--> Abstract: Displacement Analysis as a Predictive Tool for Constraining Three-Dimensional Fold-Thrust Geometries, by M. S. Wilkerson; #91012 (1992).

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ABSTRACT: Displacement Analysis as a Predictive Tool for Constraining Three-Dimensional Fold-Thrust Geometries

WILKERSON, M. SCOTT, University of Illinois, Urbana, IL

The primary problem in describing and ultimately understanding three-dimensional thrust-related fold geometries is the delineation of displacement paths within natural thrust sheets. Information about three-dimensional displacement paths permits construction and restoration of volume-balanced, thrust-related fold geometries in three dimensions. Computer models, physical models, and empirical observations provide a collective means of acquiring this information and subsequently predicting displacement orientations and magnitudes as a function of fault geometry. Specifically, computer models relating principal stress magnitudes with fault orientation allow prediction of displacement trajectories within a thrust sheet. Results suggest that intrathrust sheet displacement trajectories vary considerably as a function of overburden and structural position. This concept of lateral "wrenching" within thrust sheets is corroborated by computerized tomographic analysis of displacement trajectories in physical models. Analysis of strain markers within a sand pack indicates that layers near the surface exhibit radial displacement trajectories, whereas layers lower in the section display systematic out-of-plane movements associated with the fault geometry. Finally, empirical observations of along-strike variations in displacement in seven nonmetamorphic fold-thrust belts in North America suggest that 32 degrees is the upper limit of differential transport between adjacent cross sections in coherent thrust sheets. Taken together, these results provide insight into thrust-sheet cohere cy and help constrain three-dimensional interpretations of thrust-sheet geometries for hydrocarbon exploration.

 

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)