Geology Reference
In-Depth Information
Fig. 6.21.
Axial surface traces (
dotted lines
) that bisect the interlimb angles. Exact locations of the axial
surfaces are not yet fixed in this step. Dip domains are
numbered
Fig. 6.22.
Dip-domain cross section with axial surfaces (
dotted lines
) moved so that the dip domains match
the stratigraphic contact locations. The
dashed
axial surface will be deleted and domains
1
and
2
combined
The axial surface orientations are determined next (Fig. 6.21). Following the rela-
tionship in Fig. 6.15 for constant bed thickness, the axial surfaces bisect the hinges.
The interlimb angles are measured, bisected and the axial surfaces drawn between each
domain. Two dip domains (2 and 4) are added to those shown in Fig. 6.20 so that the
dips can be honored at the ground surface. It is tempting to insert a fault at the location
of domain 4, but the map (Fig. 6.17) shows a vertical to near-vertical domain to the
southwest in the same position as on the vertical dip on the cross section. Not far to
the southwest of the map area, the units are directly connected across the two limbs
(Cherry 1990) with no fault present. The positions of the axial surfaces in Fig. 6.21 are
only approximate; the next step is to determine their exact locations.
The locations of the axial surfaces are now adjusted until the dip domains match the
stratigraphic contacts (Fig. 6.22). The dip change of the Ppv at location 1 must be ig-
