The purpose of this project is to introduce you to field mapping of metamorphic rocks. The project will help you develop the strategies and unique field techniques used when working in layered crystalline rocks that are often complexly deformed and difficult to distinguish from one another. In these types of rocks, a firm grasp and intuitive application of basic structural and stratigraphic principles is essential for success!
You are given four field days and one drafting day to complete a geologic map and cross-section of an area west of Rochford, South Dakota. The area is comprised of ~ 2 billion year old (Early Proterozoic), low to medium grade metasedimentary and metaigneous rocks that are deformed into upright, moderately- to steeply-plunging, tight to isoclinal folds. You will subdivide and name the exposed rocks into mappable units (i.e. Formations), providing detailed descriptions of these units in your map explanation. Depending on how finely you subdivide the section and where you happen to walk, you should have from 4-6 Formations on your map. Throughout the area, you will collect orientation data on tectonic foliations that are subparallel to the axial planes of the map-scale folds in the region, as well as lineations defined by the axes of mesoscopic folds throughout the area. These data are extremely important because they define the 3D orientation of the map-scale folds in the area and will be used to construct your geologic cross section.