Use of a Lab-Field Couplet to Link Rock Classification and Facies Interpretation

Allison Tumarkin-Deratzian
Temple University (formerly Vassar College)
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Initial Publication Date: June 27, 2006 | Reviewed: November 3, 2013


Students examine hand samples in the lab, then describe formations and interpret facies succession at a local outcrop. Linked lab and field components doubly reinforce understanding of course concepts.

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Designed for an intermediate (200-level) course for undergraduate geology majors/minors. Assumes students have taken introductory physical, environmental, and/or historical geology. Could be modified for a higher-level course by varying amount of background information supplied to students, particularly in the field component.

Skills and concepts that students must have mastered

Specific requirements will vary depending on the nature of local field sites and available hand samples. In general, students should be comfortable describing sedimentary rocks, be able to identify sedimentary structures and their significance, and be familiar with Walther's Law. (If the focus is carbonates, basic familiarity with major invertebrate fossil groups may be helpful, alternatively fossil identification sheets can be provided by the instructor.)

How the activity is situated in the course

Position in course will vary depending on which lithologies and environments are emphasized. The two activities should be done in sequential lab periods, as soon as possible after the relevant lecture material. Either may be presented first, although, if the field component precedes the lab component, it may be necessary to provide more detailed background information.


Content/concepts goals for this activity

Sedimentary rock description and classification, sedimentary structures, facies interpretation, Walther's Law

Higher order thinking skills goals for this activity

Synthesis of information on lithology, sedimentary structures, fossil assemblages, etc., toward the bigger picture of facies interpretation

Other skills goals for this activity

Encourages students to work together in small groups, peer teaching

Description of the activity/assignment

Following lecture presentation of classification schemes and environments of formation for non-siliciclastic rocks, students perform a sequence of two activities (one in the lab, one in the field) designed to guide them from theoretical understanding to practical application. In the lab component, students are presented with twenty hand samples and twenty rock names and/or descriptions. Their task is to examine the samples, match the descriptions with the proper rocks, and propose a likely environment of formation for each sample. Included among the samples in the lab component are carbonates and cherts similar to those encountered in the field component, which examines a local outcrop exposing four successive carbonate formations in the Middle Paleozoic Helderberg Group. In the field component, students are first asked to differentiate between successive formations using lithology, sedimentary structures, and fossil assemblages. They then determine the probable sedimentary environment for each formation, and interpret the facies succession preserved in the outcrop to reconstruct a small portion of local geologic history. In both field and lab components, students are encouraged to work in small groups to develop their initial responses without instructor input. This arrangement ultimately improves both student understanding of the material and confidence in their own interpretations.

Determining whether students have met the goals

At the end of each component, student groups come together to discuss their interpretations with each other and with the instructor. Evaluation is based primarily on these conversations. These activities function better as a group learning experience than as a graded assignment. The instructor may choose to collect written material (e.g. charts from the lab component, field notes and outcrop sketches from the field component), but since all students should be on the same page by the end of the class discussion, these are best used to gauge student participation, rather than performance.

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