Détail de la notice
Titre du Document
Scale invariant sheath folds in salt, sediments and shear zones
Auteur(s)
ALSOP G. I. ; HOLDSWORTH R. E. ; MCCAFFREY K. J. W.
Résumé
Sheath folds are developed in a broad spectrum ot geological environments in which material flow occurs, including gravity-driven surficial deformation in ignimbrites, unconsolidated sediments and salt, together with deeper level ductile shear zones in metamorphic rocks. This study represents the first geometric comparison of sheath folds in these different settings across a wide range of scales. Elliptical closures defining eye-folds represent (y-z) cross sections through highly-curvilinear sheath folds. Our analysis of the published literature, coupled with field observations, reveals remarkably similar ellipticities (Ryz) for sheath folds in metamorphic shear zones (Ryz 4.23), salt (Ryz 4.29), sediment slumps (Ryz 4.34), glaciotectonites (Rvz 4.48), and ignimbrites (Ryz 4.34). Nested eye-folds across this range of materials (N = 1800) reveal distinct and consistent differences in ellipticity from the outer- (Ryz) to the inner-most (Ry'z') elliptical "rings" of individual sheath folds. The variation in ratios from outer to inner rings (R' = Ryz/Ry'z') in gravity-driven surficial flows typically displays a relative increase in ellipticity to define cats-eye-folds (R' < 1) similar to those observed during simple and general shear in metamorphic rocks. We show that sheath folds develop across a range of scales within these different environments, and display elliptical ratios (Ryz) that are remarkably constant (
Editeur
Elsevier
Identifiant
ISSN : 0191-8141 CODEN : JSTGD3
Source
Journal of structural geology A. 2007, vol. 29, n° 10, pp. 1585-1604 [20 pages]
Langue
Anglais
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