Identifying the characteristic signatures of fold-accommodation faults

• Published in: Journal of structural geology Vol. 56; pp. 1 - 19
• Main Authors: Deng, Hongling, Zhang, Changhou, Koyi, Hemin A.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2013
• Subjects: Angles (geometry); Characteristic signatures; Cut-off; Displacement; Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics; Earth sciences; Endogen geovetenskap; Endogenous earth sciences; Faults; Fold-accommodation faults; Geological faults; Geovetenskap; Geovetenskap med inriktning mot mineralogi, petrologi och tektonik; Hand-specimen; NATURAL SCIENCES; NATURVETENSKAP; Outcrop scale; Outcrops; Separation–distance plot; Signatures; Spatial distribution; Characteristic signatures; Fold-accommodation faults; Hand-specimen; Outcrop scale; Separation–distance plot
• ISSN: 0191-8141; 1873-1201; 1873-1201
• DOI: 10.1016/j.jsg.2013.08.006

Hand-specimen and outcrop scale examples of folds are analyzed here to identify the characteristic signatures of fold-accommodation faults. We describe and analyze the geometric and kinematic relationships between folds and their associated faults in detail including the structural position and spatial distribution of faults within a fold, the displacement distribution along the faults by applying separation–distance plots for the outcrop scale examples, and the change of cut-off angle when the fault cut across folded layers. A comparison between fold-accommodation faults and fault related folds based on their separation–distribution plots and the problem of time sequence between faulting and folding are discussed in order to distinguish fold-accommodation faults from the reverse faults geometrically and kinematically similar to them. The analysis results show that fold-accommodation faults originate and terminate within a fold and usually do not modify the geometry of the fold because of their limited displacement. The out-of-syncline thrust has a diagnostically negative slope (separation value decreasing away from the upper fault tip) in the separation–distance graph. The change of cut-off angle and the spatial distribution of faults display a close relationship with the axial surface of the fold. Our analyses show that fold-accommodation faults are kinematically consistent with the flexural slip of the fold. The interbedded strata with competence contrast facilitate formation of fold-accommodation faults. These characteristic signatures are concluded as a set of primary identification criteria for fold-accommodation faults. •We analyze hand-specimen and outcrop scale fold-accommodation faults.•The faults are geometrically and kinematically consistent with the associated fold.•Out-of-syncline thrust shows a diagnostic profile in separation–distance curve.•Mechanical stratigraphy positively influences the formation of the faults.•Several key characteristic features of fold-accommodation faults are distinguished.