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32 Cards in this Set
- Front
- Back
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Anticline
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fold that is convex in the direction of the youngest beds in the folded sequence; *Older on the inside
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Antiform
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convex upward
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Syncline
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fold that is convex in the direction of the oldest beds in the folded sequence; *Older on the outside
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Synformal
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convex downward
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Overturned Folds
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one of the limbs is overturned; *One limb has been bent further than vertical
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Recumbent Fold
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fold lies on its side
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Anticlinorium
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A regional anticline with 1st and 2nd order folds within the bed
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Synclinorium
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A regional syncline with 1st and 2nd order folds within the bed
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Hinge Zone
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Area of maximum curvature in a fold
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Hinge Line
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hing points along a single folded surfaces
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Inflection Points
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curved limb segments of opposing convexity join at these locations
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Axial Surface
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passes through successive hinge lines in a stacking of folded surfaces; *Can be planar, wavy, curviplanar
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Axial Trace
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trace of axial surface in profile vies; *Line of intersection of the axial surfaces with any other surface
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Cylindrical Folds
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Folds that posses axes, one hinge line
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Near Cylindrical Folds
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close cluster of hinge lines on stereonet
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Non-Cylindrical Folds
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no pattern to hinge lines on stereonet
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Interlimb folds
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fold tightness; *Based on angle between folds
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Gentle Folds
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interlimb angle 170-180
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Open Folds
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interlimb angle 90-170
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Tight Folds
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interlimb angle 10-90
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Isoclinical Folds
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interlimb angle 0-10
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Symmetrical Folds
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median trace and axial trace that are mutually perpendicular
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Asymmetrical Folds
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limbs of different lengths; *Median trace and axial trace intersect at some oblique angle
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Concentric Folds (parallel folds)
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uniform thickness in layers
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Similar Folds
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Individual folded layers that display thickening in the hinge and thinning in the limbs
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Class 1 Folds
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curvature of the inner-arc > outer-arc; *Isogons closer together and converge to hinge point; *Thickening of limbs
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Class 2 Folds
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ideal similar folds; *Identical curvature of inner and outer arc; *Characterized by thickening in the hinge zone
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Class 3 Folds
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curvature of the inner-arc < outer-arc
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Dip Isogon
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points of equal inclination on the outer and inner bounding surfaces of the folding layer
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Flexural Folding
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mechanical influence of layering in the rock is very strong; *Layers participate in the folding by bending and flexing; * Accommodates buckling by layer-parallel slip-detachment from the decollement
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Passive Folding
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"The favored mechanism of folding"; *Mechanical influence of layering in the rock is very weak; *"Fake folding"; *Endures distortion without much resistance; *Marked by penetrative cleavage
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Parasitic Folds (drag folds)
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asymmetric minor folds; *Layer-parallel slip is different on opposing limbs
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