HR: 0800h
AN: T51D-1365    [Abstracts]
TI: 3-D Characterization and Analysis of Fold-Fracture Relationships Using Airborne Laser Swath Mapping (ALSM) and Differential Geometry With Application to Raplee Monocline, Utah
AU: * Mynatt, I
EM: imynatt@pangea.stanford.edu
AF: Stanford University, Department of Geological and Environmental Sciences, Stanford University , Stanford, CA 94305-2115
AU: Hilley, G
EM: hilley@pangea.stanford.edu
AF: Stanford University, Department of Geological and Environmental Sciences, Stanford University , Stanford, CA 94305-2115
AU: Pollard, D D
EM: dpollard@pangea.Stanford.EDU
AF: Stanford University, Department of Geological and Environmental Sciences, Stanford University , Stanford, CA 94305-2115
AB: Folding and fracturing can be intimately related processes in which the overburden stress, the remote tectonic stress, local folding related stresses and stress perturbations due to pre-existing fractures all influence new fracture formation. As a case study, we examine the relationship between the current fold geometry and fractures of Raplee Monocline, a Laramide aged, N-S oriented, 14-km long fold exposed in the Monument Upwarp of south-eastern Utah. The study involves three distinct parts: 1) Field based characterization of the fractures on and around the fold; 2) development of accurate models of the fold's geometry using high resolution data collected by ALSM; and 3) analysis of the fold's shape using the concepts of differential geometry. Field observations of fracture characteristics in different stratigraphic units are summarized in conceptual models of five stages of fracture evolution: 1) the formation of pre-folding E-W Set I fractures by regional stress; 2) the formation of pre-folding N-S Set II fractures probably by regional stress; 3) the shearing of Set II fractures with formation of tail-cracks and the flow of fluids through these fractures; 4) right lateral shearing induced by folding creating NW-SE Set III fractures as tail-cracks of Set I fractures and as independent fractures; and 5) the formation of new Set II oriented fractures as tail-cracks from slip along bedding planes. We develop an algorithm to extract the geometry of exhumed folded surfaces using ALSM high-resolution topographic data. The fold geometry extraction and interpolation algorithm identifies areas of the landscape that are likely to be bedding surfaces, extracts elevation points from these bedding surfaces, and interpolates fold geometry between topographic exposures of bedding planes in the landscape. Using algorithms based on differential geometry, the shape characteristics of fold models of Raplee Monocline can be precisely quantified. Specific geometric characteristics of the fold model, such as magnitude and direction of maximum curvature, are compared to the observed fracture characteristics.
DE: 8108 Continental tectonics: compressional
DE: 8138 Lithospheric flexure
DE: 8164 Stresses: crust and lithosphere
SC: Tectonophysics [T]
MN: Fall Meeting 2005