For further interpretation also some small scale arial
photograhs of poor quality were used. Ground chek-
kings were conducted during three field trips of each
two to five weeks duration.
3. Interpretation and Discussion
Due to the deformation of lithologic sequences as
Figure 2: This image displays window ‘A’ of fig.1. The subset is esspecially interesting with respect to the
plunging fold axes, and open to isoclinal limbs. The b-
c-plane strikes E-W with undulations of upto 20° N
and S. The orientation of the folds with their axial pla.
nes striking E-W to NE-SW indicates a crustal shorte-
ning along the N-S-direction in deeper crustal levels
under conditions of plastic deformation (fig.2, axial
traces of syn- and antiforms). Similar structures are
reported by MATTAUER (1986) for Tibet.
a” Axial trace of synform
.-. Axial trace of antiform
^A Lineation
Figure 2
folding and refolding pattern of the metamorphic series with their x E-W striking foldaxes.
observed in the images and during the ground check
theauthors discriminate 9 stages of structural rewor-
kings. These stages could be further subdivided in
varying localities but in this work only regional aspects
have been considered.
The first two stages are only visible in outcrop dimen-
sions because they represent a foliation D, and the
isoclinal folding of this foliation D; At most the foliation
shows strike directions of E-NE and sometimes more
deviation due to the later deformation stages. The dip
is in most cases steep but flattens close to thrust pla-
nes.
The next two stages D, and D, developed, in contrast
to D,, folding structures well seen only on the satellite
images. They produced axial planes with steeply
D, is a result of dextral shearing developed under
different pT-conditions because of its brittle-ductile
nature. The observed transportation along one such à
shear plane accounts for more than 1 km lateral off-
set (fig.2, elliptical structure in the lower part of the
image). It is also displayed as open folds in the Ariab-
Nakasib suture W of the Oko Shear Zone (KocH
1995) and Imasa Shear Zone (Guvor et al. 1983,
WIPFLER 1994, HAENISCH 1996). These shear zones
trend NE subparallel to the ophiolite belts in the area
Closely related to the previous shearing is a sinistra
264
displacement of much more intensity (Ds). It can be
considered as crustal shortening during the accretion
of the Red Sea Hills terrane sequence against the
Nile craton to W / NW (ABDELSALAM 1993). Good eX
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996
