USING UNKNOWN SAND SAMPLES FOR A LARGE-SCALE, SEDIMENTATION-STRATIGRAPHY CLASS PROJECT, AND LINKAGE TO INTRODUCTORY COURSES

For over 25 years Sedimentation-Stratigraphy (GEO 312) students at Grand Valley State University (Michigan) have done grain-size analyses on unknown sand samples. The students do a sieve analysis, calculate statistics (e.g., mean, sorting, skewness, kurtosis), and do a visual estimate of roundness, sphericity, and mineralogy. Using the guidance of text and lab books (e.g., Folk's “Petrology of Sedimentary Rocks”), and graphic plots (e.g., Visher cumulative frequency plots; Friedman scatter diagrams), they write a report outlining their analytical procedure and presenting their interpretation of modes of transport, provenance, and depositional environment (beach, dune, fluvial). The project is time intensive, so students do most of the four-week-long project outside of regular lab time.

Samples presented as “unknowns” have a number of advantages for the students: (1) they learn to calculate and use statistics, but also come to realize that determining depositional environments using grain-size analysis is not a “black box” technique; (2) they are enthusiastic and observant as they search for clues as to the origin of their sample; and (3) they enjoy finally learning the geographic origin (commonly from the “far reaches of the earth”), depositional environment, and geologic history of their sample.

The project also serves as a link between students in physical geology classes and upperclassmen in Sed-Strat. The former learn about a project done by geology majors, and are enticed to collect samples for the project. Many do so during school breaks, so non-science majors think about geology while on vacation. They become aware of anthropologic effects such as beach nourishment as they choose a sample location. Many of these introductory geology students are more engaged when learning about sedimentary processes because they can relate better to the topics being investigated by their peer geology majors, and because they have contributed via sample collection. Faculty colleagues and past Sed-Strat students also enjoy collecting far-a-field samples, especially those they perceive to be “problematic,” for investigation by the next generation of students. Thus, the unknown-sand-sample lab has become a tradition in our department, one that students may be involved in or hear about before and after taking Sed-Strat.