Superposed buckle folding in the eastern Iberian Chain, Spain

The Aliaga area (eastern Iberian Chain) shows large-scale examples of buckle superposition developed during Tertiary folding. In most cases, ENE-trending folds overprint earlier NNW-SSE-trending ones. The resulting structures are mapped, analysed, and genetically classified by comparison with analogue models described by several authors. The following types are found: standard Type 1 (1a: dome-and-basin structure, 1b: unequal-wavelength overprinted folds); modified Type I (1c: T-shaped 'joined' folds; 1d: T-shaped 'abutting' folds; 1e: L-shaped folds; If: 'snake-like' folds); standard Type 2 (2a: non-cylindrical buckling of earlier axial surfaces involving hinge replacement). Different superposed sets of flexural-slip striations record successive folding episodes in snake-like folds, and hinge replacement in the case of Type 2a superpositions. Types I and 2 apparently develop where the earlier folds have interlimb angles over and below 90degrees, respectively, which fits the results of analogue modelling and theoretical analysis by previous authors. Types 1b and 1d are associated with higher W1/W2 wavelength ratios than Types la and 1c. Other controlling factors are viscosity contrast and erosion processes. Specifically, erosion of competent limestone beds in the hinge zone of a NNW-SSE-trending anticline allowed the near-vertical eastern limb to be refolded into snake-like folds. (C) 2004 Elsevier Ltd. All rights reserved.