Geology Reference
In-Depth Information
Fig. 2.14.
Plotting the orientation of the plane and its pole on an equal-area lower-hemisphere stereo-
gram. The plane has a dip of 32SE (150), and a strike of 060.
a
NESW compass directions and strike and
dip directions are marked on the overlay (
square
).
b
Overlay rotated to bring the strike to north and the
dip to east. Trace of plane and pole to plane marked on overlay.
c
Overlay returned to its original posi-
tion. The plunge and trend of the pole is 58, 330
then return the overlay to its original position to see the plane in its correct orientation
(Fig. 2.14c). Find the pole to the plane by placing the overlay in the starting position
for drawing bedding, that is, with the strike direction N-S. Along the E-W axis, count
in from the primitive circle an amount equal to the dip, then count another 90° to find
the pole (Fig. 2.14b) or, equivalently, count the dip amount up (outward) from the cen-
ter point of the diagram. Mark the position of the E-W line on the primitive circle and
return the overlay to its original position to find the trend of the pole (330°). The plunge
of the pole is 90° minus the dip. To plot planes and poles from the dip and dip azimuth
of the plane (the plane previously plotted is
= 32, 150) mark the dip direction on the
primitive circle (Fig. 2.14a), rotate the overlay to bring this direction to E-W, and count
the dip amount inward to find the point that represents the orientation of the dip vector.
The great circle projection of the bed goes through this point. Plot 90° plus the dip
along E-W to find the pole (Fig. 2.14b). Return the overlay to its original position to
see the result (Fig. 2.14c). If the plunge and trend to be plotted are those of a line,
follow the same steps as in plotting a dip vector.
δ
