Geology Reference
In-Depth Information
6.3
Illustrative Cross Sections
The purpose of an illustrative cross section is to illustrate the geometry present on a
structure contour map. It is comparable to a topographic profile in concept and con-
struction.
6.3.1
Construction by Hand or with Drafting Software
Begin by drawing the line of section on the map (A-A', Fig. 6.10a). The line of section
in Fig. 6.10a has been selected to be perpendicular to the crest of the anticline. Clearly
show the end points of the section because they will serve as the reference points for
all future measurements. The section will be compiled on a graph where the vertical
axis represents elevations and the horizontal axis is the distance along the profile
(Fig. 6.10b). For an unexaggerated profile, the vertical scale should be the same as the
map scale and the lines spaced accordingly. To construct a vertically exaggerated pro-
file, let the vertical scale be some multiple of the map scale.
Cross sections are usually drawn either to be vertical or to be inclined such that the
plane of the section is perpendicular to the direction of plunge of the structure of
Fig. 6.10.
Initial stage of cross-section
construction from a map.
The line of section is
A
-
A'
.
a
Structure contour map and
a dip measurement (at eleva-
tion 820).
b
Graph for cross-
section construction. For no
vertical exaggeration both the
horizontal and vertical scales
are the same as the map scale
