Folds Flashcards
Fold with beds that young away from the core
Anticline
Surface fold where there is no strain
Neutral-surface fold
Large scale antiform formed from smaller scale antiform and synform
Anticlinorium
Fold with the hinge zone at the top
Antiform
Fold that doesn’t have their axial surfaces approximately perpendicular (± 10 degrees) to the enveloping surface
Asymmetric fold
Box-shaped fold detached from the underlying and overlying layers
Box fold
Large-scale fold with straight limbs and sharp hinges
Chevron fold
Structures with hinge lines that laterally change curvature (< 50 degrees)
Doubly plunging fold
Fold produced near fault surfaces that appear to be pulled into a fault during movement
Drag fold
Fold that forms when a normal fault breaks and displaces between rocks but die upward into the sedimentary cover
Drape fold
Gradually opening fold is replaced by a neighboring, gradually tightening fold of opposite form
En echelon fold
Thrust sheet wherein dip flattens as it passes over a ramp
Fault-bend fold
Accommodation structures above the frontal top of a thrust
Fault propagation fold
Fold that forms from slip between layers
Flexural slip fold
Fold with 120 - 180 degrees interlimb angle
Gentle fold
Fold that plunges nearly to entirely horizontal (0 - 10 degrees)
Horizontal fold
Fold with 60 - 120 degrees interlimb angle
Open fold
Asymmetric fold in which one limb has been tilted beyond the vertical
Overturned fold
Fold with dip isogons perpendicular to the bedding throughout the fold
Parallel fold
Smaller fold related to a large structure
Parasitic fold
Irregular and isolated fold structures that typically occurs as a tightly folded vein or thin later of strongly contrasting lithology
Ptygmatic fold
A steeply plunging, inclined fold
Reclined fold
Fold with a horizontal (0 to 10 degrees) axial surface and horizontal hinge line
Recumbent fold
Fold plunging at 10 - 30 degrees
Shallow Fold
Fold with a hinge line showing extreme curvature, to the extent that the hinge line curvature approaches parallelism ( change in plunge up to 180 degrees)
Sheath fold
Fold with dip isogons parallel to each other
Similar fold
Fold steeply (60 to 80 degrees) punging
Steep fold
Fold that has their axial surfaces approximately perpendicular (± 10 degrees) to the enveloping surface
Symmetric fold
Fold with beds that young toward the core
Syncline
Large-scale synform formed from smaller-scale antiform and synform
Synclinorium
Fold with an inclined (10 - 70 degrees) axial surface
Inclined fold
Fold plunging at 30 - 60 degrees
Intermediate fold
Fold with 0 - 10 degrees limb angle or beds on both limbs are nearly parallel whether upright, overturned or recumbent
Isoclinal fold
Small fold (less than a meter) characterized by straight limbs and sharp hinges
Kink fold
Fold structure with only one tilted limb, with one limb being horizontal
Monocline
Fold with hinge zone at the bottom
Synform
Fold with 10 - 60 degrees interlimb angle
Tight fold
Fold with an axial surface nearly to entirely dipping upright (70-90 degrees)
Upright fold
Fold vertically (80-90 degrees) plunging
Vertical fold
