EVOLUTION OF PRECAMBRIAN ROCKS IN YELLOWSTONE NATIONAL PARK-- AN NSF/REU SITE PROJECT

The northern margin of Yellowstone National Park (YNP) is underlain by a sequence of Precambrian metasedimentary rocks that have preserved primary sedimentary structures, are of relatively low metamorphic grade (andalusite-staurolite zone), have undergone polyphase deformation, and are cut by at least two granitic plutons—a remarkable natural laboratory for students to apply the principles and methods learned from the “core” of a geoscience curriculum. The Yellowstone REU project was designed to provide students with a complete research experience consisting of three major components: 1) field mapping and sampling to contribute to a new geologic map of the basement rocks of YNP and formulation of testable hypotheses by smaller working groups of students to address significant questions on the petrogenesis, architecture, tectonic environment, and geologic evolution of these Precambrian rocks; 2) hands-on experience in modern analytical studies including sample preparation, training on modern instrumentation (mineral, whole-rock geochemical, and geo- and thermochronological analysis), including data acquisition, reduction, presentation, and interpretation; and 3) presentation of research results, initially by submitting an abstract for the Rocky Mountain GSA. The project design included: preparation of students via a listserv and posting of references and essential information on a dedicated webpage; initial detailed instruction in field methods, and reconnaissance field studies across the entire study area; defining focused research questions by individuals and small groups; mapping and sampling of specific areas to address these research questions, with each student playing a leadership role in directing their peers to conduct the mapping and sampling required to address their specific research question. All students participated in sample preparation (e.g., cutting thin section billets, crushing rocks, preparing powders for geochemical analysis). Initial field results have built upon and augmented earlier mapping and interpretations, and will contribute to a deeper understanding of the natural history of YNP. Assessment of learning outcomes by the students shows measurable gains in their confidence and ability to conduct significant geological research.