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Fold Vergence Identifier

Two independent ways to work out where you stand on a fold: the classic field method using minor-fold asymmetry (S/Z/M), and a quantitative check using the angle between bedding and axial-planar cleavage. Use either on its own, or both together for more confidence.

Method 1

Minor-fold asymmetry (S / Z / M)

This method needs calibrating first — the direction a Z-fold "points" relative to the nearest major hinge is a local convention, not a universal rule. Set it once from a known exposure, then classify new stations against it.

Step 1 — Calibrate

At a location where you already know you're on the limb approaching an anticline hinge (right-way-up beds), which shape do the minor folds show, looking down-plunge?

Step 2 — Classify your station

Z-shape
S-shape
M / W (symmetric)
Normal (right-way-up)
Overturned
Set your calibration, then classify a station.
Results will appear here.
Method 2

Bedding–cleavage relationship

Where axial-planar cleavage and bedding dip in roughly the same direction, their relative steepness is diagnostic: cleavage steeper than bedding indicates the anticline limb; bedding steeper than cleavage indicates the syncline limb. This also computes the bedding–cleavage intersection lineation, a common proxy for the local fold axis.

Bedding (S₀)

Cleavage (S₁, axial planar)

Ready.
Enter bedding and cleavage attitudes.
Results will appear here.