8/20/2019 Lab5_3pt

1/8

Lab 5: Interpretation of Structures from Geological Maps

Map 1

1. Is the topography of this area a ridge or a valley?

2. Which way do the beds dip?

3. Draw at least five strike lines on the limestone/mudstone contact.Is this contact a planar surface?

What is the strike of this contact?

4. Do all the units on this map have the same strike?

5. Do the beds dip shallowly or steeply?

6.   Lightly  color your geologic map and explanation.

7. What geologic structure is indicated by the contact-contour patterns on this map?

Map 2

8. What are the topographic features one would encounter when walking SE to NW acrossthis area?

9. Does the conglomerate rest on top of or underneath the sandstone?

10. Construct strike lines on all contacts where possible on both sides of the fault.What are the strike and dip directions?

Are the contacts between all units planar and parallel?

1

8/20/2019 Lab5_3pt

2/8

11. Examine the spacing of your strike lines with respect to the slope of the valley floor oneither side of the fault.Do the units dip similar angles on both sides of the fault?

Calculate the dip

12. Draw strike lines on the fault.Which way does the fault dip?

What is the angle of dip on the fault?

13. Assuming a negligible component of strike-slip, what is the motion of the fault?

14. Is this a normal fault or a reverse fault?

15. List the sequence of events that gave rise to the geology of this area (oldest to youngest)..

2

8/20/2019 Lab5_3pt

3/8

Map 3

16. Examine the topography of the area   carefully  and mentally note the position of thedrainages, hills, and ridges. Color the map and map key lightly.

17. Construct strike lines on the base of the coarse sandstone in the three areas where itcrops out. What is the orientation of the coarse sandstone? (Strike/dip, dip direction).

18. What does the coarse sandstone  overly  at each of the three areas where it crops out?

What does this tell you about the basal contact of the coarse sandstone?

19. Construct strike lines on the remaining contacts on both sides of the fault.Are the beds everywhere planar?

20. Which way do these beds dip in most of the SW corner of the map?

3

8/20/2019 Lab5_3pt

4/8

Which way do they dip elsewhere?

21. Assuming the superposition of units on the map is representative of relative age, whatis the oldest unit exposed?

22. What sort of structure is needed to explain the dip directions and map pattern of theunits below the coarse sand on either side of the fault?

23. Draw strike lines on the fault.Which way does it dip?

Does it dip steeply?

24. Assuming a negligible amount of strike-slip movement, which side moved up?

4

8/20/2019 Lab5_3pt

5/8

Is this a normal or reverse fault?

25. What constraints can you place on the age of the fault?

26. List the sequence of events, the geologic history that you interpret from this map.

5

8/20/2019 Lab5_3pt

6/8

 2 0 0

2   6   0   

 3 2 0

3   8   0   N

siltstone

sandstone

limestone

mudstone

granite

Contour Interval = 30m

Scale: 1cm = 100m

(after Simpson 1986)

Figure 1: Use this Map to answer questions 1–7

6

8/20/2019 Lab5_3pt

7/8

shale

limestone

mudstone

sandstone

conglomerate

Contour Interval = 30m

Scale: 1cm = 100m

(after Simpson 1986)

30

90

90

150

150

15090   210

210

210

N

Figure 2: Use this Map to answer questions 8–15

7

8/20/2019 Lab5_3pt

8/8

N

coarse sandstone

limestone

anhydrite

shale

gypsum and halite

Contour Interval = 30m

Scale: 1cm = 100m

(after Simpson 1986)

400

 4  0  0

 4  0  0

340 3 4 0

    3   4    0

340

 2 8 0

280

   2    8   0

   2   8   0

340  2  2  0

    3   4    0

400

    3   4    0

Figure 3: Use this Map to answer questions 16–26

8