Red Canyon Terrace Project

Dennis Dahms
,
Geography, University of Northern Iowa
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Summary

This project is designed to give students: (1) experience in mapping the details of surficial geologic deposits (Qal), (2) an understanding the geomorphic relations among surficial deposits and underlying/associated bedrock units, and (3) an appreciation for geomorphic characteristics that can be used to measure the relative ages of surficial deposits.

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Context

Audience

This 2-day project is part of a 6-week summer field course. Previous coursework in Geomorphology is appreciated, but not required.

Skills and concepts that students must have mastered

Introductory-level geological concepts.

How the activity is situated in the course

This is a stand-alone project, but it fits within a larger context of geologic field mapping.

Goals

Content/concepts goals for this activity

Content/concept goals for this project are for students to understand the relations between stream activity and glacial cycles and how the resulting deposits should be mapped and dated.

Higher order thinking skills goals for this activity

Higher order skills involve understanding how these stream/glacial cycles produce the presently-existing landscapes.

Other skills goals for this activity

Other skills goals include: (1) mapping skills, (2) correlation skills (spatial and conceptual), and (3) graphing skills.

Description of the activity/assignment

We know that glacial cycles produce changes in stream regimens downstream from the active ice margin, and that successive glacial cycles often result in separate (and usually lower) floodplains that become terraces following each cycle of stream incision. Using a suite of 4-5 glacio-fluvial terraces outside the mouth of Little PopoAgie Canyon on the east flank of Wyoming's Wind River Range, students do the following: (1) produce a map of the major terrace landforms, (2) observe the geomorphic characteristics of each map unit (this includes height above present stream, depth of fine overbank material above coarse bedload, and general weathering characteristics of the units, and whether the unit is a cut or fill terrace), and (3) measure the characteristics of soil profiles dug into each unit (including horizons Id's, depth and thickness of horizons, and carbonate morphology). Students use all this information to place the terrace units into the regional glacio-fluvial chronology by matching the relative age-data with the Pinedale/Bull Lake/Pre-Bull Lake regional sequence. Final project must include a graphic representation of stream heights that fit their interpretations of the regional glacio-fluvial stratigraphy.

Determining whether students have met the goals

Simply the quality of the maps and their interpretations of how and why they chose to separate the units as they did. Usually, the graphs of terrace elevations with distance downstream show whether they understand the concepts well, or not.

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