{"title":"Boudinage and folding of oblique single layers in bulk constrictional strain fields: Results from analogue modelling","authors":"Chao Cheng , Janet Zulauf , Gernold Zulauf , Elke Hattingen","doi":"10.1016/j.jsg.2024.105153","DOIUrl":null,"url":null,"abstract":"<div><p>We conducted scaled analogue modelling to show the influence of varying single layer initial orientation on the geometry of folds and boudins in a bulk constrictional strain field. The initial angle between the plane of shortening and the competent layer (<em>θ</em><sub><em>Z(i)</em></sub>) was incrementally increased from 0° to 90° by multiples of 11.25°. While the amount of layer thickening decreased with increasing <em>θ</em><sub><em>Z(i)</em></sub>, the deformation structures produced range from pure dome-and-basin folds to coeval folds and boudins. Based on the attitude of fold axes, there are extension-parallel (F<sub>EPR</sub>) and extension-perpendicular (F<sub>EPP</sub>) folds, with axes subparallel and subperpendicular to the principal stretching axis (<em>X</em>), respectively. Coeval growth of F<sub>EPR</sub> folds and boudins occurred when <em>θ</em><sub><em>Z(i)</em></sub> > ca. 25°. The F<sub>EPP</sub> folds can be subdivided into a first type which affect the entire layer (if <em>θ</em><sub><em>Z(i)</em></sub> ranges between 11.25 and 78.75°) and a second type, referred to as FB<sub>EPP</sub> folds, which are affecting pre-existing boudins if <em>θ</em><sub><em>Z(i)</em></sub> > 45°. The interlimb angle of all types of folds increases with increasing <em>θ</em><sub><em>Z(i)</em></sub>. Folds and boudins similar to the ones produced in this study can be found in salt domes and in tectonites of subduction zones.</p></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":null,"pages":null},"PeriodicalIF":2.6000,"publicationDate":"2024-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0191814124001056/pdfft?md5=40e619e3d937e8ac662c87a717fcde3c&pid=1-s2.0-S0191814124001056-main.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Structural Geology","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0191814124001056","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
We conducted scaled analogue modelling to show the influence of varying single layer initial orientation on the geometry of folds and boudins in a bulk constrictional strain field. The initial angle between the plane of shortening and the competent layer (θZ(i)) was incrementally increased from 0° to 90° by multiples of 11.25°. While the amount of layer thickening decreased with increasing θZ(i), the deformation structures produced range from pure dome-and-basin folds to coeval folds and boudins. Based on the attitude of fold axes, there are extension-parallel (FEPR) and extension-perpendicular (FEPP) folds, with axes subparallel and subperpendicular to the principal stretching axis (X), respectively. Coeval growth of FEPR folds and boudins occurred when θZ(i) > ca. 25°. The FEPP folds can be subdivided into a first type which affect the entire layer (if θZ(i) ranges between 11.25 and 78.75°) and a second type, referred to as FBEPP folds, which are affecting pre-existing boudins if θZ(i) > 45°. The interlimb angle of all types of folds increases with increasing θZ(i). Folds and boudins similar to the ones produced in this study can be found in salt domes and in tectonites of subduction zones.
期刊介绍:
The Journal of Structural Geology publishes process-oriented investigations about structural geology using appropriate combinations of analog and digital field data, seismic reflection data, satellite-derived data, geometric analysis, kinematic analysis, laboratory experiments, computer visualizations, and analogue or numerical modelling on all scales. Contributions are encouraged to draw perspectives from rheology, rock mechanics, geophysics,metamorphism, sedimentology, petroleum geology, economic geology, geodynamics, planetary geology, tectonics and neotectonics to provide a more powerful understanding of deformation processes and systems. Given the visual nature of the discipline, supplementary materials that portray the data and analysis in 3-D or quasi 3-D manners, including the use of videos, and/or graphical abstracts can significantly strengthen the impact of contributions.