3D geometry and kinematic evolution of the Wadi Mayh sheath fold, Oman, using detailed mapping from high-resolution photography. (August 2017)

• Record Type: Journal Article
• Authors: Cornish, Sam; Searle, Mike
• Is Part Of: Journal of structural geology. Volume 101(2017:Aug.)
• Page Start: 26
• Page End: 42
• Publication Date: 2017-08
• Subjects: Oman -- Sheath fold -- Wadi Mayh -- Geometry -- SfM -- Photography; Geology, Structural -- Periodicals; Géomorphologie structurale -- Périodiques; Geology, Structural; Periodicals; 551.805
• DOI: 10.1016/j.jsg.2017.06.009
• Languages: English
• ISSNs: 0191-8141

Abstract

Abstract: The Wadi Mayh sheath fold in north-eastern Oman is one of the largest and best-exposed sheath folds known, and presents a unique opportunity to better understand this somewhat enigmatic style of deformation. We undertook high-resolution photographic surveying along Wadi Mayh to document the sheath fold in 61 georeferenced panoramic photomerges. Here we present ten such images that provide a structural interpretation of the sheath fold and surrounding structure. We resolve this structure in a simplified three-dimensional model and in two orthogonal cross sections, and propose a kinematic evolution to explain the geometry. The Wadi Mayh sheath fold is the most prominent example within what we suggest is a composite sequence of sheath folds, which is itself enclosed within a SSW-closing recumbent syncline at the base of the major Saih Hatat nappe. Sheath folding is accommodated within Permian Saiq Formation limestones showing carpholite assemblages (6–8 kbar; 275–375 °C). A major discontinuity separates this sequence from enveloping older rock units. The sequence formed during progressive top-to-north, ductile shearing as the overlying nappe migrated northwards with respect to the underthrusting Hulw unit. This process occurred during SSW-directed exhumation of partially subducted continental crust in NE Oman, approximately 15 Ma after obduction of the Oman ophiolite initiated. Highlights: High resolution documentation of one of the largest sheath folds known. 3D structural interpretation of this feature and its context. The fold formed under progressive top-N shear at the base of a regional nappe. Context of the inferred regional stress field evolution provided.