Stratigraphic Section Investigation

Alex Lechler, Pacific Lutheran University
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This lab exercise provides a hypothetical, regional stratigraphic section for students to interpret with regards to depositional environment and tectonic change through time. The assignment is designed to develop and evaluate student scientific writing skills by having students submit a 2-4 page (double-spaced) report detailing the stratigraphic history represented by the section. A primary focus is placed on identifying how and why sedimentary environments change through time and how this change integrates into a broader story of the geologic history for the region in which the section is preserved.

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This exercise is intended for an undergraduate course in sedimentology/stratigraphy (300 or 400 level).

Skills and concepts that students must have mastered

Students should be familiar with fundamental concepts in Sed/Strat, including stratigraphic analysis, sedimentary depositional environment identification, and tectonic basin evolution. In its current form, the exercise does not require students to identify lithology from hand sample, thin section, or field analysis, but these could be integrated easily if required resources are available. In any case, student understanding of clastic and carbonate sedimentary rock identification and classification at an intermediate level is required.

How the activity is situated in the course

This is a stand-alone exercise that can be implemented as a mid-term lab investigation or take-home assignment. Given that students need to integrate their understanding of clastic, carbonate, allochem, and tectonic environments for completion of this investigation, the activity should be assigned after each of these fundamental concepts has been covered.


Content/concepts goals for this activity

The primary content/concept goals for this assignment are: stratigraphic analysis, interpretation of lithologic descriptions with regards to depositional environments, and developing science writing skills.

Higher order thinking skills goals for this activity

Students will be required to synthesize observations and interpretations for this investigation as well as integrate knowledge for a range of sedimentologic topics commonly covered in undergraduate Sed/Strat courses.

Other skills goals for this activity

A primary emphasis is placed on developing science writing skills, specifically report writing.

Description and Teaching Materials

This activity is intended for students to work independently (or in small groups) to investigate the hypothetical stratigraphic section. Students can work on the assignment either in the lab or outside of class. Students are encouraged to check in with the instructor (or the instructor can proactively ask the students) to discuss their preliminary interpretations and plans for integration into the complete regional geologic history. The hand-sketched hypothetical stratigraphic section is the only material required.
Stratigraphic Investigation Assignment (Acrobat (PDF) 225kB May28 14)

Teaching Notes and Tips

The drawn section includes details specific to topics/processes discussed in a particular course (e.g., importance of glauconite). Accordingly, it may be necessary or desired to edit some of the units to suit the needs of your particular course. In general, students successfully grasp the fundamental concepts of stratigraphic analysis but the integration with tectonic history presents unique challenges. Additionally, students often struggle to use the context of neighboring stratigraphic units effectively (e.g., interpreting a specific and unique depositional environment for a relatively nondescript medium-grained sandstone with no defining texture or structure is difficult in isolation, but is much easier when a neighboring unit of oolitic limestone is considered), so this should be stressed throughout the activity.

The parallel focus of developing science writing skills presents a distinct set of challenges. Some discussion of how to approach science writing, particularly for students who have likely never done so, is needed prior to and during this assignment.


Standard evaluation procedures are used. Accuracy and justification of student interpretations and depth of detail of student observations are specifically focused on. Broad assessment of student writing skills is a parallel focus of assessment. For many students, science writing skills are in the early stage of development so this assignment often generates subsequent writing assignments intended to refine these skills.

References and Resources