early history of life, and serves to illustrate the paleontological record of the Proterozoic. This exercise is the first laboratory exercise in the course that asks students to engage with and speculate upon the environmental and biological causes of the observed fossil record. The students' goal is to be able to identify some of the main environmental factors that combine to produce the diversity of stromatolite forms.
Determining whether students have met the goals
Students have conversations during the lab exercise, in which they propose hypotheses to explain their observations about stromatolites. Students hand in the product of their exercise and it is evaluated. Finally, students answer questions about stromatolite construction and microfossil preservation on the midterm exam. More information about assessment tools and techniques.
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