Page 308 - Laboratory Manual in Physical Geology

D. Cardboard Model 4
Letters A – H are ages from oldest ( A ) to youngest ( H ). This model shows a plunging anticline.. The anticline plunges to the
north, following the general rule that anticlines plunge in the direction in which the fold closes .
1. Finalize Cardboard Model 4 as follows. Complete the north and east sides of the block. Draw strike and dip symbols

on the map at points I, II, III, IV, and V. Draw the proper symbol on the map along the axis of the fold, including its
direction of plunge. Also draw the proper symbol on the geologic map to indicate the orientation of beds in formation J.
2. How do the directions of strike and dip differ from those in Model 3?

E. Cardboard Model 5
Letters A – H are ages from oldest ( A ) to youngest ( H ). This model shows a plunging syncline. Two of the sides are complete
and two remain incomplete.

1. Finalize Cardboard Model 5 as follows. Complete the north and east sides of the diagram. Draw strike and dip symbols on
the map at points I, II, III, IV, and V to show the orientation of layer G. Synclines plunge in the direction in which the fold
opens . Draw the proper symbol along the axis of the fold (on the map) to indicate its location and direction of plunge.
2. In which direction (bearing, trend) does this syncline plunge?

F. Cardboard Model 6
This model shows a fault that strikes due west and dips 45° to the north. Three sides of the diagram are complete, but the east
side is incomplete.

1. Finalize Cardboard Model 6 as follows. At point I, draw a symbol from FIGURE 10.7 to show the orientation of the fault .
On the west edge of the block, draw arrows parallel to the fault, indicating relative motion. Label the hanging wall and the
footwall. Complete the east side of the block. Draw half-arrows ( FIGURE 10.7 ) parallel to the fault, to indicate its relative

motion. Now look at the geologic map and at points II and III. Write U on the side that went up and D on the side that
went down. At points IV and V, draw strike and dip symbols for formation B.
2. Is the fault in this model a normal fault or a reverse fault? Why?

3. On the geologic map, what happens to the contact between units A and B where it crosses the fault?

4. Could the same offset along this fault have been produced by strike-slip motion?

5. REFLECT & DISCUSS There is a general rule that, as erosion of the land proceeds, contacts migrate downdip . Is this true

in this example? Explain.

278