Structural Geology (Geol 4013/6013)

Lab Exercise 8Questions (20)

Name: ______

Foliation
  • Lineation
  • Two drill holes intersecting a plane

Study Chapter 19 of the Lab Manual by Donal M. Ragan:
“Structural Geology, an Introduction to Geometrical Techniques”.

Problem 1: Plot the following set of lineations (given in plunge, trend) with the symbol on the same tracing paper using the stereonet. Label each lineation (e.g., a, b).

id / (plunge, trend) / id / (plunge, trend) / id / (plunge, trend)
a / 32, 087 / b / 43, 217 / c / 12, N12E
d / 88. 092 / e / 86, 270 / f / 59, N60E
g / 59, S60E
  1. Inspect the distribution. What kind of pattern the data distribution displays?
  1. Random patternb. Small circlec. Great circle

d. Maximae. Girdle

Problem 2: A poly-deformed metamorphic rock contains two mineral lineations that lie on the same foliation plane. The first lineation is oriented 14, N10E, and the second one is
oriented 58, S58E. Plot the two lineations using the 1 and 2 symbols.

  1. What is the attitude of the foliation plane on which these lineations occur?

  1. S18W, 16SE
/
  1. 023, 36NW
/
  1. S43E, 26SW
/
  1. N02E, 61E
/
  1. N84W, 30SW

  1. What is the rake (pitch) of lineation 1 (1) on the foliation plane?

  1. 47S
/
  1. 32S
/
  1. 16N
/
  1. 56S
/
  1. 12S

  1. What is the rake (pitch) of lineation 2 (2) on the foliation plane?

  1. 17N
/
  1. 75S
/
  1. 60N
/
  1. 51S
/
  1. 10S

  1. What is the angle between the two lineations (1 and 2) on the plane of the foliation?

  1. 26o
/
  1. 48o
/
  1. 89o
/
  1. 32o
/
  1. 18o

Problem 3: A slip lineation on a fault plane has a rake of 68NE. The fault is oriented N52E, 83SE.

  1. What is the plunge of the lineation?

  1. 67
/
  1. 80
/
  1. 19
/
  1. 23
/
  1. 48

  1. What is the trend of the lineation?

  1. S36W
/
  1. N23W
/
  1. S24E
/
  1. N70E
/
  1. N42W

Problem 4: A slickenside surface is oriented: N10E, 80W. Fibrous slickenlines on the surface trend N60W.

  1. What is the plunge of the lineation?

a.37b.28 c.90 d.53 e.79

  1. What is the rake (pitch) of the lineation on the slickenside surface?

a.26W b.86N c.S24E d.47S e.32E

Problem 5: In the Granite Wash Mountains of Arizona, the bedding in a flysch sequence is oriented N47E, 34NW. A spaced cleavage in this unit is oriented N22E, 68SE. The intersection of the bedding with the spaced cleavage produces a pronounced intersection lineation that is visible on bedding-plane surfaces.

  1. What is the attitude of the intersection lineation?

  1. N18E, 46
/
  1. N27E, 13
/
  1. N33E, 60
/
  1. N62E, 21
/
  1. N49W, 43

Problem 6: A fault plane displays two different sets of slip lineation.

One set is oriented 22, 325, and the other set is oriented 49, 041.

11. What is the orientation of the fault plane (slip plane) that contains the two slip lineations?

  1. N48W, 23SW b. 036, 16NW c. N55W, 49NE d. S12E, 36E e. S73W, 20SE

Problem 7: Bedding on one limb of a fold strikes 030o and dips 20o SE. On this gentle limb, a linear structure, which is the crest of a ripple mark, pitches 42oE (show the lineation with the  symbol).
The fold was formed about a horizontal axis (show it with the  symbol).

