Lab Exercise 1 – Attitudes of Lines and Planes by drg59916


									Lab Exercise 5 – Fault; Kinematic Analysis
Lab Manual: Structural Analysis & Synthesis: A Laboratory Course in Structural Geology, 3rd

Reading: Lab Manual, Chapters 9 & 10, pages 76-94

    Measuring translational and rotational slip; tilting
    Determine the stress ellipsoid given a population of faults
    Kinematic analysis
    Determine the principal stresses

Problems: Attach all your plots for full credit!

/ 10 pts           Problem 9.1

Answer:            Amount of slip: ---------------------------------------

/ 10 pts           Problem 9.2

Answer: Slip: -------------------------------------

/ 10 pts           Problem 9.3

Answer 1: -------------------------------------------------------------------------------------------------------


Answer 2: Direction of rotation: --------------------------         Amount of rotation: --------------------

/0 pts Problem 9.4
Do not return solution to this problem. Answers are provided for your inspection!

 Problem 9.4                            post-Rohan Tuff/pre-Helm's post-Helm's Deep Sandstone
                                        Deep Sandstone tilting     tilting

 Northeastern fault block               8° toward 104°                         5° toward 23°
 Central fault block                    7° toward 62°                          3o toward 12°
 Western fault block                                                           3o toward 12°

Lab Exercise 5                                                                                                          1 of 8
/0 pts Problems 9.5 (NOTE: use Map G.25!)
NOTE: Answers are given below for your inspection! (do not return answers to this problem).
9.5    (1) Fault A: Normal fault; post-Lower Miocene, pre-Middle Miocene
           Fault B: Left-slip tear fault; post-Triassic, pre-Middle Miocene (by inference that tear fault
           is related to thrust) (Fault C)
           Fault C: Thrust fault; post-Triassic, pre-Middle Miocene
           Fault D: Left-slip fault; post-Middle Miocene, pre-Miocene (upper, Tm) Fault E: Thrust
           fault; post-Silurian (may wish to accept post-Triassic if the two thrusts are considered
           related), pre-Jurassic

        (2) Contact "a":   nonconformity
            Contact "b":   intrusive
            Contact "c":   angular unconformity
            Contact "d":   disconformity

            Structure at "e":   trough of northeast-plunging syncline
            Structure at "f":   fenster
            Structure at "g":   klippe
            Structure at "h":   axial region of northeast-trending overturned anticline

        (3) Overturned dips: The 77°W dip in the Ordovician just west of Fault E. The 47°W dip in the
             Silurian just east of Fault E. The 72°W dip in the Pennsylvanian-Permian just east of Fault

        (4) Tm must be younger than other Miocene units because it overlaps fault D that cuts the middle
               Miocene unit

        (5) 20 km based on presence of klippe

        (6) 1. Deposition of Cambrian through Devonian rocks; unconformity; deposition of
                Pennsylvanian through Triassic rocks
             2. Folding and associated thrusting of these rocks along faults C and E; tear fault B forms
             during this time
             3. Intrusion of Jurassic plutons
             4. Uplift and erosion
             5. Deposition of Eocene through lower Miocene rocks
             6. Normal faulting (fault A) and associated tilting of Eocene-lower Miocene rocks
             7. Post-faulting erosion
             8. Deposition of middle Miocene rocks
             9. Southwest tilting of middle Miocene rocks
            10. Left-slip faulting along fault D
            11. Erosion (probable)
            12. Deposition of Tm unit
            13. Erosion to present

Lab Exercise 5                                                                                        2 of 8
/0 pts           Problem 9.6

NOTE: Answers are provided for your inspection!

9.6                    Mirkwood fault        Bree Creek fault        Gollum Ridge fault North Bree
                                                                                        Creek fault

1. Type                North - normal;       Normal separation;      Normal separation;     Normal
                                             probably normal         probably true          separation;
                       South -reverse        slip.. Preservation     normal slip because    probably true
                       (probably reverse     of Tertiary strata in   hanging wall rocks     normal slip
                       fault with minor      hanging wall            are consistently       because entire
                       normal reactivation   suggest at least a      younger                Tertiary section
                       post-Tr               significant                                    preserved in
                                             component of                                   hanging wall
                                             normal slip                                    rocks

