Influence of lateral variations in décollement strength on the structure of fold-and-thrust belts: Insights from viscous wedge models

Sreetama Roy, Ernst Willingshofer, Santanu Bose*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Fold-and-thrust belts (FTBs) evolve over a mechanically weak basal décollement that separates the overlying intensely deformed rocks from the underlying less deformed ones. Although deformation structures in FTBs commonly show lateral continuity, a closer inspection reveals distinctive variations in structural style (e.g., fold style) along and across mountain belts. This study uses laboratory-scale viscous models to investigate the influence of lateral décollement strength variations on the spatio-temporal evolution of strain patterns in FTBs. These experiments, simulating crustal-scale deformation, show notable changes in the mode of tectonic wedge growth, including the topographic evolution and ductile strain pattern distribution. For example, the deformation front propagates faster over weakly coupled décollement than the laterally adjacent strongly coupled segment, leading to along-strike variations of the topographic slope and curved outline of the deformation front. Constrictional strain, characteristic of regions of weak coupling, is transient and replaced by flattening strain beyond ∼20 % bulk shortening. The latter prevails in regions over strong décollement, whereas complex strain histories mark the transition zone between weak and strong décollements. Based on our modelling results, we propose that variations in décollement strength may cause the segmentation of deformation processes and the development of transverse faults in FTBs.

Original languageEnglish
Article number105170
JournalJournal of Structural Geology
Volume184
DOIs
Publication statusPublished - Jul 2024

Bibliographical note

Publisher Copyright:
© 2024 Elsevier Ltd

Funding

SB acknowledges financial supports from the project funded by SERB, Government of India, (Project No. EMR/2015/000910) . SB also acknowledges the support of the Department of Geology, Presidency University, Kolkata, for providing infrastructural facilities received through the UGC -CAS and DST -FIST grants of Govt. of India. SR received the Inspire fellowship (No. DST/INSPIRE Fellowship/2016/IF160071) for doctoral research in India. SR also carried out the experiments as a Trans National Facility Access Researcher at the ESL-TecLab, Dept. of Geo Sciences, Utrecht University, Netherlands under the supervision of EW. This work benefited from EPOS-NL Facility Access to ESL-TecLab, supported by the Dutch Research Council (NWO) . We thank Stefan Schmalholz, Christoph von Hagke and one anonymous reviewer for their constructive reviews that have substantially improved this manuscript. We also thank Jianhua Li for handling the manuscript as an editor.

FundersFunder number
SERB, Government of IndiaEMR/2015/000910
Department of Geology, Presidency University, Kolkata
Dutch Research Council (NWO)
Not addedDST/INSPIRE Fellowship/2016/IF160071

    Keywords

    • Basal décollement
    • Coupling strength
    • Fold-and-thrust belts
    • Segmentation
    • Transverse faults

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