Structural Geology (Geol 4013/6013)
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Lab Exercise 7 (Study Chapter 14 through 18 of the Lab Manual!
Name: ______________________
Questions (35 pts), map (30), cross section (35)
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
Folds; Refolds (superposed folds); Structural
Analysis of folds
Geological map of folded/faulted area with
unconformity
Problem 1, Page 409 (Chapter 14). Plot the fold data in Table 14.10 on Figure 14.12 and identify the fold orientation
for each case.
NOTES: ‘D’ is the dip of the hinge plane. ‘P’ is the plunge of the hinge line. ‘R’ is the pitch of the hinge line.
1. What is the fold name for D (90, P (0)?
a. Recumbent b. Subvertical c. Subhorizontal d. Upright
e. Moderately plunging
2. What is the fold name for D (0), R (0)?
a. Recumbent b. Gently inclined c. Subhorizontal d. Upright
e. Moderately plunging
3. What is the fold name for D (20), P (20)?
a. Recumbent b. Subvertical c. Gently plunging d. Gently inclined
e. Moderately plunging
4. What is the fold name for D (10), P (5)?
a. Recumbent b. Subvertical c. Subhorizontal d. Upright
e. Moderately plunging
5. What is the fold name for D (40), P (20)?
a. Subvertical b. Gently plunging c. Subhorizontal d. Recumbent e. Moderately plunging
6. What is the fold name for D (65), P (40)?
a. Recumbent b. Subvertical c. Subhorizontal d. Upright
e. Moderately plunging
7. What is the fold name for D (85), P (80)?
Recumbent b. Subvertical c. Subhorizontal d. Upright
e. Moderately plunging
8. What is the fold name for D (65), P (50)?
Recumbent b. Subvertical c. Subhorizontal d. Upright
e. Moderately plunging
9. What is the fold name for D (85), P (40)?
Subvertical b. Gently plunging c. Subhorizontal d. Recumbent e. Moderately plunging
10. What is the fold name for D (90), R (90)?
Recumbent b. Subvertical c. Subhorizontal d. Upright
e. Moderately plunging
Attach Figure 14.12 with your points plotted on it!
Problem 2, Page 409 (Chapter 14). Draw the dip isogons at 10o intervals on the fold in Figure 14.37.
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Problem 1, Page 467 (Chapter 17).
Follow the guide on Page 459, Section 17.4, and convert the map of Figure 17.16 (a) into the down-plunge view using
the fold axis (30/090).
Structural Geology (Geol 4013/6013)
Lab 7. Page 1
Hint: Copy (trace) Figure 17.16 onto a transparent graph paper, or a tracing paper, and then draw 1 cm wide square
grids on it. Then deform the squares into rectangle grids using the amount of plunge in the direction of the plunge.
See instructions on page 459 of the book.
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SUPERPOSED FOLDING - Figure 18.17, from Page 485, Chapter 18, is a geological map of an area in which the rocks
have undergone two episodes of folding. Determine the geometrical relationships between the two sets of folds.
Follow all the steps given, and attach all your stereograms.
Plot the data both as  (i.e., poles) and  (i.e., planes as cyclograms) diagram.
Plot data for domains 1, 2, and 3 on separate tracing papers – Attach all the three plots!
Use the following symbols on your nets:
1 Fold axis of the 1st generation fold
 Pole to folded bedding (folded layer)
