Page 307 - Laboratory Manual in Physical Geology

A CTIVIT Y 10.5 Cardboard Model Analysis and Interpretation

Name: ______________________________________ Course/Section: ______________________ Date: ___________

Tear Cardboard Models 1–6 from the back of your lab manual. Cut and fold them as noted in red on each model.
A. Cardboard Model 1
This model shows Ordovician (green), Silurian (light gray), Devonian (bule-gray), Mississippian (dark gray), Pennsylvanian
(yellow), and Permian (salmon) formations striking due north and dipping 24° to the west. Provided are a complete geologic
map (the top of the diagram) and three of the four vertical cross sections (south, east, and west sides of the block diagram).
1. Finalize Cardboard Model 1 as follows. First construct the vertical cross section on the north side of the block so it shows

the formations and their attitudes (dips). On the map, draw a strike and dip symbol on the Mississippian sandstone that

dips 24° to the west (see FIGURES 10.3 or 10.5 for the strike and dip symbol).
2. Explain the sequence of events that led to the existence of the formations and the relationships that now exist among them

in this block diagram.

B. Cardboard Model 2
This model is slightly more complicated than the previous one. The geologic map is complete, but only two of the cross
sections are available. Letters A – G are ages from oldest ( A ) to youngest ( G ).

1. Finalize Cardboard Model 2 as follows. First, complete the north and east sides of the block. Notice that the rock units
define a fold. This fold is an anticline, because the strata are convex upward and the oldest formation ( A ) is in the center
(inside) of the fold. It is symmetric (non-plunging), because its axis is horizontal. (Refer back to FIGURE 10.8 for the

differences between plunging and non-plunging folds if you are uncertain about this.) On the geologic map, draw strike
and dip symbols to indicate the attitudes of formation E (gray formation) at points I, II, III, and IV. Also draw the proper
symbol on the map (top of model) along the axis of the fold (refer to FIGURE 10.5 ).

2. How do the strikes at all four locations compare with each other?

3. How does the dip direction at points I and II compare with the dip direction at points III and IV? In your answer, include
the dip direction at all four points.

C. Cardboard Model 3
This cardboard model has a complete geologic map. However, only one side and part of another are complete.
Letters A – E are ages from oldest ( A ) to youngest ( E ).

1. Finalize Cardboard Model 3 as follows. Complete the remaining two-and-a-half sides of this model, using as guides the
geologic map on top of the block and the one-and-a-half completed sides. On the map, draw strike and dip symbols
showing the orientation of formation C at points I, II, III, and IV. Also draw the proper symbol along the axis of the fold
(refer to FIGURE 10.5 ).
2. How do the strikes of all four locations compare with each other?

3. How does the dip direction (of formation C ) at points I and II compare with the dip direction at points III and IV?

Include the dip direction at all four points in your answer .

4. Is this fold plunging or non-plunging? ________________ 5. Is it an anticline or a syncline? __________________

6. On the basis of this example, how much variation is there in the strike at all points in a non-plunging fold?

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