Laboratory Manual for Introductory Geology 4e

FIGURE 10.12 Patterns of plunging folds.
N
A
28
Z
30
Y
Q
Anticline
22
A
A'
9
25
Syncline
X
W
27
A'
(b) Cross section of folds along the A–A’ line.
Anticline
(a) Map view of plunging anticline and syncline.
Hinge traces of the folds are indicated by labeled
lines, with arrows indicating the direction of plunge.
EXERCISE 10.13
Interpreting Simple Geologic Maps
Name:
Course:
Section:
Date:
For each of the following geologic maps, identify the structure or geologic features portrayed. Does the map show a fault,
fold, tilted strata, dike, pluton, unconformity, or some combination? To answer these questions, you may need to refer to
the block diagrams presented earlier in the chapter. Remember—think in three dimensions! With a little practice, geologists
learn to recognize the basic patterns quickly. (Note: The geologic periods in the maps below, in order from oldest to youngest,
are the Ordovician, Silurian, Devonian, Triassic, Jurassic, Cretaceous, and Tertiary.)
Map A Map B Map C
43
Dt
Jrt
Tr
56
6
Db
Dn
Jrt Jurassic Tinta Formation
Tr Triassic Jones Shale
Dt Devonian Tella Formation
Db Devonian Bouser Formation
Dn Devonian Norfolk Shale
Sh Silurian Hallo Formation
(a) Describe the geologic features of Map A.
N
Sh
N
Da
Kg 15
Db
27
Dn
i. -aged strata are overlain at an unconformity by -aged strata.
What type of unconformity is it?
ii. The Triassic and Jurassic strata dip in a direction at a angle.
iii. The Silurian and Devonian strata dip in a direction at a angle.
Tb
Sc
Tb Tertiary basalt
Kg Cretaceous granite
Da Devonian Alsen Formation
Db Devonian Becraft Limestone
Dn Devonian Norfolk Shale
Sc Silurian Cligfell Formation
Dn
Db
Ka
Ka
Ka
Kb
Dp
Sw
Si
Ot
12
Kb
10
Kb
Dp
Dp
Sw
Sw
N
Cretaceous Altoona Formation
Cretaceous Barrell Formation
Devonian Potomoo Limestone
Silurian Wala Shale
Silurian Jack Formation
Ordovician Trent Formation
11
Si
12
(continued)
262 CHAPTER 10 INTERPRETING GEOLOGIC STRUCTURES