Geology Reference
In-Depth Information
Fig. 18 a
View from the Zini Pass looking southward to the broadly
cylindrical folds of Ordovician quartzites plunging under the Silurian
black shales of Sebkha Leimhagen,
b
View of the breached fold east of
the sebkha (for location, see Fig.
19
a),
c
Detail of the eroded hinge of
fold (
b
). Numbers correspond to stratigraphic levels as follows
(Destombes
2006
):
1
Zini Fm (Middle Arenig),
grey
quartzite;
2
iron and clay layers;
4
sandy clay;
5 green
sandstone;
6
sandy clays
with worm tracks;
7
bedded sandstones;
8
micaceous sandstones with
worm tracks, followed upward by micaceous clay;
9
11
Premier Bani
Group (Llandeilo), with
9
metre-
thick
sandstone beds intercalated with
thin
-bedded sandstone;
10
ne-grained
thin
bedded sandstones with
one
Asaphidaea
cephalon (
Ogygiocaris
? sp.);
11
massive
greyish
green
quartzite with
Vexillium
-
8
Tachilla Fm (Llanvirn) with
2
coarse
Lingula
sandstones;
3
oolithic
-
converted into a low peneplain, then recently uplifted and
subjected to differential erosion.
The eastern border of the Liemhagen lowland corridor
consists of a remarkable system of open folds, labelled the
Jbel Rich (Fig.
19
a). Their axes are parallel to those of
the Jbel Zini folds, but the folded beds now belong to the
Lower-Middle Devonian System. Geosite B8 illustrates
folded structure and stratigraphy, which is typi
(Lubeseder et al.
2009
). An educational panel should be
emplaced at geosite B8 at the southwest extremity of a
typical perched syncline formed by Rich 1 and Rich 2 at the
northwest border of the Jbel Rich fold train (Fig.
19
b).
The Rich succession has economic potential as it includes
Orthoceras
- and Goniatite-rich limestones similar to those
exploited for the marble industry in the Ta
lalt region
ed by the
repetition of limestone-clay-sandstone lithologies (
(Eastern Anti-Atlas; Saddiqi et al.
2011
).
Once across the Rich folds, the road toMseied goes straight
across a wide plain with poor, shaly outcrops. This corridor is
underlain by the Middle-Upper Devonian silts and shales,
)
that corresponds to superimposed transgression-regression
cycles at the northern border of the West African Craton
“
Rich
”
Fig. 19 a
Interpretation of the Google Earth image of the Jbel Rich
folds west of Mseied. The successive Rich formations are numbered
R1
R4
.
Double white arrows
synclinal axes.
b
South-western tip of the
isolated perched syncline west of the J. Rich folds train
-
