Research Article| January 01, 2000 Predicting the orientation of joints from fold shape: Results of pseudo–three-dimensional modeling and curvature analysis Mark P. Fischer; Mark P. Fischer 1Department of Geology and Environmental Geosciences, Northern Illinois University, DeKalb, Illinois 60115-2854, USA Search for other works by this author on: GSW Google Scholar M. Scott Wilkerson M. Scott Wilkerson 2Department of Geology and Geography, DePauw University, Greencastle, Indiana 46135, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Mark P. Fischer 1Department of Geology and Environmental Geosciences, Northern Illinois University, DeKalb, Illinois 60115-2854, USA M. Scott Wilkerson 2Department of Geology and Geography, DePauw University, Greencastle, Indiana 46135, USA Publisher: Geological Society of America Received: 19 May 1999 Revision Received: 19 Aug 1999 Accepted: 08 Sep 1999 First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2000) 28 (1): 15–18. https://doi.org/10.1130/0091-7613(2000)28<15:PTOOJF>2.0.CO;2 Article history Received: 19 May 1999 Revision Received: 19 Aug 1999 Accepted: 08 Sep 1999 First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Mark P. Fischer, M. Scott Wilkerson; Predicting the orientation of joints from fold shape: Results of pseudo–three-dimensional modeling and curvature analysis. Geology 2000;; 28 (1): 15–18. doi: https://doi.org/10.1130/0091-7613(2000)28<15:PTOOJF>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search 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. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Pinned oroclines, a type of curved orogen which results from lateral pinning of a growing fold‐thrust belt, tend to resemble parabolic Newtonian curvature modified by different degrees of flattening at the flow front. We propose that such curves can be generated by Newtonian crustal flow driven by topographic variations. In our model, regional topographic differences create a regional flow which produces a parabolic flow front upon interaction with lateral bounding obstacles. Local topographic variations modify the parabolic curves and yield more flat‐crested, non‐Newtonian‐like curvatures. The degree of modification depends on the relative strength of the local driving potential, which in turn is dependent on rock type and fluid pressure. On the basis of a finite difference, thin‐skin, tectonic simulation, we demonstrate that both Newtonian‐like and non‐Newtonian‐like curved orogens can be produced within a Newtonian crust. In effect, the shape of curved orogens in plan may provide insight into the rheology of the Earth's upper crust over geological time scales.
Using recent geologic mapping combined with digital elevation data, aerial photo interpretation, and cross section balancing, we describe the three‐dimensional (3‐D) geometry and kinematics of the Nuncios Fold Complex in the Monterrey Salient of northeastern Mexico. This map‐scale, evaporite‐cored detachment fold structure involves Upper Jurassic through Cretaceous rocks deformed during the Laramide orogeny and comprises two westward plunging anticlines and an intervening, eastward plunging syncline. Seven balanced cross sections and a 3‐D model of this north vergent structure document substantial along‐strike variations in both fold geometry and detachment depth, suggesting that 3‐D flow of the detachment layer may have occurred during folding. Comparison of folds in the Monterrey Salient with those in the neighboring Parras Basin suggests that the latter south vergent folds root to a shallower detachment. We suggest that northward transport of the Monterrey Salient folds on the lower evaporite detachment may have been inhibited by a thick sequence of foreland basin rocks in the northeastern Parras and southern La Popa basins and that the smaller, south verging folds formed where the lower detachment was abandoned and slip was transferred to the shallower detachment, forming a triangle zone at the front of the Sierra Madre orogenic wedge.
Backstripping corrections to determine tectonic subsidence as a function of time are an integral part of quantitative basin analysis. These corrections involve tedious and time-consuming calculations to correct for both compaction and sediment loading of the strata. We developed a program for both the Macintosh and IBM* personal computers to utilize their graphic capabilities to quickly and efficiently generate plots for these calculations. The program produces plots for 1) uncompacted stratigraphy versus time, 2) basement subsidence versus time, 3) basement subsidence versus the square root of time, and 4) subsidence rate versus time. The program was created to serve as an instructional tool for classroom teaching of basin analysis. Its use assists students in interpretating plots resulting from backstripping methods and in applying them to basin analysis.
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