Folds and types

short and simple description about fold and faults.how they occur and came into exist.
types of folds and its explanation.with figures and diagrams

1. INTRODUCTION Name : Imad Hussain From : Yar Hussain Swabi KP Pakistan University of Swabi : Geology department Presentation Topic : FOLDS AND ITS TYPES

2. FOLDS ( FOLDS are bends or wavelike features in layered rocks result of geological process)

3. EXPLANATION F old shows behavior of a ductile material. M ost metamorphic rocks are intensely folded because it is ductile under the high pressure and temperature environment of deep burial and tectonic stresses. F olding took place when the rock was buried at a moderate depth where higher temperature and confining pressure favor ductile behavior.

4. TERMINOLOGY Axial plane: An imaginary plane containing all of the hinge lines of a fold . H inge line/Axis: Line about which a fold appears to be hinged. Line of maximum curvature of a folded surface . L imb : Portion of a fold shared by an anticline and a syncline

5. TERMINOLOGY The H inge connects the two limbs of a fold. H inge P oint is the point of maximum curvature and is located in the center of the hinge zone. •If the hinge line appears as a straight line it is called a fold Axis . •The A xial S urface (or axial plane when approximately planar) connects the hinge line of two or more folded surfaces.

6. •The Axial trace represents the intersection between the axial plane and the surface of observation. •The Inflection point is where there is a change in curvature of a fold limb. •The Interlimb angle is the angle enclosed by the two limbs of a fold. •The Enveloping surface is the surface tangent to individual hinges along a folded layer

7. TYPES 1) Anticline : is a fold shaped like an arch with the oldest rocks in the center of the fold. Usually the rock layers dip away from the axis .

8. TYPES 2) Syncline : The fold shaped like a trough with the youngest rocks in the center of the fold. The layered rock Usually dips toward the syncline’s Axis.

9. Fig: A nticline and Syncline F old

10. TYPES PLUNGING FOLD A fold in which the axis is not horizontal On surface leveled by erosion of exposed beds. However , plunging anticlines and synclines are distinguished from one another by directions of dip or by relative ages of beds.

11. TYPES OPEN FOLD A fold with gently dipping limbs and the angle between the limbs is large . ISOCLINAL FOLD one in which limbs are nearly parallel to one another, implies larger shortening stress.

12. TYPES MONOCLINE : A local steeping in a gentle regional dip; a steplike fold in rock. OVERTURNED FOLD : A fold in which both limbs dip in the same direction . RECUMBENT FOLD : A fold overturned to such an extent that the limbs are essentially horizontal . UPRIGHT FOLD : A fold with a vertical axial plane .

13. FIGURE