The development of sheath folds in viscously stratified materials in simple shear conditions: An analogue approach

Damiano Dell'Ertole*, Wouter P. Schellart

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Sheath folds are highly non-cylindrical folds occurring in a variety of geological settings, and have been studied using different approaches. With the present work, we provide a quantitative analysis of the generation and development of sheath folds in a viscously layered system in simple shear conditions. The sheath folds develop from an initial non-cylindrical deflection located on the highly viscous layer. The analogue experiments investigated the influence of (1) variations in the viscosity ratio between the high viscosity layer and the matrix (ηhvlm), (2) variations in the ratio between the amplitude of the initial deflection and the thickness of the high viscosity layer (Af/Thvl), and (3) progressive simple shear (γ). The results show that increases in ηhvlm will produce progressively less elongated sheath folds, while increases in Af/Thvl will result in more elongated sheath folds. We present regime diagrams with ηhvlm and Af/Thvl for different shear strains illustrating under which conditions sheath folds form. In case the original deflection amplitude and layer thickness as well as γ can be retrieved for sheath folds in nature, then their geometry can be used to quantify the effective ηhvlm.

Original languageEnglish
Pages (from-to)129-141
Number of pages13
JournalJournal of Structural Geology
Volume56
DOIs
Publication statusPublished - Nov 2013

Keywords

  • Analogue model
  • Ductile deformation
  • Sheath fold
  • Simple shear

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