1 Pole to the first generation axial plane (AP1)
11. What is the orientation of the 1st-generation fold axis (1, symbol: 11) in domain 1?
a. S14E, 36 b. N67W, 30 c. N57E, 12 d. N23W, 67 e. S28E, 66
12. What is the orientation of the 1st-generation fold axis (1, symbol: 12) in domain 2?
a. S64W, 33 b. N35W, 48 c. S27E, 26 d. S47W, 13 e. N82W, 16
13. What is the orientation of the 1st-generation fold axis (1, symbol: 13) in domain 3?
a. N27W, 20 b. N30, 76
c. N52W, 44 d. S22W, 41 e. N82E, 34
14. What is the orientation of the 1st-generation axial plane (AP1, symbol: 11) in domain 1?
a. S44E, 56SW b. N61W, 30NE
c. N15E, 12SE
d. N23W, 26SW e. N75W. 77N
15. What is the orientation of the 1st-generation axial plane (AP1, symbol: 12) in domain 2?
a. N14E, 54NW b. N50E, 79SE
c. S56E, 23NE
d. N31W, 63NE e. S28E, 66NE
st
16. What is the orientation of the 1 -generation axial plane (AP1, symbol: 13) in domain 3?
a. N33E, 54NW b. S71W, 23NW c. N30W, 62NE d. S42W, 55SE e. S08E, 16SW
For the following two questions use the following symbols:
2 Fold axis of the 2nd-generation fold.
2 Pole to the 2nd-generation axial plane (AP2). Use the 2 symbol for the 2nd-generation axial trace
You need to combine the data from the three domains on a single synoptic diagram!
17. What is the orientation of the 2nd-generation fold axis ( 2, symbol: 2?
Note: This is the pole to the great circle containing all three 1!
a. N75E, 62 b. N31W, 33 c. S12E, 65 d. N42E, 36 e. N80W, 25
18. What is the orientation of the 2nd-generation axial plane (AP2, symbol: 2?
Note: AP2 is the best fit great circle containing 2 & AT2 (2nd-generation fold axial traces, from map)!
a. S23E, 42SW b. N18W, 39NE c. N14W, 63NE d. N43W, 59SW e. S87E, 46SW
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Structural Geology (Geol 4013/6013)
Lab 7. Page 2
STRUCTURAL ANALYSIS
Problem 1, Page 490. Find both the  axis (i.e., finding the pole to the great circle containing the poles to the folded
surfaces) and  axis (i.e., finding the intersection of the cyclographic projections of the folded surfaces) for the fold
data in Table 18.2 and Table 18.3 (copied below).
Do this on two separate transparent papers; one for Table 18.2 and the other for Table 18.3!
For each, you need to show both  and  diagrams!
Table 18.2: Plunge (p) and trend (t) of the dip vectors. NOTE: After finding the dip vector, draw the great
circle through it, and then find its pole (). The pole to the great circle through the s is the fold axis.
No
p/t
No
p/t
No
p/t
No
p/t
No
p/t
1
80/045
3
70/202
5
50/172
7
60/195
9
60/187
2
44/188
4
60/065
6
55/087
8
41/117
10
44/105
Table 18.3: Plunge (p) and trend (t) of the pole vectors. NOTE: Plot each pole. Then draw the great circle
perpendicular to each pole. Fold axis is at the intersection of the great circles!
No
p/t
No
p/t
No
p/t
No
p/t
No
p/t
1
10/225
3
20/022
5
40/352
7
30/015
9
30/007
2
46/008
4
40/245
6
35/267
8
49/297
10
44/285
19. What is the fold axis for data of Table 18.2?
a. N14W, 60 b. S48E, 40 c. S45E, 12 d. S31W, 67
e. S80E, 19
20. What is the approximate (best fit) fold axis for data of Table 18.3?
a. S23E, 63
b. N70E, 23 c. S79E, 28 d. N36W, 28 e. S76E, 26
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Problem 2, Page 490 (Ch. 18) using the fold data on Figure 18.23. Use both  and  diagrams.
21. What is the orientation of the fold axis?
a. S64W, 33
b. N23E, 80
c. S73E, 62
d. N41W, 36
e. N90E, 31
22. What is the orientation of the fold axial plane?
a. N13E, 49NW b. N36W, 36E c. S30E, 63NE d. N42W, 25SW e. S28W, 16NW
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Problem 3, Page 491-492 (Chapter 18) using the data shown on Figure 18.24 (and Table 18.4).
Determine the orientation of the fold axis, axial plane, the interlimb angle for the fold represented by these data.
Make sure to plot the data both as  and  diagrams (i.e. poles and cyclographically).
