Tom Morris

Brigham Young University

Undergraduate required course in sedimentary geology

Students need to correctly understand grain size, bedforms, water depths and their relationships. Students should have gained this understanding from their experiences in lab and by studying the text.

This is part of a sequence of exercises culminating on the outcrop.

The main goal of this exercise is to give the students an opportunity to realize the importance for consistency in calculating and reporting data. The students should see that when choosing variables used to calculate data they must be consistent in using variables that represent either the minimum or maximum estimate when reporting data ranges. The students also experience gathering and applying quantitative and non-quantitative field data. Students will apply their knowledge of flow, grain size and sedimentary structures to gather data.

Evaluate field data. Defend calculated data and methods for data collection. Apply concepts of flow and sedimentary structures to interpret observations.

Group dynamics, team work and leadership roles are secondary goals in this exercise. The students also orally present their findings and defend them to the class.

An important part of making a field estimate is being able to give reasonable maximum and minimum values. In order to do this, students need to learn to be consistent in choosing variables when making these calculations. In this exercise the students determine flow velocities of an exhumed fluvial channel in the Jurassic Morrison Formation. They are divided into groups and given only the task without any instruction as to how to go about doing it. The students must collaborate to decide which variables are needed to determine flow velocities. They also must come up with a plan of how to collect the data from the channel and what their data represents. The students then calculate a range of values representing the minimum and maximum flow velocities. In one aspect of the exercise the students are delighted to discover that they are able to make relatively precise quantitative calculations (based on grain size, bedforms, and water depths). However, in another aspect they are challenged with the dilemma of having to make estimations based on very non-quantitative field problems (e.g. channel width). The groups are then asked to report and defend their calculations. The importance of being consistent in choosing variables used to calculate the discharge is discussed (e.g. max., min., etc.). Group dynamics and leadership roles also become obvious during the exercise.

The students are given a limited time limit to make their observations and calculations so if the group does not effectively work together it will be difficult to complete their task. For example, while part of the group estimate grain size and flow conditions the other members of the team gather channel width data. The group also selects one team leader to report their findings and works together to defend their calculations.

Students are evaluated by the group when they report their calculated data. Students compare reported calculations and determine which groups seem most correct or most off. A discussion follows to emphasize the goal of the activity and what the approximate calculated value should have been.