Geology Reference
In-Depth Information
constant (Fig. 11.5b). If material has been transported across the chosen pin lines by
displacement on an upper detachment (Fig. 11.5c) or into or out of the region by layer-
parallel simple shear (Fig. 11.5d), the structure should be regionally balanced, even if
the region of interest is not locally balanced. Thus for a regionally balanced structure
a vertical pin lines may represent a
working
pin line (Fig. 11.5b,c) that will restore with
an offset or a tilt. A valid cross section might fail to restore to a rectangle because of
unrecognized transport across a working pin line. The restoration reveals these oth-
erwise hidden displacements.
11.2.2
Palinspastic vs. Geometric Restoration
Restoration is a purely geometric manipulation of the cross section according to a spe-
cific set of rules. A geometric restoration (Fig. 11.6) is a restoration that is not specifi-
cally related to the direction of transport that formed the structure. A palinspastic
restoration is the restoration of the units to their correct pre-deformation configura-
tion by exactly reversing the displacements that formed the structure. The indepen-
dence of the restoration from the transport direction is illustrated in Fig. 11.6. Two
different cross sections through a fold have been restored. Normally it is assumed that
Fig. 11.6.
Geometric restoration of a
cross section in any direction