2. Attitude            N-S to N20°E; 35°W    N5°W - N5°E;            N5°W - N5°E;           N21°E - N45°E;
                                             75°W                    75°W                   80°NW
3. Strike separation   Indeterminate         Poorly constrained      4100 meters            Minimum 5800
                                                                     measured from Tts-     meters based on
Dip separation                                                       Tb contact             separation of Kdt
(check for                                                           (projected to fault)   unit
consistency with
student cross

4. Age                 Post Miocene, pre-    Post Cretaceous is      Post Miocene           Post Miocene
                       Pliocene              only constraint

Lab Exercise 5                                                                                        3 of 8
Lab Exercise 5 cont’d - Chapter 10 Problems

/ 10 pts           Problem 10.1

NOTE: Use Fig. G-26
Attach your Figure G-26 after solving the problem!

/ 20 pts           Problem 10.2

Attach your equal area net!

Orientation of 1: ------------------------
Orientation of 2: ------------------------        Orientation of 3: ------------------------

/ 10 pts           Problem 10.3

Attach your equal area net!
Orientation of the stress ellipsoid: _________________________

/0 pts     Problem 10.4 (Solution is provided for inspection!)
10.4       Strain: Regional east-west shortening after the Mississippian
                    Regional east-west extension followed shortening
                    Orientation of faults in part governed by bedding surfaces during
           Stress: Early deformation: 1 = east-west, 2 = north-south, 3 = vertical
                    Later deformation: 1 = vertical, 2 = north-south, 3 = east-west

/0 pts     Problem 10.4 (Solution is provided for inspection!)

10.5   Note: events 2 and 3 below are permissively the same event. Depends on                    whether
granodiorite is considered to be folded.

           Strain: North-south shortening in southeast block between Mississippian and
           Cretaceous (F1 folds)
                   East-west shortening in southeast block between Mississippian and Cretaceous but after
                   north-south shortening (Cretaceous granodiorite could be folded) (F2 folds)
                   East-west shortening through map area - post Eocene, pre Miocene (F3 folds)
                   East-west extension, post Miocene (normal faults)

           Stress: D1: 1 = north-south, 2 = east-west, 3 = vertical
                   D2: 1 = east-west, 2 = north-south, 3 = vertical
                   D3: 1 = east-west, 2 = north-south, 3 = vertical
                   D4: 1 = vertical, 2 = north-south, 3 = east-west

Lab Exercise 5                                                                                             4 of 8
/0 pts Problem 10.6 (solution provided!)

10.6 (1) 2 = north-south, 3 = east-west (1 = vertical)
     (2) 2 = north-south, 3 = east-west (1 = vertical)
     (3) 1 = north-south, 3 = east-west (2 = vertical)
     (4) Paradox is that 1 and 2 both have the same orientation. Stress ellipsoid orientations can be
          derived from answers 10.6(2) and 10.6(3). If the magnitudes of 1 and 2 are very close to one
          another minor perturbations of the stress field could case these stress axes to switch. (Note:
          Duebendorfer doesn’t believe this. He interprets the strike slip faults to be extensional transfer

/0 pts Problem 10.7 (solution provided!)

10.7 (1) See solution below
     (2) See solution below
     (3) See solution below
     (4) Clockwise rotation of 3
     (5) Vertical principal stress could increase due to loading associated with voluminous magmatism
         Vertical principal stress could decrease due to crustal thinning associated with normal faulting

Lab Exercise 5                                                                                        5 of 8
Lab Exercise 5   6 of 8
0 pts      Problem 10.8 (Solution provided!)

10.8 (1) See solution below
     (2) (3) Not reproducible for manual
     (4) Key points:
                 (a) Development of structures proceeds sequentially from south to north
                 (b) 1 oriented due north-south and 3 oriented due east-west early in
        collisional history
                 (c) About a 25° to 30° clockwise rotation in horizontal stress directions
                 later in history as southeast Asia is "extruded" from the main part of Asia
                 (d) In the far north 1 and 2 switch orientations such that 1 is vertical.

/0 pts            Problem 10.9 (solution provided)

See solution below!

/ 10 pts          Problem 10.10 - Do this:

Attach your equal area net and answers!

Lab Exercise 5                                                                                  7 of 8
Lab Exercise 5   8 of 8

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