Assembling a Geologic History

Goals

• Combining information from several field labs into a coherent history
• Recognizing gaps in information and gaps of periods of geologic time not represented in a region
• (For some versions), integrating primary literature with field observations

Skills

• Higher-order integration of concepts and observations
• Communication in writing, orally and through posters

This field lab or assignment is most appropriate after a sequence of visits to different field sites. Other field lab examples in this mini-collection, for example Local Stratigraphy, Glacial Geology in the Field, Geologic Mapping I, and Adopt an Outcrop are the types of field labs that can be integrated into this final product. If an additional field lab is required to integrate the others at this later stage, it will probably take several hours to a full day. The required equipment will range from none (if the lab is a synthesis of previous field work) to typical field gear (compass, maps, graph paper, etc.).

In southeastern Minnesota, the following field labs are integrated into the geologic history:

• Several labs observing and describing Cambrian and Ordovician sedimentary rocks (incorporating stratigraphic section measuring, geologic mapping, fossil collecting and interpretation, measurement of sedimentary and post-depositional structures), for instance Local Stratigraphy and Geologic Mapping I
• At least one lab in a gravel pit, describing glacial deposits, for instance Glacial Geology in the Field
• An all-day field trip (or two) to areas of the state with exposed Precambrian bedrock
• Fieldwork on the local river, for instance Floodplains

These localities are specific to constructing a geologic history of southeastern Minnesota. You will have to adapt it to fit the needs of your course and the specifics of your part of the country.

The focus of this integrative lab and report should be on the compilation and interpretation of the students' own observations and measurements from a period of several weeks of field labs. You can require that the students include their earlier lab reports, illustrations and field notes.

One question that often arises is whether or not to allow and encourage students to use published reports of the geologic history as they compile their own version.

Allowing published sources permits students to:

• Improve their information literacy skills by searching for relevant articles and reports.
• Realize that most published geologic histories (especially in books about regional geology) have less detail than the students observed and recorded in the field.
• Gain an opportunity for students to integrate their own field observations with published accounts of the geology.

Instructors can help students use published materials correctly by:

• Reminding students that the assessment will focus on their field observations and interpretations of the observation, not on whether they came up with a "right" answer according to what the publications say.
• Make clear that assessment will be based, in part, on the student's discussion of more than one possible interpretation of the data.
• Reassuring students about the validity of their field methods and observations.
• Insisting on a correct and consistent procedure to acknowledge all sources of ideas and other content, including both published materials and ideas from student peers.

This assignment can be done by small student groups, instead of by individual students. It also lends itself to alternative ways of reporting, such as poster presentations and a culminating discussion (or even a series of questions on a final examination).

In most cases, assessment of a regional geologic history should focus on the detailed and in-depth thinking the student has brought to bear on questions of what happened when. If this project is a culmination of several previous labs, students most likely will already have been assessed on the reports and illustrations from those labs. You can check to see if any comments have been addressed in the final versions of stratigraphic sections, maps, etc., but the emphasis should be on the integrative thinking the student has done in putting the final geologic history together. (Note that this thinking may well be supported by new diagrams).

Assuming that students are allowed to use published sources for their final product, you should make clear that the assessment will focus on their observations and interpretations of the field observations, not on whether they came up with a "right" answer according to what the publications say. You may also want to make clear that assessment will be based, in part, on the student's discussion of more than one possible interpretation of the data. Part of the assessment should also be on their correct use of citations and acknowledgements.