1. Folds analysis techniques Goal: To apply some of the basic geometric techniques for analyzing folds and refolded folds.

2. 1. Foliation bedding intersections Three cases for overturned fold: a)Bedding upright, dipping more shallowly than foliation b)Bedding overturned dipping more steeply than foliation c)Bedding highly oblique to foliation

3. Note that for cylindrical folds, bedding- foliation intersection lineation lies close to fold hinge.

4. 2. π-axes and β-axes Define fold axis using measurements of bedding from around the fold Plot on stereonet

5. π-girdle: best-fit girdle to poles to bedding π-axis: pole to π-girdle

6. Finding π-axes 1. Plot poles to bedding2. Find best-fit great circle

7. β-axis: defined by intersections of bedding planes plotted on net

8. Find a fold axis using these bedding measurements 050°, 80°-SE 350°, 44°-NE 088°, 72°-NW Use both π-axis and β-axis methods

9. 3. Refolded folds

10. Refolded folds recognition 1.Can often be found in outcrop 2.Regional patterns in facing direction 3.Interference patterns

12. Interpret these maps: Draw in F 1 and F 2 axes and indicate plunge directions

13. Steps to interpret maps 1.Draw two lines representing fold axes. Which one is refolded? 2.Identify pattern of younger and older rocks. e.g. youngest on outside 3.Is the hook/boomerang shape a syncline or anticline? 4.Decide what kind of fold refolded the first fold.