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Predicting the orientation of joints from fold shape; results of pseudo-three-dimensional modeling and curvature analysis

Mark P. Fischer and M. Scott Wilkerson
Predicting the orientation of joints from fold shape; results of pseudo-three-dimensional modeling and curvature analysis
Geology (Boulder) (January 2000) 28 (1): 15-18

Abstract

We treat layers of sedimentary rock as elastic plates and predict the orientations of joints by assuming that they open parallel to the maximum instantaneous stretch of a layer. Because the direction of maximum instantaneous stretch is parallel to the maximum curvature of a surface, we hypothesize that joints will trend parallel to the minimum curvature of an elastically deformed layer. After constructing pseudo-three-dimensional trishear models of Laramide-style uplifts that grow self-similarly, we calculated the direction of minimum-curvature axes during the evolution of the fold. Our analysis of minimum-curvature axes in evolving folds suggests several important characteristics for fold-related joint sets: (1) joints that are neither parallel nor perpendicular to the fold axis may be induced by local fold-related strains; (2) at any time during folding, joint orientations may vary according to the structural position on a fold; (3) at any location on a fold, joint orientation may depend on when a joint forms during the evolution of the fold; and (4) joint patterns in trishear folds may vary with stratigraphic position. Natural folds that evolve along simple geometric pathways may develop fold-related joint sets, the orientation, dominance, abutting relationships, spacing, and continuity of which will vary systematically throughout the structure. This variation in joint-system architecture may reflect the history of fold growth.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 28
Serial Issue: 1
Title: Predicting the orientation of joints from fold shape; results of pseudo-three-dimensional modeling and curvature analysis
Affiliation: Northern Illinois University, Department of Geology and Environmental Geosciences, DeKalb, IL, United States
Pages: 15-18
Published: 200001
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 32
Accession Number: 2000-018567
Categories: Structural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
Secondary Affiliation: DePauw University, Department of Geology and Geography, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200006
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