NSF Award
1523955
Folded rock layers are among the most fundamental, instructive and charismatic geologic structures. Folds are studied to investigate mountain building, to understand the engineering properties of rock, to predict the underground movement of water or hydrocarbons, and to give insight into the fundamental processes of folding itself. These applications rely on the accurate interpretation of rock deformation within a fold. Various conceptual and mathematical models predict fold-related deformation. To assess the capabilities of such predictive models, data from natural examples are required. This can be challenging, because most geologic folds at Earth's surface are only partially exposed, with major portions of the fold either buried underground or eroded away. The Whaleback Anticline in Bear Valley, east-central Pennsylvania, is a unique locale where a complete large-scale fold is exposed; strip mining for coal early in the last century revealed it in exquisite detail. This outstanding exposure permits observation of the complete three-dimensional form of the folded surface and provides a highly detailed record of deformation across the fold. This project will use cutting-edge digital imaging techniques and traditional geologic fieldwork to produce a comprehensive data set against which to test hypotheses about folding. In addition to the scientific goals of the project, the research is contributing to achievement of societally relevant outcomes in the areas of science, technology, engineering, and mathematics (STEM) education, including the development of a diverse, globally competitive STEM workforce through graduate and undergraduate student training; the development of research infrastructure of three universities; the broadening of participation of underrepresented groups in science; and increased public scientific literacy and public engagement with science and technology. The Whaleback Anticline is an important educational field trip location for dozens of university geology departments throughout the eastern United States, and it is a well-used recreation site for the local community. As part of this proposed project we will preserve, expand and curate geological observations from the Whaleback, for use by researchers, educators and the community. <br/><br/>Deformation associated with folding is recorded by distributed strain and discrete secondary structures. These features are of fundamental importance to understanding mechanisms and sequence of fold evolution and are of practical importance as records and hosts for fluid migration in and around folds. Incomplete data from natural examples limits the ability to evaluate geometric and physics-based models of folding. Recent advances in digital imaging and analysis now make it possible to produce quantitative three-dimensional descriptions of noncylindrical folds and evaluate the relationships of these forms to the distribution and evolution of fold-related strain. This project has the following objectives: 1) to produce a high-resolution digital surface model of an iconic fold, the Whaleback Anticline in Bear Valley, east-central Pennsylvania; 2) to document the spatial variability of strain around the fold with new observations of grain-scale strain, anisotropy of magnetic susceptibility, and detailed mapping of mesoscale structures in the folded layer; 3) to test the hypothesis that surface curvature controls the spatial variation and style of observed strain around a fold; 4) to evaluate stratigraphic and rheological influences on fold strain, through finite element analysis; 5) to demonstrate the utility of structure-from-motion photogrammetry as a tool for structural geology research and 6) to produce educational resources that will preserve and expand access to a world-class field locality and engage the local community.
