Geoscience Reference
In-Depth Information
preserve and emphasize information for further interpretation.
Inking in will involve the following as appropriate to the area.
1. Structural symbols should be checked and redrawn using
permanent mapping pens with waterproof ink, at different
thicknesses (or in different colours) for faults and
unconformities. Ensure the symbols are consistently
marked relative to their locations: convention is for the
locality to lie at the intersection of strike line and dip tick
(planar feature), or the head of the arrow (linear feature).
Make strike lines and plunge arrows long enough (
c
. 6 mm)
so that they can be traced, or their azimuth determined, if
necessary (for instance if the data are lost). Make sure
bearings of all data are retrievable in case of imperfect
plotting (e.g. in a notebook, unambiguously keyed to the
locality on the map). Omit symbols only to avoid
congestion, and then omit data that are less crucial to your
study (e.g. joints, vein orientations). This important
recording process is summarized in the fl owchart below.
10
Rotate compass dial
to strike or plunge
direction
Align static arrow
and lines with
grid N lines
Place long edge
of compass
at locality point
Lay compass
on map
Plot structural
data on a map
Plane
or line?
L
P
Draw
c
.6 mm line using long edge of
compass, starting at locality point
Draw
c
.6 mm strike line using long edge
of compass, with locality point halfway
Add arrowhead pointing in plunge
direction at locality end of line
Add short tick at 90° to strike line, halfway
along strike line on down-dip side
Annotate with plunge
angle near arrowhead
Annotate with dip angle
near short dip tick
Linear datum
plotted
Planar datum
plotted
2. Other annotations such as locality numbers and brief notes
can be rewritten in ink, and may be repositioned for clarity
at the same time.
3. Lines marking certain geological boundaries can be inked
in and those marking uncertain geological boundaries can
be left in pencil, but may need renewing.
4. Exposures can be outlined in ink and coloured strongly,
but areas where rock units are inferred should only be
coloured very lightly. Figure 10.12 (p. 227) compares a fi eld
map with the corresponding 'inked-in' map.