  1. What is the plunge of the lineation?

  1. 18
/
  1. 23
/
  1. 36
/
  1. 13
/
  1. 53

  1. What is the plunge of the lineation on the steep limb of the fold dipping 53NW?

  1. 43
/
  1. 32
/
  1. 61
/
  1. 65
/
  1. 62

  1. What is the plunge on an overturned limb dipping 49SE?

  1. 46
/
  1. 65
/
  1. 30
/
  1. 11
/
  1. 27

Problem 8: On a plunging overturned fold the upper limb strikes 022o and dips 27oSE (pole symbol: u);
the overtuned limb strikes 090 and dip 58oS (pole symbol: o). On the upper limb a lineation pitches 27oS (symbol: u), and a lineation on the overturned limb (symbol: o)pitches 36oW.

Plot the data using the stereonet, and label all the great circles (i.e., upper limb, overturned limb).

Use the following symbols:Lineation (o and u); Fold axis (); Pole to bedding (o and u) in the two limbs

You need to do the following:

  • Find the fold axis () at the intersection of the limbs.
  • De-plunge the fold axis (i.e., bring  to the E-W diameter and then move it to the primitive).
    While doing this, also rotate the poles(o and u) to the two limbs, and the two lineations (o and u), on their small circles, the same amount as the plunge of the fold axis(), and in the same sense.
    Mark the new positions of these elements with a prime mark(’o and ’u and ’o and ’u).
  • Un-dip the overturned limb. This requires you to rotate the pole of the overturned limb, after it has been rotated during de-plunging (’o), to the center. First bring it to the E-W diameter and then move it to the center. Notice that overturned limbs have rotated beyond 90 degrees. So, the correct way is to move the rotated pole of the overturned limb first to the primitive, and then to the center from the other side (i.e.,the angle of rotation must be greater than 90). While you do this, keep track of the lineation on the overturned limb, i.e. move the (’o and ’u) to the new positions:”o and ”u ).
  1. Could the two lineations represent the same original pre-fold structure which was subsequently folded?
  1. Yesb. No
  1. Why?
  1. Because the fold is chevron
  2. Because the rotated lineations, after unplunging the fold axis and de-dipping the overturned limb move to the same horizontal position on the stereonet
  3. Because the rotated lineations, after unplunging the fold axis and de-dipping the overturned limb are perpendicular to each other
  4. Because the rotated lineations, after unplunging the fold axis and de-dipping the overturned limb are 180 to each other
  5. b and c

Attach your stereogram!
Problem 9: Mineral lineation occurs on foliation planesof the Lion Den mylonite at Battleship Peak Arizona.
The mylonitic foliation at this locality is oriented N22W, 73SW (symbol for its pole: 1). The rake (pitch) of the mineral lineation on the mylonitic foliation is 20N (show the lineation with the symbol: 1).

The foliation in the Lion Den mylonite was folded subsequent to the formation of the mylonite.
In fact the mylonitic gneiss occurs on the limb of a large antiform. Mylonitic foliation, at a second locality (South Ridge) on the second limb of the fold, is oriented N64W, 48NE (pole symbol: 2). Assume that the mineral lineation formed while mylonite was horizontal.

  1. What was the orientation of the lineation (o) prior to folding? Hint: First, calculate the plunge and bearing of the fold axis () from the two foliations (1 and 2). Then unplunge the fold and de-dip the foliation. While doing this, rotate the lineation in the same sense and amount (1 goes to o)

  1. N78E, 0
/
  1. S47E, 0
/
  1. N43E, 0
/
  1. S20E, 0
/
  1. N29W, 0

  1. What is the predicted present-day orientation of the lineation at South Ridge, i.e., on the second foliation?

  1. N20W, 39
/
  1. S37E, 10
/
  1. N53E, 65
/
  1. S62E, 62
/
  1. S49W, 30

Attach your stereonet!

  1. What is the nature of the data in Question 1, page 502 of your Lab Manual?

  1. N28W, 46NE
/
  1. N37E, 43NW
/
  1. N33E, 60SE
/
  1. N46W, 30SW
/
  1. N19W, 43SW

  1. What is the orientation of the horizontal trace of this fabric?

  1. S10W, 89
/
  1. N27E, 50
/
  1. N46W, 00
/
  1. N64E, 22
/
  1. N69W, 10

Structural Geology Lab 8, Page 1