23. What is the approximate attitude of the fold axis?
a. N24W, 16
b. S26E, 23
c. N35E, 23
d. S33E, 46
24. What is the attitude of the axial plane?
a. S44E, 56SW b. N36W, 37NE
c. N15E, 12SE
d. N11E, 26SE
25. What is the Interlimb angle
a. 47o
b. 86o
c. 35o
d. 105o
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Structural Geology (Geol 4013/6013)
e. S82E, 36
e. N24W, 90
e. 18o
Lab 7. Page 3
GEOLOGICAL MAP AND CROSS SECTION
Map 18 (attached) is a geological map of a folded and faulted area, with an angular unconformity.
The topographic contours are marked with the dashed lines. Notice that the fault is not vertical!
The scale of the map is given in the legend.
Read the instructions for the map, and draw all the necessary structural contours for units ‘C’ and ‘F’
(color these units for clarity). Also draw the structural contours for the fault. Answer the following questions:
26. What is the orientation of the units above the unconformity?
a. 010, 40NW
b. 000, 6E
c. 090, 63NE
d. N35W, 25SW e. S81W, 36NW
27. What is the attitude of the easternmost unit C?
a. N34E, 25NW b. S4E, 22SW
c. S61E, 37NE
d. N23W, 39NE e. S43E, 16SW
28. What is the attitude of the second most eastern unit C, next to B
a. S24E, 61SW
b. N46W, 33NE c. N54E, 12SE
d. N39W, 61SW e. N4W, 22NE
29. What is the attitude of unit C at the corner of the diamond-shaped outcrop, near B?
a. S14E, 56SW
b. N51W, 35NE c. S4E, 22SW
d. N22W, 04SW e. N5E. 77N
30. What is the attitude of unit C immediately east of the fault?
a. S4E, 69SW
b. N34W, 35NE c. N54E, 42E
d. N32E, 4SE
e. N4W, 22NE
31. What is the attitude of unit C west of the fault?
a. N14E, 34NW b. N25E, 70SE
c. S35E, 23NE
d. N18W, 63NE e. S4E, 22NE
32. What is the attitude of the fault?
a. S41E, 54NW b. N12E, 68NW c. N25E, 12SE
d. N71W, 39NE e. S76E, 66NE
33. What is the vertical displacement across the fault?
a. 100 m b. 50 m c. 300 m d. 200 m e. 400 m
34. What kind of fault is this? Hint: Identify the hanging wall and see which side dropped!
a. Normal fault b. reverse fault c. strike-slip fault
35. What is the vertical thickness of unit G?
a. 50 m b. 100 m c. 150 m d. 200 m e. 250 m
Draw a cross section along XY on the given profile!
/30 pts
Attach your cross section!
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Cross section
Figure 5.10 (attached) is a map from a folded area.
The attitudes of the bedding in different units are indicated with the strike and dip symbols.
Use the profile below the map to make a cross section along BB’.
NOTES:
Use the attitudes that are closest to the line of section!
Make sure to keep the thicknesses constant.
Make sure to remove the angularity along the fold axial traces (i.e., make hinges round!)
/35 pts
Attach your cross section!
Structural Geology (Geol 4013/6013)
Lab 7. Page 4
Measurement with Brunton Compass
The specimen on the Table is a fold in foliation (i.e., foliation in a gneiss is folded). The gneiss also has a lineation
on the foliation marked with the black line.
Do the following:
1. Measure the attitude of the hinge line of the fold.
Hinge line = ______________________
2. Measure the attitude of the axial trace (any is ok) of the fold.
Axial trace: ______________________
3. Measure the attitude of the foliation on the limbs (measure two per limb).
___________________
_____________________
____________________
____________________
4. Find the attitude of the fold axis (i.e., intersection of the folded foliation).
You can get this by intersecting the great circles of the four foliations OR by putting their poles on the same
great circle (called the profile plane) and then finding the pole to this great circle (profile plane)
Fold axis = ______________________
5. Do the fold axis and hinge line plot near each other? What does this mean?
Meaning: _______________________________________________________________________________
6. Measure the attitude of the lineation on the foliation
Structural Geology (Geol 4013/6013)
Lineation = _______________________
Lab 7. Page 5