HR: 08:45h
AN: T41F-04    [Abstracts]
TI: Constraining Fold Geometry by Application of Airborne Laser Swath Mapping at Sheep Mountain Anticline, Wyoming
AU: * Pollard, D D
EM: dpollard@pangea.stanford.edu
AF: David D. Pollard, Geological and Environmental Sciences Stanford University, Stanford, CA 94305, United States
AU: Lovely, P J
EM: plovely@stanford.edu
AF: David D. Pollard, Geological and Environmental Sciences Stanford University, Stanford, CA 94305, United States
AB: Sheep Mountain anticline (SMA), Wyoming, is an asymmetric fold resulting from Laramide compression that activated an underlying basement-cored thrust fault. Excellent outcrop exposures and a wealth of data, including detailed structural maps and kinematic interpretations of five fracture sets, make SMA an ideal site for studies relating the mechanics of fold evolution to present day fold geometry and fracture patterns. One of many challenges in relating folding to fracturing arises because most fractures are below the resolution of industry standard seismic imaging. Another stems from the differences in length scales: typical fold wave lengths are 1 to 10 km whereas typical fracture trace lengths are 1 to 100 m. Therefore, new methods must be found to constrain fold geometry at sites where outcrop fracture data is available. To constrain fold geometry at SMA we have obtained an airborne laser swath mapping (ALSM) digital elevation model (DEM) from the National Center for Airborne Laser Mapping (NCALM). We present and describe the DEM, on which we have mapped bedding-plane exposures of several prominent stratigraphic horizons. We use differential geometry to characterize the curvature of these outcrop exposures, considering both principle curvatures, and classifying the surfaces into the eight different fundamental geological shapes. This new characterization of the fold shape is compared to a similar analysis based upon a structural contour map of SMA prepared using standard techniques. Future work with these data will include the construction of a refined 3D model of fold geometry by interpolation of mapped bedding exposures, mechanical analysis of folding induced stress perturbations throughout the history of structural growth, and the analysis of these stress perturbations as they relate to observed fracture sets.
DE: 8000 STRUCTURAL GEOLOGY
DE: 8005 Folds and folding
DE: 8010 Fractures and faults
DE: 8040 Remote sensing
DE: 8169 Sedimentary basin processes
SC: Tectonophysics [T]
MN: 2007 Fall Meeting