Laboratory Manual for Introductory Geology 4e

EXERCISE 10.10
Completing Block Diagrams (continued)
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(c) Complete the map view and cross-section faces for Block 4. Be sure to add arrows showing the direction of slip.
Describe the nature of the faulting. Is it dip-slip? If so, is it normal or reverse? Is it strike-slip? If so, is it left-lateral or
right-lateral? Explain your reasoning.
10.4 Geologic Maps
10.4.1 Introducing Geologic Maps and Map Symbols
Now that you’ve become comfortable reading and interpreting block diagrams, we
can focus more closely on how to interpret geology on the map-view surface. A map
that shows the positions of contacts, the distribution of rock units, the orientation
of layers, the positions of faults and folds, and other geologic data is called a geologic
map (FIG. 10.9a). Contacts between rock units are shown by lines (traces),
and the units themselves are highlighted by patterns and/or colors and symbols
that indicate their ages. The orientation of beds, faults, and foliations, as well as the
position of fold hinges, can be represented by strike and dip symbols. The map’s
explanation (or legend) defines all the symbols, abbreviations, and colors on the map.
FIGURE 10.9b, a geologic map of the Bull Creek quadrangle in Wyoming, illustrates
the components of a geologic map. All geologic maps should have a scale, north
arrow, and explanation.
FIGURE 10.9 Geologic maps.
12
Block diagram
15
12
Geologic map
N
Cretaceous Long Sandstone
Unconformity
Triassic Fields Shale
Triassic Zephyr Formation
15
2 km
Permian Anther Group
(a) A geologic map is the top surface of a block diagram. It shows the pattern of geologic units and structures as you would
see them by looking straight down from above.
(continued)
256 CHAPTER 10 INTERPRETING GEOLOGIC STRUCTURES