Laboratory Manual for Introductory Geology 4e

EXERCISE 10.12
Name:
Course:
Constructing a Cross-Section View of a Block Diagram
Section:
Date:
(a) The map surface of the block diagram in the figure below provides strikes and dips of the layers shown. From this
information, show the layers with their proper angles in the front and side cross-section faces. Note that the strike
of the layers is perpendicular to the front face of the block.
Block diagram with strikes and dips 0f the layers.
30
50
What kind of structure is shown?
(b) Complete the map view and cross-section views of the block diagrams below by showing a sequence of
sedimentary rocks with the indicated orientations. Show at least three layers in each block, and plot the strike and
dip symbol on the map surface.
N
Block A: 090°/40° S. Block B: 000°/60° E.
(c) Complete the cross-section views of the block below.
Block diagram for creating cross-section views.
1 2 3 4 3 2
50 50 30 30
Earlier, in the context of discussing block diagrams, we distinguished between nonplunging
folds and plunging folds. We can recognize these folds on geologic maps
simply by the pattern of color bands representing formations—on a map, the formation
contacts of nonplunging folds trend parallel to the hinge trace, whereas those of
plunging folds curve around the hinge trace so that we can see the fold nose. Furthermore,
we can distinguish between anticlines and synclines by the age relationships of
the color bands—strata get progressively younger away from the hinge of an anticline
and progressively older away from the hinge of a syncline. If the hinge isn’t shown on
the map, you can draw it in where the reversal of age takes place. See FIGURE 10.12 for
an example of a map and cross section of plunging folds.
10.4 GEOLOGIC MAPS
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