folds, descriptive goals: 1) to understand the basic geometric elements of folds and 2) to classify...

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

Classify Me

Classify Me

Classify Me

Classification: Interlimb angle

• Gentle 180–170°

• Open 170–90°

• Tight 90–10°

• Isoclinal 10–0°

Classify Me

Classify Me

Classify Me

Classification based on shape

• Cylindrical folds

• Chevron or kink folds

• Cuspate folds

• Symmetrical vs. Asymmetrical folds

Classify Me

Classify Me

Symmetrical ??

Fold Vergence

Vergence ??

Classification: Layer thickness

• Parallel or concentric folds

• Similar folds

Classify Me

Classify Me

Classify Me

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

Disharmonic Folds

Map symbols used for folds

• Anticlines and synclines

• Overturned anticlines and synclines

• Plunging folds