Toward the Improvement of Reasoning and Writing Skills in Sedimentary Geology

Abstract

A series of exercises has been gathered into an inquiry-based writing assignment for an undergraduate course in sedimentary geology, the purpose of which is to improve students' skills in geological reasoning, problem solving, and writing. The seven exercises contain petrographic data relating to the mineral composition of detrital sediments, and these data are to be plotted in various formats including QFL triangular diagrams, X-Y graphs, and histograms. Students then write an interpretive report explaining the results and meaning of each individual plot and integrating the results into a general discussion of the major controls on composition. Although the objective of each data set tends to be readily apprehended, students must rely on their own powers of geological reasoning to interpret these seven exercises. Their synthesis addresses the most important factors that control or influence detrital mineral composition: parent rock, tectonic setting, topography in source area, climate, transport distance, durability of grains, depositional environment, and diagenesis. In the final analysis, students come to realize the complexity involved in the making of a detrital sediment.