Folds, descriptive Goals: 1) To understand the basic geometric elements of folds and 2) to classify folds based on their shape.
Outline 1.The basics: Synforms and antiforms 2.Geometric elements of folds 3.Classification schemes
Synforms and Antiforms Monocline Synform — Includes synclines and synformal anticlines Antiform — Includes anticlines and anticlinal synclines
Geometric elements of folds-I Fold profile plane Fold hinge Hinge zone Fold limb
Geometric elements of folds-II Inflection point Axial plane Axial trace
Simple and complex fold elements
Wavelength and amplitude
Classification: Orientation of hinge/axial surface
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Classification: Interlimb angle Gentle 180–170° Open 170–90° Tight 90–10° Isoclinal 10–0°
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Classification based on shape Cylindrical folds Chevron or kink folds Cuspate folds Symmetrical vs. Asymmetrical folds
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Symmetrical ??
Fold Vergence
Vergence ??
Classification: Layer thickness Parallel or concentric folds Similar folds
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Dip-isogon classification Class-1A Class-1B (parallel) Class-1C Class-2 (similar) Class-3
Parasitic folds
What happens in non-similar folds?
Disharmonic Folds
Map symbols used for folds Anticlines and synclines Overturned anticlines and synclines Plunging folds